- Record Type:OSHA Instruction
- Current Directive Number:TED 1.15 CH-1
- Old Directive Number:TED 1.15 CH-1
- Title:OSHA Technical Manual
- Information Date:
NOTE: In the text below, there are formatting errors, and several images are missing. For a paper copy of the full text of the directive, please contact the Directives Officer, Office of Management Systems and Organization, DAP at 202-693-2002.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment Subject: OSHA Technical Manual
A. Purpose. This Instruction transmits revised pages and additional chapters to the OSHA Technical Manual (OTM), OSHA Instruction TED 1.15.
B. Scope. This Instruction applies nationwide.
C. Action.
- 1. Remove and replace existing pages with the attached CH-1 pages as listed:
- Remove Existing Pages Insert Replacement Pages
- TED 1.15, Table of Contents: TED 1.15 CH-1, Table of Contents:
- Page I:1-28 thru 1-32 Page I:1-28 thru 1-32
- Page I:2-3 Page I:2-3
- Page II:4-8 Page II:4-8
- Page II:5-2 Page II:5-2
- Page II:5-4 Page II:5-4
- Page V:1-1 Page V:1-1
- Page V:1-4 Page V:1-4
- Page V:3-6 Page V:3-6
- Section II, Chapter 7, "Legionnaires' Disease"
- Section III, Chapter 2, "Petroleum Refining Processes"
- 2. File the transmittal pages of this instruction after the transmittal pages of the OSHA Instruction TED 1.15.
D. Federal Program Change. This Instruction describes a Federal program change which affects State programs. Each Regional Administrator shall:
- 1. Ensure that this change is promptly forwarded to each State designee using a format consistent with the Change Two-way Memorandum in Appendix A, State Plan Policies and Procedures Manual (SPM).
- 2. Explain the content of this change to the State designee as requested.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- 3. Ensure that the State shall respond to this change within 70 days in accordance with paragraph I.1.a.(2)(a) and (b), Chapter III of the SPM.
- 4. Ensure that the State's acknowledgment shall include (a) the State's plan to adopt and implement an identical change (b) the State's plan to develop an alternative, which is as effective, or the reasons why no change is necessary to maintain a program which is as effective. The State shall submit the plan supplement within 6 months in accordance with I.1.a.(3)(a), Chapter III of the SPM.
- 5. Review policies, instructions and guidelines issued by the State to determine that this change has been communicated to State compliance personnel.
E. Summary of Changes. Two new chapters have been added. Section II, Chapter 7, "Legionnaires' Disease" and Section III, Chapter 2, "Petroleum Refining Processes." Typographical errors have been corrected as well as an update on the sampling method for nitrous oxide. Table II, 4-3 "WBGT CORRECTION FACTORS IN DEGREES C" on page II: 4-8 of the Heat Stress chapter cited the ACGIH 1991-1992 "Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices" as the reference source but reflected the ACGIH 1990-1991 edition. ACGIH, in its 1991-1992 edition had removed trademarks and the vapor barrier clothing type from its table. This change updates the ACGIH 1991-1992 edition changes.
Joseph A. Dear Assistant Secretary
Distribution: National, Regional and Area Offices All Compliance Officers State Designees NIOSH Regional Program Directors 7(c)(1) Project Managers
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
CONTENTS _______________________________________________________________________
Section I. Sampling, Measurement Methods, and Instruments ..........ii
- Chapter 1. Personal Sampling for Air Contaminants ..............ii Chapter 2. Sampling for Surface Contaminants...................iii Chapter 3. Technical Equipment ................................iii Chatper 4. Sample Shipping and Handling .........................v
Section II. Health Hazards ...........................................v
- Chapter 1. Polymer Matrix Materials: Advanced Composites .......v Chapter 2. Indoor Air Quality Investigation ....................vi Chapter 3. Ventilation Investigation ..........................vii Chapter 4. Heat Stress .......................................viii Chapter 5. Noise Measurement ...................................ix Chapter 6. Laser Hazards ........................................x Chapter 7. Legionnaires' Disease ...............................xi
Section III: Safety Hazards ........................................xii
- Chapter 1. Oilwell Derrick Stability: Guywire Anchor Systems..xii Chapter 2. Petroleum Refining Processes ......................xiii Chapter 3. Pressure Vessel Guidelines .........................xiv Chapter 4. Industrial Robots and Robot System Safety ...........xv
Section IV: Construction Operations ................................xvi
- Chapter 1. Demolition .........................................xvi Chapter 2. Excavations: Hazard Recognition in Trenching and Shoring ............................................xvi Chapter 3. Controlling Lead Exposures in the Construction Industry: Engineering and Work Practice Controls .........................................xviii
Section V: Health Care Facilities ..................................xix
- Chapter 1. Hospital Investigations: Health Hazards ...........xix Chapter 2. [Reserved] Chapter 3. Controlling Occupational Exposure to Hazards Drugs ..............................................xix
Section VI: Ergonomics .............................................xxi
- Chapter 1. Back Disorders and Injuries ........................xxi
Section VII: Personal Protective Equipment ........................xxii
- Chapter 1. Chemical Protective Clothing ......................xxii
Section VIII: Safety and Health Management .......................xxiii
- [Future chapters]
Section IX: Miscellaneous ........................................xxiii
- Chapter 1. Metric System Conversion .........................xxiii
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SECTION I. SAMPLING, MEASUREMENT METHODS, AND INSTRUMENTS
CHAPTER 1. PERSONAL SAMPLING FOR AIR CONTAMINANTS__________________I:1-1
- A. INTRODUCTION_____________________________________________I:1-1
- B. GENERAL SAMPLING PROCEDURES______________________________I:1-2
- C. SAMPLING TECHNIQUES______________________________________I:1-3
- Detector Tubes .....................................I:1-3 Total Dust and Metal Fume...........................I:1-4 Respirable Dust.....................................I:1-4 Solid Sorbent Tubes.................................I:1-5 Midget Impingers and Bubblers.......................I:1-6 Vapor Badges........................................I:1-7
- D. SPECIAL SAMPLING PROCEDURES______________________________I:1-8
- Asbestos............................................I:1-8 Sampling for Welding Fumes..........................I:1-9
- E. EQUIPMENT PREPARATION AND CALIBRATION___________________I:1-10
- Alkaline Batteries.................................I:1-10 Rechargeable Ni-Cad Batteries......................I:1-10 Time of Calibration................................I:1-10 Electronic Flow Calibrators........................I:1-10 Calibration........................................I:1-10
- F. FILTER WEIGHING PROCEDURE_______________________________I:1-12
- G. BIBLIOGRAPHY____________________________________________I:1-13
- APPENDIX I:1-1. DETECTOR TUBES AND PUMPS____________________I:1-14
- APPENDIX I:1-2. ELECTRONIC FLOW CALIBRATORS_________________I:1-17
- APPENDIX I:1-3. MANUAL BURET BUBBLE METER TECHNIQUE_________I:1-19
APPENDIX I:1-4. SHELF LIFE OF SAMPLING MEDIA PROVIDED BY SLTC___________________________________________________I:1-21
- APPENDIX I:1-5. SAMPLING FOR SPECIAL ANALYSES_______________I:1-22
APPENDIX I:1-6. SAMPLING AND ANALYTICAL ERRORS (SAEs)_______I:1-26 ! ii
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
CHAPTER 2. SAMPLING FOR SURFACE CONTAMINATION_____________________I:2-1
- A. INTRODUCTION_____________________________________________I:2-1
- B. GENERAL TECHNIQUE FOR WIPE SAMPLING______________________I:2-2
- Filter Media and Solvents...........................I:2-2 Procedure...........................................I:2-3
- C. SPECIAL TECHNIQUE FOR WIPE SAMPLING______________________I:2-4
- Acids and Bases.....................................I:2-4 Direct Reading Instruments..........................I:2-4 Aromatic Amines.....................................I:2-4
- D. SPECIAL CONSIDERATIONS___________________________________I:2-4
- E. BIBLIOGRAPHY_____________________________________________I:2-4
APPENDIX I:2-1. TEMPLATE SAMPLES THAT COVER 100 SQUARE CENTIMETERS________________________________________________I:2-6
APPENDIX I:2-2. FLOURESCENT SCREENING FOR CARCINOGENIC AROMATIC AMINES____________________________________________I:2-7
CHAPTER 3. TECHNICAL EQUIPMENT____________________________________I:3-1
- A. INTRODUCTION_____________________________________________I:3-1
- B. CALIBRATION______________________________________________I:3-2
- Shipping Instructions...............................I:3-2 Postal Regultions...................................I:3-2 Special Instructions................................I:3-2
- C. BATTERIES________________________________________________I:3-3
- Alkaline Batteries..................................I:3-3 Rechargeable Ni-Cad Batteries.......................I:3-3
- D. ADVERSE CONDITIONS________________________________________I:3-3
- Adverse Temperature Effects.........................I:3-3 Explosive Atmospheres...............................I:3-3 Atmospheres Containing Carcinogens..................I:3-4
- E. DIRECT-READING INSTRUMENTS________________________________I:3-4
- Mercury Analyzer-Gold Film Analyzer.................I:3-4 Ozone Meter.........................................I:3-4 Toxic Gas Meters....................................I:3-5
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- Photoionization Meters..............................I:3-6 Infrared Analyzers..................................I:3-6 Direct-Reading Dust Monitors........................I:3-7 Combustible Gas Meters..............................I:3-8 Oxygen Meters.......................................I:3-9
- F. BIOAEROSOL MONITORS_______________________________________I:3-9
- Description and Applications........................I:3-9 Calibration........................................I:3-10 Special Considerations.............................I:3-10 Maintenance........................................I:3-10
- G. RADIATION MONITORS AND METERS____________________________I:3-10
- Light..............................................I:3-10 Ionizing Radiation.................................I:3-10 Nonionizing Radiation..............................I:3-11
- H. AIR VELOCITY MONITORS AND METERS_________________________I:3-11
- Flow Hoods.........................................I:3-11 Thermoanemometer...................................I:3-11 Other Velometers...................................I:3-12
- I. NOISE MONITORS AND METERS________________________________I:3-12
- Sound Level Meters and Dosimeters..................I:3-12 Personal Dosimeters................................I:3-13 Octave Band Analyzers..............................I:3-13
- J. ELECTRONIC TESTING METERS________________________________I:3-14
- Description and Applications.......................I:3-14 Calibration........................................I:3-14 Maintenance........................................I:3-14
- K. HEAT STRESS INSTRUMENTS__________________________________I:3-14
- Description and Applications.......................I:3-14 Calibration........................................I:3-14 Maintenance........................................I:3-14
- L. BIBLIOGRAPHY_____________________________________________I:3-15
- APPENDIX I:3-1. CALIBRATION INTERVALS_______________________I:3-16
APPENDIX I:3-2. GENERAL PROCEDURES FOR RETURNING INSTRUMENTS TO OCL________________________________________I:3-20
- APPENDIX I:3-3. INSTRUMENT CHART____________________________I:3-21
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
CHAPTER 4. SAMPLE SHIPPING AND HANDLING___________________________I:4-1
- A. INTRODUCTION______________________________________________I:4-1
- Sample Collection...................................I:4-1 Bulk Samples........................................I:4-2
- B. MAILING INSTRUCTIONS______________________________________I:4-2
- Sample Identification...............................I:4-2 Filter Cassettes....................................I:4-3 Solid Sorbent Tubes.................................I:4-3 Midget Impinger or Fritted Glass Bubbler Samples....I:4-3 Wipe Samples........................................I:4-4 Bulk Samples........................................I:4-4 Soil Samples........................................I:4-4
- C. FEDERAL MAILING REGULATIONS_______________________________I:4-5
- Jurisdiction........................................I:4-5 Responsibility......................................I:4-5 Hazardous Materials.................................I:4-5
SECTION II. HEALTH HAZARDS
CHAPTER 1. POLYMER MATRIX MATERIALS: ADVANCED COMPOSITES________II:1-1
- A. INTRODUCTION____________________________________________II:1-1
- B. OVERVIEW OF THE INDUSTRY________________________________II:1-2
- Industrial Composites..............................II:1-2 Advanced Composites................................II:1-2
- C. THE MANUFACTURING PROCESS_______________________________II:1-3
- D. POLYMER MATRIX COMPOSITE (PMC) RESIN SYSTEMS____________II:1-4
- Resins.............................................II:1-4 Thermosites........................................II:1-4 Thermoplastics.....................................II:1-5 Fiber Reinforcements...............................II:1-5 Solvents...........................................II:1-6
- E. DESCRIPTION OF THE PROCESSES____________________________II:1-7
- Resin Formulation..................................II:1-7 Prepegging.........................................II:1-7 Wet Filament Winding...............................II:1-7 Hand Lay-Up Prepeg.................................II:1-8 Automated Tape Lay-Up..............................II:1-8
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- Resin Transfer Molding.............................II:1-8 Pultrusion.........................................II:1-8 Injection Molding..................................II:1-8 Vacuum Bagging and Autoclave Curing................II:1-9 Machining and Finishing...........................II:1-10 Field Repair......................................II:1-10
- F. HEALTH HAZARD INFORMATION______________________________II:1-10
- Resins............................................II:1-10 Curing Agents.....................................II:1-12 Reinforcement Fibers..............................II:1-12 Dusts.............................................II:1-13 Solvents..........................................II:1-14
- G. WORKPLACE CONTROLS_____________________________________II:1-15
- Engineering Controls..............................II:1-15 Work Practice Controls............................II:1-16 Personal Protective Equipment.....................II:1-16 Administrative Controls...........................II:1-16
- H. BIBLIOGRAPHY___________________________________________II:1-17
- APPENDIX II:1-1. GLOSSARY__________________________________II:1-18
CHAPTER 2. INDOOR AIR QUALITY INVESTIGATION______________________II:2-1
- A. INTRODUCTION____________________________________________II:2-1
- Causal Factors.....................................II:2-1 Incidence..........................................II:2-1 Recommended Ventilation Rates......................II:2-2
- B. ACUTE HEALTH EFFECTS OF MAJOR INDOOR AIR CONTAMINANTS___II:2-2
- Types of Building Problems.........................II:2-2 Major Indoor Air Contaminants......................II:2-2
- C. INVESTIGATION GUIDELINES________________________________II:2-4
- Employer and Employee Interviews...................II:2-4 Walkaround Inspection..............................II:2-5 Environmental Evaluation...........................II:2-6
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- D. SAMPLING INSTRUMENTATION AND METHODS____________________II:2-7
- Low Contaminant Levels.............................II:2-7 Screening..........................................II:2-7 Option Screening for Common Indoor Air Contaminants Based on Professional Judgment................II:2-7
- E. RECOMMENDATIONS FOR THE EMPLOYER_______________________II:2-10
- Engineering Recommendations.......................II:2-10 Administrative and Work Practice Recommendations..II:2-10
- F. REFERENCES_____________________________________________II:2-12
- G. BIBLIOGRAPHY___________________________________________II:2-13
- APPENDIX II:2-1. INVESTIGATING OFFICE-RELATED COMPLAINTS___II:2-14
- APPENDIX II:2-2. SAMPLING AND ANALYTICAL METHODS___________II:2-15
CHAPTER 3. VENTILATION INVESTIGATION_____________________________II:3-1
- A. INTRODUCTION____________________________________________II:3-1
- B. HEALTH EFFECTS__________________________________________II:3-1
- C. STANDARDS AND CODES_____________________________________II:3-2
- Consensus Standards................................II:3-2 OSHA Regulations...................................II:3-3
- D. INVESTIGATION GUIDELINES________________________________II:3-3
- Equipment Operability..............................II:3-3 Measurements.......................................II:3-6 Good Practices.....................................II:3-8
- E. PREVENTION AND CONTROL_________________________________II:3-11
- Elements of a Good Maintenance Program............II:3-11 Dealing with Microorganisms.......................II:3-11 Volatile Organic or Reactive Chemicals............II:3-11 Tobacco Smoke in Air..............................II:3-11
- F. BIBLIOGRAPHY___________________________________________II:3-13
- APPENDIX II:3-1. VENTILATION PRIMER________________________II:3-14
- APPENDIX II:3-2. GLOSSARY__________________________________II:3-20
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- APPENDIX II:3-3. OSHA AND CONSENSUS STANDARDS______________II:3-23
APPENDIX II:3-4. TROUBLESHOOTING AN EXHAUST SYSTEM -- SOME HELPFUL HINTS________________________________________II:3-29
CHAPTER 4. HEAT STRESS___________________________________________II:4-1
- A. INTRODUCTION____________________________________________II:4-1
- Causal Factors.....................................II:4-1 Definitions........................................II:4-1
- B. HEAT DISORDERS AND HEALTH EFFECTS_______________________II:4-2
- Heat Stroke........................................II:4-2 Heat Exhaustion....................................II:4-3 Heat Cramps........................................II:4-3 Heat Collapse (Fainting)...........................II:4-3 Heat Rashes........................................II:4-3 Heat Fatigue.......................................II:4-3
- C. INVESTIGATION GUIDELINES________________________________II:4-4
- Employer and Employee Interviews...................II:4-4 Walkaround Inspection..............................II:4-4 Work Load Assessment...............................II:4-5
- D. SAMPLING METHODS________________________________________II:4-6
- Body Temperature Measurements......................II:4-6 Environmental Measurements.........................II:4-6 Wet Bulb Globe Temperature Index...................II:4-6 Other Thermal Stress Indices.......................II:4-7
- E. CONTROL_________________________________________________II:4-8
- Acclimatization....................................II:4-8 Fluid Replacement..................................II:4-9 Engineering Controls...............................II:4-9 Administrative Controls and Work Practices........II:4-10
- F. PERSONAL PROTECTIVE EQUIPMENT__________________________II:4-11
- Reflective Clothing...............................II:4-11 Auxiliary Body Cooling............................II:4-11 Respirator Use....................................II:4-12
- G. BIBLIOGRAPHY___________________________________________II:4-13
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
APPENDIX II:4-1A. HEAT STRESS: GENERAL WORKPLACE REVIEW___________________________________________________II:4-14
APPENDIX II:4-1B. HEAT STRESS-RELATED ILLNESS AND ACCIDENT FOLLOW-UP_______________________________________II:4-16
APPENDIX II:4-2. MEASUREMENT OF WET BULB GLOBE TEMPERATURE______________________________________________II:4-17
CHAPTER 5. NOISE MEASUREMENT_____________________________________II:5-1
- A. DEFINITIONS_____________________________________________II:5-1
- Threshold and Criterion Levels.....................II:5-1 Exchange Rate......................................II:5-2
- B. EFFECTS_________________________________________________II:5-3
- Auditory Effects...................................II:5-3 Extra-auditory Effects.............................II:5-3
- C. INSTRUMENT PERFORMANCE__________________________________II:5-3
- Effects of the Environment.........................II:5-3 Effects of Sound...................................II:5-4
- D. NOISE MEASUREMENTS______________________________________II:5-4
- Instruments........................................II:5-4 Accuracy...........................................II:5-6 Calibration........................................II:5-6 Sampling Strategy..................................II:5-6 Sampling Protocol..................................II:5-7
- E. ULTRASONICS_____________________________________________II:5-8
- Applicability of 29 CFR 1910.95....................II:5-8 Health Effects.....................................II:5-9 Controls...........................................II:5-9
- F. GENERAL NOISE INSPECTION DATA__________________________II:5-10
- Information to Be Collected.......................II:5-10 Evaluation of Hearing Protection..................II:5-11
- G. EVALUATION OF THE HEARING CONSERVATION PROGRAM_________II:5-13
- Agricultural Worksites............................II:5-13 Maritime Worksites................................II:5-13 Construction Worksites............................II:5-13 General Industry Worksites........................II:5-14
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- H. CONTROL________________________________________________II:5-14
- I. BIBLIOGRAPHY___________________________________________II:5-16
APPENDIX II:5-1. EVALUATING NOISE EXPOSURE ON EMPLOYEES WEARING SOUND-GENERATING HEADSETS________________________II:5-17
CHAPTER 6. LASER HAZARDS_________________________________________II:6-1
- A. INTRODUCTION____________________________________________II:6-1
- B. NONBEAM LASER HAZARDS___________________________________II:6-2
- Industrial Hygiene.................................II:6-2 Explosion Hazards..................................II:6-3 Nonbeam Optical Radiation Hazards..................II:6-3 Collateral Radiation...............................II:6-3 Electrical Hazards.................................II:6-4 Flammability of Laser Beam Enclosures..............II:6-4
- C. BIOLOGICAL EFFECTS OF THE LASER BEAM____________________II:6-5
- Eye Injury.........................................II:6-5 Thermal Injury.....................................II:6-5 Other..............................................II:6-5
- D. LASER HAZARD CLASSIFICATIONS____________________________II:6-6
- Introduction.......................................II:6-6 Laser Hazard Classes...............................II:6-7 How to Determine the Class of Lasers During Inspection....................................II:6-8 ANSI Z 136.2 Optical Fiber Service Group Designations..................................II:6-9
- E. INVESTIGATIONAL GUIDELINES_____________________________II:6-10
- Requirements of Laser Standards...................II:6-10 Laser Exposure Limits.............................II:6-12 Laser Hazard Computations.........................II:6-13 NHZ Example Summary...............................II:6-15 Intrabeam Optical Density Determination...........II:6-16
- F. CONTROL MEASURES AND SAFETY PROGRAMS___________________II:6-18
- Control Measures -- Overview......................II:6-18 Laser Safety Officer (LSO)........................II:6-18 Class I, Class II and Class IIIA Lasers...........II:6-18 Beam Path Controls................................II:6-18 Laser-Controlled Area.............................II:6-20
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- Class IV Laser Controls -- General Requirements...II:6-21 Entryway Control Measures (Class IV)..............II:6-22 Temporary Laser-Controlled Area...................II:6-23 Administrative and Procedural Controls............II:6-23 Engineering Controls..............................II:6-24 Laser Use Without Protective Housing (All Classes).....................................II:6-25 Optical-Fiber (Light-Wave) Communication Systems (OFCS).......................................II:6-26
- G. BIBLIOGRAPHY___________________________________________II:6-26
APPENDIX II:6-1. FDA/CDRH REQUIREMENTS FOR LASER PRODUCTS___________________________________________II:6-28
APPENDIX II:6-2. FDA/CDRH FEDERAL LASER PRODUCT PERFORMANCE STANDARD EVALUATION OUTLINE__________________II:6-29
APPENDIX II:6-3. THE AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI)_________________________________________II:6-31
- APPENDIX II:6-4. WARNING SIGNS_____________________________II:6-33
- APPENDIX II:6-5. GLOSSARY OF LASER TERMS___________________II:6-36
CHAPTER 7. LEGIONNAIRES' DISEASE_________________________________II:7-1
- A. INTRODUCTION____________________________________________II:7-1
- B. DISEASE RECOGNITION_____________________________________II:7-1
- Causative Agent ...................................II:7-1 Symptoms ..........................................II:7-2 Incidence .........................................II:7-2 Risk Factors ......................................II:7-2 Diagnosis .........................................II:7-2 Transmission ......................................II:7-4
- C. SOURCE IDENTIFICATION___________________________________II:7-4
- Conditions That Promote Growth ....................II:7-4 Common Sources of Contaminated Water ..............II:7-4 Monitoring ........................................II:7-5 Microbiological Analysis of Water Samples .........II:7-5 Interpretation of Sample Results ..................II:7-6
- D. INVESTIGATION PROTOCOL__________________________________II:7-6
- Community Health Concerns .........................II:7-6 Types of Investigations ...........................II:7-6
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- Level-One Investigation ..........................II:7-7 Level-Two Investigation ..........................II:7-9
- E. CONTROLS_______________________________________________II:7-10
- General Discussion ...............................II:7-10 Cooling Towers, Evaporative Condensers, and Fluid Coolers ...................................II:7-10 Domestic Hot-Water Systems........................II:7-12 Domestic Cold-Water Systems.......................II:7-13 HVAC Systems .....................................II:7-14
- F. BIBLIOGRAPHY___________________________________________II:7-16
- APPENDIX II:7-1. EMPLOYEE AWARENESS PROGRAM________________II:7-18
APPENDIX II:7-2. PHYSICAL SURVEY AND WATER SAMPLING PROTOCOL_________________________________________________II:7-25
- APPENDIX II:7-3. WATER SAMPLING GUIDELINES_________________II:7-28
- APPENDIX II:7-4. LEGIONNAIRES' DISEASE CASE IDENTIFICATION_II:7-29
APPENDIX II:7-5. WATER TREATMENT PROTOCOLS FOR FACILITIES THAT HAVE EXPERICENCED A LEGIONNAIRES' OUTBREAK__________II:7-36
SECTION III. SAFETY HAZARDS
CHAPTER 1. OILWELL DERRICK STABILITY: GUYWIRE ANCHOR SYSTEMS___III:1-1
- A. INTRODUCTION___________________________________________III:1-1
- Causal Factors....................................III:1-1 Industry Recommendations..........................III:1-2 Application.......................................III:1-2
- B. TYPES OF GUYWIRE ANCHORS_______________________________III:1-2
- Manufacture Anchors...............................III:1-2 Shop-Made (In-House Fabricated) Anchors...........III:1-2
- C. STABILITY CONSIDERATIONS_______________________________III:1-3
- Foundation........................................III:1-3 Guywires..........................................III:1-3 Guywire Anchors...................................III:1-4
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- D. OBSERVATIONS, DIRECTIONS, AND CONCLUSIONS______________III:1-5
- Visual Observations...............................III:1-5 Support Manual....................................III:1-5 Conclusion........................................III:1-5
- E. BIBLIOGRAPHY___________________________________________III:1-6
CHAPTER 2. PETROLEUM REFINING PROCESSES_________________________III:2-1
- A. INTRODUCTION___________________________________________III:2-1
- B. OVERVIEW OF THE PETROLEUM INDUSTRY_____________________III:2-2
- Basic Refinery Process--Description and History ..III:2-2 Basics of Crude Oil ..............................III:2-4 Basics of Hydrocarbon Chemistry ..................III:2-5 Major Refinery Products ..........................III:2-9 Common Refinery Chemicals Used ..................III:2-10
- C. PETROLEUM REFINING OPERATIONS_________________________III:2-11
- Introcution .....................................III:2-11 Refining Operations .............................III:2-11
D. DESCRIPTION OF PETROLEUM REFINING PROCESSES AND RELATED HEALTH AND SAFETY CONSIDERATIONS____________III:2-15
- Crude Oil Pretreatment (Desalting) ..............III:2-15 Crude Oil Distillation (Fractionation) ..........III:2-17 Solvent Extraction and Dewaxing .................III:2-20 Thermal Cracking ................................III:2-23 Catalytic Cracking ..............................III:2-26 Hydrocracking ...................................III:2-29 Catalytic Reforming .............................III:2-31 Catalytic Hydrotreating .........................III:2-33 Isomerization ...................................III:2-35 Polymerization ..................................III:2-37 Alkylation ......................................III:2-39 Sweetening and Treating Processes ...............III:2-41 Unsaturated Gas Plants ..........................III:2-43 Amine Plants ....................................III:2-44 Saturate Gas Plants .............................III:2-45 Asphalt Production ..............................III:2-45 Hydrogen Production .............................III:2-46 Blending ........................................III:2-47 Lubricant, Wax, and Grease Manufacturing Processes ......................................III:2-48
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- E. OTHER REFINERY OPERATIONS_____________________________III:2-49
- Heat Exchangers, Coolers, and Process Heaters ...III:2-49 Steam Generation ................................III:2-50 Pressure-Relief and Flare Systems ...............III:2-51 Wastewater Treatment ............................III:2-52 Cooling Towers ..................................III:2-53 Electric Power ..................................III:2-54 Gas and Air Compressors .........................III:2-55 Marine, Tank-Car, and Tank-Truck Loading and Unloading ......................................III:2-55 Pumps, Piping, and Valves .......................III:2-56 Tanks Storage ...................................III:2-57
- F. BIBLIOGRAPHY__________________________________________III:2-58
APPENDIX III:2-1. GLOSSARY OF TERMS ASSOCIATED WITH PETROLEUM REFINING PROCESSES_______________________III:2-59
CHAPTER 3. PRESSURE VESSEL GUIDELINES___________________________III:3-1
- A. INTRODUCTION___________________________________________III:3-1
- B. RECENT CRACKING EXPERIENCE IN PRESSURE VESSELS_________III:3-2
- Deaerator Service.................................III:3-2 Amine Service.....................................III:3-4 Wet Hydrogen Sulfide..............................III:3-4 Ammonia Service...................................III:3-5 Pulp Digester Service.............................III:3-5 Summary of Service Cracking Experience............III:3-6
- C. NONDESTRUCTIVE EXAMINATION METHODS_____________________III:3-6
- Visual Examination (VT)...........................III:3-6 Liquid Penetrant Test (PT)........................III:3-7 Magnetic Particle Test (MT).......................III:3-7 Radiography (RT)..................................III:3-7 Ultrasonic Testing (UT)...........................III:3-7 Detection Probabilities and Flaw Sizing...........III:3-8
- D. INFORMATION FOR SAFETY ASSESSMENT______________________III:3-9
- E. BIBLIOGRAPHY___________________________________________III:3-9
APPENDIX III:3-1. RECORDKEEPING DATA FOR STEEL VESSELS AND LOW-PRESSURE STORAGE TANKS__________________________III:3-10
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
CHAPTER 4. INDUSTRIAL ROBOTS AND ROBOT SYSTEM SAFETY____________III:4-1
- A. INTRODUCTION___________________________________________III:4-1
- Accidents -- Past Studies............................III:4-1 Robot Safeguarding................................III:4-2
- B. TYPES AND CLASSIFICATION OF ROBOTS_____________________III:4-2
- Servo and Nonservo................................III:4-2 Type of Path Generated............................III:4-2 Robot Components..................................III:4-4 Control Systems...................................III:4-4 Robot Programming by Teaching Methods.............III:4-5 Degrees of Freedom................................III:4-7
- C. HAZARDS________________________________________________III:4-7
- Type of Accidents.................................III:4-8 Sources of Hazards................................III:4-9
- D. INVESTIGATION GUIDELINES______________________________III:4-10
- E. CONTROL AND SAFEGUARDING PERSONNEL____________________III:4-10
- Risk Assessment..................................III:4-10 Safeguarding Devices.............................III:4-11 Awareness Devices................................III:4-11 Safeguarding the Teacher.........................III:4-11 Operator Safeguards..............................III:4-11 Attended Continuous Operation....................III:4-11 Maintenance and Repair Personnel.................III:4-11 Maintenance......................................III:4-12 Safety Training..................................III:4-12 General Requirements.............................III:4-12
- F. BIBLIOGRAPHY__________________________________________III:4-13
APPENDIX III:4-1. GLOSSARY FOR ROBOTICS AND ROBOTIC SYSTEMS_________________________________________III:4-14
APPENDIX III:4-2. OTHER ROBOTIC SYSTEMS NOT COVERED BY THIS CHAPTER_________________________________________III:4-18
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SECTION IV. CONSTRUCTION OPERATIONS
CHAPTER 1. DEMOLITION____________________________________________IV:1-1
- A. PREPARATORY OPERATIONS__________________________________IV:1-1
- Engineering Survey.................................IV:1-1 Utility Location...................................IV:1-2 Medical Services and First Aid.....................IV:1-2 Police and Fire Contact............................IV:1-2 Fire Prevention and Protection.....................IV:1-2
- B. SPECIAL STRUCTURE DEMOLITION____________________________IV:1-4
- Safe Work Practices When Demolishing a Chimney, Stack, Silo, or Cooling Tower.................IV:1-4 Demolition of Prestressed Concrete Structures......IV:1-5 Safe Work Practices When Working in Confined Spaces........................................IV:1-7
- C. SAFE BLASTING PROCEDURES________________________________IV:1-7
- General Safe Work Practices........................IV:1-7 Transportation of Explosives.......................IV:1-8 Storage of Explosives..............................IV:1-9 Proper Use of Explosives...........................IV:1-9 Procedures After Blasting.........................IV:1-10
- D. BIBLIOGRAPHY___________________________________________IV:1-11
CHAPTER 2. EXCAVATIONS: HAZARD RECOGNITION IN TRENCHING
- A. INTRODUCTION____________________________________________IV:2-1
- B. DEFINITIONS_____________________________________________IV:2-1
- C. OVERVIEW: SOIL MECHANICS_______________________________IV:2-3
- Tension Cracks.....................................IV:2-3 Sliding............................................IV:2-3 Toppling...........................................IV:2-3 Subsidence and Bulging.............................IV:2-3 Heaving or Squeezing...............................IV:2-4 Boiling............................................IV:2-4
- D. DETERMINATION OF SOIL TYPE______________________________IV:2-4
- Stable Rock........................................IV:2-4 Type A Soils.......................................IV:2-4
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- Type B Soils.......................................IV:2-5 Type C Soils.......................................IV:2-5 Layered Geological Strata..........................IV:2-5
- E. TEST EQUIPMENT AND METHODS FOR EVALUATING SOIL TYPE_____IV:2-5
- Pocket Pentrometer.................................IV:2-5 Shearvane (Torvane)................................IV:2-5 Thumb Penetration Test.............................IV:2-5 Dry Strength Test..................................IV:2-5 Plasticity or Wet Thread Test......................IV:2-6 Visual Test........................................IV:2-6
- F. SHORING TYPES___________________________________________IV:2-6
- Pneumatic Shoring..................................IV:2-8 Screw Jacks........................................IV:2-8 Single-Cylinder Hydraulic Shores...................IV:2-8 Underpinning.......................................IV:2-8
- G. SHIELDING TYPES_________________________________________IV:2-9
- H. SLOPING AND BENCHING___________________________________IV:2-10
- Sloping...........................................IV:2-10 Benching..........................................IV:2-11
- I. SPOIL__________________________________________________IV:2-12
- Temporary Spoil...................................IV:2-12 Permanent Spoil...................................IV:2-12
- J. SPECIAL HEALTH AND SAFETY CONSIDERATIONS_______________IV:2-13
- Competent Person..................................IV:2-13 Surface Crossing of Trenches......................IV:2-13 Ingress and Egress................................IV:2-13 Exposure to Vehicular traffic.....................IV:2-13 Exposure to Falling Loads.........................IV:2-13 Warning Systems for Mobile Equipment..............IV:2-14 Hazardous Atmospheres and Confined Spaces.........IV:2-14 Emergency Rescue Equipment........................IV:2-14 Standing Water and Water Accumulation.............IV:2-15 Inspections.......................................IV:2-15
- K. BIBLIOGRAPHY___________________________________________IV:2-16
- APPENDIX IV:2-1. SITE ASSESSMENT QUESTIONS_________________IV:2-17
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
CHAPTER 3. CONTROLLING LEAD EXPOSURES IN THE CONSTRUCTION
- INDUSTRY: ENGINEERING AND WORK PRACTICE CONTROLS____________IV:3-1
- A. INTRODUCTION____________________________________________IV:3-1
- B. ENGINEERING AND WORK PRACTICE CONTROLS__________________IV:3-2
- Engineering Controls...............................IV:3-2 Work Practice Controls.............................IV:3-3
- C. OPERATIONS______________________________________________IV:3-6
- Open Abrasive Blast Cleaning.......................IV:3-6 Vacuum Blast Cleaning..............................IV:3-9 Wet Abrasive Blast Cleaning........................IV:3-9 High-Pressure Water Jetting........................IV:3-9 High-Pressure Water Jetting with Abrasive Injection....................................IV:3-10 Ultra High-Pressure Water Jetting.................IV:3-10 Sponge Jetting....................................IV:3-11 Carbon Dioxide (Dry Ice) Blasting.................IV:3-11 Welding, Burning, and Torch Cutting...............IV:3-12 Work Practice Controls............................IV:3-13 Spray Painting with Lead-Based Paint..............IV:3-13 Manual Scraping and Sanding of Lead-Based Paints..IV:3-13 Manual Demolition and/or Removal of Plaster Walls or Building Components.......................IV:3-14 Heat Gun Removal of Lead-Based Paint..............IV:3-14 Chemical Stripping of Lead-Based Paint............IV:3-15 Encapsulation of Lead-Based Paint.................IV:3-15 Power Tool Cleaning...............................IV:3-16 Use of Lead Pots..................................IV:3-16 Soldering and Brazing.............................IV:3-17 Use of Lead-Containing Mortar in Chemical (Acid) Storage and Process Tanks....................IV:3-18 Handling Lead Shot, Bricks or Sheets, and Lead Foil Panels..................................IV:3-18 Reinsulation Over Existing Mineral Wool...........IV:3-19 Removal and Repair of Stained Glass Windows.......IV:3-19 Industrial Vacuuming..............................IV:3-19 Miscellaneous Activities..........................IV:3-20
- D. BIBLIOGRAPHY___________________________________________IV:3-21
APPENDIX IV:3-1. LEAD-RELATED CONSTRUCTION TASKS AND THEIR PRESUMED 8-HOUR TWA EXPOSURE LEVELS______________________IV:3-22
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SECTION V. HEALTH-CARE FACILITIES
CHAPTER 1. HOSPITAL INVESTIGATIONS: HEALTH HAZARDS_______________V:1-1
- A. INTRODUCTION_____________________________________________V:1-1
- Incidence and Causal Factors........................V:1-1 Guidance............................................V:1-1
- B. TYPICAL HAZARDS AND HEALTH EFFECTS_______________________V:1-2
- C. INVESTIGATION GUIDELINES_________________________________V:1-2
- Hospital Records....................................V:1-2 Hospital Safety Program.............................V:1-2 Walkaround..........................................V:1-2 Screening Samples...................................V:1-3
- D. SAMPLING METHODS_________________________________________V:1-4
- Lasers..............................................V:1-4 X-Ray Machines......................................V:1-5 Electrical Equipment................................V:1-5
- E. CONTROLS AND PREVENTION__________________________________V:1-5
- Engineering.........................................V:1-5 Work Practices......................................V:1-7 Personal Protective Equipment.......................V:1-7
- F. BIBLIOGRAPHY_____________________________________________V:1-9
APPENDIX V:1-1. BIOLOGICAL AGENTS -- BLOOD AND BODY FLUIDS ___________________________________________________V:1-11
- APPENDIX V:1-2. CHEMICAL AGENTS_____________________________V:1-12
- APPENDIX V:1-3. PHYSICAL AGENTS_____________________________V:1-14
CHAPTER 2. [RESERVED]_____________________________________________V:2-1
CHAPTER 3. CONTROLLING OCCUPATIONAL EXPOSURE TO HAZARDOUS DRUGS___V:3-1
- A. INTRODUCTION_____________________________________________V:3-1
- B. CATEGORIZATION OF DRUGS AS HAZARDOUS_____________________V:3-2
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- C. BACKGROUND: HAZARDOUS DRUGS AS OCCUPATIONAL RISKS_______V:3-3
- Mechanism of Action.................................V:3-3 Animal Data.........................................V:3-4 Human Data at Therapeutic Levels....................V:3-4 Occupational Exposure -- Air-Borne Levels...........V:3-4 Occupational Exposure -- Biological Evidence of Absorption.....................................V:3-5 Occupational Exposure -- Human Effects..............V:3-5
- D. WORK AREAS_______________________________________________V:3-6
- Pharmacy or Other Preparation Areas.................V:3-6 Administration of Drugs to Patients.................V:3-7 Disposal of Drugs and Contaminated Materials........V:3-7 Survey of Current Work Practices....................V:3-7
- E. PREVENTION OF EMPLOYEE EXPOSURE__________________________V:3-8
- Hazardous Drug Safety and Health Plan...............V:3-8 Drug Preparation Precautions........................V:3-9 Drug Administration................................V:3-13 Caring for Patients Receiving HDs..................V:3-15 Waste Disposal.....................................V:3-15 Spills.............................................V:3-16 Storage and Transport..............................V:3-17
- F. MEDICAL SURVEILLANCE____________________________________V:3-18
- Preplacement Medical Examinations..................V:3-18 Periodic Medical Examinations......................V:3-19 Postexposure Examinations..........................V:3-19 Exit Examinations..................................V:3-19 Exposure and Health Outcome Linkage................V:3-20 Reproductive Issues................................V:3-20
- G. HAZARD COMMUNICATION____________________________________V:3-20
- Written Hazard Communication.......................V:3-21 MSDSs..............................................V:3-21
- H. TRAINING AND INFORMATION DISSEMINATION__________________V:3-22
- Employee Information...............................V:3-22 Employee Training..................................V:3-22
- I. RECORDKEEPING___________________________________________V:3-23
- J. REFERENCES______________________________________________V:3-23
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- APPENDIX V:3-1. SOME COMMON DRUGS CONSIDERED HAZARDOUS______V:3-30
- APPENDIX V:3-2. SOME AEROSOLIZED DRUGS______________________V:3-32
SECTION VI. ERGONOMICS
CHAPTER 1. BACK DISORDERS AND INJURIES___________________________VI:1-1
- A. INTRODUCTION____________________________________________VI:1-1
- General............................................VI:1-1 Incidence..........................................VI:1-1
- B. BACK INJURIES___________________________________________VI:1-2
- Contributing Factors...............................VI:1-2 Manual Materials Handling..........................VI:1-2
- C. BACK DISORDERS__________________________________________VI:1-2
- Factors Associated with Back Disorders.............VI:1-2 Signs and Symptoms.................................VI:1-2
- D. INVESTIGATION GUIDELINES________________________________VI:1-3
- Records Review.....................................VI:1-3 Employer Interviews and Employee Interviews........VI:1-3 Walkaround.........................................VI:1-3 Evaluation.........................................VI:1-3
- E. PREVENTION AND CONTROL__________________________________VI:1-3
- Engineering Controls...............................VI:1-3 Administrative Controls and Work Practices.........VI:1-4 Other..............................................VI:1-4
- F. BIBLIOGRAPHY____________________________________________VI:1-5
- APPENDIX VI:1-1. IN-DEPTH ANALYSIS__________________________VI:1-6
- APPENDIX VI:1-2. EVALUATION OF LIFTING TASKS:
- NIOSH WORK PRACTICE GUIDE TO MANUAL LIFTING_______________VI:1-9
- APPENDIX VI:1-3. VIDEO TAPE GUIDELINES AND ANALYSIS________VI:1-11
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SECTION VII. PERSONAL PROTECTIVE EQUIPMENT
CHAPTER 1. CHEMICAL PROTECTIVE CLOTHING_________________________VII:1-1
- A. INTRODUCTION___________________________________________VII:1-1
- B. PROTECTIVE CLOTHING APPLICATIONS_______________________VII:1-2
- C. THE CLOTHING ENSEMBLE__________________________________VII:1-2
- Level of Protection...............................VII:1-3 Ensemble Selection Factors........................VII:1-5
- D. CLASSIFICATION OF PROTECTIVE CLOTHING__________________VII:1-6
- E. PROTECTIVE CLOTHING SELECTION FACTORS_________________VII:1-10
- Clothing Design..................................VII:1-10 Material Chemical Resistance.....................VII:1-10 Physical Properties..............................VII:1-11 Ease of Decontamination..........................VII:1-11 Cost.............................................VII:1-12 Chemical Protective Clothing Standards...........VII:1-12
- F. GENERAL GUIDELINES____________________________________VII:1-12
- G. MANAGEMENT PROGRAM____________________________________VII:1-15
- Written Management Program.......................VII:1-15 Program Review and Evaluation....................VII:1-15 Types of Standard Operating Procedures...........VII:1-16 Selection of Protective Clothing Components......VII:1-16
- H. CLOTHING DONNING, DOFFING, AND USE____________________VII:1-16
- Donning the Ensemble.............................VII:1-16 Doffing an Ensemble..............................VII:1-17 User Monitoring and Training.....................VII:1-19 Work Mission Duration............................VII:1-19
- I. DECONTAMINATION PROCEDURES____________________________VII:1-20
- Definition and Types.............................VII:1-20 Prevention of Contamination......................VII:1-20 Types of Contamination...........................VII:1-20 Decontamination Methods..........................VII:1-21 Testing the Effectiveness of Decontamination.....VII:1-21 Decontamination Plan.............................VII:1-22
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- Decontamination for Protective Clothing Reuse....VII:1-23 Emergency Decontamination........................VII:1-23
- J. INSPECTION, STORAGE, AND MAINTENANCE__________________VII:1-23
- Inspection.......................................VII:1-23 Storage..........................................VII:1-24 Maintenance......................................VII:1-26
- K. TRAINING______________________________________________VII:1-26
- L. HEAT STRESS___________________________________________VII:1-27
- M. BIBLIOGRAPHY__________________________________________VII:1-28
SECTION VIII. SAFETY AND HEALTH MANAGEMENT
CHAPTER 1. [RESERVED]__________________________________________VIII:1-1
SECTION IX. GENERAL
CHAPTER 1. METRIC SYSTEM CONVERSION______________________________IX:1-1
- A. INTRODUCTION____________________________________________IX:1-1
- B. THE METRIC SYSTEM_______________________________________IX:1-2
- C. THE CONVERSION PROCESS__________________________________IX:1-3
- D. CONVERSION PRECISION____________________________________IX:1-4
- Significant Number of Digits.......................IX:1-4 Number of Carried Digits...........................IX:1-4 "Rounding" of Numbers..............................IX:1-5
- E. CONVERSION EQUIVALENTS__________________________________IX:1-5
- Temperature........................................IX:1-5 Length.............................................IX:1-6 Area...............................................IX:1-6 Velocity...........................................IX:1-7 Volume.............................................IX:1-7
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- Mass (Weight)......................................IX:1-7 Density............................................IX:1-7 Pressure...........................................IX:1-8 Stress.............................................IX:1-8 Work ..............................................IX:1-8 Power..............................................IX:1-8 Miscellaneous......................................IX:1-9
- F. REFERENCES______________________________________________IX:1-9
- OSHA Instruction TED 1.15 September 22, 1995 Office of Science and Technology Assessment
- - A violation is not established if the measured exposure is in the "possible overexposure" region. It should be noted that the closer the LCL comes to exceeding the PEL, the more probable it becomes that the employer is in noncompliance.
- - If measured results are in this region, the CSHO should consider further sampling, taking into consideration the seriousness of the hazard, pending citations, and how close the LCL is to exceeding the PEL.
- - If further sampling is not conducted, or if additional measured exposures still fall into the "possible overexposure" region, the CSHO should carefully explain to the employer and employee representative in the closing conference that the exposed employee(s) may be overexposed but that there was insufficient data to document noncompliance. The employer should be encouraged to voluntarily reduce the exposure and/or to conduct further sampling to assure that exposures are not in excess of the standard.
SAMPLING METHODS
The LCL and UCL are calculated differently depending upon the type of sampling method used. Sampling methods can be classified into one of three categories:
- * Full-period, Continuous Single Sampling. Full-period, continuous single sampling is defined as sampling over the entire sample period with only one sample. The sampling may be for a full-shift sample or for a short period ceiling determination.
- * Full-period, Consecutive Sampling. Full-period, consecutive sampling is defined as sampling using multiple consecutive samples of equal or unequal time duration which, if combined, equal the total duration of the sample period. An example would be taking four 2-hour charcoal tube samples. There are several advantages to this type of sampling.
- - If a single sample is lost during the sampling period due to pump failure, gross contamination, etc., at least some data will have been collected to evaluate the exposure.
- - The use of multiple samples will result in slightly lower sampling and analytical errors.
- - Collection of several samples allows conclusions to be reached concerning the manner in which differing segments of the work day affect overall exposure.
- * Grab Sampling. Grab sampling is defined as collecting a number of short-term samples at various times during the sample period which, when combined, provide an estimate of exposure over the total period. Common examples include the use of detector tubes or direct-reading instrumentation (with intermittent readings).
CALCULATIONS
If the initial and final calibration flow rates are different, a volume calculated using the highest flow rate should be reported to the laboratory. If compliance is not established using the lowest flow rate, further sampling should be considered.
Generally, sampling is conducted at approximately the same temperature and pressure as calibration, in which case no correction for temperature and pressure is
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
required and the sample volume reported to the laboratory is the volume actually measured. Where sampling is conducted at a substantially different temperature or pressure than calibration, an adjustment to the measured air volume may be required depending on sampling pump used, in order to obtain the actual air volume sampled.
The actual volume of air sampled at the sampling site is reported, and used in all calculations.
- * For particulates, the laboratory reports mg/m(3) of contaminant using the actual volume of air collected at the sampling site. The value in mg/m(3) can be compared directly to OSHA Toxic and Hazardous Substances Standards (e.g., 29 CFR 1910.1000).
- * The laboratory normally does not measure concentrations of gases and vapors directly in parts per million (ppm). Rather, most analytical techniques determine the total weight of contaminant in collection medium. Using the air volume provided by the CSHO, the lab calculates concentration in mg/m(3) and converts this to ppm at 25 degrees C and 760 mm Hg using Equation I:1-6A. This result is to be compared with the PEL without adjustment for temperature and pressure at the sampling site.
Equation I:1-6A
_____________________________________________________________________
| |
| ppm(NTP) = mg/m(3)(24.45)/(Mwt) |
| |
| Where: |
| |
| 24.45 = molar volume at 25 degrees C (298 degrees K) and 760 mm Hg |
| |
| Mwt = molecular weight |
| |
| NTP = Normal Temperature and Pressure at 25 degrees C and |
| 760 mm Hg |
|_____________________________________________________________________|
- * If it is necessary to know the actual concentration in ppm at the sampling site, it can be derived from the laboratory results reported in ppm at NTP by using the following equation:
Equation I:1-6B _______________________________________________________________________ | | | ppm(PT) = ppm(NTP) (760)/(P) (T)/(298) | | | | where: | | | | P = sampling site pressure (mm of Hg) | | | | T = sampling site temperature (degrees K) | | | | 298 = temperature in degrees Kelvin (273 degrees | | K + 25 degrees) | |_______________________________________________________________________| Equation I:1-6C _______________________________________________________________________ | | | since ppm(NTP) = mg/m(3) (24.45)/(Mwt) | | | | ppm(PT) = mg/m(3) X 24.45/Mwt X 760/P X T/298 | |_______________________________________________________________________|
NOTE: When a laboratory result is reported as mg/m(3) contaminant, concentrations expressed as ppm (PT) cannot be compared directly to the standards table without converting to NTP.
NOTE: Barometric pressure can be obtained by calling the local weather station or airport, request the unadjusted barometric pressure. If these sources are not available then a rule of thumb is: for every 1000 feet of elevation, the barometric pressure decreases by 1 inch of Hg.
CALCULATION METHOD FOR A FULL-PERIOD, CONTINUOUS SINGLE SAMPLE
Obtain the full-period sampling result (value X), the PEL and the SAE. The SAE can be obtained from the Chemical Information Manual.
Divide X by the PEL to determine Y, the standardized concentration. That is:
Equation I:1-6D ________________________________________________________________ | | | Y = X/PEL | |________________________________________________________________|
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Compute the UCL (95%) as follows:
Equation I:1-6E ________________________________________________________________ | | | UCL(95%) = Y + SAE | |________________________________________________________________|
Compute the LCL (95%) as follows:
Equation I:1-6F ________________________________________________________________ | | | LCL(95%) = Y - SAE | |________________________________________________________________|
Classify the exposure according to the following classification system:
- * If the UCL less than or equal to 1, a violation does not exist.
- * If LCL less than or equal to 1 and the UCL greater than 1, classify as possible overexposure.
- * If LCL greater than 1, a violation exists.
SAMPLE CALCULATION FOR FULL-PERIOD, CONTINUOUS SINGLE SAMPLE
A single fiberglass filter and personal pump were used to sample for carbaryl for a 7-hour period. The CSHO was able to document that the exposure during the remaining unsampled one-half hour of the 8-hour shift would equal the exposure measured during the 7-hour period. The laboratory reported 6.07 mg/m(3). The SAE for this method is 0.23. The PEL is 5.0 mg/m(3). Step 1. Calculate the standardized concentration.
- Y = 6.07/5.0 = 1.21
Step 2. Calculate confidence limits.
- LCL = 1.21 - 0.23 = 0.98
Since the LCL does not exceed 1.0, noncompliance is not established. The UCL is calculated:
- UCL = 1.21 + 0.23 = 1.44
Step 3. Classify the exposure.
Since the LCL less than or equal to 1.0 and the UCL less than 1.0, classify as possible overexposure.
CALCULATION METHOD FOR FULL-PERIOD CONSECUTIVE SAMPLING
The use of multiple consecutive samples will result in slightly lower sampling and analytical errors than the use of one continuous sample since the inherent errors tend to partially cancel each other. The mathematical calculations, however, are somewhat more complicated. If preferred, the CSHO may first determine if compliance or noncompliance can be established using the calculation method noted for a full-period, continuous, single-sample measurement. If results fall into the "possible overexposure" region using this method, a more exact calculation should be performed using equation I:1-6G.
Equation I:1-6G
________________________________________________________________
| |
| * Obtain X(1), X(2) ..., X(n), the n consecutive |
| concentrations on one workshift and their time durations, |
| T(1), T(2), ..., T(n). |
| |
| Also obtain the SAE in listed in the OSHA-91B sample |
| report form |
| |
| * Compute the TWA exposure. |
| |
| * Divide the TWA exposure by the PEL to find Y, the |
| standardized average (TWA/PEL). |
| |
| * Compute the UCL (95%) as follows: |
| UCL (95%) = Y + SAE (Equation I:1-6E) |
| |
| * Compute the LCL (95%) as follows: |
| LCL (95%) = Y - SAE (Equation I:1-6F) |
|________________________________________________________________|
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Classify the exposure according to the following classification system:
- * If UCL less than or equal to 1, a violation does not exist.
* If LCL 1, and the UCL greater than 1, classify as possible + overexposure.
- * If LCL greater than 1, a violation exists.
When the LCL less than or equal to 1.0 and UCL greater than 1.0, the results are in the "possible overexposure" region and the CSHO must analyze the data using the more exact calculation for full-period consecutive sampling, as follows:
(For I:1-6H, Click Here)
SAMPLE CALCULATION FOR FULL-PERIOD CONSECUTIVE SAMPLING
If two consecutive samples had been taken for carbaryl instead of one continuous sample, and the following results were obtained:
- --SAMPLE--
- Sampling rate (L/min) 2.0 2.0 Time (min) 240 210 Volume (L) 480 420 Weight (mg) 3.005 2.457 Concentration (mg/m(3) 6.26 5.85
- The SAE for carbarly is 0.23
Step 1. Calculate the UCL and the LCL from the sampling and analytical
- results:
- TWA = (6.26 mg/m(3)) 240 min + (5.85 mg/m(3)) 210 min 450 min = 6.07 mg/m(3) Y = 6.07 mg/m(3)/PEL = 6.07/5.0 = 1.21 Assuming a continuous sample: LCL = 1.21 - 0.23 = 0.98 UCL = 1.21 + 0.23 = 1.44
Step 2. Since the LCL less than 1.0 and UCL greater than 1.0, the results
- are in the possible overexposure region, and the CSHO must analyze the data using the more exact calculation for full-period consecutive sampling as follows:
Since the LCL greater than 1.0, a violation is established.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
GRAB SAMPLING
If a series of grab samples (e.g., detector tubes) is used to determine compliance with either an 8-hour TWA limit or a ceiling limit, consult with the ARA for Technical Support regarding sampling strategy and the necessary statistical treatment of the results obtained.
SAEs FOR EXPOSURE TO CHEMICAL MIXTURES
Often an employee is simultaneously exposed to a variety of chemical substances in the workplace. Synergistic toxic effects on a target organ is common for such exposures in many construction and manufacturing processes. This type of exposure can also occur when impurities are present in single chemical operations. New permissible exposure limits for mixtures, such as the recent welding fume standard (5 mg/m(3)), address the complex problem of synergistic exposures and their health effects. In addition, 29 CFR 1910.1000 contains a computational approach to assess exposure to a mixture. This calculation should be used when components in the mixture pose a synergistic threat to worker health.
Whether using a single standard or the mixture calculation, the sampling and analytical error (SAE) of the individual constituents must be considered before arriving at a final compliance decision. These SAEs can be pooled and weighted to give a control limit for the synergistic mixture. To illustrate this control limit, the following example using the mixture calculation is shown:
The mixture calculation is expressed as:
Equation I:1-6I. ________________________________________________________________ | | | E(m) = (C(1)/L(1) + C(2)/L(2)) + ... C(n)/L(n) | | | | Where: | | | | E(m) = equivalent exposure for a mixture | | (E(m) should be less than or equal to 1 for compliance) | | C = concentration of a particular substance | | L = PEL | |________________________________________________________________|
For example, to calculate exposure to three different but synergistic substances:
Material 8-hr. exposure 8-hr TWA PEL (ppm) SAE
Substance 1 500 1000 0.089 Substance 2 80 200 0.11 Substance 3 70 200 0.18
Using Equation I:1-6I: E(m) = 500/1000 + 80/200 + 70/200 = 1.25
Since E(m) greater than 1, an overexposure appears to have occurred; however, the SAE for each substance also needs to be considered:
- * Exposure ratio (for each substance) Y(n) = C(n)/L(n)
* Ratio to total exposure R(1) = Y(1)/E(m), ...R(n) = Y(n)/E(m) The SAEs (95% confidence) of the substance comprising the mixture can be pooled by: (RS(t))(2) = [(R(1))(2)(SAE(1))(2)+(R(2))(2)(SAE(2))(2) + ... (R(n))(2)(SAE(n))(2)]
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
The mixture Control Limit (CL) is equivalent to: 1 + RS(t)
If E(m) less than or equal to CL, then an overexposure has not been established at the 95% confidence level; further sampling may be necessary.
If E(m) greater than 1 and E(m) greater than CL, then an overexposure has occurred (95% confidence).
Using the mixture data above:
- Y(1) = 500/1000 Y(2) = 80/200 Y(3) = 70/200 Y(1) = 0.5 Y(2) = 0.4 Y(3) = 0.35 R(1) = Y(1)/E(m) = 0.4 R(2) = 0.32 R(3) = 0.28
(RS(t))(2) = (0.4)(2)(0.089)(2)+(0.32)(2)(0.11)(2)+(0.28)(2)(0.18)(2)
- RS(t) = [(RS(t))(2)](1/2) = 0.071
- CL = 1 + RS(t) = 1.071
- E(m) = 1.25
Therefore E(m) greater than CL and an overexposure has occurred within 95% confidence limits. This calculation is also used when considering a standard such as the one for total welding fumes. A computer program is available for personal computers which will calculate a control limit for any synergistic mixture. The program will run on any IBM compatible computer.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- equivalent) or polyvinyl chloride filters for substances that are unstable on paper-type filters are commonly used. (See the OCIS Chemical Sampling Information on specific sampling and analytical OCIS methods for details.)
Preloading a group of vials with appropriate filters is a convenient method. (The Whatman smear tabs should be inserted with the tab end out.) Always wear clean plastic gloves when handling filters. Gloves should be disposable and should not be powdered.
PROCEDURE
Follow these procedures when taking wipe samples:
- * If multiple samples are to be taken at the worksite, prepare a rough sketch of the area(s) or room(s) to be wipe sampled.
- * Use a new set of clean, impervious gloves for each sample to avoid contamination of the filter by the hand (and the possibility of false positives) and prevent contact with the substance.
- * Withdraw the filter from the vial. If a damp wipe sample is desired, moisten the filter with distilled water or other solvent as recommended in the Chemical Information Manual.
- CAUTION
- Skin, personal protective equipment, or surfaces that come into contact with food or tobacco products must be wiped either DRY or with distilled water, never with organic solvents. Skin wipes should not be done for materials with high skin absorption. It is recommended that hands and fingers be the only skin surfaces wiped. Before any skin wipe is taken, explain why you want the sample and ask the employee about possible skin allergies to the chemicals in the sampling filter or medium. If the employee refuses, do not force the issue.
- * Wipe a section of the surface to be sampled using a template with an open area of exactly 100 cm(2). (See Appendix I:2-1.)
- * For surfaces smaller than 100 cm(2) use a template of the largest size possible. Be sure to document the size of the area wiped. For curved surfaces, the wiped area should be estimated as accurately as possible and then documented.
- * Maximum pressure should be applied when wiping.
- * To ensure that all of the partitioned area is wiped, start at the outside edge and progress toward the center by wiping in concentric squares of decreasing size.
- * If the filter dries out during the wiping procedure, rewet the filter.
- * Without allowing the filter to come into contact with any other surface, fold the filter with the exposed side in, then fold it over again. Place the filter in a sample vial, cap and number it, and note the number at the sample location on the sketch. Include notes with the sketch giving any further description of the sample (e.g., "Fred Employee's respirator, inside"; "Lunch table").
- * At least one blank filter treated in the same fashion, but without wiping, should be submitted for each sampled area.
- * Submit the samples to the Salt Lake Technical Center (SLTC) with an OSHA 91 form.
OSHA Instruction TED 1.15 September 22, 1995 Office of Science and Technology Assessment
C. SPECIAL TECHNIQUE FOR WIPE SAMPLING ________________________________________________________________________
ACIDS AND BASES
When examining surfaces for contamination with strong acids or bases, (e.g., hydrochloric acid, sodium hydroxide), pH paper moistened with water may be used. However, results should be viewed with caution due to potential interference.
DIRECT-READING INSTRUMENTS
For some types of surface contamination, direct-reading instruments may be used (e.g., mercury sniffer for mercury).
AROMATIC AMINES
Screening may determine the precise areas of carcinogenic aromatic amine contamination. This is an optional procedure. (See Appendix I:2-2.)
D. SPECIAL CONSIDERATIONS _________________________________________________________________________
Due to their volatility, most organic solvents are not suitable for wipes. Other substances are not stable enough as samples to be wipe sampled reliably. If necessary, judge surface contamination by other means, (e.g., by use of detector tubes, photoionization analyzers, or other similar instruments). Consult the OCIS Chemical Sampling Information.
Some substances should have solvent added to the vial as soon as the wipe sample is placed in the vial (e.g., benzidine). These substances are indicated with an "X" next to the solvent notation in the OCIS Chemical Sampling Information.
Do not take surface wipe samples on skin if:
- * OSHA or ACGIH shows a "skin" notation and the substance has a skin LD(50) of 200 mg/kg or less, or an acute oral LD(50) of 500 mg/kg or less; or
- * the substance is an irritant, causes dermatitis or contact sensitization, or is termed corrosive.
- OSHA Instruction TED 1.15 September 22, 1995 Office of Science and Technology Assessment
Table II:4-3 to correct Table II:4-2 for various kinds of clothing.
Use of Table II:4-2 requires knowledge of the WBGT and approximate workload. Workload can be estimated using the data in Table II:4-1, and sample calculations are presented in Figure II:4-1.
MEASUREMENT
Portable heat stress meters or monitors are used to measure heat conditions. These instruments can calculate both the indoor and outdoor WBGT index according to established ACGIH Threshold Limit Value equations. With this information and information on the type of work being performed, heat stress meters can determine how long a person can safely work or remain in a particular hot environment.
See Appendix II:4-2 for an alternate method of calculation.
TABLE II:4-2. PERMISSIBLE HEAT EXPOSURE THRESHOLD LIMIT VALUES ________________________________________________________________________ | | | | | ------ Work load* ------ | | | | Work/rest regimen Light Moderate Heavy | | | | | | Continuous work 30.0 deg. C 26.7 deg. C 25.0 deg. C | | (86 deg. F) (80 deg. F) (77 deg. F) | | 75% Work, 25% rest, 30.6 deg. C 28.0 deg. C 25.9 deg. C | | each hour (87 deg. F) (82 deg. F) (78 deg. F) | | 50% Work, 50% rest, 31.4 deg. C 29.4 deg. C 27.9 deg. C | | each hour (89 deg. F) (85 deg. F) (82 deg. F) | | 25% Work, 75% rest, 32.3 deg. C 31.1 deg. C 30.0 deg. C | | each hour (90 deg. F) (88 deg. F) (86 deg. F) | | | | * Values are in degree C and degree F, WBGT. | | | | These TLVs are based on the assumption that nearly all acclimatized, | | fully clothed workers with adequate water and salt intake should be | | able to function effectively under the given working conditions | | without exceeding a deep body temperature of 38 degree C (100.4 degree | | F). They are also based on the assumption that the WBGT of the work | | area is different from that of the rest area, a time-weighted average | | should be used (consult the ACGIH 1992-1993 Threshold Limit Values | | for Chemical Substances and Physical Agents and Biological Exposure | | Indices (1992). | | | | These TLVs apply to physically fit and acclimatized individuals | | wearing light summer clothing. If heavier clothing that impeds sweat | | or has a higher insulation value is required, the permissible heat | | exposure TLVs in Table II:4-2 must be be reduced by the corrections | | shown in Table II:4-3. | | | |________________________________________________________________________| Source: ACGIH 1992
OTHER THERMAL STRESS INDICES
The effective temperature index (ET) combines the temperature, the humidity of the air, and air velocity. This index has been used extensively in the field of comfort ventilation and air-conditioning. ET remains a useful measurement technique in mines and other places where humidity is high and radiant heat is low.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
The Heat-Stress Index (HSI) was developed by Belding and Hatch in 1965. Although the HSI considers all environmental factors and work rate, it is not completely satisfactory for determining an individual worker's heat stress and is also difficult to use.
TABLE II:4-3. WBGT CORRECTION FACTORS IN DEGREES C _________________________________________________________________________ | | | Clo* WBGT | | Clothing type value correction | | | | Summer lightweight working clothing 0.6 0 | | Cotton coveralls 1.0 -2 | | Winter work clothing 1.4 -4 | | Water barrier, permeable 1.2 -6 | | | | *Clo: Insulation value of clothing. One clo = 5.55 kcal/m(2)/hr of | | heat exchange by radiation and convection for each degree C difference | | in temperature between the skin and the adjusted dry bulb temperature. | | | |_________________________________________________________________________|
Source: ACGIH 1992. Note: Deleted from previous version are trade names and "fully encapsulating suit, gloves, boots, and hood" including its clo value of 1.2 and WBGT correction of -10.
E. CONTROL _________________________________________________________________________
Ventilation, air cooling, fans, shielding, and insulation are the five major types of engineering controls used to reduce heat stress in hot work environments.
Heat reduction can also be achieved by using power assists and tools that reduce the physical demands placed on a worker. However, for this approach to be successful, the metabolic effort required for the worker to use or operate these devices must be less than the effort required without them. Another method is to reduce the effort necessary to operate power assists.
The worker should be allowed to take frequent rest breaks in a cooler environment.
ACCLIMATIZATION
The human body can adapt to heat exposure to some extent. This physiological adaptation is called acclimatization. After a period of acclimatization, the same activity will produce fewer cardiovascular demands. The worker will sweat more efficiently (causing better evaporative cooling), and thus will more easily be able to maintain normal body temperatures.
A properly designed and applied acclimatization program decreases the risk of heat-related illnesses. Such a program basically involves exposing employees to work in a hot environment for progressively longer periods. NIOSH (1986) says that, for workers who have had previous experience in jobs where heat levels are high enough to produce heat stress, the regimen should be 50% exposure on day 1, 60% on day 2, 80% on day 3, and 100% on day 4. For new workers who will be similarly exposed, the regimen should be 20% on day 1, with a 20% increase in exposure each additional day.
- OSHA Instruction TED 1.15 September 22, 1995 Office of Science and Technology Assessment
SECTION II: CHAPTER 5
NOISE MEASUREMENT
A. DEFINITIONS _________________________________________________________________________
THRESHOLD AND CRITERION LEVELS
The threshold level is the A-weighted sound level at which a personal noise dosimeter begins to integrate noise into a measured exposure. For example, if the threshold level on a sound level meter is set at 80 decibels (dB), it will capture and integrate into the computation of dose all noise in the employee's hearing zone that exceeds 80 dB. Sound levels below this threshold would not be included in the computation of noise dose.
_________________________________________________________________
| | | A. Definition.......................................II:5-1 | | | | B. Effects..........................................II:5-3 | | | | C. Instrument Performance...........................II:5-3 | | | | D. Noise Measurements...............................II:5-4 | | | | E. Ultrasonics......................................II:5-8 | | | | F. General Noise Inspection Data....................II:5-10 | | | | G. Evaluation of the Hearing Conservation Program...II:5-13 | | | | H. Control..........................................II:5-14 | | | | I. Bibliography.....................................II:5-16 | | | | Appendix II:5-1. Evaluation Noise Exposure on | | Employees Wearing Sound-Generating | | Headsets............................II:5-17 | |_________________________________________________________________| The criterion level is the continuous equivalent A-weighted sound level that constitutes 100% of an allowable noise exposure. In other words, the criterion level is the permissible exposure limit (PEL). For OSHA purposes, this is 90 decibels, averaged over an 8-hour period on the A scale of a standard sound level meter set on slow response. Noise measurements taken with an instrument set on the A weighting scale are expressed as dBA.
Paragraphs 29 CFR 1910.95(a) and (b) of the OSHA Occupational Noise Exposure Standard date back to the 1969 Walsh-Healey Act. Because this early standard predated noise dosimetry and OSHA had no instructions for taking noise measurements, the first dosimeters that were developed used 90 dBA both as the threshold and criterion levels.
Paragraph 1910.95(c) of the 1983 Hearing Conservation Amendment to the Occupational Noise Exposure Standard requires employers to administer a continuing, effective hearing conservation program for all employees whose noise exposures equal or exceed an 8-hour TWA of 85 dBA or, equivalently, of a noise dose that is equal to 50 percent of the PEL. The standard requires that all continuous, intermittent, and impulsive sound levels from 80 dB to 130 dB be included in the measurement of dose. In other words, the threshold level for noise measurement purposes is 80 dB.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Differences between sound-measuring instruments must be taken into account when measuring employee noise exposure. For example, because a dosimeter with an 80 dBA threshold integrates all noise above 80 dB into the dose, such a dosimeter will report a higher noise are dose than the dose reported by a dosimeter with a 90 dBA threshold if both instruments used side-by-side to evaluate the same noise exposure (see Table II:5-1).
Dosimeters can be used to calculate both the continuous equivalent A-weighted sound level (L(A)) and the 8-hour time-weighted average (TWA) for the time period sampled, using the following formulas:
L(A) = 16.61 Log(10)[(D)/(12.5T)] + 90 (Eq. II:5-1a)
TWA = 16.61 Log(10)[(D)/(100)] + 90 (Eq. II:5-1b)
where:
L(A) = the continuous equivalent A-weighted sound level in
decibels for the time period sampled D = the dosimeter readout in percent noise dose T = the sampling time in hours TWA = the 8-hour time-weighted average in decibels. Equation II:5-1b is used for enforcement purposes, and equation II:5-1a can be used to assist in evaluating hearing protectors and engineering controls.
EXCHANGE RATE
The exchange rate is the increase or decrease in decibels corresponding to twice (or half) the noise dose. This means that the sound level at 90 dB is twice that at 85 dB (assuming that duration is held constant). The OSHA exchange rate is 5 dB (see Table D-2 of the construction noise standard, 29 CFR 1926.52, and Tables G-16 and G-16a of the general industry noise standard, 29 CFR 1910.95).
Only instruments using a 5 dB exchange rate may be used for OSHA compliance measurements. CSHOs should be aware that noise dosimeters used by the Department of Defense use a 4 dB exchange rate, while instruments used by the Environmental Protection Agency and most foreign governments use a 3 dB exchange rate.
The hypothetical exposure situations shown in Table II:5-1 illustrate the relationship between criterion level, threshold, and exchange rate and show the importance of using a dosimeter with an 80 dBA threshold to characterize an employee's noise exposure. For example, an instrument with a 90 dBA threshold will not capture any noise below that level, and will thus give a readout of 0% even if the employee being measured is actually being exposed to 89 dBA for 8 hours (i.e., to 87% of the allowable noise dose over any 8-hour period).
TABLE II:5-1. DOSIMETER READOUT, IN PERCENT OF MEASURED DOSE _______________________________________________________________________ | | | Dosimeter with Dosimeter with | | threshold threshold | | Exposure Conditions set at 90 dBA set at 80 dBA | | | | 90 dBA for 8 hours 100.0% 100.0% | | 89 dBA for 8 hours 0.0% 87.0% | | 85 dBA for 8 hours 0.0% 50.0% | | 80 dBA for 8 hours 0.0% 25.0% | | 79 dBA for 8 hours 0.0% 0.0% | | 90 dBA for 4 hours plus | | 80 dBA for 4 hours 50.0% 62.5% | | 90 dBA for 7 hours plus | | 89 dBA for 1 hour 87.5% 98.4% | | 100 dBA for 2 hours plus | | 89 dBA for 6 hours 100.0% 165.3% | | | | * Assumes 5 dB exchange rate, 90 dBA PEL, ideal threshold | | activation, and continuous sound levels. | |_______________________________________________________________________|
- OSHA Instruction TED 1.15 September 22, 1995 Office of Science and Technology Assessment
B. EFFECTS _________________________________________________________________________
AUDITORY EFFECTS
Chronic noise-induced hearing loss is a permanent sensorineural condition that cannot be treated medically. It is initially characterized by a declining sensitivity to high-frequency sounds, usually at frequencies above 2000 Hz.
Exposure of a person with normal hearing to workplace noise at levels equal to or exceeding the PEL may cause a shift in the worker's hearing threshold. Such a shift is called a standard (or significant) threshold shift and is defined as a change in hearing thresholds of an average 10 dB or more at 2000, 3000, and 4000 Hertz (Hz) in either ear. Workers experiencing significant threshold shifts are required by 29 CFR 1910.95(g)(8) to be fitted with hearing protectors and to be trained in their use.
EXTRA-AUDITORY EFFECTS
In addition to effects on hearing, noise:
- * Interferes with speech * Causes a stress reaction * Interferes with sleep * Lowers morale * Reduces efficiency * Causes annoyance * Interferes with concentration * Causes fatigue.
C. INSTRUMENT PERFORMANCE _________________________________________________________________________
EFFECTS OF THE ENVIRONMENT
Temperature, humidity, atmospheric pressure, wind, and dust can all affect the performance of noise-measuring instruments and their readings. Magnetic fields can also affect the performance of instruments. Each of these factors is discussed below.
TEMPERATURE
Sound-measuring equipment should perform within design specifications over an ambient temperature range of -20 degrees F to 140 degrees F (-29 degrees C to 60 degrees C).
If the temperature at the measurement site is outside this range, refer to the manufacturer's specifications to determine if the sound level meter or dosimeter is capable of performing properly.
Sound-measuring instruments should not be stored in automobiles during hot or cold weather because this may cause warm-up drift, moisture condensation, and weakened batteries, all of which can affect instrument performance.
HUMIDITY
OSHA noise instruments will perform accurately as long as moisture does not condense or deposit on the microphone diaphragm. If excessive moisture or rain is a problem in a given exposure situation, the Assistant Regional Administrator (ARA) for Technical Support should be consulted.
ATMOSPHERIC PRESSURE
Both atmospheric pressure and temperature affect the output of sound level calibrators; atmospheric pressure is the more important of these two factors. When checking an acoustical calibrator, always apply the corrections for atmospheric pressure that are specified in the manufacturer's instruction manual.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
In general, if the altitude of the measurement site is less than 10,000 feet above sea level, no pressure correction is needed.
If the measurement site is at an altitude higher than 10,000 feet, or if the site is being maintained at greater-than-ambient pressure (e.g., in underwater tunnel construction), use the following equation to correct the instrument reading: C = 10 log {[(460 + t)/528](0.5)[30/B]} (Eq. II:5-2)
where:
C = correction, in decibels, to be added to or subtracted from
the measured sound level, t = temperature in degrees Fahrenheit, and B = barometric pressure in inches of mercury.
NOTE: For high altitude locations, C will be positive; in hyperbaric conditions, C will be negative. WIND OR DUST
Wind or dust blowing across the microphone of the dosimeter or sound level meter produces turbulence, which may cause a positive error in the measurement. A wind screen should be used for all outdoor measurements and whenever there is significant air movement or dust inside a building (e.g., when cooling fans are in use or wind is gusting through open windows). The Assistant Regional Administrator for Technical Support should be consulted for advice about special instrumentation if extreme air turbulence is encountered at the measurement site.
MAGNETIC FIELDS
Certain equipment and operations, such as heat sealers, induction furnaces, generators, transformers, electromagnets, arc welding, and radio transmitters generate electromagnetic fields that can induce current in the electronic circuitry of sound level meters and noise dosimeters and cause erratic readings. If sound level meters or dosimeters must be used near such devices or operations, the extent of the field's interference should be determined by consulting the manufacturer's instructions and the Assistant Regional Administrator for Technical Support.
EFFECTS OF SOUND
For sound level meters and noise dosimeters equipped with omnidirectional microphones, the effects of microphone placement and orientation are negligible in a typically reverberant environment. If the measurement site is nonreverberant and/or the noise source is highly directional, the manufacturer's literature should be consulted to determine proper microphone placement and orientation.
For determining compliance with the impulse noise provision of 29 CFR 1910.95(b)(1) or 29 CFR 1926.52(e), the unweighted peak mode setting of the GenRad 1982 or 1983, Quest 155, or equivalent impulse precision sound level meter should be used.
D. NOISE MEASUREMENTS _________________________________________________________________________
INSTRUMENTS
Several sound measuring instruments are available to CSHOs. These include noise dosimeters, sound level meters, and octave-band analyzers. The uses and limitations of each kind of instrument are discussed below.
NOISE DOSIMETER
The noise dosimeters used by OSHA meet the American National Standards Institute (ANSI) Standard S1.25-1978, "Specifications for Personal Noise Dosimeters," which set performance and accuracy tolerances.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SECTION II: CHAPTER 7
LEGIONNAIRES' DISEASE
A. INTRODUCTION ______________________________________________________________________
This chapter provides information to assist industrial hygienists in the assessment of work sites for potential Legionnaires' disease. It provides information on disease recognition, investigation procedures to identify probable water sources, and control strategies. The primary focus of this document is on the control and prevention of contaminated water sources, not on case identification, an area of expertise primarily exercised by local health departments frequently in conjunction with the Centers for Disease Control and Prevention (CDC) in Atlanta. Appendices include details on conducting an employee awareness program, water sampling protocols and guidelines for acceptable levels of the organism in water, procedures for identifying new cases of the disease, and water treatment and control strategies for facilities where an outbreak has occurred.
___________________________________________________________________
| | | A. Introduction . . . . . . . . . . . . . . . . II-7:1 | | | | B. Disease Recognition. . . . . . . . . . . . . II:7-1 | | | | C. Source Identification. . . . . . . . . . . . II:7-4 | | | | D. Investigation Protocol . . . . . . . . . . . II:7-6 | | | | E. Controls . . . . . . . . . . . . . . . . . . II:7-10 | | | | F. Bibliography . . . . . . . . . . . . . . . . II:7-16 | | | | Appendix II:7-1. Employee Awareness Program . . II:7-18 | | | | Appendix II:7-2. Physical Survey and Water | | Sampling Protocol. . . . . . . . . . . . . . II:7-25 | | | | Appendix II:7-3. Water Sampling Guidelines. . . II:7-28 | | | | Appendix II:7-4. Legionnaires' Disease Case | | Identification . . . . . . . . . . . . . . . II:7-29 | | | | Appendix II:7-5. Water Treatment Protocols for | | Facilities that have Experienced a | | Legionnaires' Outbreak . . . . . . . . . . . II:7-36 | |___________________________________________________________________|
B. DISEASE RECOGNITION ______________________________________________________________________
CAUSATIVE AGENT
Legionella pneumophila was first identified in 1977 by the CDC as the cause of an outbreak of pneumonia that caused 34 deaths at a 1976 American Legion Convention in Philadelphia. L. pneumophila had undoubtedly caused previous pneumonia outbreaks, but the organism's slow growth and special growth requirements prevented earlier discovery.
The diseases produced by Legionella are called legionellosis. More than 34 species of Legionella have been identified, and more than 20 linked with human diseases. L. pneumophila causes the pneumonia known as
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Legionnaires' disease and the flu-like Pontiac fever. L. pneumophila has also been implicated in wound infections, pericarditis, and endocarditis without the presence of pneumonia. Because the majority of legionellosis is caused by L. pneumophila, this chapter will deal exclusively with that organism. Cases where other species of Legionella are involved in disease require actions similar to those to control Legionnaires' disease.
The L. pneumophila bacteria are gram-negative rods that exist in a number of distinguishable serogroups. Each serogroup contains further subtypes that have different surface structures on the cell membrane and can be distinguished by special tests.
Evidence indicates that some Legionella serogroups are more virulent than others. L. pneumophila serogroup 1 is the most frequently identified form of the bacterium isolated from patients with Legionnaires' disease, although other serogroups and subtypes of the bacterium are frequently isolated from water sources. Serogroups 4 and 6 are the next most frequently linked with disease.
SYMPTOMS
Legionnaires' disease has an incubation period of 2 to 10 days. Severity ranges from a mild cough and low fever to rapidly progressive pneumonia and coma. Early symptoms include malaise, muscle aches, and slight headache. Later symptoms include high fever (up to 105 degrees F), a dry cough, and shortness of breath. Gastrointestinal symptoms including vomiting, diarrhea, nausea, and abdominal pain are common. The disease is treated with erythromycin or a combination of erythromycin and rifampin.
Pontiac fever is a nonpneumonia, flu-like disease associated with, and likely caused by, the Legionella bacterium. This disease has an "attack rate" of 90% or higher among those exposed, and a short incubation period, 1-3 days. Complete recovery usually occurs in 2-5 days without medical intervention. The factors that cause the same organism to produce two illnesses with major differences in attack rate and severity are not known.
INCIDENCE
In the U.S., Legionnaire's disease is considered to be fairly common and serious, and the Legionella organism is one of the top three causes of sporadic, community-acquired pneumonia. Because it is difficult to distinguish this disease from other forms of pneumonia, many cases go unreported. Approximately 1,000 cases are reported annually to the CDC, but it is estimated that over 25,000 cases of the illness occur each year and cause more than 4,000 deaths.
RISK FACTORS
Legionnaires' disease is frequently characterized as an "opportunistic" disease that most frequently attacks individuals who have an underlying illness or weakened immune system. The most susceptible include persons who are elderly, smokers, and immunosuppressed. Individuals with chronic obstructive pulmonary disease (COPD), organ transplant patients, and persons taking corticosteroid therapy are also at elevated risk. The attack rate for the average population is approximately 5% or less. The fatality rate is similar to that of other forms of pneumonia, approximately 15%.
DIAGONOSIS
CDC guidelines define two types of cases of Legionelloses, probable and confirmed. A probable case of Legionnaire's disease is a person who experienced an illness clinically compatible with Legionnaire's and has a single antibody titer of 256 or higher (discussed below), and can be associated with a population of individuals who have experienced confirmed cases of the disease (outbreak). A confirmed case of Legionella requires a physician's diagnosis of pneumonia based on a chest x-ray and positive laboratory test results. A laboratory test is
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
necessary for confirmation because the symptoms and x-ray evidence of Legionnaires' disease resemble those of other types of pneumonia. Various methods are used to confirm the presence of the disease.
CULTURE OF THE ORGANISM
The definitive laboratory method of confirming the presence of the disease is by culturing viable cells of Legionella from sputum, bronchial washing, or autopsy on special media. Further identification of the cultured cells will identify the species and serogroup. Special tests may determine subtype of certain isolates. The sensitivity of this test to detect the disease is reported to be about 70%.
URINE ANTIGEN TEST
The detection of antigen from L. pneumophila in the urine is considered a reliable measure of the disease. These antigenic materials may include L. pneumophila cells or portions of cells in the urine during and after the disease. The presence of antigen in the urine is a strong indicator of the disease, and a patient may have a positive response for several months following the disease. The sensitivity of this test is limited because the only commercially available urinary antigen test detects only serogroup 1 forms of L. pneumophila. The CDC recommends only the radioimmunoassay (RIA) test because the latex antigen (LA) test has a high false-positive rate. Fortunately, 80-90% of the clinically diagnosed cases are caused by serogroup 1. The absence of a positive urinary test is not proof that a patient did not have Legionnaires' disease, but merely indicates the absence of antigen in the urine at the time of the test.
DIRECT FLUORESCENT ANTIBODY (DFA) STAINING
Direct fluorescent antibody staining of lung aspirates can detect L. pneumophila. However, this test is frequently negative during the initial stages of the disease because few organisms are present in the aspirate or sputum. This test also requires an antigen-specific reagent. There are a multitude of serogroups and subtypes of L. pneumophila, and a test will be negative if the exact antigen-specific reagent is not included.
SEROLOGY (ANTIBODY TITERS)
An increase in the antibody level in the serum of infected persons occurs several weeks after the onset of the disease. A fourfold increase in the antibody titer coupled with a physician's diagnosis of pneumonia is considered a reliable indicator of disease. This is measured by comparing the antibody level 4 to 8 weeks after onset (convalescent titer) to an initial (acute) titer at the beginning of the disease. Pontiac fever also produces an elevated antibody titer, but the flu-like symptoms of this disease do not match those of Legionnaires' disease.
Frequently only a convalescent titer has been measured from individuals who had symptoms of the disease. For situations in which these cases are associated with an outbreak of Legionnaires' disease, a single titer of 256 to 1 or higher is generally used as a presumptive indication of disease (probable case). Antibody strength is determined by the number of dilutions of serum which elicit a positive antibody response. The reciprocal value of the number of dilutions is the antibody titer. For example, an antibody titer of 256 means a positive antibody test of the patients's serum following serial dilutions of 1:2, then 1:4, then 1:16, etc., until the 1:256 dilution point is reached.
The indirect fluorescent antibody (IFA) test is the accepted diagnostic tool for demonstrating L. pneumophilia exposure. Another widely used test of antibody response is the enzyme-linked immunosorbent assay method (ELISA). CDC believes that direct comparison of results between IFA and ELISA is not reliable because there are insufficient data to compare the two. The ELISA method has gained wide medical acceptance as a useful means of demonstrating exposure to Legionella.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
TRANSMISSION
The likelihood of contracting Legionnaires' disease is related to the level of contamination in the water source, the susceptibility of the person exposed, and the intensity of exposure to the contaminated water. Disease transmission usually occurs via inhalation of an aerosol of water contaminated with the organism. Aspiration of contaminated water into the lungs may also cause the disease. In the Philadelphia Legionnaires' disease outbreak, the hotel's cooling tower was identified as the likely source of the disease, although domestic water sources were not evaluated.
The disease has been associated with domestic hot-water systems in a number of outbreaks. In many instances it has been difficult to identify a likely source for aerosolization of the suspected water source. Although transmission of the disease other than through direct inhalation of aerosols may occur, the mechanisms are not clearly understood. The organism requires water, and the disease cannot occur in the absence of a contaminated water source.
There is no evidence that the disease can be transmitted from one person to another.
C. SOURCE IDENTIFICATION ______________________________________________________________________
Conditions that Promote Growth
L. pneumophila bacteria are widely distributed in water systems. They tend to grow in biofilms or slime on the surfaces of lakes, rivers and streams, and they are not eradicated by the chlorination used to purify domestic water systems. Low and even nondetectable levels of the organism can colonize a water source and grow to high concentrations under the right conditions.
Conditions that promote growth of the organism include heat, sediment, scale, and supporting (commensal) microflora in water. Common water organisms including algae, amoebae, and other bacteria appear to amplify Legionella growth by providing nutrients or harboring the organism. Because of its ability to remain viable in domestic water systems, it is capable of rapid multiplication under the proper conditions.
Water conditions that tend to promote the growth of Legionella include:
- * stagnation;
- * temperatures between 20 degrees and 50 degrees C (68-122 degrees F) (The optimal growth range is 35-46 degrees C [95-115 degrees F].);
- * pH between 5.0 and 8.5;
- * sediment that tends to promote growth of commensal microflora; and
- * micro-organisms including algae, flavobacteria, and Pseudomonas, which supply essential nutrients for growth of Legionella or harbor the organism (amoebae, protozoa).
COMMON SOURCES OF CONTAMINATED WATER
Water sources that frequently provide optimal conditions for growth of the organisms include:
- * cooling towers, evaporative condensers, and fluid coolers that use evaporation to reject heat. These include many industrial processes that use water to remove excess heat;
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- * domestic hot-water systems with water heaters that operate below 60 degrees C (140 degrees F) and deliver water to taps below 50 degrees C (122 degrees F).
- * humidifiers and decorative fountains that create a water spray and use water at temperatures favorable to growth;
- * spas and whirlpools;
- * dental water lines, which are frequently maintained at temperature above 20 degrees C (68 degrees F) and sometimes as warm as 37 degrees C (98.6 degrees F) for patient comfort; and
- * other sources including stagnant water in fire sprinkler systems and warm water for eye washes and safety showers.
Water stored below 20 degrees C (68 degrees F) is generally not a source for amplified L. pneumophila levels. However, high levels of bacteria have been measured in the water supplying ice machines. The source of amplification in this case was thought to be heat from the condenser coil of the ice maker to the cold water supply. However, no cases of Legionnaires' disease have been linked to consumption of ice made from contaminated water.
MONITORING
AIR
An air sample applied to special culture plates by an Andersen-type sampler sometimes demonstrates the presence of the organism in the air. However, negative results are frequent because of the difficulty in maintaining viability of the organism on the culture plates. Air sampling for Legionella is strongly not recommended as a means of measuring potential exposure because of the high likelihood of false negatives.
WATER
Analysis of water samples from a source suspected of being contaminated with L. pneumophila is a valuable means of identifying potential sources of the disease. A qualified microbiological laboratory experienced in Legionella detection can determine the number of organisms present in colony forming units (CFU) per volume of water and can identify the different serogroups of Legionella pneumophila in the sample. Appendix II:7-2 provides details on the collection, storage, and shipping of water samples.
MICROBIOLOGICAL ANALYSIS OF WATER SAMPLES
Cultured Samples
Water samples are cultured on special buffered charcoal yeast extract (BCYE) culture media. Selective isolation processes to eliminate other microbial overgrowth can determine the number of CFU of L. pneumophila per milliliter of water. This process of growth and isolation is time-consuming, and results typically require 7-14 days from the time of submission.
Cultured samples can also be analyzed to identify specific serogroups. Matching the same serogroup and subtype of organism in the patient as found in a water source is considered strong evidence of an associated link.
DIRECT FLORESCENCE ANTIBODY (DFA)
The number of organisms in a water sample can also be determined via direct florescence antibody (DFA) conjugate tests that stain the organism with a fluorescent dye. This test is unable to distinguish between live and dead bacteria and may also have some cross-reactivity with other bacteria. Sample results can be available in one or two days, and this method can be useful in screening water samples. Use caution, however, in interpreting the results since the potential exists for both false positive and negative results.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
DNA AMPLIFICATION
A relatively new method for rapid, specific detection of the organism in water employs a polymerase chain reaction (PCR) process to amplify and then detect portions of DNA unique to L. pneumophila. This method can produce results in 1 day, and preliminary evidence indicates that its sensitivity and specificity are comparable to those of cell culture, which can take 10-14 days to obtain results. Further testing may lead to acceptance of this technique as the method of choice for monitoring water sources for contamination.
INTERPRETATION OF SAMPLE RESULTS
The probability of infection with L. pneumophila is a function both of the intensity of the exposure dose and the level of host susceptibility. Because total eradication of Legionella may not be possible, an acceptable control strategy is to minimize the number of organisms present in a water source. Ample evidence indicates that Legionella levels are readily controllable. A survey of over 1,000 cooling towers indicates that approximately 60% contained nondetectable levels of L. pneumophila when measured by DFA analysis for the number of organisms per milliliter of water (detection limit is 10 bacteria per milliliter of water). In another survey of 663 cooling towers, 57% contained Legionella that were not detected when measured by culture (detection limit less than 1 CFU/mL).
Other studies of domestic hot-water sources indicate that although the organism is common, especially in large hot-water systems, practical control measures can limit the potential for amplification.
A private consulting firm and microbiological laboratory, PathCon Inc., Norcross, Georgia, has introduced suggested guidelines for control of the organism based on the number of CFU of L. pneumophila per milliliter of water (Appendix II:7-3). These guidelines vary depending on the water source, a recognition by the authors that dose is related both to the potential for exposure and to concentration. For example, recommended exposure limits for contaminated water from a humidifier, which would involve direct exposure to an aerosol are lower than for a cooling tower where the opportunity for exposure is normally less. Work operations such as maintenance on cooling towers may involve direct exposure to cooling tower mist, and precautions to minimize exposure are always necessary. The authors recognize that these guidelines are based on limited data, but they represent the best available information and must suffice until the dose effect of L. pneumophila is better understood.
D. INVESTIGATION PROTOCOL ______________________________________________________________________
COMMUNITY HEALTH CONCERNS
It is important to remember that an outbreak of Legionnaires' disease among workers may have its origin in the community and may not be related to the work environment. A Legionnaires' outbreak is both an occupational and a public-health concern, and the investigation may include local public health departments and the Centers for Disease Control (CDC). To minimize employee risk and maximize the effectiveness of effort, close coordination among OSHA, other public agencies, and the employer is imperative.
TYPES OF INVESTIGATIONS
The course of action chosen during an investigation of a facility should be based on the degree of certainty that the site is the source of a reported illness. For this reason, two investigation protocols are based on differing levels of suspected risk for exposure to Legionella. It is important to remember that these procedures are provided only to assist in the investigation of potential Legionnaires' cases. Individual
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
circumstances may require changes in the investigation. All cases require sound professional judgment in deciding the appropriate course of action.
A level-one investigation may be initiated when there is a probable basis for suspecting that workplace water sources are contaminated with Legionella, or when there is information that one case of Legionnaires' disease may exist.
A level-two investigation should be conducted when more then one possible case of Legionnaires' disease has been reported at a facility.
If two or more cases of the disease can be attributed to a work site, assume that a Legionnaires' disease outbreak has occurred. If evidence indicates that the outbreak is still in progress (that is, at least one of the cases has occurred in the last 30 days), prompt actions should be undertaken to provide maximum protection to employees and eliminate the hazard. Appendix II:7-5 includes examples of actions required to control water sources where an outbreak has occurred.
Both investigations follow the same general pattern and include a preliminary opening conference, a walk-through of the facility to conduct a physical assessment of the water systems, a more detailed examination of the systems including a review of maintenance records, assessment of findings, and a closing conference to present control actions based on the findings.
LEVEL-ONE INVESTIGATION
Use the following procedure when Legionnaires' disease may be related to the work environment.
STEP 1
Obtain an overview of all water systems at the facility. A facilities engineer or experienced member of the building maintenance staff should be available to explain system operation and assist in the walkthrough investigation. This person should have a working knowledge of the system's design and current operation.
The overview of the water systems should include plumbing systems, heating-ventilating-air-conditioning (HVAC) systems, and other water reservoirs. A review of the plumbing system should include both hot and cold domestic water systems, water heaters, distribution pipes, water coolers, water treatment equipment, connections to process water systems protected (or unprotected) by backflow preventers, and storage tanks.
The HVAC system review should include cooling towers, evaporative condensers, fluid coolers, humidifiers, direct evaporative air-cooling equipment, indirect evaporative air-cooling equipment, air washers for filtration, etc. Note the location of the fresh-air intakes of the building's air-handling units relative to water sources such as the cooling towers.
Investigate other potential sources of employee exposure including decorative fountains, plant misters, whirlpools, spas, tepid-water eye-washes and safety showers, humidifiers, and water for cooling industrial processes.
Review maintenance records on water systems including water heaters and cooling towers. The records should include temperature checks of domestic water, visual and physical checks of cooling towers, and reports of cooling-tower water-quality assessment and chemical treatment.
Identify the locations of portions of the system in which water is allowed to stagnate such as storage tanks or unused plumbing pipe sections ("dead legs"), or infrequently used faucets. Check for cross-connections between domestic and process water systems, and note the condition and type of back-flow prevention devices.
Investigate recent major maintenance or changes in the system's operation. Determined if there were recent or frequent losses of water pressure from the incoming water supply due to line breakage or street repairs. The failure of a back-flow prevention device under loss of pressure can contaminate the system.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
STEP 2
Conduct a walk-through investigation of the facility. Equipment you will need includes a thermometer for measuring water temperatures, a flashlight, and a film or video camera to record observations.
Measure and record the temperature of water drawn from each storage-type water heater in the facility. This temperature may be significantly below the water heater's gauge temperature because of heat stratification. Note the presence of rust and scale in this water.
Record the maximum temperature of water at faucets connected to each water heater on the system. Record temperatures at locations near, intermediate, and distant from the heaters. It may be necessary to run the water for several minutes before it reaches a temperature maximum.
Examine the water temperature and the potential for stagnation of cold-water storage tanks used for reserve capacity or to maintain hydrostatic pressure. These should be protected from temperature extremes and covered to prevent contamination. Record the temperature of the domestic cold-water lines at various locations within the facility. Note both the initial temperature and the final equilibrium temperature on the cold-water line, and record the time required to reach equilibrium, because this can be an indicator of the amount of stagnation in the system.
Evaluate cooling towers, evaporative condensers, and fluid coolers for biofilm growth, scale buildup, and turbidity. Record the location of the tower relative to fresh-air intakes, kitchen exhausts, leaves, plant material, or other sources of organic material that might contribute to the growth of the organism.
Record the general condition of the cooling tower. Determine the presence and condition of drift eliminators, which are designed to limit the vapor release from the units, along with the basin temperature of the water in the cooling tower if it is currently being operated. If the cooling tower is operating and is suspected of being contaminated, wear appropriate respiratory protection in the form of a half-face piece respirator equipped with a HEPA or similar type of filter capable of effectively collecting one-micron paricles during the examination of the system.
Note the location and evaluate the condition of the sumps for the cooling tower(s), evaporative condenser(s), and fluid cooler(s). These sumps are sometimes located indoors to protect them from freezing. Record the locations of any cross-connections between the cooling tower water system and any domestic water system. These may supply a back-up source of cool water to refrigeration condenser units or serve to supply auxiliary cooling units.
The lack of a regular maintenance schedule or water-treatment program for a cooling tower or evaporative condenser system strongly suggests a potential for Legionella contamination.
STEP 3
Assess the results of the walkthrough investigation to determine the course of action. If no potential problems are identified, the operating temperatures measured at water heaters are 60 degrees C (140 degrees F) or above, and the delivery temperature at distant faucets is 50 degrees C (122 degrees F) or higher, no further action will be necessary. However, if the system is poorly maintained and operating temperatures are below recommended minimums, then recommendations for corrective action should be made.
STEP 4
Recommend Control Actions. Details of suggested control actions are discussed in Section E. These actions may include disinfection of the domestic water system via heat treatment, chlorination, or other means, and cleaning and disinfecting the cooling tower system according to the Wisconsin Division of Health protocol for "Control of Legionella in Cooling Towers" or a similar process for cleaning heat rejection systems that follows sound practices to minimize potential for Legionella growth.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Additional actions may include eliminating dead legs in the plumbing system, insulating plumbing lines and installing heat tracing to maintain proper temperatures in the system, eliminating rubber gaskets, and removing or frequently cleaning fixtures such as aerators and shower heads.
Corrective actions limited to raising the water heater temperature without evaluating the system for points of stagnation, heat loss and gain, cross-contamination, and other factors that contribute to growth are generally not sufficient.
For a level-one investigation it is not recommended that water samples be collected to confirm the presence of Legionella in the system. The absence of proper operating conditions alone is sufficient for assuming that the water system can pose an unnecessary risk to the employees. Take water samples after the completion of the control actions to confirm that the corrective measures were successful. The employer may also want to obtain samples before starting corrective actions to assess the extent of the problem.
The employer should take necessary corrective actions even if the results of presampling are negative. Water sampling can produce false negatives, a contaminated portion of the system may have been missed, and the absence of Legionella organisms at the time of sampling does not insure that the system will remain negative.
If, after control actions, the Legionella levels in a water source exceed the guidelines in Appendix II:7-3, re-examine the water system to determine if potential contamination points within the system were overlooked and reassess control procedures to determine if they were performed properly. Repeat the procedures as needed until contamination levels meet the guidelines.
LEVEL-TWO INVESTIGATION
A level-two investigation is similar to a level-one investigation with several additional steps. Supplemental actions include: (1) medical surveillance of all employees currently on sick leave to identify any new cases, (2) employee awareness training on the disease to minimize employee concerns and aid in early recognition of new cases, (3) assessment of past sick-leave absences for undetected cases of the disease, and (4) collection of water samples during the walk-through assessment.
STEP 1
Assess water systems as described for a level-one investigation.
STEP 2
Conduct a second walkthrough survey of the facility and collect water samples. Estimate the size of the building and the number of water services during the initial walkthrough and prearrange supply and shipping of the required number of sterile sample containers with the appropriate laboratory. (See Appendix II:7-2 for water sampling procedures.)
STEP 3
Initiate an employee awareness program and monitor current sick leave for new cases. It is important to ensure that employees understand the early symptoms of the disease and seek medical assistance promptly. It is imperative not to alarm the workers. It is equally important to stress the importance of the need to know the health status of all employees on sick leave. (See Appendix II:7-1, Employee Awareness Program.)
STEP 4
Review worker absences to detect other cases. This requires identification of all employees who took three or more consecutive days of sick leave from approximately six weeks before the case of Legionnaires' disease was identified up to the present. Request those employees who may have had pneumonia during this period to undergo additional voluntary tests for evidence of Legionnaires' disease. (See Appendix II:7-4, Case Identification.)
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
STEP 5
Assess results of worker absence survey and analysis of water systems. If evidence indicates more than one case of Legionnaires' disease at the workplace, then the site should be treated as having an outbreak. Take immediate control of all water sources to eliminate potential for exposure, and take measures to eliminate the hazard. (See Appendix II:7-5.)
No action is necessary if the results of the investigation are negative, that is, (1) all water and HVAC systems are well maintained and in good operating condition; (2) all water sample results are negative or acceptably low (Appendix II:7-3); and (3) no new cases of the disease have been identified at the work site. Under these circumstances, assume that the site is not the origin of the identified case.
STEP 6
For recommended control actions, see the level-one investigation.
ONGOING OUTBREAK
If the evidence indicates that two or more cases of Legionnaires' disease have occurred at a site, and at least one of the cases was within the last 30 days, assume that an outbreak is in progress and requires a high-priority investigation and prompt action. Conduct a level-two investigation as outlined above, and take the following precautions to protect building occupants.
Immediately initiate control measures to prevent additional exposures to all water systems that have a reasonable potential for worker exposure including hot and cold domestic water, cooling towers, humidifiers, and any other potential sources of water exposure. Collect appropriate water samples to determine Legionella levels before shutting down the water systems (Appendix II:7-2). These sample results will be invaluable in establishing the cause of the outbreak. A member of the building maintenance or engineering staff who has a working knowledge of the system's design and current operation can explain how the water system operates and the proper procedure for a controlled shutdown.
These control actions need not require facility shutdown. Temporary provisions can allow work to continue: bottled water can be supplied for drinking, shutting off water heaters can eliminate hot-water access, and temporary cooling towers can allow work to continue.
E. CONTROLS ______________________________________________________________________
GENERAL DISCUSSION
This section contains background information on water system operations and proper controls to prevent Legionella amplification. This discussion encompasses a variety of water systems, some of which have not been implicated with outbreaks of Legionnaires' disease. Nevertheless, it is important to remember that any water system can be a source of disease if the water in it is subjected to conditions that promote growth of the organism. Remember, however, that the primary sources of exposure to contaminated water are heat rejection systems (cooling towers, fluid coolers, etc.) and domestic hot-water systems.
COOLING TOWERS, EVAPORATIVE CONDENSERS, AND FLUID COOLERS
The function of cooling towers, evaporative condensers, and fluid coolers is to reject heat from system fluids through evaporation. Cooling towers remove heat from condenser water via direct-contact evaporation in a wet
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
airstream. This cooled water circulates through the condenser side of a mechanical refrigeration unit to absorb heat. Evaporative condensers operate similarly, except that the refrigerant condenser coils are directly inside the wet air stream and water passing over the coils directly cools the refrigerant. Fluid coolers are employed to reject heat from industrial processes, computer-room air conditioners, etc. Like evaporative condensers, fluid coolers have heat-exchanger coils directly in the wet air stream.
Because all of these systems use a fan to move air through a recirculated water system, a considerable amount of water vapor is introduced into the surroundings despite the presence of drift eliminators designed to limit vapor release. In addition, this water may be in the ideal temperature range for Legionella growth, 20-50 degrees C, 68-122 degrees F.
INSPECTION AND MAINTENANCE
Visual inspection and periodic maintenance of the system are the best ways to control growth of Legionella and related organisms. Good maintenance is necessary both to control Legionella growth and for effective operation. The system should be properly monitored and maintained to prevent buildup of scale and sediment and bio-fouling, all of which support Legionella growth and reduce operating efficiency.
BIOCIDE
Unfortunately, measurements of water quality such as total bacterial counts, total dissolved solids, and pH have not proven to be good indicators of Legionella levels in cooling towers. Periodic use of biocides is needed to ensure control of Legionella growth.
Little information exists on the demonstrated effectiveness of many commercial biocides for preventing Legionella growth in actual operations. Recent Australian studies indicate that Fentichlor [2,2'-thiobis(4-chlorophenol) used weekly for 4 hours at 200 ppm, or bromo-chloro-dimethyl-hydantoin (BCD) in a slow-release cartridge at an initial concentration of 300 ppm are effective in controlling the growth of Legionella. There are no U.S. suppliers of Fentichlor, although the chemical is liscensed by the EPA for water treatment in cooling towers. Towerbrom 60M(TM), a chlorotriazine and sodium bromide salt mixture, has been reported to be effective when alternated with BCD for control of Legionella in U.S. studies of Legionella contamination of cooling towers. The Australian study also indicates that quaternary ammonium compounds, widely used for control of bio-fouling in cooling towers, are not effective in controlling Legionella.
Traditional oxidizing agents such as chlorine and bromine have been proven effective in controlling Legionella in cooling towers. Continuous chlorination at low free residual levels can be effective in controlling Legionella growth. It is important, however, that the proper oxidant level be established and maintained because free residual chlorine above 1 ppm may be corrosive to metals in the system and may damage wood used in cooling towers; free residual levels below 1 ppm may not adequately control Legionella growth. Chlorine also combines with organic substances in water to form toxic by-products that are of environmental concern. Frequent monitoring and control of pH is essential for maintaining adequate levels of free residual chlorine. Above a pH of 8.0, chlorine effectiveness is greatly reduced. Proper control of pH will maintain the effectiveness of chlorination and minimize corrosion.
Bromine is an effective oxidizing biocide. It is frequently added as a bromide salt and generated by reaction with chlorine. Bromine's effectiveness is less dependent than chlorine on the pH of the water; it is less corrosive; and it also produces less toxic environmental by-products.
The effectiveness of any water-treatment regimen depends on the use of clean water. High concentrations of organic matter and dissolved solids in the water will reduce the effectiveness of any biocidal agent. Each sump should be equipped with a "bleed," and make-up water should be supplied to reduce the concentration of dissolved solids.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
DESIGN
One of the most effective means of controlling the growth of Legionella is to maintain sump water at a low temperature. Sump-water temperatures depend on tower design, heat load, flow rate, and ambient dry-bulb and wet-bulb temperatures. Under ideal conditions, sump-water temperatures in evaporative devices approach the ambient wet-bulb temperature, and that may be low enough to limit Legionella amplification. System design should recognize the value of operating with low sump-water temperatures.
High-efficiency drift eliminators are essential for all cooling towers. Older systems can usually be retrofitted with high-efficiency models. A well-designed and well-fitted drift eliminator can greatly reduce water loss and potential for exposure.
Other important design features include easy access or easily disassembled components to allow cleaning of internal components including the packing (fill). Enclosure of the system will prevent unnecessary drift of water vapor, and other design features to minimize the spray generated by these systems are also desirable.
FREQUENCY OF CLEANING
Cooling towers should be cleaned and disinfected at least twice a year. Normally this maintenance will be performed before initial start-up at the beginning of the cooling season and after shut-down in the fall. Systems with heavy bio-fouling or high levels of Legionella may require additional cleaning. Any system that has been out of service for an extended period should be cleaned and disinfected. New systems require cleaning and disinfecting because construction material residue can contribute to Legionella growth.
WISCONSIN PROTOCOL
Acceptable cleaning procedures include those described in the Wisconsin Protocol. This procedure calls for an initial shock treatment with 50 ppm free residual (total) chlorine, addition of detergent to disperse bio-fouling, maintenance of 10 ppm chlorine for 24 hours, and a repeat of the cycle until there is no visual evidence of biofilms. To prevent exposure during cleaning and maintenance, wear proper personal protective equipment: a Tyvek-type suit with a hood, protective gloves, and a properly fitted respirator with a high-efficiency particulate (HEPA) filter or a filter effective at removing one-micron particles.
RECORDKEEPING
A description of the operating system (which includes all components cooled by the system) and details of the make-up water to the system should be available. Written procedures for proper operation and maintenance of the system should indicate the use of scale and corrosion inhibitors, antifoaming agents, and biocides or chlorine use and should be readily available. Log books should list dates of inspections and cleanings, water-quality test results, and maintenance.
DOMESTIC HOT-WATER SYSTEMS
BACKGROUND
Domestic hot-water systems are frequently linked to Legionnaires' outbreaks. The term "domestic" applies to all nonprocess water used for lavatories, showers, drinking fountains, etc., in commerical, residential, and industrial settings. Disease transmission from domestic hot water may be by inhalation or aspiration of Legionella-contaminated aerosolized water. Water heaters that are maintained below 60 degrees C (140 degrees F) and contain scale and sediment tend to harbor the bacteria and provide essential nutrients for commensal micro-organisms that foster growth of L. pneumophila. Large water heaters like those used in hospitals or industrial settings frequently contain cool zones near the base where cold water enters and scale and sediment accumulate. The temperature and sediment in these zones can provide ideal conditions for amplification of the organism. Dead legs and nonrecirulated plumbing lines that allow hot water to stagnate also provide areas for growth of the organism.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
DESIGN
Water systems designed to recirculate water and minimize dead legs will reduce stagnation. If potential for scalding exists, appropriate, fail-safe scald-protection equipment should be employed. For example, pressure-independent, thermostatic mixing valves at delivery points can reduce delivery temperatures. Point-of-use water heaters can eliminate stagnation of hot water in infrequently used lines. Proper insulation of hot-water lines and heat tracing of specific lines can help maintain distribution and delivery temperatures.
MAINTENANCE
To minimize the growth of Legionella in the system, domestic hot water should be stored at a minimum of 60 degrees C (140 degrees F) and delivered at a minimum of 50 degrees C (122 degrees F) to all outlets. The hot-water tank should be drained periodically to remove scale and sediment and cleaned with chlorine solution if possible. The tank must be thoroughly rinsed to remove excess chlorine before reuse.
Eliminate dead legs when possible, or install heat tracing to maintain 50 degrees C (122 degrees F) in the lines. Rubber or silicone gaskets provide nutrients for the bacteria, and removing them will help control growth of the organism. Frequent flushing of these lines should also reduce growth.
Domestic hot-water recirculation pumps should run continuously. They should be excluded from energy conservation measures.
CONTROL
Raising the water-heater temperature can control or eliminate Legionella growth. Pasteurize the hot water system by raising the water-heater temperature to a minimum of 70 degrees C (158 degrees F) for 24 hours and then flushing each outlet for 20 minutes. It is important to flush all taps with the hot water because stagnant areas can "re-seed" the system. Exercise caution to avoid serious burns from the high water temperatures used in Pasteurization.
Periodic chlorination of the system at the tank to produce 10 ppm free residual chlorine and flushing of all taps until a distinct odor of chlorine is evident is another means of control. In-line chlorinators can be installed in the hot water line; however, chlorine is quite corrosive and will shorten the service life of metal plumbing. Control of the pH is extremely important to ensure that there is adequate residual chlorine in the system.
Alternative means to control Legionella growth include the use of metal ions such as copper or silver (which have a biocidal effect) in solution. Ozonization injects ozone into the water. Ultraviolet (UV) radiation also kills microorganisms. Commercial, in-line UV systems are effective and can be installed on incoming water lines or on recirculating systems, but stagnant zones may diminish the effectiveness of this treatment. Scale buildup on the UV lamp surface can rapidly reduce light intensity and requires frequent maintenance to ensure effective operation.
DOMESTIC COLD-WATER SYSTEMS
Domestic cold water systems are not a major problem for Legionella growth. Maintaining cold-water lines below 20 degrees C will limit the potential for amplification of the bacteria. It is surprising, however, that elevated levels of Legionella have been measured in ice machines in hospitals. Cold-water lines near heat sources in the units are believed to have caused the amplification.
Dental water lines have recently been recognized as common sources of water contaminated with high concentrations of microorganisms including Legionella. However, to date an increased risk of disease among dental staff or patients has not been demonstrated. Dental water line operating conditions are especially appropriate for Legionella proliferation because the water is stagnant a majority of the time, the narrow plastic tubing encourages biofilm formation, and the water temperature is usually 20 degrees C (68 degrees F) or higher-some systems maintain water at 37 degrees C (98.6 degrees F). Filtration of water at the point of use with
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
replaceable, in-line, 1-micron filters is a FDA approved method of minimizing risk to patients and staff in a dental facility.
Water tanks that allow water to remain uncirculated for long periods can also promote growth of bacteria. Such tanks should be eliminated or designed to reduce storage time to a day or less. They should also be covered to prevent contamination and protected from temperature extremes.
Cross-contaminations of the domestic cold-water system with other systems should always be suspected. All connections to process water should be protected by a plumbing code-approved device (e.g., back-flow preventer, air gap, etc.).
If significant contamination of the domestic cold water system occurs, the source of contamination must be determined. Inspect the system for "dead legs" and areas where water may stagnate. Elimination of these sections or frequent flushing of taps to drain the stagnant areas may be necessary to limit growth of the organism. Insulate cold-water lines that are close to hot-water lines to reduce the temperature in the line.
If the cold-water lines have significant contamination, hyperchlorination can eradicate Legionella. Free chlorine levels of 20 to 50 ppm are allowed to remain for one hour at 50 ppm, or two hours at 20 ppm. Faucets are then allowed to run until the odor of chlorine is present, and the water is allowed to remain for approximately two hours.
HVAC SYSTEMS
HVAC systems are not normally amplification sites for Legionella. The organism cannot survive without water, and a properly operated, well-maintained HVAC system is unlikely to be a source of problems. However, the HVAC system can disseminate contaminated water aerosols.
Water-aerosol sources are classified as either external or internal. External sources may emit contaminated aerosolized water that is drawn into a system's fresh-air intake.
- * Mist discharged from cooling towers, evaporative condensers, and fluid coolers can be ingested by the HVAC fresh air intake. When evaluating this path, you should consider: - prevailing wind direction and velocity, - building effects (e.g., low-pressure zones on leeward sides of buildings and on roof), - architectural screen walls, and - distance from tower to intake.
- * Fresh-air intake areaways, typically concrete plenums located at grade level, supply fresh air to air handlers in the basement or lower levels of buildings and can collect organic material (e.g. leaves, dirt, etc.) and water from rain or irrigation.
Do not ignore direct paths such as through an open window. The transmission path through the HVAC system is torturous, and the bacteria may die from desiccation in the airstream or impact on internal surfaces like filters, duct lining, etc. When evaluating exteral sources, examine the potential for direct transmission.
Internal sources may provide contaminated aerosolized water that is then disseminated by the air-distribution system.
- * Contaminated water can leak from pipes into HVAC ducts, where it can be aerosolized and distributed by the system. Potential sources of contaminated water include domestic water systems, fire-sprinklers, refrigeration condensers, etc.
- * HVAC system humidifiers can be hazards. Four types are common: - Heated-pan humidifiers use a heat source to evaporate water from a pan open to the air stream. Intermittent
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- use of the device coupled with a warm pan of water may support Legionella growth. Contaminant-free water is essential.
- - Direct steam-type humidifiers inject boiler-generated steam directly into the air stream. These systems normally operate above 70 degrees C (158 degrees F), and Legionella cannot survive at that temperature.
- - Atomizing humidifiers use mechanical devices or pneumatic air to create a water mist that evaporates into the air stream. A contaminant-free water source is essential.
- - Direct evaporative air coolers may be used as humidifiers. These devices mix water and air in direct contact to create a cool, wet air stream by evaporation. These devices include sumps, which may stagnate when not in use.
- * When draining properly, the water that passes through the condensate pans of cooling coils in an air handler is normally not a source of growth for the organism because of the low temperature of water condensate.
- * Indirect evaporative air cooling in systems designed for dryer climates. One common design circulates cool water from a cooling tower sump through a water coil in the supply air stream. If the coil develops a leak, then pumped cooling tower water will be injected directly into the supply air stream with potentially deleterious effects if the sump water is contaminated with Legionella.
- * Indirect evaporative air cooling is also found in air-to-air heat exchangers. One side of the heat exchanger is an evaporative-cooled wet air stream, and the other side supplies air for the conditioned space. If the heat exchanger leaks, the wet air stream can mix with supply air and cause problems if the wet air stream is contaminated with Legionella.
- * Many air-handling systems designed for dryer climates employ direct evaporative air cooling. Wet evaporative coolers, slinger air coolers and rotary air coolers common in commercial applications. These devices mix water and air in direct contact to create a cool, wet air stream by evaporation. If these systems are using 100% outside air in a dry climate, the water sump temperature may be low and will not represent a significant risk. However, improperly operated and maintained systems that use warm, stagnant sump water can present problems.
- * Other equipment may also be potential sources of Legionella. - Residential humidifiers are small, free-standing, portable units that use an internal fan and wet media to disseminate a wet air stream. The sumps of these devices are frequently contaminated with Legionella. Daily cleaning is necessary to maintain acceptable water quality, but these units seldom receive appropriate maintenance, and their use in the commercial or industrial workplace is strongly discouraged.
- - Computer room air-conditioners typically include humidifiers and frequently are not well maintained. They may contain a sump filled with contaminated water.
DESIGN
The following are issues to consider when designing HVAC systems to minimize risk from Legionella contamination. Most apply to all types of microbial contamination.
- * Minimize use of water reservoirs, sumps, and pans. Chemically untreated, stagnant, warm-water sources provide an ideal environment for Legionella growth.
- * Provide a way to drain water sumps when not in use, e.g., an electric solenoid valve on the sump drain. If an HVAC sump is
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- used during the hours when a building is occupied, drain the sump during unoccupied hours.
- * Provide a "bleed" for water sumps so that dissolved solids do not form sediments in the sump.
- * Slope and drain sumps from the bottom so that all the water can drain out and allow the pan to dry.
- * Locate HVAC fresh-air intakes so that they do not draw the mist from a cooling tower, evaporative condenser, or fluid cooler into the system. The American Conference of Governmental Industrial Hygienists publishes "Guidelines For The Assessment Of Bioaerosols In The Indoor Environment," which lists recommended minimum distances between cooling towers and fresh-air intakes.
- * Design indirect evaporative cooling systems with the knowledge that the failure of the heat exchanger will allow wet systems to mix with the air-distribution systems.
- * Use steam or atomizing humidifiers instead of units that use recirculated water. Do not use raw steam from the central heating boiler because it contains corrosion inhibitors and anti-scaling chemicals. Atomizing humidifiers must have contaminant-free water.
OPERATION AND MAINTENANCE
Operate all HVAC equipment as originally designed, and maintain it so that it can perform as designed. Test all HVAC equipment periodically to insure that it is performing as designed.
Inactive sumps must be properly drained and bled to prevent accumulation of sediments. Maintenance failures can produce contaminated, stagnant water that can become an ideal environment for Legionella growth if heated (e.g., by sunlight).
F. BIBLIOGRAPHY ______________________________________________________________________
American Water Works Association, A Procedure for Disinfecting Water Mains
- AWWA C601 1981; Denver CO.
Best, M., A. Goetz, and V. L. Yu. "Heat eradication measures for control
- of nosocomial Legionnaires' disease." American Journal of Infection Control, 12, (1), 1984, pp. 26-30.
Broadbent, C. R. "Legionella in Cooling Towers: Practical Research,
- Design, Treatment and Control Guidelines." Delivered at 1992 Inter. Symp. on Legionella, Amer. Society for Micro., Jan. 26-29, 1992, Orlando Fl.
Chartered Institution of Building Services Engineers, Minimising The Risk
- of Legionnaires' Disease, Delta House, 222 Balham High Rd., London 1987.
England, A. C. et al. "Sporadic legionellosis in the U.S.: the first 1000
- cases." Ann. Inter. Med. 94, 1981, p. 164.
Gilpin, R. W., A. M. Kaplan, and E. F. Goldstein "Quantitation of
- Legionella pneumophila in one thousand commercial and industrial cooling towers." Proceedings 48th Inter. Water Conference, Oct. 24-26, 1988, Pittsburg, pp.13-19.
Health and Safety Executive (UK), "The Control of legionellosis including
- Legionnaires' disease." Health and Safety Series Booklet, HS (G)70,
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Library and Information Services, Broad Lane, Sheffield S37HQ, Tel: (0742)
- 752539.
Health Department Victoria; Melbourne Austrailia, "Guidelines for the
- Control of Legionnaires' Disease" in Environmental Health Standards, 1989.
Morris, G. K. and B. G. Shelton. Legionella in Environmental Samples:
- Hazard Analysis and Suggested Remedial Actions. March 1991, Pathogen Control Assoc., Norcross, Georgia.
Muder, R. R., V. L. Yu, and A. H. Woo. "Mode of transmission of Legionella
- pneumophila." Arch Intern Med, 146, (1986), pp. 1607-1612.
Muraca, P., J. E. Stout, and V. L. Yu. "Comparative assessment of
- chlorine, heat, ozone, and UV light for killing Legionella pneumophila within a model plumbing system." Applied and Environmental Microbiology, 53, (2), 1987, p. 447-453.
Muraca, P. W., V. L. Yu, and R. N. Goetz. "Disinfection of water
- distribution systems for Legionella: a review of application procedures and methodologies." Infect Control Hosp Epidemiol, 11, (2), 1990, pp. 79-88.
Muraca, P.W., J. E. Stout, V. L. Yu, and Y. C. Ying. "Legionnaires'
- disease in the work environment: implications for environmental health."
- Am. Ind. Hyg. Assoc., 49, (11), 1988, pp. 584-590.
Nalco Chemical Company. Cooling Water Chlorination, Technifax, TF-132,
- Nalco Chemical Co., Naperville, Ilinois, 1986.
Nguyen, M. H., J. E. Stout, and V. L. Yu. "Legionellosis." Lower
- Respiratory Tract Infections, 5, (3), September 1991, pp. 561-584.
Stout, J. E., V. L. Yu, and M. S. Muraca. "Isolation of Legionella
- pneumophila from the cold water of hospital ice machines: implications for origin and transmission of the organism." Infection Control, 7786, (4), 1985, pp. 141-146.
Stout, J. E., V. L. Yu, M. S. Muraca, J. Joly, N. Troup, and L. S.
- Tompkins. "Potable water as a cause of sporadic cases of community-acquired Legionnaires' disease." New England Journal of Medicine, 326, January 16, 1992, pp. 151-155.
Wisconsin Division of Health. Control of Legionella in Cooling Towers,
- Summary Guidelines, June 1987, Wisconsin Department of Health and Social Sciences.
Williams, J. F. et. al. "Microbial contamination of dental unit
- waterlines: prevalance, intensity and microbiological characteristics."
- J.of American Dental Association, 124, October 1993, pp. 59-65.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
APPENDIX II:7-1. Employee Awareness Program ___________________________________________________________________________
The purpose of an employee awareness program is to inform the employees of the potential outbreak, and to educate them about the disease. This educational program should be part of a level-two investigation or for a Legionnaires' disease outbreak. This program is of critical importance to aid in early recognition of the disease. It is also important to help alleviate employee concerns about the disease. This program should supplement the case identification program to discover previously undetected cases of the illness at the work site.
The employer should implement the following elements of this program immediately upon recognition of more than one probable or confirmed case of disease in the work place:
- 1. An initial employee training session which provides basic information about the disease and actions being taken to investigate the problem.
- 2. An ongoing general information service to provide updates and answer questions that may arise among employees.
- 3. Medical and psychological counseling services when an outbreak has occurred.
Below is a sample letter and supplemental information on the disease that the employer can use for informing employees of a potential or actual outbreak.
______________________________________________________________________
DATE:
MEMO TO: ALL EMPLOYEES
FROM: MANAGEMENT OFFICIAL
SUBJECT: Legionnaires' Disease
On _________________, we were notified that one of the employees of our company had contracted legionellosis, commonly referred to as Legionnaires' disease. The employee is assigned to _________________ on
___________ shift.
We want to share with you some general information concerning the disease. In addition, we want to tell you what we are currently doing here at
_____________________ to ensure all necessary steps are taken to address health concerns.
Legionellosis, or Legionnaire's disease, is a type of pneumonia caused by Legionella bacteria. Legionnaires' disease is not contagious, and you cannot catch it from another person. The bacteria are common and grow in water. People often receive low-level exposure in the environment without getting sick. Legionellosis usually occurs only when someone who is already susceptible receives concentrated exposure to the bacteria. Persons who are heavy smokers, elderly, or whose ability to resist infection is reduced are more likely to contract Legionnaires' disease than healthy nonsmokers. According to the Centers for Disease Control in Atlanta, there are between 10,000 and 50,000 cases of Legionnaire's disease every year in the U.S. We are cooperating fully with local health officials who are investigating this matter. Most cases of legionellosis are isolated and are not associated with an outbreak. To date, _____
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
case(s) of the disease has/have occurred among employees in this facility.
To identify any other cases, we will review sick-leave records for the period ____________ to _____________. Employees who took more than three consecutive days of sick leave will be identified, and we will attempt to determine if any in that group experienced pneumonia-like symptoms (fever, shortness of breath, cough). Those who used three or more consecutive days of sick leave during this period can expect to be contacted by a representative of our company for an interview. If you experienced a pneumonia-like illness in the past two months but used fewer then three consecutive days of sick leave, contact _________________ to arrange an interview.
To assure that you are being protected during the interim, we are also instituting a medical surveillance program to identify any new or old cases. Part of this surveillance will be to ask you a few questions about your illness when you call in sick to your supervisor. In addition, we are offering counseling and employee information services. If you would like to take advantage of these services or want more information, contact your manager. For the present, please pay attention to the following important points:
WHAT YOU SHOULD DO NOW:
1. If you are not sick, there is no need for you to see a doctor.
2. If you are now sick with a cough and fever:
- A. See your private doctor or contact __________ to arrange to see a _______________ physician.
- B. Tell the physician that you work in a building that may be involved in a Legionnaires' disease outbreak.
- C. If you see a physician, notify _______________ so that your illness can be tracked.
If you have any concerns or questions concerning this issue, please ask your manager. Your health and safety are of great concern to us, and we will be grateful for your cooperation in this matter. As further information develops we will keep you informed.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SAMPLE INFORMATION TO BE OBTAINED BY INTERVIEW WITH EMPLOYEES CALLING IN ON SICK LEAVE.
- Interviewer:__________________________Date:_______________
SUPERVISOR SURVEY FORM
We are screening employee illnesses as a result of our Legionnaire's disease incident. You are not obligated to participate in the survey, but your participation will help you and your fellow workers.
We recommend that you see a physician if you currently have pneumonia-like symptoms such as severe chills, high fever, a cough, and difficult breathing.
______________________________________________________________________
Are you currently experiencing these symptoms? Yes_____ No_____ Prefer not to answer______
- - If the answer to the question is "No," do not complete the rest of this form. Thank you for your cooperation.
- - If the answer is "Yes," please read the statement below and complete the bottom half of this form (Employee name, etc).
- - If you answer is "Prefer not to answer," please complete ONLY the bottom half of this form (Employee name, etc).
STATEMENT: You will be contacted by ______________ to obtain additional information necessary to complete our survey.
Thank you!
______________________________________________________________________
Employee's Name _______________________________________________
Work Telephone Number _______________________________
Home Telephone Number _______________________________
Shift: Day ___ Swing ___ Graveyard ___ Rotating ___
Branch _______________________/Organization Code _______________
Employee's Supervisor _____________________________________________
Telephone Number _______________________________________________
Date _____________________________________
PLEASE FORWARD TO ________________ BY 10:00 am EACH DAY
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
BACKGROUND
Legionnaires' disease is a common name for one of the several illnesses caused by Legionella bacteria. Legionnaires' disease is an infection of the lungs that is a form of pneumonia. A person can develop Legionnaires' disease by inhaling water mist contaminated with Legionella.
Legionella bacteria are widely present at low levels in the environment: in lakes, streams, and ponds. At low levels the chance of getting Legionnaires' disease from a water source is very slight. The problem arises when high concentrations of the organism grow in water sources. Water heaters, cooling towers, and warm, stagnant water can provide ideal conditions for the growth of the organism.
Scientists have learned much about the disease and about the Legionella bacteria since it was first discovered in 1976. The following questions and answers will help you learn more of what is currently known about Legionnaires' disease.
Q. What are the symptoms of Legionnaires' disease?
- A. Early symptoms of the illness are much like the flu. After a short time (in some cases a day or two), more severe pneumonia-like symptoms may appear. Not all individuals with Legionnaires' disease experience the same symptoms. Some may have only flu-like symptoms, but to others the disease can be fatal.
- Early flu-like symptoms:
- * slight fever * headache * aching joints and muscles * lack of energy, tired feeling * loss of appetite
- Common pneumonia-like symptoms:
- * high fever (102 degrees to 105 degrees F, or 39 degrees to 41 degrees C) * cough (dry at first, later producing phlegm) * difficulty in breathing or shortness of breath * chills * chest pains
Q. How common is Legionnaires' disease?
- A. It is estimated that in the United States there are between 10,000 and 50,000 cases each year.
Q. How does a person get Legionnaires' disease?
- A. A person must be exposed to water contaminated with Legionella bacteriua. This exposure may happen by inhaling or drinking water contaminated with the Legionella bacteria. For example, inhaling contaminated water mist from a cooling tower, a humidifier, or even a shower or sink can cause the disease.
Q. How soon after being exposed will a person develop symptoms of the disease?
- A. If infection occurs, disease symptoms usually appear within 2 to 10 days.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Q. Are some people at a higher risk of developing Legionnaires' disease?
- A. Yes, some people have lower resistance to disease and are more likely to develop Legionnaires' disease. Some of the factors that can increase the risk of getting the disease include:
- * organ transplants (kidney, heart, etc.), * age (older persons are more likely to get disease), * heavy smoking, * weakened immune system (cancer patients, HIV-infected individuals), * underlying medical problem (respiratory disease, diabetes, cancer, renal dialysis, etc.), * certain drug therapies (corticosteroids), and * heavy consumption of alcoholic beverages.
Q. Is Legionnaires' disease spread from person to person?
- A. No. Legionnaires' disease is not contagious and cannot be transmitted from one person to another.
Q. What causes Legionnaires disease?
- A. Legionnaires' disease is caused by inhaling water contaminated with rod-shaped bacteria called Legionella pneumophila. There are over 30 different species of Legionella, many of which can cause disease. Legionella pneumophila is the most common species that causes disease.
Q. Does everyone who inhales Legionella into the lungs develop Legionnaires' disease?
- A. No. Most people have resistance to the disease. It is thought that fewer than 5 out of 100 persons exposed to water contaminated with Legionella will develop Legionnaires' disease.
Q. Is Legionnaires' disease easy to diagnose?
- A. No. The pneumonia caused by Legionella is not easy to distinguish from other forms of pneumonia. A number of diagnostic tests allow a physician to identify the disease. These tests can be performed on a sample of sputum, blood, or urine.
Q. How is Legionnaires' disease treated?
- A. Erythromycin is currently the antibiotic of choice. Early treatment reduces the severity and improves chances for recovery. In many instances this antibiotic may be prescribed without the physician's knowledge that the disease is Legionnaires' because erythromycin is effective in treating a number of types of pneumonia.
Q. How did Legionnaires' disease get its name?
- A. Legionnaires' disease got its name from the first outbreak in which the organism was identified as the cause. This outbreak occurred in 1976, in a Philadelphia hotel where the Pennsylvania American Legion was having a convention. Over 200 Legionnaires and visitors at this convention developed pneumonia, and some died. From lung tissue, a newly discovered bacterium was found to be the cause of the pneumonia and was named Legionella pneumophila.
Q. Is Legionnaire's disease a new disease?
- A. No, Legionnaires' disease is not new, but it has only recently been identified. Unsolved pneumonia outbreaks that occurred before 1976 are now known to have been Legionnaires' disease. Scientists are still studying this disease to learn more about it.
Q. Are Legionella bacteria widespread in the environment?
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- A. Yes, studies have shown that these bacteria can be found in both natural and man-made water sources. Natural water sources including streams, rivers, freshwater ponds and lakes, and mud can contain the organism in low levels.
Q. Could I get the disease from natural water sources?
- A. It is unlikely. In the natural environment the very low levels of this organism in water sources probably cannot cause disease.
Q. What water conditions are best for growth of the organism?
- A. Warm, stagnant water provides ideal conditions for growth. At temperatures between 68 degrees and 122 degrees F the organism can multiply. Temperatures of 90-105 degrees F are ideal for growth. Rust (iron), scale, and other micro-organisms can also promote the growth of Legionella.
Q. What common types of water are of greatest concern?
- A. Water mist from cooling towers or evaporative condensers, evaporative coolers (swamp coolers), humidifiers, misters, showers, faucets, and whirlpool baths can be contaminated with the organism and if inhaled or swallowed can cause the disease.
Q. Can Legionnaires' disease be prevented ?
- A. Yes. Avoiding water conditions that allow the organism to grow to high levels is the best means of prevention. Specific preventive steps include:
- * Regular maintenance and cleaning of cooling towers and evaporativecondensers to prevent growth of Legionella. This should include twice-yearly cleaning and periodic use of chlorine or other effective biocide.
- * Maintain domestic water heaters at 140 degrees F (60 degrees C). The temperature of the water should be 122 degrees F or higher at the faucet.
- * Avoid conditions that allow water to stagnate. Large water-storage tanks exposed to sunlight can produce warm conditions favorable to high levels of Legionella. Frequent flushing of unused water lines will help alleviate stagnation.
Q. Do you recommend that I operate my home water heater at 140 degrees F?
- A. Probably not if you have small children or infirm elderly persons who could be at serious risk of being scalded by the hot water. However, if you have persons living with you who are at high risk of contracting the disease, then operating the water heater at a minimum temperature of 140 degree F is probably a good idea.
Q. What can be done if a water system is already contaminated or is suspected of being contaminated?
- A. Special cleaning procedures can eliminate Legionella from water sources. In many cases these procedures involve the use of chlorine-producing chemicals or high water temperatures. Professional assistance should be sought before attempting to clean a water system.
Q. Can my home water heater also be a source of Legionella contamination?
- A. Yes, but evidence indicates that smaller water systems such as those used in homes are not as likely to be infected with Legionella as larger systems in work places and public buildings.
Q. Can Legionella bacteria cause other diseases?
- A. Yes. In addition to Legionnaires' disease, the same bacteria also cause a flu-like disease called Pontiac fever.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Q. How does Pontiac fever differ from Legionnaires' disease?
- A. Unlike Legionnaires disease, which can be a serious and deadly form of pneumonia, Pontiac fever produces flu-like symptoms that may include fever, headache, tiredness, loss of appetite, muscle and joint pain, chills, nausea, and a dry cough. Full recovery occurs in 2 to 5 days without antibiotics. No deaths have been reported from Pontiac fever.
Q. Are there other differences between Legionnaires' disease and Pontiac fever?
- A. Yes. Unlike Legionnaires' disease, which occurs in only a small percentage of persons who are exposed, Pontiac fever will occur in approximately 90% of those exposed. In addition, the time between exposure to the organism and appearance of the disease (called the incubation period) is generally shorter for Pontiac fever than for Legionnaires' disease. Symptoms of Pontiac fever can appear within one to three days after exposure.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
APPENDIX II:7-2. Physical Survey and Water Sampling Protocol(*) __________________________________________________________________________
__________
Footnote(*) Source: Dennis, P. J. L. "An Unnecessary Risk: Legionnaires' Disease" in Biological Contaminants in Indoor Environments, ASTP STP 1071, P. R. Morey, J. C. Feeley, Sr., and J. A. Otten, Eds. American Society for Testing and Materials, Philadelphia. 1990.
Arrange with the appropriate laboratory for supply and shipment of sterile sampling containers, and for analysis of water samples. During the initial walk-through, estimate the size of the building and the number of water services at the facility to determine the number of samples and the size of the purchase order.
When investigating the water services within a building, it will be helpful to obtain or prepare a simple schematic diagram of the water services. Note the following features:
1. The location of the incoming supply and/or private source.
2. The location of storage tanks, water treatment systems, and pumps.
3. The location of water heaters and boilers.
4. The type of fittings used in the system (e.g., taps, showers, valves) and the material from which the pipework is made.
5. The location of all cooling towers, evaporative condensers, and fluid coolers at the facility. The location and type of all systems served by the cooling tower water including sump tanks, condensers, and indirect evaporative cooling coils in air handling units.
6. The location of any evaporative cooling systems or humidifiers.
7. The location of ornamental fountains, whirlpools, eye washes, safety showers, or other water sources within or near the facility.
Trace the route of the service from the point of entry of the water supply. Note the condition of pipes, jointing methods used, insulation, sources of heat, and the kind of insulation in water storage tanks. Also note carefully any disconnected fittings, "dead legs," and cross-connections with other services.
Once you have identified these features, take water samples from:
1. The incoming water supply.
2. Each storage tank and water heater.
3. A representative number of faucets for each of the hot and cold water systems in the facility.
4. All cooling towers, evaporative condensers, humidifiers, spas, showers, etc.
5. The water entering or leaving any other type of fitting or piece of equipment under particular suspicion.
It is important not to overlook any potential water sources in the building. Water from ice machines, hand spray bottles, decorative fountains, and for plastic injection molding equipment have been implicated in past outbreaks or have been found to be significantly contaminated. The ability to maintain an open mind is essential in conducting an investigation because of the variety of potential sources of contamination at a facility.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
WATER SAMPLING PROCEDURE
Wear appropriate respiratory protection in the form of a half-face piece respirator equipped with a HEPA filter or a similar type of filter media capable of effectively collecting particles in the one micron size range during the examination of water systems if a significant potential exists for exposure to high concentrations of contaminated aerosols.
Collect samples in polypropylene (nalgene) containers (250 mL-1 L) that have been autoclaved at 121 degrees C for 15 minutes. The microbiological laboratory that will analyze the samples should be able to provide the bottles. A local hospital or state health department should be able to autoclave the bottles. It is important not to flush the system to be sampled before collecting samples. Collect at least a 250 mL sample. Measure the temperature of the sampled water. It is preferable to accomplished this by measuring the water stream flowing from the water source and not by placing thethermometer in the sample container. To avoid cross-contamination of the samples, sanitize the thermometer with isopropyl alcohol before measuring the temperature of each sample. When measuring temperature from faucets, showers, water fountains, etc., record the initial water temperature, and then allow the fixture to discharge until the temperature stabilizes. Record the initial and final temperatures, and the time needed to stabilize.
DOMESTIC WATER HEATERS
- 1. Take a sample of water from the bottom drain.
- 2. Collect a sample of water from the outlet pipe if the plumbing provides for access.
FAUCETS AND SHOWERS
- 1. Collect a "before-flush" (initial flow) sample of water.
- 2. Collect an "after-flush" sample of water when the maximum temperature has been reached.
The initial (before-flush) sample is intended to indicate the level of contamination at the sample point or fitting, and the final sample should reveal the quality of the water being supplied to the fitting. Collect sterile-swab samples from faucets or shower heads by removing the fitting and vigorously swabbing the interior. Swab samples may be positive for Legionella even when water samples from the source are negative. Sterile test tubes containing sterilized swabs are available for convenient sampling and shipping.
COOLING TOWERS
- 1. Take a sample from the incoming supply to the tower.
- 2. Take samples from any storage tanks or reservoirs in the system (i.e., chilled-water return tanks or header tanks).
- 3. Take a sample from the basin of the cooling tower at a location distant from the incoming make-up water, and from the water returning from the circulation system at the point of entry to the tower.
- 4. Take a sample of any standing water in the condensate trays or from the cooling coils.
HUMIDIFIERS, SWAMP COOLERS, AND SPAS
Take a sample from the water reservoirs. Sample the incoming water supply if it is accessible.
For cooling towers, humidifiers, swamp coolers, and building water services, collect samples of sludge, slimes, or sediments, particularly where accumulations occur. Take swabs of shower heads, pipes, and faucets and rehydrate from water taken from the sampling site. Swab areas of scale buildup (i.e., remove shower heads, faucet screens, and aerators). Use prepackaged sterile swabs and small glass or polypropylene bottles (autoclaved) for this purpose.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SAMPLE TRANSPORTATION
Prepare samples for shipment carefully.
- 1. Wrap vinyl tape clockwise around the neck of each bottle to hold its screw cap firmly in place and seal the interface between the cap and the bottle.
- 2. Wrap absorbent paper around bottles, and place the bottles in a sealable (zip-lock) plastic bag.
- 3. Place the sealed plastic bag in an insulated container (styrofoam chest or box).
Samples should not be refrigerated or shipped at reduced temperature. They should be protected from temperature extremes such as sunlight or other external heat or cold sources. Ship to laboratory using overnight mail. If shipping on a Friday, make arrangements for weekend receipt. The samples should be stored at room temperature (20 degrees +/- 5 degrees C) and processed within 2 days.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
APPENDIX II:7-3. WATER SAMPLING GUIDELINES(*) __________________________________________________________________________
__________
Footnote(*) Adapted from George K. Morris, Ph.D., and Brian G. Shelton, Pathcon Technical Bulletin 1.3, Legionella in Environmental Samples: Hazard Analysis and Suggested Remedial Actions, June 1991, Pathogen Control Association, 270 Scientific Dr., Suite 3, Norcross, Georgia 30092.
Use the following guidelines to assess the effectiveness of water system maintenance. These guidelines are based on limited data and are subject to change. They are intended to apply only to water systems being used by healthy individuals and are not necessarily protective for persons who are immunocompromised.
The levels requiring action vary for the source of exposure based on the assumption that some routes or exposure result in a greater dose to the lung. For this reason, humidifiers and similar devices such as misters and evaporative condensers which produce an aerosol mist that can be directly inhaled should be controlled to lower levels. Remember that these numbers are only guidelines, and the goal is zero detectable Legionella in a water source. Levels of Legionella equal to or greater than the values in the table constitute a need for action, as described below.
Action 1: Prompt cleaning and/or biocide treatment of the system.
Action 2: Immediate cleaning and/or biocide treatment. Take prompt steps to prevent employee exposure.
- 1 100 10 1 2 1000 100 10
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
APPENDIX II:7-4. LEGIONNAIRES' DISEASE CASE IDENTIFICATION ___________________________________________________________________________
The purpose of this phase of an investigation will be to identify cases of Legionnaires' disease among the workers. The investigation will include identification of all employees who took three or more consecutive days of sick leave days from six weeks before the Legionnaires' case was identified to the present. Following a screening process, all employees who have been identified as having had pneumonia, or potentially having had pneumonia, during this period will be requested to undergo voluntary medical testing to detect evidence of Legionnaires' disease. A physician's diagnosis of pneumonia or pneumonia-like symptoms that include a fever (101 degrees F) and cough indicate a need for further evaluation. A sample program is described below:
1. Examine sick-leave records to identify all employees who used three or more consecutive days of sick leave from 6 weeks before the earliest known case to the present. These employees will be interviewed. If it appears that a employee experienced a pneumonia-like illness, the attached surveillance questionnaire will be completed. Employees who feel that they might have had symptoms of Legionnaires' disease but did not use three or more consecutive days of sick leave should also be interviewed.
2. Employees who have experienced a pneumonia-like illness and have seen a physician should be requested to sign a medical release form to allow the company and/or OSHA to obtain additional information from the physician.
3. The physicians of all employees who have seen a physician and have signed a medical release will be interviewed using the physician interview survey form (attached).
4. Employees participating in surveys such as the one described above must be informed of their Privacy Act rights as well as their right to protect their own medical information. Physician-patient confidentiality must not be violated. Necessary medical information may be communicated only with the patient's written permission. When seeking employees' permission, clearly inform them that the purpose of obtaining a proper diagnosis and sharing this information with the Agency is to protect them and their fellow workers against the potential threat of legionellosis. All medical records will be handled in accordance with 29 CFR 1913.10. It may be necessary for the CSHO to obtain medical releases from the employees interviewed so that amplifying information can be obtained from a company health unit or the employee's physician.
5. Arrangements similar to that described above should be sought for permanent contract employees controlled by separate contractor organizations in the building, e.g., janitors, cafeteria workers, security personnel.
6. Based on an interview with the employee's physician, potential cases should be considered for a clinical test to detect additional cases. Most probably this will be a serological test to determine the antibody level of the individual. A single antibody titer of 1/256 or greater based on a physician's diagnosis of pneumonia should be interpreted as a probable case of Legionnaires' disease. In the event that a antibody titer level for Legionella was obtained at the time of illness, or if serum collected from the patient at the early phase of the illness (acute phase) is available, then an antibody titer level should be determined from this sample to determine the convalescent to acute titer ratio. A fourfold increase in this titer will be sufficient to confirm a case of Legionnaires' disease.
7. Other diagnostic tests may also be appropriate. If the potential case occurred recently, then a urine antigen test may detect
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- Legionella pneumophila serogroup-1 antigen. A positive urine antigen test for a diagnosed pneumonia case is also accepted as a evidence of a confirmed case. However, this test is available only for Legionella pneumophila serogroup-1 infections. Culture currently symptomatic individuals for Legionella. A positive culture indicates confirmation.
8. If this process detects one or more additional cases of disease, then the facility should be considered to have experienced an outbreak. The immediacy of the action will depend on whether the outbreak is ongoing or occurred 30 days or more in the past.
9. Take prompt action to control exposure at the site if there is evidence that the outbreak is still occurring. Whatever the circumstances, initiate control procedures and continue medical surveillance of the workforce to detect any new cases of disease and identify the water source responsible for the outbreak.
______________________________________________________________________
- HEALTH SURVEILLANCE QUESTIONNAIRE - LEGIONELLOSIS
Records show that you took sick leave for three consecutive days or more. We would like to ask a few questions.
1. Name: (last)____________________,(first)__________________
- Age:______ Sex: ______ Work Location: ____________________
- Home Phone:___________ Work Phone:________________________
2. Dates of absence(s):______________________________________
3. Stated reason for absence:________________________________
Ask about the following symptoms:
4. Fever: Yes ____ No____ If yes, highest temperature _____.
5. Cough: Yes____ No ____
6. Headache: Yes_____ No_____
7. Diarrhea: Yes_____ No_____
8. Shortness of breath: Yes ____ No ____
9. Chest pain: Yes ____ No ____
10. Did you see a physician about these symptoms? Yes ___ No ___
- Was a chest x-ray taken? Yes_____ No_____
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- Were you diagnosed as having pneumonia? Yes ___ No ___
- Were you tested for legionellosis? Yes_____ No_____
- Physician's name:______________________Phone:_____________
- Physician's Address:______________________________________
11. Were you admitted to a hospital? Yes ____ No ____
- If yes, which hospital?_____________________________________
- Admission Date: _________________ Date released: __________
12. Interviewer:_____________________________Date:______________
________________________________________________________________________
We are calling to inform you that _______________________ is a patient of yours and an employee at ____________. He/she has signed a medical release giving us permission to contact you to obtain information about her/his recent illness. This questionnaire will be used to determine if your patient's recent illness could be classified as a pneumonia that may have been caused by exposure to Legionella at the workplace.
1. Name of Physician: _______________________________________
- Address:__________________________________________________
- Phone:_____________________________
2. Date of visit(s): (1st)________ (2nd)________ (3rd)________
3. What was the patient's complaint?:_________________________
- ___________________________________________________________
- Cough? yes no unknown Short of breath? yes no unknown History of fever? yes no unknown
4. Physical Findings: _______________________________________
- __________________________________________________________
- Abnormal chest or lung findings: _________________________
- __________________________________________________________
- Rales? yes no not examined Dyspnea? yes no not examined Cyanosis? yes no not examined Temperature ______
- Other: __________________________________________________
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
5. Chest X-ray done? yes no
6. Sputum culture? yes no
- Results: ______________________________________________
- Sputum cultured for Legionella? yes no Laboratory:___________________________________________
7. Diagnostic testing? yes no
- Type of test: Urine Antigen Test, Direct Fluorescent Antibody Serology Tests:
- Indirect Fluorscent Antibody (IFA) ______
- ELISA ________
8. Diagnosis or impression: _____________________________________
______________________________________________________________________
Background
Employee's Name:_________________________ Age:_____ Gender:_____
(last, first) Home:_____________________________________________________________
- (city, zip)
Race/Ethnicity: white, black, native American, Hispanic, Asian
Other (circle one)
Are you currently taking any oral steroid medications?: Y/N
On what date did you first become ill?: ---/---/---
How many days were you ill?: _______
Was anyone else in your family ill?: Y/N
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
If Yes, who? ______________________________________
What symptoms did they have? ______________________________
Since ___________, have any of your friends been diagnosed with pneumonia?: Yes/No
If Yes, who? _______________________________________________
Work Exposure
During the 10 days prior to your illness:
Job Description: ________________________________________________
Primary work area: ______________________________________________
list all areas in _______ building where you spend any time:
- Area Hours per week
_______________________________ _______________________________
_______________________________ _______________________________
_______________________________ _______________________________
_______________________________ _______________________________
_______________________________ _______________________________
Did you shower at work?: Yes/No
If Yes, where and how may times per week?: _________________
List all places you eat lunch:____________________________________
List all places where you take break: ____________________________
List all restrooms you use: ______________________________________
Do you smoke in the restrooms (or spend "extra" time, i.e., if a lounge is present): Yes/No
If Yes, Where:_______________________________
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Did you attend any training courses outside of the building?: Yes/No
If Yes, where were they held? _______________________________
Do you have a second job?: Yes/No
If Yes, what job and where:
_________________________________________________________________
Any other places that you have not mentioned where you spend time while on the job?:
__________________________________________________________________
Community Exposure (During the 10 days prior to your illness)
Did you use any health clubs?: Yes/No
If Yes, which ones?: ________________________________________
How many times?______________________________________________
Did you use any hot tubs (whirlpool spas)?: Yes/No
If Yes, list which hot tubs and when used:
_____________________________________________________________
Did you attend any churches?: Yes/No
If Yes, where_________________________________________
How many times?____________
Have you had any dental work performed? Yes/No
If Yes, where_________________________________________
How many times?____________
Which grocery stores did you go to?: _____________________________
How often?__________________
Did you go to the movies?: Yes/No
If Yes, which one? ________________________________
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
How often?____________
Did you go to any shopping malls?: Yes/No
If Yes, which one(s)?__________________________
Did you go to any other public places which you feel might be significant (i.e. public meetings, schools etc.)?: Yes/No
If Yes, where? ___________________________________________
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
APPENDIX II:7-5. WATER TREATMENT PROTOCOLS FOR FACILITIES THAT
_________________________________________________________________________
BACKGROUND
This section describes actions required to abate the threat of further infection in a building in which an outbreak of Legionnaires' disease has occurred. For purposes of this document, an "outbreak of Legionnaires' disease" may be said to exist when medically confirmed cases of Legionnaires' disease are epidemiologically associated with a building or some portion of a building. This usually means that two or more confirmed cases of Legionnaires' disease have been identified within a six-week period at the site.
Under most circumstances evacuation of the building is not recommended. It will be necessary, following confirmation of an outbreak, to isolate individuals who are at high risk of contracting the disease from all potential sources of infection. Individuals at high risk include the immunosuppressed, such as persons who have had organ transplants, individuals receiving chemotherapy including corticosteriods, and other individuals in poor health. In addition, a medical monitoring program must be instituted to track all workers currently on sick leave.
Following these initial actions, the building must be inspected to identify all potential Legionella sources including the HVAC cooling systems (cooling towers, evaporative condensers), domestic water systems, humidifiers, and any sources of water that is maintained above 20ø C (68ø F) and has a potential for being aerosolized.
Before flushing or disinfecting the water in these suspected sources, take water samples for analysis to determine the predominant serotypes and subtypes of L. pneumophila in the water source and to determine the number of colony forming units (CFU) per unit of water. This information will be helpful in identifying the source of the disease if the subtype of L. pneumophila has been identified in the afflicted worker population. Because of the 10-day to two-week delay in obtaining sample results, corrective action should begin immediately.
Because sampling for Legionella can be inconclusive, sampling results alone should not determine the appropriate course of action in a building where an outbreak has occurred. ALL POTENTIAL SOURCES OF CONTAMINATION WILL BE ASSUMED TO BE CONTAMINATED AND TREATED ACCORDINGLY IN THE EVENT THAT AN OUTBREAK HAS OCCURRED. Water sampling and testing must be in accordance with currently accepted, state-of-the-art procedures.
Treatment of potential sources of contamination following sampling is described below. After the treatment collect and analyze water samples for CFU of L. pneumophila to determine the effectiveness of the treatment. Upon re-use of a water system following treatment, periodic maintenance and regular water sampling are essential to ensure that the maintenance continues to be effective. Included are proper maintenance procedures for controlling the organism in a facility's water sources.
COOLING TOWERS AND EVAPORATIVE CONDENSERS
An HVAC condenser water system absorbs heat from the AC refrigeration units and rejects it to the atmosphere through evaporation in cooling towers. Evaporative condensers operate similarly to cooling towers except
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
that refrigerant coils are inside the water path, and water passes over the coils to cool the refrigerant gas directly. Because both cooling towers and evaporative condensers use a fan system to move air through a recirculated water system, they introduce a considerable amount of water vapor into the surroundings even with drift eliminators designed to limit vapor release. In addition, this water is typically in the 20-50 degrees C (68-122 degrees F) range, ideal for L. pneumophila growth.
WATER SAMPLING PROTOCOL
Before starting decontamination, collect an adequate number of water samples in sterile containers. These samples should be cultured to determine the degree of contamination and the subtype of L. pneumophila before treatment. Collect at least three water samples (200 milliliters to 1 liter volume). Include water from the incoming make-up water supply, water from the basin of the unit most distant from the make-up water source, and recirculated water from the HVAC system at its point of return to the unit.
CLEAN-UP PROCEDURE
- 1. Clean and disinfect the entire cooling system including attached chillers and/or storage tanks (sumps) following the "Wisconsin Protocol" Emergency Protocol.
- a. "Shock" treat cooling tower water at 50 ppm free residual chlorine.
- b. Add dispersant. c. Maintain 10 ppm chlorine for 24 hours. d. Drain system. e. Refill and repeat steps a through d. f. Inspect system for visual evidence of biofilm. If found, repeat steps a through d.
- g. Perform mechanical cleaning (cooling tower design may require modified procedures).
- h. Refill system, bring chlorine to 10 ppm, and circulate for one hour.
- i. Flush system. j. Refill with clean water in accordance with an effective water treatment program. The unit is now ready to be returned to service.
- 2. Identify and eliminate all water leaks into the cooling water system.
- 3. After completing step 1, sample the cooling water for analysis of CFU of L. pneumophila. The unit may be put into service provided the medical monitoring program has been implemented. If sample culture results indicate detectable levels of L. pneumophila, repeat chlorination and resample the water.
- 4. Once the nondetectable level for L. pneumophila has been achieved, institute maintenance as outlined in the Wisconsin Protocol to insure continued safe and proper operation.
- a. Inspect equipment monthly. b. Drain and clean quarterly. c. Treat circulating water for control of microorganisms, scale, and corrosion. This should include systematic use of biocides and rust inhibitors, preferably supplied by continuous feed, and monthly microbiologic analysis to ensure control of bacteria.
- d. Document operation and maintenance in a log or maintenance records book.
- 5. Test cooling-system water at the following intervals to verify that there is no significant growth of Legionella.
- a. Test weekly for the first month after return to operation. b. Test every two weeks for the next two months. c. Test monthly for the next three months.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
The standard for Legionella concentration throughout the six months of monitoring is fewer than 10 CFU per milliliter (based on PathCon guidelines). If no water samples exceed this level, monitoring may be suspended. The maintenance program must continue indefinitely.
If any sample contains 10 or more CFU Legionella per milliliter, take immediate steps to reduce levels to acceptable limits. These steps may include increased frequency of application or concentration of biocides, pH adjustment, additional "shock" treatments, or any other action that reduces Legionella levels. Take new water samples and begin the testing schedule again.
Make the results of all water monitoring tests available to building occupants.
DOMESTIC WATER SYSTEMS
Domestic water systems are designed to provide heated water for washing, cleaning, consumption, etc. A large building may have multiple independent systems. These systems usually include a boiler or heater, a recirculating piping system, and pipes terminating in taps and fixtures. Operating temperatures vary depending on system design, energy conservation programs, and intended use of the water. It is recommended that water heaters be kept at a minimum of 60 degrees C (140 degrees F) and all water be delivered at each outlet at a minimum of 50 degrees C (122 degrees F).
It is essential to identify all parts of the domestic water systems where water may stagnate (e.g., "dead legs" or laterals that have been capped off, storage tanks that have "dead zones" or are not frequently used). For treatment to be effective, the stagnant zones must be removed from the system. Rubber and plastic gaskets in the plumbing system may also serve as a Legionella growth medium. Eliminate or minimize use of these materials and substitute materials not conducive to Legionella growth. It is also important to identify and test the integrity of all backflow preventers to assure protection of domestic water from cross-contamination with process water through a building code-approved method.
WATER SAMPLING PROTOCOL
Collect water samples before beginning treatment to determine potential contamination. Draw 200 milliliters to 1 litr of water from the draw-off valve of all water heaters into a sterile container. Check the temperature of the water in these units to determine if it is significantly lower than the set temperature. Sample a representative number of domestic hot-water faucets or outlets. It is important not to flush the faucet before taking a sample because the end section of the water system may be a source of contamination. Collect a 200 milliliter to 1 liter "preflush sample" of the first hot water drawn from the outlet. Allow the water to run and measure the temperature, and then collect a second, "postflush" sample when the water temperature is constant. Submit the water samples to a laboratory qualified to measure CFU of Legionella per milliliter of water.
Use the clean-up procedure below to treat all hot-water systems that have either been tested and found to contain detectable levels of Legionella or have been assumed to be contaminated.
CLEAN-UP PROCEDURE
- 1. Disinfect the system using any effective chemical, thermal, or other treatment method. For example:
- a. Pasteurize the hot water system by heating the water to at least 70 degrees C (158 degrees F) and maintain this temperature for a minimum of 24 hours. Maintaining the temperature at 70 degrees C (158 degrees F) and continuously flush each faucet on the system with hot water for 20 minutes.
- b. Use an accepted chemical disinfectant such as chlorine or an acceptable biocide treatment to clean the system. Thoroughly flush the system after treatment to remove all traces of the corrosive and possibly toxic chemicals.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- c. Follow any other technique that has demonstrated effectiveness and safety.
- 2. Maintain domestic water heaters at 60 degrees C (140 degrees F) and water delivered at the faucet at a minimum of 120 degrees F (50 degrees C). Where these temperatures cannot be maintained, control Legionella growth with a safe and effective alternative method.
- 3. After treatment, resample the hot water from each storage tank. If Legionella are detected, re-treat and resample the water system. If no measurable levels are found in this system and all other potential sources have also been addressed, go to the next step.
- 4. Test the domestic hot- or warm-water system for Legionella on the following schedule to assure that recontamination has not occurred:
- a. Weekly for the first month after resumption of operation.
- b. Every two weeks for the next two months. c. Monthly for the next three months.
Use the Pathcon criteria for Legionella in domestic water systems during the monitoring period. If 10 or more CFU per milliliter of water are present, re-treat the system according to steps 1-3 above. Resume weekly testing (step 4a) after retreatment. If levels remain below 1 CFU per milliliter, no further monitoring is necessary. If the levels are between 1 and 9 CFU per milliliter, continue monthly sampling of the water indefinitely and continue efforts to determine the source of contamination.
Make test results available to building residents.
TEPID WATER SYSTEMS
Warm-water systems or tepid water systems dilute domestic hot water from a water heater with cold water upstream from the outlet source are not recommended. Warm water left in these lines is at ideal temperatures for amplification of L. pneumophila. Localized mixing at the source to temper very hot water is more acceptable. Another alternative is "instantaneous" point of delivery heating of water using individual steam heating systems at each outlet.
DOMESTIC COLD-WATER SYSTEMS
Domestic cold-water systems are designed to provide water for drinking, washing, cleaning, toilet flushing, etc. These systems have not been a major source of concern for Legionnaires' disease because L. pneumophila will not amplify at low temperatures. Cold-water storage and delivery should be at less than 20 degrees C (68 degrees F) to minimize potential for growth. Cold-water lines near hot-water lines should be insulated. Try to eliminate stagnant places in the system as dead legs or storage tanks that are not routinely used.
Detectable levels of L. pneumophila in the system may indicate contamination of the source water supply and should represent the maximum allowable level in the system.
If sampling of the system indicates a level of contamination significantly greater than that of the incoming domestic water supply system, treat the system and identify the source of contamination or amplification. By definition, these systems have no provision for heating water, and therefore disinfection cannot be by heat treatment.
Follow the clean-up procedure below if cold-water systems are shown to contain measurable Legionella or are assumed to be contaminated.
CLEAN-UP PROCEDURE
- 1. Clean and disinfect all cold water systems including storage tanks, drinking fountains, water lines, and water outlets.
- a. Use an accepted chemical disinfectant such as chlorine or other acceptable biocide.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- b. Use any other technology that has been shown to be safe and effective.
- 2. Ensure that cold-water systems are maintained so that conditions do not promote growth of Legionella. Maintain temperatures 20 degrees C (68 degrees F) and keep residual chlorine in the range of 1-2 ppm. In practice this level of chlorination may be objectionable and may also be excessively corrosive to metal pipes and containers.
- 3. Take samples according to sampling guidelines. If analysis shows no detectable Legionella and all other potential sources have been addressed, go to step 4.
- 4. Flush all cold-water outlets and fountains for four minutes, twelve hours before re-entry.
- 5. When steps 1 through 4 have been successfully completed, return the building to normal operation but test the domestic cold-water system for Legionella according to the following schedule:
- a. Weekly for the first month after resumption of operation. b. Every two weeks for the next two months. c. Monthly for the next three months
The same criteria used for hot water systems described above will also be used for the cold-water system during the monitoring period. Ten or more CFU per milliliter of water require retreatment of the system according to steps 1-3 above. Following retreatment, resume weekly testing and repeat the schedule outlined in 4a-c. If Legionella levels remain below 1 CFU per milliliter, additional monitoring is not necessary. If levels are between 1-9 CFU per milliliter, continue monthly sampling of the water source indefinitely and try to identify the source of contamination.
Make monitoring results available to building occupants.
HVAC AIR DISTRIBUTION SYSTEMS
Under normal conditions HVAC systems are not likely to be sources of L. pneumophila unless water contaminated with the bacteria enters the system. Under normal conditions, condensate pans on coiling coils should not serve as a water source in which amplification of the bacteria can occur because the temperature of the water is below 20 degrees C (68 degrees F). Improperly drained condenser pans may produce tepid conditions that can encourage microbial and fungal growth. Proper maintenance will lessen problems related to other diseases such as humidifier fever and asthmatic responses, and will minimize the possibility of a Legionnaires' outbreak.
Most probably, for a Legionnaires' disease outbreak to be linked directly with the HVAC system, Legionella-contaminated water must continuously enter the system, be aerosolized, and be delivered to building occupants. Examine the systems to rule out this possibility.
- 1. Inspect the entire air distribution system (including return and exhaust systems) for visual evidence of water accumulation.
- 2. Eliminate all water leaks and remove any standing water found in the system. Replace or eliminate any water-damaged insulation in the system.
- 3. Operate the HVAC system using 100% outside air for 8 hours before returning the building to normal operation.
Sampling of air in the ducts to prove that the duct system is free of Legionella is not required and would be pointless. No reliable way to detect Legionella in the air is available, and Legionella can live only in water. If the ducts are dry, they cannot serve as a source of Legionella.
Following return of the building to normal operation, keep outside-air supply rates as high as possible for one month. At a minimum, the outdoor air requirements of ASHRAE Ventilation Standard 62-1989 must be met.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
HUMIDIFIERS AND MISTERS
Many HVAC systems supply humidified air to building occupants to maintain comfort. Improperly maintained humidifiers can be both amplifiers and disseminators of a variety of bioaerosols; however, generally the cool temperatures in HVAC systems are not conducive to growth of L. pneumophila. Cold-water humidifiers in HVAC systems must be connected to a domestic water source and provided with a drain line to remove the water. Stand-alone, console-type humidifiers that re-circulate water for humidification should not be used because the water in these systems becomes contaminated with micro-organisms rapidly. These stand-alone units have been linked to an outbreak of Legionnaires' disease in a hospital. Ideally, HVAC humidifiers should use steam injection systems that eliminate potential microbe problems.
Cold-water humidifiers require rigorous maintenance to ensure that the water source does not contribute to potential problems. Since humidifiers discharge into HVAC air distribution systems, inspect for standing water and treat according to the HVAC Air Distribution System protocol above. Where water in humidifiers has been sampled and shown to contain measurable Legionella, or where such water has been assumed to be contaminated with Legionella, use the following protocol.
- 1. Disinfect water in piping or reservoirs feeding the humidifier with chlorine or other effective biocides.
- 2. Sample the humidifier water to assure "kill" of Legionella. Samples must have no detectable CFU of Legionella per milliliter of water. If one or more are detected, repeat treatment and sampling.
- 3. Ensure that an adequate maintenance program is in effect to reduce the growth of Legionella. Water storage temperatures should be above or below the 20-50 degrees C (68-122 degrees F) range, and the system must be kept clean.
- 4. Before using the humidifier, flush the piping and/or reservoir thoroughly to remove biocides.
- 5. When steps 1 through 4 have been successfully completed, return the humidifier to operation and test the unit's water system to detect recontamination with Legionella according to the schedule below:
- a. Weekly for the first month. b. Every two weeks for the next two months. c. Monthly for the next three months.
The criterion for Legionella in humidifier water systems during monitoring is fewer than 1 CFU per milliliter. If no samples exceed the criterion, suspend monitoring and continue the maintenance program indefinitely.
If any sample shows 1 or more CFU of Legionella per milliliter, re-treat and retest the system according to the schedule above (4a-c).
Make monitoring results available to building occupants.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SECTION III: CHAPTER 2
PETROLEUM REFINING PROCESSES
A. INTRODUCTION _____________________________________________________________________
The petroleum industry began with the successful drilling of the first commercial oil well in 1859, and the opening of the first refinery two years later to process the crude into kerosene. The evolution of petroleum refining from simple distillation to today's sophisticated processes has created a need for health and safety management procedures and safe work practices. To those unfamiliar with the industry, petroleum refineries may appear to be complex and confusing places. Refining is the processing of one complex mixture of hydrocarbons into a number of other complex mixtures of hydrocarbons. The safe and orderly processing of crude oil into flammable gases and liquids at high temperatures and pressures using vessels, equipment, and piping subjected to stress and corrosion requires considerable knowledge, control, and expertise.
Safety and health professionals, working with process, chemical, instrumentation, and metallurgical engineers, assure that potential physical, mechanical, chemical, and health hazards are recognized and provisions are made for safe operating practices and appropriate protective measures. These measures may include hard hats, safety glasses and goggles, safety shoes, hearing protection, respiratory protection, and ___________________________________________________________________
| | | A. Introduction ...................................... III:2-1 | | B. Overview of the Petroleum Industry ................ III:2-2 | | C. Petroleum Refining Operations .................... III:2-11 | | D. Description of Petroleum Refining Processes and | | Related Health and Safety Considerations ..... III:2-15 | | E. Other Refinery Operations ........................ III:2-49 | | F. Bibliography ..................................... III:2-58 | | Appendix III:2-1. Glossary ............................ III:2-59 | |___________________________________________________________________|
protective clothing such as fire resistant clothing where required. In addition, procedures should be established to assure compliance with applicable regulations and standards such as hazard communications, confined space entry, and process safety management.
This chapter of the technical manual covers the history of refinery processing, characteristics of crude oil, hydrocarbon types and chemistry, and major refinery products and by-products. It presents information on technology as normally practiced in present operations. It describes the more common refinery processes and includes relevant safety and health information. Additional information covers refinery utilities and miscellaneous supporting activities related to hydrocarbon processing. Field personnel will learn what to expect in various facilities regarding typical materials and process methods, equipment, potential hazards, and exposures.
The information presented refers to fire prevention, industrial hygiene, and safe work practices, and is not intended to provide comprehensive guidelines for protective measures and/or compliance with regulatory requirements. As some of the terminology is industry-specific, a glossary is provided as an appendix. This chapter does not cover petrochemical processing.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
B. OVERVIEW OF THE PETROLEUM INDUSTRY _____________________________________________________________________
BASIC REFINERY PROCESS -- DESCRIPTION AND HISTORY
Petroleum refining has evolved continuously in response to changing consumer demand for better and different products. The original requirement was to produce kerosene as a cheaper and better source of light than whale oil. The development of the internal combustion engine led to the production of gasoline and diesel fuels. The evolution of the airplane created a need first for high-octane aviation gasoline and then for jet fuel, a sophisticated form of the original product, kerosene. Present-day refineries produce a variety of products including many required as feedstocks for the petrochemical industry.
DISTILLATION PROCESSES
The first refinery, opened in 1861, produced kerosene by simple atmospheric distillation. Its by-products included tar and naphtha. It was soon discovered that high-quality lubricating oils could be produced by distilling petroleum under vacuum. However, for the next 30 years kerosene was the product consumers wanted. Two significant events changed this situation: (1) invention of the electric light decreased the demand for kerosene, and (2) invention of the internal combustion engine created a demand for diesel fuel and gasoline (naphtha).
THERMAL CRACKING PROCESSES
With the advent of mass production and World War I, the number of gasoline-powered vehicles increased dramatically and the demand for gasoline grew accordingly. However, distillation processes produced only a certain amount of gasoline from crude oil. In 1913, the thermal cracking process was developed, which subjected heavy fuels to both pressure and intense heat, physically breaking the large molecules into smaller ones to produce additional gasoline and distillate fuels. Visbreaking, another form of thermal cracking, was developed in the late 1930s to produce more desirable and valuable products.
CATALYTIC PROCESSES
Higher-compression gasoline engines required higher-octane gasoline with better antiknock characteristics. The introduction of catalytic cracking and polymerization processes in the mid- to late 1930s met the demand by providing improved gasoline yields and higher octane numbers.
Alkylation, another catalytic process developed in the early 1940s, produced more high-octane aviation gasoline and petrochemical feedstocks for explosives and synthetic rubber. Subsequently, catalytic isomerization was developed to convert hydrocarbons to produce increased quantities of alkylation feedstocks. Improved catalysts and process methods such as hydrocracking and reforming were developed throughout the 1960s to increase gasoline yields and improve antiknock characteristics. These catalytic processes also produced hydrocarbon molecules with a double bond (alkenes) and formed the basis of the modern petrochemical industry.
TREATMENT PROCESSES
Throughout the history of refining, various treatment methods have been used to remove nonhydrocarbons, impurities, and other constituents that adversely affect the properties of finished products or reduce the efficiency of the conversion processes. Treating can involve chemical reaction and/or physical separation. Typical examples of treating are chemical sweetening, acid treating, clay contacting, caustic washing, hydrotreating, drying, solvent extraction, and solvent dewaxing. Sweetening compounds and acids desulfurize crude oil before processing and treat products during and after processing.
Following the Second World War, various reforming processes improved gasoline quality and yield and produced higher-quality products. Some of these involved the use of catalysts and/or hydrogen to change molecules and remove sulfur. A number of the more commonly used treating and reforming processes are described in this chapter of the manual.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Table III:2-1. History of Refining _____________________________________________________________________ Year Process name Purpose By-products, etc. 1862 Atmospheric distillation Produce kerosene Naphtha, tar, etc. 1870 Vacuum distillation Lubricants (original) Asphalt, residual Cracking feedstocks coker feedstocks (1930s) 1913 Thermal cracking Increase gasoline Residual, bunker fuel 1916 Sweetening Reduce sulfur & odor Sulfur 1930 Thermal reforming Improve octane number Residual 1932 Hydrogenation Remove sulfur Sulfur 1932 Coking Produce gasoline Coke basestocks 1933 Solvent extraction Improve lubricant Aromatics viscosity index 1935 Solvent dewaxing Improve pour point Waxes 1935 Cat. polymerization Improve gasoline Petrochemical yield & octane feedstocks number 1937 Catalytic cracking Higher octane Petrochemical gasoline feedstocks 1939 Visbreaking Reduce viscosity Increased distillate, tar 1940 Alkylation Increase gasoline High-octane aviation octane & yield gasoline 1940 Isomerization Produce alkylation Naphtha feedstock 1942 Fluid catalytic Increase gasoline Petrochemical cracking yield & octane feedstocks 1950 Deasphalting Increase cracking Asphalt feedstock 1952 Catalytic reforming Convert low-quality Aromatics naphtha 1954 Hydrodesulfurization Remove sulfur Sulfur 1956 Inhibitor sweetening Remove mercaptan Disulfides 1957 Catalytic Convert to molecules Alkylation isomerization with high octane feedstocks number 1960 Hydrocracking Improve quality and Alkylation reduce sulfur feedstocks 1974 Catalytic dewaxing Improve pour point Wax 1975 Residual Increase gasoline Heavy residuals hydrocracking yield from residual _____________________________________________________________________
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and technology Assessment
BASICS OF CRUDE OIL
Crude oils are complex mixtures containing many different hydrocarbon compounds that vary in appearance and composition from one oil field to another. Crude oils range in consistency from water to tar-like solids, and in color from clear to black. An "average" crude oil contains about 84% carbon, 14% hydrogen, 1-3% sulfur, and less than 1% each of nitrogen, oxygen, metals, and salts. Crude oils are generally classified as paraffinic, naphthenic, or aromatic, based on the predominant proportion of similar hydrocarbon molecules. Mixed-base crudes have varying amounts of each type of hydrocarbon. Refinery crude base stocks usually consist of mixtures of two or more different crude oils.
Relatively simple crude-oil assays are used to classify crude oils as paraffinic, naphthenic, aromatic, or mixed. One assay method (United States Bureau of Mines) is based on distillation, and another method (UOP "K" factor) is based on gravity and boiling points. More comprehensive crude assays determine the value of the crude (i.e., its yield and quality of useful products) and processing parameters. Crude oils are usually grouped according to yield structure.
Table III:2-2. Typical Approximate Characteristics and Properties and Gasoline Potential of Various Crudes (Representative average numbers) _____________________________________________________________________ Crude Paraffins Aroma- Naphth- Sulfur API Naph. Octane source tics enes gravity yield + number (% vol) (% vol) (% vol) (% wt) (approx.) (% vol) (typical) Nigerian 37 9 54 0.2 36 28 60 -Light Saudi 63 19 18 2 34 22 40 -Light Saudi 60 15 25 2.1 28 23 35 -Heavy Venezuela 35 12 53 2.3 30 2 60 -Heavy Venezuela 52 14 34 1.5 24 18 50 -Light USA - - - 0.4 40 - - -Midcont. Sweet USA 46 22 32 1.9 32 33 55 -W. Texas Sour North Sea 50 16 34 0.4 37 31 50 -Brent _____________________________________________________________________
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Crude oils are also defined in terms of API (American Petroleum Institute) gravity. The higher the API gravity, the lighter the crude. For example, light crude oils have high API gravities and low specific gravities. Crude oils with low carbon, high hydrogen, and high API gravity are usually rich in paraffins and tend to yield greater proportions of gasoline and light petroleum products; those with high carbon, low hydrogen, and low API gravities are usually rich in aromatics.
Crude oils that contain appreciable quantities of hydrogen sulfide or other reactive sulfur compounds are called "sour." Those with less sulfur are called "sweet." Some exceptions to this rule are West Texas crudes, which are always considered "sour" regardless of their H(2)S content, and Arabian high-sulfur crudes, which are not considered "sour" because their sulfur compounds are not highly reactive.
BASICS OF HYDROCARBON CHEMISTRY
Crude oil is a mixture of hydrocarbon molecules, which are organic compounds of carbon and hydrogen atoms that may include from one to 60 carbon atoms. The properties of hydrocarbons depend on the number and arrangement of the carbon and hydrogen atoms in the molecules. The simplest hydrocarbon molecule is one carbon atom linked with four hydrogen atoms: methane. All other variations of petroleum hydrocarbons evolve from this molecule.
Hydrocarbons containing up to four carbon atoms are usually gases; those with five to 19 carbon atoms are usually liquids; and those with 20 or more are solids. The refining process uses chemicals, catalysts, heat, and pressure to separate and combine the basic types of hydrocarbon molecules naturally found in crude oil into groups of similar molecules. The refining process also rearranges their structures and bonding patterns into different hydrocarbon molecules and compounds. Therefore it is the type of hydrocarbon, (paraffinic, naphthenic, or aromatic) rather than its specific chemical compounds that is significant in the refining process.
(For III:2-1, Click Here)
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
THREE PRINCIPAL GROUPS OR SERIES OF HYDROCARBON COMPOUNDS THAT OCCUR NATURALLY IN CRUDE OIL
PARAFFINS
The paraffinic series of hydrocarbon compounds found in crude oil have the general formula C(n)H(2n+2) and can be either straight chains (normal) or branched chains (isomers) of carbon atoms. The lighter, straight-chain paraffin molecules are found in gases and paraffin waxes. Examples of straight-chain molecules are methane, ethane, propane, and butane (gases containing from one to four carbon atoms), and pentane and hexane (liquids with five to six carbon atoms). The branched-chain (isomer) paraffins are usually found in heavier fractions of crude oil and have higher octane numbers than normal paraffins. These compounds are saturated hydrocarbons, with all carbon bonds satisfied, that is, the hydrocarbon chain carries the full complement of hydrogen atoms.
AROMATICS
Aromatics are unsaturated ring-type (cyclic) compounds which react readily because they have carbon atoms that are deficient in hydrogen. All aromatics have at least one benzene ring (a single-ring compound characterized by three double bonds alternating with three single bonds between six carbon atoms) as part of their molecular structure. Naphthalenes are fused double-ring aromatic compounds. The most complex aromatics, polynuclears (three or more fused aromatic rings), are found in heavier fractions of crude oil.
NAPHTHENES
Naphthenes are saturated hydrocarbon groupings with the general formula C(n)H(2n), arranged in the form of closed rings (cyclic) and found in all fractions of crude oil except the very lightest. Single-ring naphthenes (monocycloparaffins) with five and six carbon atoms predominate, with two-ring naphthenes (dicycloparaffins) found in the heavier ends of naphtha.
(For III:2-2, Click Here
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
OTHER HYDROCARBONS
ALKENES
Alkenes are mono-olefins with the general formula C(n)H(2n) and contain only one carbon-carbon double bond in the chain. The simplest alkene is ethylene, with two carbon atoms joined by a double bond and four hydrogen atoms. Olefins are usually formed by thermal and catalytic cracking and rarely occur naturally in unprocessed crude oil.
DIENES AND ALKYNES
Dienes, also known as diolefins, have two carbon-carbon double bonds. The alkynes, another class of unsaturated hydrocarbons, have a carbon-carbon triple bond within the molecule. Both these series of hydrocarbons have the general formula C(n)H(2n-2). Diolefins such as 1,2-butadiene and 1,3-butadiene, and alkynes such as acetylene occur in C(5) and lighter fractions from cracking. The olefins, diolefins, and alkynes are said to be unsaturated because they contain less than the amount of hydrogen necessary to saturate all the valences of the carbon atoms. These compounds are more reactive than paraffins or naphthenes and readily combine with other elements such as hydrogen, chlorine, and bromine.
NONHYDROCARBONS
SULFUR COMPOUNDS
Sulfur may be present in crude oil as hydrogen sulfide (H(2)S), as compounds (e.g., mercaptans, sulfides, disulfides, thiophenes, etc.), or as elemental sulfur. Each crude oil has different amounts and types of sulfur compounds, but as a rule the proportion, stability, and complexity of the compounds are greater in heavier crude-oil fractions. Hydrogen sulfide is a primary contributor to corrosion in refinery processing units. Other corrosive substances are elemental sulfur and mercaptans. Moreover, the corrosive sulfur compounds have an obnoxious odor.
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OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
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Pyrophoric iron sulfide results from the corrosive action of sulfur compounds on the iron and steel used in refinery process equipment, piping, and tanks. The combustion of petroleum products containing sulfur compounds produces undesirables such as sulfuric acid and sulfur dioxide. Catalytic hydrotreating processes such as hydrodesulfurization remove sulfur compounds from refinery product streams. Sweetening processes either remove the obnoxious sulfur compounds or convert them to odorless disulfides, as in the case of mercaptans.
OXYGEN COMPOUNDS
Oxygen compounds such as phenols, ketones, and carboxylic acids occur in crude oils in varying amounts.
NITROGEN COMPOUNDS
Nitrogen is found in lighter fractions of crude oil as basic compounds, and more often in heavier fractions of crude oil as nonbasic compounds that may also include trace metals such as copper, vanadium, and/or nickel. Nitrogen oxides can form in process furnaces. The decomposition of nitrogen compounds in catalytic cracking and hydrocracking processes forms ammonia and cyanides that can cause corrosion.
TRACE METALS
Metals including nickel, iron, and vanadium are often found in crude oils in small quantities and are removed during the refining process. Burning heavy fuel oils in refinery furnaces and boilers can leave deposits of vanadium oxide and nickel oxide in furnace boxes, ducts, and tubes. It is also desirable to remove trace amounts of arsenic, vanadium, and nickel prior to processing as they can poison certain catalysts.
(For III:2-5, Click Here
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SALTS
Crude oils often contain inorganic salts such as sodium chloride, magnesium chloride, and calcium chloride in suspension or dissolved in entrained water (brine). These salts must be removed or neutralized before processing to prevent catalyst poisoning, equipment corrosion, and fouling. Salt corrosion is caused by the hydrolysis of some metal chlorides to hydrogen chloride (HCl) and the subsequent formation of hydrochloric acid when crude is heated. Hydrogen chloride may also combine with ammonia to form ammonium chloride (NH(4)Cl), which causes fouling and corrosion.
CARBON DIOXIDE
Carbon dioxide may result from the decomposition of bicarbonates present in or added to crude, or from steam used in the distillation process.
NAPHTHENIC ACIDS
Some crude oils contain naphthenic (organic) acids, which may become corrosive at temperatures above 450 degrees F when the acid value of the crude is above a certain level.
MAJOR REFINERY PRODUCTS
GASOLINE
The most important refinery product is motor gasoline, a blend of hydrocarbons with boiling ranges from ambient temperatures to about 400 degrees F. The important qualities for gasoline are octane number (antiknock), volatility (starting and vapor lock), and vapor pressure (environmental control). Additives are often used to enhance performance and provide protection against oxidation and rust formation.
KEROSENE
Kerosene is a refined middle-distillate petroleum product that finds considerable use as a jet fuel and around the world in cooking and space heating. When used as a jet fuel, some of the critical qualities are freeze point, flash point, and smoke point. Commercial jet fuel has a boiling range of about 375-525 degrees F, and military jet fuel 130-550 degrees F. Kerosene, with less-critical specifications, is used for lighting, heating, solvents, and blending into diesel fuel.
LIQUEFIED PETROLEUM GAS (LPG)
LPG, which consists principally of propane and butane, is produced for use as fuel and is an intermediate material in the manufacture of petrochemicals. The important specifications for proper performance include vapor pressure and control of contaminants.
DISTILLATE FUELS
Diesel fuels and domestic heating oils have boiling ranges of about 400-700 degrees F. The desirable qualities required for distillate fuels include controlled flash and pour points, clean burning, no deposit formation in storage tanks, and a proper diesel fuel cetane rating for good starting and combustion.
RESIDUAL FUELS
Many marine vessels, power plants, commercial buildings and industrial facilities use residual fuels or combinations of residual and distillate fuels for heating and processing. The two most critical specifications of residual fuels are viscosity and low sulfur content for environmental control.
COKE AND ASPHALT
Coke is almost pure carbon with a variety of uses from electrodes to charcoal briquets. Asphalt, used for roads and roofing materials, must be inert to most chemicals and weather conditions.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SOLVENTS
A variety of products, whose boiling points and hydrocarbon composition are closely controlled, are produced for use as solvents. These include benzene, toluene, and xylene.
PETROCHEMICALS
Many products derived from crude oil refining such as ethylene, propylene, butylene, and isobutylene are primarily intended for use as petrochemical feedstocks in the production of plastics, synthetic fibers, synthetic rubbers, and other products.
LUBRICANTS
Special refining processes produce lubricating oil base stocks. Additives such as demulsifiers, antioxidants, and viscosity improvers are blended into the base stocks to provide the characteristics required for motor oils, industrial greases, lubricants, and cutting oils. The most critical quality for lubricating-oil base stock is a high viscosity index, which provides for greater consistency under varying temperatures.
COMMON REFINERY CHEMICALS
LEADED GASOLINE ADDITIVES
Tetraethyl lead (TEL) and tetramethyl lead (TML) are additives formerly used to improve gasoline octane ratings but are no longer in common use except in aviation gasoline.
OXYGENATES
Ethyl tertiary butyl ether (ETBE), methyl tertiary butyl ether (MTBE), tertiary amyl methyl ether (TAME), and other oxygenates improve gasoline octane ratings and reduce carbon monoxide emissions.
CAUSTICS
Caustics are added to desalting water to neutralize acids and reduce corrosion. They are also added to desalted crude in order to reduce the amount of corrosive chlorides in the tower overheads. They are used in some refinery treating processes to remove contaminants from hydrocarbon streams.
SULFURIC ACID AND HYDROFLUORIC ACID
Sulfuric acid and hydrofluoric acid are used primarily as catalysts in alkylation processes. Sulfuric acid is also used in some treatment processes.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
C. PETROLEUM REFINING OPERATIONS _____________________________________________________________________
INTRODUCTION
Petroleum refining begins with the distillation, or fractionation, of crude oils into separate hydrocarbon groups. The resultant products are directly related to the characteristics of the crude processed. Most distillation products are further converted into more usable products by changing the size and structure of the hydrocarbon molecules through cracking, reforming, and other conversion processes as discussed in this chapter. These converted products are then subjected to various treatment and separation processes such as extraction, hydrotreating, and sweetening to remove undesirable constituents and improve product quality. Integrated refineries incorporate fractionation, conversion, treatment, and blending operations and may also include petrochemical processing.
REFINING OPERATIONS
Petroleum refining processes and operations can be separated into five basic areas:
FRACTIONATION
Fractionation (distillation) is the separation of crude oil in atmospheric and vacuum distillation towers into groups of hydrocarbon compounds of differing boiling-point ranges called "fractions" or "cuts."
CONVERSION
Conversion processes change the size and/or structure of hydrocarbon molecules. These processes include:
- * decomposition (dividing) by thermal and catalytic cracking,
- * unification (combining) through alkylation and polymerization, and
- * alteration (rearranging) with isomerization and catalytic reforming .
TREATMENT
Treatment processes are intended to prepare hydrocarbon streams for additional processing and to prepare finished products. Treatment may include the removal or separation of aromatics and naphthenes as well as impurities and undesirable contaminants. Treatment may involve chemical or physical separation such as dissolving, absorption, or precipitation using a variety and combination of processes including desalting, drying, hydrodesulfurizing, solvent refining, sweetening, solvent extraction, and solvent dewaxing.
FORMULATING AND BLENDING
Formulating and blending is the process of mixing and combining hydrocarbon fractions, additives, and other components to produce finished products with specific performance properties.
OTHER REFINING OPERATIONS
Other refinery operations include light-ends recovery, sour-water stripping, solid waste and wastewater treatment, process-water treatment and cooling, storage, and handling, product movement, hydrogen production, acid and tail-gas treatment, and sulfur recovery.
Auxiliary operations and facilities include steam and power generation; process and fire water systems; flares and relief systems; furnaces and heaters; pumps and valves; supply of steam, air, nitrogen, and other plant gases; alarms and sensors; noise and pollution controls; sampling, testing, and inspecting; and laboratory, control room, maintenance, and administrative facilities.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
(For III:2-6, Click Here
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Table III:2-3 OVERVIEW OF PETROLEUM REFINING PROCESSES _________________________________________________________________________
Process Action Method Purpose Feedstock(s) Product(s)
- name
FRACTIONATION PROCESSES
Atmospheric Separation Thermal Separate Desalted Gas, gas oil, distillation fractions crude oil distillate, residual Vacuum Separation Thermal Separate Atmosph- Gas oil, lube distillation w/o eric stock, residual cracking tower residual
CONVERSION PROCESSES-DECOMPOSITION
Catalytic Alteration Catalytic Upgrade Gas oil, Gasoline,
cracking gasoline coke petrochemical distillate feedstock Coking Polymerize Thermal Convert Residual, Naphtha, gas oil, vacuum heavy oil, coke residuals tar Hydrocrack- Hydrogenate Catalytic Convert Gas oil, Lighter, ing to oil, cracked higher-quality lighter residual products HCs *Hydrogen Decompose Thermal/ Produce Desul- Hydrogen, CO, Steam cat. hydrogen furized CO(2) Reforming gas, O(2), steam *Steam Decompose Thermal Crack Atm tower Cracked naphtha, Cracking large hvy fuel/ coke,residual molecules distillate Visbreaking Decompose Thermal Reduce Atmospheric Distillate, tar viscosity tower residual
CONVERSION PROCESSES-UNIFICATION
Alkylation Combining Catalytic Unite Tower Iso-octane
- olefins isobutane/ (alkylate) & crckr isopar- olefin affins Grease Combining Thermal Combine Lube oil, Lubricating compounding soaps fatty acid, grease & oils alky metal Polymeriza- Polymerize Catalytic Unite 2 Cracker High-octane tion or more olefins naphtha, olefins petrochemi-
- cal stocks
CONVERSION PROCESSES-ALTERATION or REARRANGEMENT
Catalytic Alteration/ Catalytic Upgrade Coker/hydro- High oct.
reforming dehydration low- cracker reformate/ octane naphtha aromatic naphtha Isomeriza- Rearrange Catalytic Convert Butane, Isobutane/ tion strght pentane, pentane/ chain to hexane hexane branch
________________________________________________________________________
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Table III:2-3 OVERVIEW OF PETROLEUM REFINING PROCESSES (cont.) ______________________________________________________________________
Process
name Action Method Purpose Feedstock(s) Product(s)
TREATMENT PROCESSES
*Amine Treatment Absorption Remove Sour gas, Acid free
- Treating acidic HCs w/CO(2) gases & contam- & H(2)S liquid HCs inants Desalting Dehydra- Absorption Remove Crude oil Desalted tion contamin- crude oil ants Drying & Treatment Abspt/therm Remove Liq HCs, Sweet & dry Sweeten- H(2)O LPG,alky. hydrocarbons ing & sulfur feedstk cmpds *Furfural Solvent Absorption Upgrade Cycle oils High quality Extraction extr. mid & lube diesel & distillate feedstocks lube oil & lubes
Hydrodesul- Treatment Catalytic Remove High-sulfur Desulfurized
furization sulfur, residual/ olefins contamin- gas oil ants Hydrotreat Hydrogena- Catalytic Remv Residuals, Cracker feed, ing tion impurities cracked distillate, saturate HCs lube HCs *Phenol Solvent Abspt/therm Improve Lube oil High quality extrac- extr. visc. base stocks lube oils tion index, color Solvent Treatment Absorption Remove Vac. tower Heavy lube deasphalt- asphalt residual, oil, asphalt ing propane
Solvent Treatment Cool/filter Remve wax Vac. tower Dewaxed lube
dewaxing from lube lube oils basestock stocks Solvent Solvent Abspt/ Separate Gas oil, High-octane Extraction extr. precip. unsat. reformate, gasoline oils distillate Sweetening Treatment Catalytic Remv Untreated High-quality H(2)S, distillate/ distilate/ convert gasoline gasoline mercaptan
_____________________________________________________________________
*NOTE: These processes are not depicted in the refinery process flow chart.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
D. DESCRIPTION OF PETROLEUM REFINING PROCESSES AND RELATED HEALTH AND SAFETY CONSIDERATIONS
_____________________________________________________________________
CRUDE OIL PRETREATMENT (DESALTING)
Crude oil often contains water, inorganic salts, suspended solids, and water-soluble trace metals. As a first step in the refining process, to reduce corrosion, plugging, and fouling of equipment and to prevent poisoning the catalysts in processing units, these contaminants must be removed by desalting (dehydration).
The two most typical methods of crude-oil desalting, chemical and electrostatic separation, use hot water as the extraction agent. In chemical desalting, water and chemical surfactant (demulsifiers) are added to the crude, heated so that salts and other impurities dissolve into the water or attach to the water, and then held in a tank where they settle out. Electrical desalting is the application of high-voltage electrostatic charges to concentrate suspended water globules in the bottom of the settling tank. Surfactants are added only when the crude has a large amount of suspended solids. Both methods of desalting are continuous. A third and less-common process involves filtering heated crude using diatomaceous earth.
The feedstock crude oil is heated to between 150 degrees and 350 degrees F to reduce viscosity and surface tension for easier mixing and separation of the water. The temperature is limited by the vapor pressure of the crude-oil feedstock. In both methods other chemicals may be added. Ammonia is often used to reduce corrosion. Caustic or acid may be added to adjust the pH of the water wash.
Wastewater and contaminants are discharged from the bottom of the settling tank to the wastewater treatment facility. The desalted crude is continuously drawn from the top of the settling tanks and sent to the crude distillation (fractionating) tower.
HEALTH AND SAFETY CONSIDERATIONS
Fire Prevention and Protection
The potential exists for a fire due to a leak or release of crude from heaters in the crude desalting unit. Low boiling point components of crude may also be released if a leak occurs.
Safety
Inadequate desalting can cause fouling of heater tubes and heat exchangers throughout the refinery. Fouling restricts product flow and heat transfer and leads to failures due to increased pressures and temperatures. Corrosion, which occurs due to the presence of hydrogen sulfide, hydrogen chloride, naphthenic (organic) acids, and other contaminants in the crude oil, also causes equipment failure. Neutralized salts (ammonium chlorides
__________________________________________________________________________
Feedstocks From Process Typical products......... To
Crude Storage Treating Desalted crude........... Atmospheric
distillation tower Wastewater............... Treatment
__________________________________________________________________________
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
(For III:2-7, Click Here
and sulfides), when moistened by condensed water, can cause corrosion. Overpressuring the unit is another potential hazard that causes failures.
Health
Because this is a closed process, there is little potential for exposure to crude oil unless a leak or release occurs. Where elevated operating temperatures are used when desalting sour crudes, hydrogen sulfide will be present. There is the possibility of exposure to ammonia, dry chemical demulsifiers, caustics, and/or acids during this operation. Safe work practices and/or the use of appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as heat, and during process sampling, inspection, maintenance, and turnaround activities.
Depending on the crude feedstock and the treatment chemicals used, the wastewater will contain varying amounts of chlorides, sulfides, bicarbonates, ammonia, hydrocarbons, phenol, and suspended solids. If diatomaceous earth is used in filtration, exposures should be minimized or controlled. Diatomaceous earth can contain silica in very fine particle size, making this a potential respiratory hazard.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
CRUDE OIL DISTILLATION (FRACTIONATION)
The first step in the refining process is the separation of crude oil into various fractions or straight-run cuts by distillation in atmospheric and vacuum towers. The main fractions or "cuts" obtained have specific boiling-point ranges and can be classified in order of decreasing volatility into gases, light distillates, middle distillates, gas oils, and residuum.
ATMOSPHERE DISTILLATION TOWER
At the refinery, the desalted crude feedstock is preheated using recovered process heat. The feedstock then flows to a direct-fired crude charge heater where it is fed into the vertical distillation column just above the bottom, at pressures slightly above atmospheric and at temperatures ranging from 650 degrees to 700 degrees F (heating crude oil above these temperatures may cause undesirable thermal cracking). All but the heaviest fractions flash into vapor. As the hot vapor rises in the tower, its temperature is reduced. Heavy fuel oil or asphalt residue is taken from the bottom. At successively higher points on the tower, the various major products including lubricating oil, heating oil, kerosene, gasoline, and uncondensed gases (which condense at lower temperatures) are drawn off.
The fractionating tower, a steel cylinder about 120 feet high, contains horizontal steel trays for separating and collecting the liquids. At each tray, vapors from below enter perforations and bubble caps. They permit the vapors to bubble through the liquid on the tray, causing some condensation at the temperature of that tray. An overflow pipe drains the condensed liquids from each tray back to the tray below, where the higher temperature causes re-evaporation. The evaporation, condensing, and scrubbing operation is repeated many times until the desired degree of product purity is reached. Then side streams from certain trays are taken off to obtain the desired fractions. Products ranging from uncondensed fixed gases at the top to heavy fuel oils at the bottom can be taken continuously from a fractionating tower. Steam is often used in towers to lower the vapor pressure and create a partial vacuum. The distillation process separates the major constituents of crude oil into so-called straight-run products. Sometimes crude oil is "topped" by distilling off only the lighter fractions, leaving a heavy residue that is often distilled further under high vacuum.
Table III:2-5. Atmospheric Distillation Processes _____________________________________________________________________ Feedstocks From Process Typical products. To Crude Desalting Separation Gases............ Fuel or gas recovery Naphthas......... Reforming or treating Kero or distillates..... Treating Gas oil.......... Catalytic cracking Residual......... Vacuum tower or visbreaker _____________________________________________________________________
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
(For III:2-8, Click Here
VACUUM DISTILLATION TOWER
In order further to distill the residuum or topped crude from the atmospheric tower at higher temperatures, reduced pressure is required to prevent thermal cracking. The process takes place in one or more vacuum distillation towers. The principles of vacuum distillation resemble those of fractional distillation and, except that larger-diameter columns are used to maintain comparable vapor velocities at the reduced pressures, the equipment is also similar. The internal designs of some vacuum towers are different from atmospheric towers in that random packing and demister pads are used instead of trays. A typical first-phase vacuum tower may produce gas oils, lubricating-oil base stocks, and heavy residual for propane deasphalting. A second-phase tower operating at lower vacuum may distill surplus residuum from the atmospheric tower, which is not used for lube-stock processing, and surplus residuum from the first vacuum tower not used for deasphalting. Vacuum towers are typically used to separate catalytic cracking feedstocks from surplus residuum.
OTHER DISTILLATION TOWERS (COLUMNS)
Within refineries there are numerous other, smaller distillation towers called columns, designed to separate specific and unique products. Columns all work on the same principles as the towers described above. For example, a depropanizer is a small column designed to separate propane and lighter gases from butane and heavier components. Another larger column is used to separate ethyl benzene and xylene. Small "bubble" towers called strippers use steam to remove trace amounts of light products from heavier product streams.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
HEALTH AND SAFETY CONSIDERATIONS
Fire Prevention and Protection
Even though these are closed processes, heaters and exchangers in the atmospheric and vacuum distillation units could provide a source of ignition, and the potential for a fire exists should a leak or release occur.
Safety
An excursion in pressure, temperature, or liquid levels may occur if automatic control devices fail. Control of temperature, pressure, and reflux within operating parameters is needed to prevent thermal cracking within the distillation towers. Relief systems should be provided for overpressure and operations monitored to prevent crude from entering the reformer charge.
The sections of the process susceptible to corrosion include (but may not be limited to) preheat exchanger (HCl and H(2)S), preheat furnace and bottoms exchanger (H(2)S and sulfur compounds), atmospheric tower and vacuum furnace (H(2)S, sulfur compounds, and organic acids), vacuum tower (H(2)S and organic acids), and overhead (H(2)S, HCl, and water). Where sour crudes are processed, severe corrosion can occur in furnace tubing and in both atmospheric and vacuum towers where metal temperatures exceed 450 degrees F. Wet H(2)S also will cause cracks in steel. When processing high-nitrogen crudes, nitrogen oxides can form in the flue gases of furnaces. Nitrogen oxides are corrosive to steel when cooled to low temperatures in the presence of water.
Chemicals are used to control corrosion by hydrochloric acid produced in distillation units. Ammonia may be injected into the overhead stream prior to initial condensation and/or an alkaline solution may be carefully injected into the hot crude-oil feed. If sufficient wash-water is not injected, deposits of ammonium chloride can form and cause serious corrosion. Crude feedstocks may contain appreciable amounts of water in suspension which can separate during startup and, along with water remaining in the tower from steam purging, settle in the bottom of the tower. This water can be heated to the boiling point and create an instantaneous vaporization explosion upon contact with the oil in the unit.
Health
Atmospheric and vacuum distillation are closed processes and exposures are expected to be minimal. When sour (high-sulfur) crudes are processed, there is potential for exposure to hydrogen sulfide in the preheat exchanger and furnace, tower flash zone and overhead system, vacuum furnace and tower, and bottoms exchanger. Hydrogen chloride may be present in the preheat exchanger, tower top zones, and overheads. Wastewater may contain water-soluble sulfides in high concentrations and other water-soluble compounds such as ammonia, chlorides, phenol, mercaptans, etc., depending upon the crude feedstock and the treatment chemicals. Safe work practices and/or the use of appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as heat and noise, and during sampling, inspection, maintenance, and turnaround activities.
Table III:2-6. VACUUM DISTILLATION PROCESS _____________________________________________________________________ Feedstocks From Process Typical products...... To Residuals Atmospheric Separation Gas oils..... Catalytic cracker tower Lubricants... Hydrotreating or solvent extraction Residual..... Deasphalter, visbreaker, or coker _____________________________________________________________________ III:2-19 OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
(For III:2-9, Click Here) SOLVENT EXTRACTION AND DEWAXING Solvent treating is a widely used method of refining lubricating oils as well as a host of other refinery stocks. Since distillation (fractionation) separates petroleum products into groups only by their boiling-point ranges, impurities may remain. These include organic compounds containing sulfur, nitrogen, and oxygen; inorganic salts and dissolved metals; and soluble salts that were present in the crude feedstock. In addition, kerosene and distillates may have trace amounts of aromatics and naphthenes, and lubricating oil base-stocks may contain wax. Solvent refining processes including solvent extraction and solvent dewaxing usually remove these undesirables at intermediate refining stages or just before sending the product to storage. SOLVENT EXTRACTION The purpose of solvent extraction is to prevent corrosion, protect catalyst in subsequent processes, and improve finished products by removing unsaturated, aromatic hydrocarbons from lubricant and grease stocks. The solvent extraction process separates aromatics, naphthenes, and impurities from the product stream by dissolving or precipitation. The feedstock is first dried and then treated using a continuous countercurrent solvent treatment operation. In one type of process, the feedstock is washed with a liquid in which the substances to be removed are more soluble than in the desired resultant product. In another process, selected solvents are added to cause impurities to precipitate out of the product. In the adsorption process, highly porous solid materials collect liquid molecules on their surfaces. III:2-20 OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment The solvent is separated from the product stream by heating, evaporation, or fractionation, and residual trace amounts are subsequently removed from the raffinate by steam stripping or vacuum flashing. Electric precipitation may be used for separation of inorganic compounds. The solvent is then regenerated to be used again in the process. The most widely used extraction solvents are phenol, furfural, and cresylic acid. Other solvents less frequently used are liquid sulfur dioxide, nitrobenzene, and 2,2' dichloroethyl ether. The selection of specific processes and chemical agents depends on the nature of the feedstock being treated, the contaminants present, and the finished product requirements.
Table III:2-7. SOLVENT EXTRACTION PROCESS _____________________________________________________________________
Feedstocks From Process Typical products ...... To
Naphthas Atm. tower Treating High octane
gasoline........ Treating or blending Distillates Refined Fuels.... Treating or blending Kerosene Spent agents..... Treatment or recycle
_____________________________________________________________________
(For III:2-10, Click Here
Diagrams in Figures II:2-10, 11, 12, 13, 15, and 20 reproduced with the permission of Shell International Petroleum Company Limited.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Table III:2-8. SOLVENT DEWAXING PROCESS _____________________________________________________________________ Feedstocks From Process Typical products. To Lube basestock Vacuum tower Treating Dewaxed lubes or wax........... Hydrotreating Spent agents..... Treatment or recycle _____________________________________________________________________
SOLVENT DEWAXING
Solvent dewaxing is used to remove wax from either distillate or residual basestocks at any stage in the refining process. There are several processes in use for solvent dewaxing, but all have the same general steps, which are: (1) mixing the feedstock with a solvent, (2) precipitating the wax from the mixture by chilling, and (3) recovering the solvent from the wax and dewaxed oil for recycling by distillation and steam stripping. Usually two solvents are used: toluene, which dissolves the oil and maintains fluidity at low temperatures, and methyl ethyl ketone (MEK), which dissolves little wax at low temperatures and acts as a wax precipitating agent. Other solvents that are sometimes used include benzene, methyl isobutyl ketone, propane, petroleum naphtha, ethylene dichloride, methylene chloride, and sulfur dioxide. In addition, there is a catalytic process used as an alternate to solvent dewaxing.
HEALTH AND SAFETY CONSIDERATIONS
Fire Prevention and Protection
Solvent treatment is essentially a closed process and, although operating pressures are relatively low, the potential exists for fire from a leak or spill contacting a source of ignition such as the drier or extraction heater. In solvent dewaxing, disruption of the vacuum will create a potential fire hazard by allowing air to enter the unit.
Health
Because solvent extraction is a closed process, exposures are expected to be minimal under normal operating conditions. However, there is a potential for exposure to extraction solvents such as phenol, furfural, glycols, methyl ethyl ketone, amines, and other process chemicals. Safe work practices and/or the use of appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat, and during repair, inspection, maintenance, and turnaround activities.
(For III:2-11, Click Here
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Table III:2-9. VISBREAKING PROCESS _____________________________________________________________________ Feedstocks From Process Typical products.. To Residual Atmospheric Decompose Gasoline or tower distillate ...... Treating or blending Vacuum Vapor............ Hydrotreater tower Residue.......... Stripper or recycle Gases............ Gas plant _____________________________________________________________________
THERMAL CRACKING
Because the simple distillation of crude oil produces amounts and types of products that are not consistent with those required by the marketplace, subsequent refinery processes change the product mix by altering the molecular structure of the hydrocarbons. One of the ways of accomplishing this change is through "cracking," a process that breaks or cracks the heavier, higher boiling-point petroleum fractions into more valuable products such as gasoline, fuel oil, and gas oils. The two basic types of cracking are thermal cracking, using heat and pressure, and catalytic cracking.
(For III:2-12, Click Here
The first thermal cracking process was developed around 1913. Distillate fuels and heavy oils were heated under pressure in large drums until they cracked into smaller molecules with better antiknock characteristics. However, this method produced large amounts of solid, unwanted coke. This early process has evolved into the following applications of thermal cracking: visbreaking, steam cracking, and coking.
VISBREAKING PROCESS
Visbreaking, a mild form of thermal cracking, significantly lowers the viscosity of heavy crude-oil residue without affecting the boiling point range. Residual from the atmospheric distillation tower is heated (800-950 degrees F) at atmospheric pressure and mildly cracked in a heater. It is then quenched with cool gas oil to control overcracking, and flashed in a distillation tower. Visbreaking is used to reduce the pour point of waxy residues and reduce the viscosity of residues used for blending with lighter fuel oils. Middle distillates may also be produced, depending on product demand. The thermally cracked residue tar, which accumulates in the bottom of the fractionation tower, is vacuum flashed in a stripper and the distillate recycled.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
STEAM CRACKING PROCESS
Steam cracking is a petrochemical process sometimes used in refineries to produce olefinic raw materials (e.g., ethylene) from various feedstocks for petrochemicals manufacture. The feedstocks range from ethane to vacuum gas oil, with heavier feeds giving higher yields of by-products such as naphtha. The most common feeds are ethane, butane, and naphtha. Steam cracking is carried out at temperatures of 1,500-1,600 degrees F, and at pressures slightly above atmospheric. Naphtha produced from steam cracking contains benzene, which is extracted prior to hydrotreating. Residual from steam cracking is sometimes blended into heavy fuels.
COKING PROCESSES
Coking is a severe method of thermal cracking used to upgrade heavy residuals into lighter products or distillates. Coking produces straight-run gasoline (coker naphtha) and various middle-distillate fractions used as catalytic cracking feedstocks. The process so completely reduces hydrogen that the residue is a form of carbon called "coke." The two most common processes are delayed coking and continuous (contact or fluid) coking. Three typical types of coke are obtained (sponge coke, honeycomb coke, and needle coke) depending upon the reaction mechanism, time, temperature, and the crude feedstock.
Delayed Coking
In delayed coking the heated charge (typically residuum from atmospheric distillation towers) is transferred to large coke drums which provide the long residence time needed to allow the cracking reactions to proceed to completion. Initially the heavy feedstock is fed to a furnace which heats the residuum to high temperatures (900-950 degrees F) at low pressures (25-30 psi) and is designed and controlled to prevent premature coking in the heater tubes. The mixture is passed from the heater to one or more coker drums where the hot material is held approximately 24 hours (delayed) at pressures of 25-75 psi, until it cracks into lighter products. Vapors from the drums are returned to a fractionator where gas, naphtha, and gas oils are separated out. The heavier hydrocarbons produced in the fractionator are recycled through the furnace.
After the coke reaches a predetermined level in one drum, the flow is diverted to another drum to maintain continuous operation. The full drum is steamed to strip out uncracked hydrocarbons, cooled by water injection, and decoked by mechanical or hydraulic methods. The coke is mechanically removed by an auger rising from the bottom of the drum. Hydraulic decoking consists of fracturing the coke bed with high-pressure water ejected from a rotating cutter.
Table III:2-10. COKING PROCESSES _____________________________________________________________________ Feedstocks From Process Typical products... To Residual Atmospheric & Decompo- Naphtha, gasoline.. Distillation vacuum sition column, catalytic blending cracker Clarified Catalytic Coke............... Shipping, oil cracker recycle Tars Various units Gas oil............ Catalytic cracking Wastewater Treatment (sour) Gases Gas plant _____________________________________________________________________
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
(For III:2-13, Click Here
CONTINUOUS COKING
Continuous (contact or fluid) coking is a moving-bed process that operates at temperatures higher than delayed coking. In continuous coking, thermal cracking occurs by using heat transferred from hot, recycled coke particles to feedstock in a radial mixer, called a reactor, at a pressure of 50 psi. Gases and vapors are taken from the reactor, quenched to stop any further reaction, and fractionated. The reacted coke enters a surge drum and is lifted to a feeder and classifier where the larger coke particles are removed as product. The remaining coke is dropped into the preheater for recycling with feedstock. Coking occurs both in the reactor and in the surge drum. The process is automatic in that there is a continuous flow of coke and feedstock.
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
Because thermal cracking is a closed process, the primary potential for fire is from leaks or releases of liquids, gases, or vapors reaching an ignition source such as a heater. The potential for fire is present in coking operations due to vapor or product leaks. Should coking temperatures get out of control, an exothermic reaction could occur within the coker.
Safety
In thermal cracking when sour crudes are processed, corrosion can occur where metal temperatures are between 450º and 900 degrees F. Above 900 degrees F coke forms a protective layer on the metal. The furnace, soaking drums, lower part of the tower, and high-temperature exchangers are usually subject to corrosion. Hydrogen sulfide corrosion in coking can also occur when temperatures are not properly controlled above 900 degrees F.
Continuous thermal changes can lead to bulging and cracking of coke drum shells. In coking, temperature control must often be held within a 10-20 degrees F range, as high temperatures will produce coke that is too hard to cut out of the drum. Conversely, temperatures that are too low will result in a high asphaltic-content slurry. Water or steam injection may be used to prevent buildup of coke in delayed coker furnace tubes. Water must be completely drained from the coker, so as not to cause an explosion upon recharging with hot coke. Provisions for alternate means of egress from the working platform on top of coke drums are important in the event of an emergency.
Health
The potential exists for exposure to hazardous gases such as hydrogen sulfide and carbon monoxide, and trace polynuclear aromatics (PNAs) associated with coking operations. When coke is moved as a slurry, oxygen depletion may occur within confined spaces such as storage silos, since wet carbon will adsorb oxygen. Wastewater may be highly alkaline and
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
contain oil, sulfides, ammonia, and/or phenol. The potential exists in the coking process for exposure to burns when handling hot coke or in the event of a steamline leak, or from steam, hot water, hot coke, or hot slurry that may be expelled when opening cokers. Safe work practices and/or the use of appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as heat and noise, and during process sampling, inspection, maintenance, and turnaround activities. (Note: coke produced from petroleum is a different product from that generated in the steel-industry coking process.)
CATALYTIC CRACKING
Catalytic cracking breaks complex hydrocarbons into simpler molecules in order to increase the quality and quantity of lighter, more desirable products and decrease the amount of residuals. This process rearranges the molecular structure of hydrocarbon compounds to convert heavy hydrocarbon feedstocks into lighter fractions such as kerosene, gasoline, LPG, heating oil, and petrochemical feedstocks.
Catalytic cracking is similar to thermal cracking except that catalysts facilitate the conversion of the heavier molecules into lighter products. Use of a catalyst (a material that assists a chemical reaction but does not take part in it) in the cracking reaction increases the yield of improved-quality products under much less severe operating conditions than in thermal cracking. Typical temperatures are from 850-950 degrees F at much lower pressures of 10-20 psi. The catalysts used in refinery cracking units are typically solid materials (zeolite, aluminum hydrosilicate, treated bentonite clay, fuller's earth, bauxite, and silica-alumina) that come in the form of powders, beads, pellets or shaped materials called extrudites.
There are three basic functions in the catalytic cracking process:
Reaction: Feedstock reacts with catalyst and cracks into different hydrocarbons.
Regeneration: Catalyst is reactivated by burning off coke.
Fractionation: Cracked hydrocarbon stream is separated into various products.
The three types of catalytic cracking processes are fluid catalytic cracking (FCC), moving-bed catalytic cracking, and Thermofor catalytic cracking (TCC). The catalytic cracking process is very flexible, and operating parameters can be adjusted to meet changing product demand. In addition to cracking, catalytic activities include dehydrogenation, hydrogenation, and isomerization.
FLUID CATALYTIC CRACKING
The most common process is FCC, in which the oil is cracked in the presence of a finely divided catalyst which is maintained in an aerated or fluidized state by the oil vapors. The fluid cracker consists of a
Table III:2-11. CATALYTIC CRACKING PROCESS _____________________________________________________________________ Feedstock From Process Typical products.... To Gas oils Towers, Decompo- Gasoline............ Treater or coker sition, blend Visbreaker alteration Gases............... Gas plant Deasphalted Deasphalter Middle distillates.. Hydrotreat, oils blend, or recycle Petrochem feedstocks Petrochem or other Residue............. Residual fuel blend _____________________________________________________________________
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
(For III:2-14, Click Here
catalyst section and a fractionating section that operate together as an integrated processing unit. The catalyst section contains the reactor and regenerator, which with the standpipe and riser forms the catalyst circulation unit. The fluid catalyst is continuously circulated between the reactor and the regenerator using air, oil vapors, and steam as the conveying media.
A typical FCC process involves mixing a preheated hydrocarbon charge with hot, regenerated catalyst as it enters the riser leading to the reactor. The charge is combined with a recycle stream within the riser, vaporized, and raised to reactor temperature (900-1,000 degrees F) by the hot catalyst. As the mixture travels up the riser, the charge is cracked at 10-30 psi.
In the more modern FCC units, all cracking takes place in the riser. The "reactor" no longer functions as a reactor; it merely serves as a holding vessel for the cyclones. This cracking continues until the oil vapors are separated from the catalyst in the reactor cyclones. The resultant product stream (cracked product) is then charged to a fractionating column where it is separated into fractions, and some of the heavy oil is recycled to the riser.
Spent catalyst is regenerated to get rid of coke that collects on the catalyst during the process. Spent catalyst flows through the catalyst stripper to the regenerator, where most of the coke deposits burn off at the bottom where preheated air and spent catalyst are mixed. Fresh catalyst is added and worn-out catalyst removed to optimize the cracking process.
MOVING BED CATALYTIC CRACKING
The moving-bed catalytic cracking process is similar to the FCC process. The catalyst is in the form of pellets that are moved continuously to the top of the unit by conveyor or pneumatic lift tubes to a storage hopper, then flow downward by gravity through the reactor, and finally to a regenerator. The regenerator and hopper are isolated from the reactor by steam seals. The cracked product is separated into recycle gas, oil, clarified oil, distillate, naphtha, and wet gas.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
THERMOFOR CATALYTIC CRACKING
In a typical thermofor catalytic cracking unit, the preheated feedstock flows by gravity through the catalytic reactor bed. The vapors are separated from the catalyst and sent to a fractionating tower. The spent catalyst is regenerated, cooled, and recycled. The flue gas from regeneration is sent to a carbon-monoxide boiler for heat recovery.
HEALTH AND SAFETY CONSIDERATIONS
Fire Prevention and Protection
Liquid hydrocarbons in the catalyst or entering the heated combustion air stream should be controlled to avoid exothermic reactions. Because of the presence of heaters in catalytic cracking units, the possibility exists for fire due to a leak or vapor release. Fire protection including concrete or other insulation on columns and supports, or fixed water spray or fog systems where insulation is not feasible and in areas where firewater hose streams cannot reach, should be considered. In some processes, caution must be taken to assure prevent explosive concentrations of catalyst dust during recharge or disposal. When unloading any coked catalyst, the possibility exists for iron sulfide fires. Iron sulfide will ignite spontaneously when exposed to air and therefore mus be wetted with water to prevent it from igniting vapors. Coked catalyst may be either cooled below 120 degrees F before they are dumped from the reactor, or dumped into containers that have been purged and inerted with nitrogen and then cooled before further handling.
Safety
Regular sampling and testing of the feedstock, product, and recycle streams should be performed to assure that the cracking process is working as intended and that no contaminants have entered the process stream. Corrosives or deposits in the feedstock can foul gas compressors. Inspections of critical equipment including pumps, compressors, furnaces, and heat exchangers should be conducted as needed. When processing sour crude, corrosion may be expected where temperatures are below 900 degrees F. Corrosion takes place where both liquid and vapor phases exist, and at areas subject to local cooling such as nozzles and platform supports.
When processing high-nitrogen feedstocks, exposure to ammonia and cyanide may occur, subjecting carbon steel equipment in the FCC overhead system to corrosion, cracking, or hydrogen blistering. These effects may be minimized by water wash or corrosion inhibitors. Water wash may also be used to protect overhead condensers in the main column subjected to fouling from ammonium hydrosulfide. Inspections should include checking for leaks due to erosion or other malfunctions such as catalyst buildup on the expanders, coking in the overhead feeder lines from feedstock residues, and other unusual operating conditions.
Health
Because the catalytic cracker is a closed system, there is normally little opportunity for exposure to hazardous substances during normal operations. The possibility exists of exposure to extremely hot (700 degrees F) hydrocarbon liquids or vapors during process sampling or if a leak or release occurs. In addition, exposure to hydrogen sulfide and/or carbon monoxide gas may occur during a release of product or vapor.
Catalyst regeneration involves steam stripping and decoking, and produces fluid waste streams that may contain varying amounts of hydrocarbon, phenol, ammonia, hydrogen sulfide, mercaptan, and other materials depending upon the feedstocks, crudes, and processes. Inadvertent formation of nickel carbonyl may occur in cracking processes using nickel catalysts, with resultant potential for hazardous exposures. Safe work practices and/or the use of appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat; during process sampling, inspection, maintenance and turnaround activities; and when handling spent catalyst, recharging catalyst, or if leaks or releases occur.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
HYDROCRACKING
Hydrocracking is a two-stage process combining catalytic cracking and hydrogenation, wherein heavier feedstocks are cracked in the presence of hydrogen to produce more desirable products. The process employs high pressure, high temperature, a catalyst, and hydrogen. Hydrocracking is used for feedstocks that are difficult to process by either catalytic cracking or reforming, since these feedstocks are characterized usually by a high polycyclic aromatic content and/or high concentrations of the two principal catalyst poisons, sulfur and nitrogen compounds.
The hydrocracking process largely depends on the nature of the feedstock and the relative rates of the two competing reactions, hydrogenation and cracking. Heavy aromatic feedstock is converted into lighter products under a wide range of very high pressures (1,000 - 2,000 psi) and fairly high temperatures (750-1,500 degrees F), in the presence of hydrogen and special catalysts. When the feedstock has a high paraffinic content, the primary function of hydrogen is to prevent the formation of polycyclic aromatic compounds. Another important role of hydrogen in the hydrocracking process is to reduce tar formation and prevent buildup of coke on the catalyst. Hydrogenation also serves to convert sulfur and nitrogen compounds present in the feedstock to hydrogen sulfide and ammonia.
Hydrocracking produces relatively large amounts of isobutane for alkylation feedstocks. Hydrocracking also performs isomerization for pour-point control and smoke-point control, both of which are important in high-quality jet fuel.
HYDROCRACKING PROCESS
In the first stage, preheated feedstock is mixed with recycled hydrogen and sent to the first-stage reactor, where catalysts convert sulfur and nitrogen compounds to hydrogen sulfide and ammonia. Limited hydrocracking also occurs.
After the hydrocarbon leaves the first stage, it is cooled and liquefied and run through a hydrocarbon separator. The hydrogen is recycled to the feedstock. The liquid is charged to a fractionator. Depending on the products desired (gasoline components, jet fuel, and gas oil), the fractionator is run to cut out some portion of the first stage reactor outturn. Kerosene-range material can be taken as a separate side-draw product or included in the fractionator bottoms with the gas oil.
The fractionator bottoms are again mixed with a hydrogen stream and charged to the second stage. Since this material has already been subjected to some hydrogenation, cracking, and reforming in the first stage, the operations of the second stage are more severe (higher temperatures and pressures). Like the outturn of the first stage, the second stage product is separated from the hydrogen and charged to the fractionator.
HEALTH AND SAFETY CONSIDERATIONS
Fire Prevention and Protection
Because this unit operates at very high pressures and temperatures, control of both hydrocarbon leaks and hydrogen releases is important to prevent fires. In some processes, care is needed to ensure that explosive concentrations of catalytic dust do not form during recharging.
Table III:2-12. HYDROCRACKING PROCESS
_____________________________________________________________________
Feedstocks From Process Typical products..... To
High pour Catalytic Decomposi- Kerosene, jet fuel...Blending
point cracker tion
residuals Atmospheric, Hydrogena- Gasoline,............Blending
vacuum tower tion distillates
Gas oil Vacuum tower, Heavy Recycle, reformer
coker naphthas
Hydrogen Reformer Gas..................Gas plant
_____________________________________________________________________
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
(For III:2-15, Click Here
Safety
Inspection and testing of safety relief devices are important due to the very high pressures in this unit. Proper process control is needed to protect against plugging reactor beds. Unloading coked catalyst requires special precautions to prevent iron sulfideinduced fires. The coked catalyst should either be cooled to below 120 degrees F before dumping, or be placed in nitrogen-inerted containers until cooled.
Because of the operating temperatures and presence of hydrogen, the hydrogen-sulfide content of the feedstock must be strictly controlled to a minimum to reduce the possibility of severe corrosion. Corrosion by wet carbon dioxide in areas of condensation also must be considered. When processing high-nitrogen feedstocks, the ammonia and hydrogen sulfide form ammonium hydrosulfide, which causes serious corrosion at temperatures below the water dew point. Ammonium hydrosulfide is also present in sour water stripping.
Health
Because this is a closed process, exposures are expected to be minimal under normal operating conditions. There is a potential for exposure to hydrocarbon gas and vapor emissions, hydrogen and hydrogen sulfide gas due to high-pressure leaks. Large quantities of carbon monoxide may be
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
released during catalyst regeneration and changeover. Catalyst steam stripping and regeneration create waste streams containing sour water and ammonia. Safe work practices and/or the use of appropriate personal protective equipment may be needed for exposure to chemicals and other hazards such as noise and heat, during process sampling, inspection, maintenance, and turnaround activities, and when handling spent catalyst.
CATALYTIC REFORMING
Catalytic reforming is an important process used to convert low-octane naphthas into high-octane gasoline blending components called reformate. Reforming represents the total effect of numerous reactions such as cracking, polymerization, dehydrogenation, and isomerization taking place simultaneously. Depending on the properties of the naphtha feedstock (as measured by the paraffin, olefin, naphthene, and aromatic content) and catalysts used, reformates can be produced with very high concentrations of toluene, benzene, xylene, and other aromatics useful in gasoline blending and petrochemical processing. Hydrogen, a significant by-product, is separated from the reformate for recycling and use in other processes.
A catalytic reformer comprises a reactor section and a product-recovery section. More or less standard is a feed preparation section in which, by combination of hydrotreatment and distillation, the feedstock is prepared to specification. Most processes use platinum as the active catalyst. Sometimes platinum is combined with a second catalyst (bimetallic catalyst) such as rhenium or another noble metal.
There are many different commercial catalytic reforming processes including platforming, powerforming, ultraforming, and Thermofor catalytic reforming. In the platforming process, the first step is preparation of the naphtha feed to remove impurities from the naphtha and reduce catalyst degradation. The naphtha feedstock is then mixed with hydrogen, vaporized, and passed through a series of alternating furnace and fixed-bed reactors containing a platinum catalyst. The effluent from the last reactor is cooled and sent to a separator to permit removal of the hydrogen-rich gas stream from the top of the separator for recycling. The liquid product from the bottom of the separator is sent to a fractionator called a stabilizer (butanizer). It makes a bottom product called reformate; butanes and lighter go overhead and are sent to the saturated gas plant.
Some catalytic reformers operate at low pressure (50-200 psi), and others operate at high pressures (up to 1,000 psi). Some catalytic reforming systems continuously regenerate the catalyst in other systems. One reactor at a time is taken off-stream for catalyst regeneration, and some facilities regenerate all of the reactors during turnarounds.
HEALTH AND SAFETY CONSIDERATIONS
Fire Prevention and Protection
This is a closed system; however, the potential for fire exists should a leak or release of reformate gas or hydrogen occur.
Safety
Operating procedures should be developed to ensure control of hot spots during start-up. Safe catalyst handling is very important. Care must be taken not to break or crush the catalyst when loading the beds, as the small fines will plug up the reformer screens. Precautions against dust when regenerating or replacing catalyst should also be considered. Also, water wash should be considered where stabilizer fouling has occurred due to the formation of ammonium chloride and iron salts. Ammonium chloride may form in pretreater exchangers and cause corrosion and fouling. Hydrogen chloride from the hydrogenation of chlorine compounds may form acid or ammonium chloride salt.
Health
Because this is a closed process, exposures are expected to be minimal
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
under normal operating conditions. There is potential for exposure to hydrogen sulfide and benzene should a leak or release occur.
Small emissions of carbon monoxide and hydrogen sulfide may occur during regeneration of catalyst. Safe work practices and/or appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat; during testing, inspecting, maintenance and turnaround activities; and when handling regenerated or spent catalyst.
Table III:2-13. CATALYTIC REFORMING PROCESS _____________________________________________________________________ Feedstocks From Process Typical products...To Desulfurized Coker Rearrange, High octane naphtha dehydro- gasoline...........Blending genate Naphthene- Hydro- Aromatics..........Petrochemical rich cracker fractions Hydrode- Hydrogen...........Recycle, sulfur hydrotreat, etc. Straight-run Atmospheric Gas................Gas plant naphtha fractionator _____________________________________________________________________
(For III:2-16, Click Here
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
CATALYTIC HYDROTREATING
Catalytic hydrotreating is a hydrogenation process used to remove about 90% of contaminants such as nitrogen, sulfur, oxygen, and metals from liquid petroleum fractions. These contaminants, if not removed from the petroleum fractions as they travel through the refinery processing units, can have detrimental effects on the equipment, the catalysts, and the quality of the finished product. Typically, hydrotreating is done prior to processes such as catalytic reforming so that the catalyst is not contaminated by untreated feedstock. Hydrotreating is also used prior to catalytic cracking to reduce sulfur and improve product yields, and to upgrade middle-distillate petroleum fractions into finished kerosene, diesel fuel, and heating fuel oils. In addition, hydrotreating converts olefins and aromatics to saturated compounds.
CATALYTIC HYDRODESULFURIZATION PROCESS
Hydrotreating for sulfur removal is called hydrodesulfurization. In a typical catalytic hydrodesulfurization unit, the feedstock is deaerated and mixed with hydrogen, preheated in a fired heater (600-800 degrees F) and then charged under pressure (up to 1,000 psi) through a fixed-bed catalytic reactor. In the reactor, the sulfur and nitrogen compounds in the feedstock are converted into H(2)S and NH(3). The reaction products leave the reactor and after cooling to a low temperature enter a liquid/gas separator. The hydrogen-rich gas from the high-pressure separation is recycled to combine with the feedstock, and the low-pressure gas stream rich in H(2)S is sent to a gas treating unit where H(2)S is removed. The clean gas is then suitable as fuel for the refinery furnaces. The liquid stream is the product from hydrotreating and is normally sent to a stripping column for removal of H(2)S and other undesirable components. In cases where steam is used for stripping, the product is sent to a vacuum drier for removal of water. Hydrodesulfurized products are blended or used as catalytic reforming feedstock.
OTHER HYDROTREATING PROCESSES
Hydrotreating processes differ depending upon the feedstocks available and catalysts used. Hydrotreating can be used to improve the burning characteristics of distillates such as kerosene. Hydrotreatment of a kerosene fraction can convert aromatics into naphthenes, which are cleaner-burning compounds.
Lube-oil hydrotreating uses catalytic treatment of the oil with hydrogen to improve product quality. The objectives in mild lube hydrotreating include saturation of olefins and improvements in color, odor, and acid nature of the oil. Mild lube hydrotreating also may be used following solvent processing. Operating temperatures are usually below 600 degrees F and operating pressures below 800 psi. Severe lube hydrotreating, at temperatures in the 600-750 degrees F range and hydrogen pressures up to 3,000 psi, is capable of saturating aromatic rings, along with sulfur and nitrogen removal, to impart specific properties not achieved at mild conditions.
Hydrotreating also can be employed to improve the quality of pyrolysis gasoline (pygas), a by-product from the manufacture of ethylene. Traditionally, the outlet for pygas has been motor gasoline blending, a suitable route in view of its high octane number. However, only small portions can be blended untreated owing to the unacceptable odor, color, and gum-forming tendencies of this material. The quality of pygas, which is high in diolefin content, can be satisfactorily improved by hydro-treating, whereby conversion of diolefins into mono-olefins provides an acceptable product for motor gas blending.
HEALTH AND SAFETY CONSIDERATIONS
Fire Prevention and Protection
The potential exists for fire in the event of a leak or release of product or hydrogen gas.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Table III:2-14. HYDRODESULFURIZATION PROCESS
_____________________________________________________________________
Feedstocks From Process Typical products.....To
Naphthas, Atmospheric & Treating, Naphtha............Catalytic
distillates vacuum tower hydrogena- reformer
Sour gas tion Hydrogen...........Recycle
oil,
Residuals Catalytic & Distillates........Blending
thermal cracker H(2)S,
ammonia............Sulfur plant,
treater
Gas................Gas plant
_____________________________________________________________________
Safety
Many processes require hydrogen generation to provide for a continuous supply. Because of the operating temperatures and presence of hydrogen, the hydrogen sulfide content of the feedstock must be strictly controlled to a minimum to reduce corrosion. Hydrogen chloride may form and condense as hydrochloric acid in the lower-temperature parts of the unit. Ammonium hydrosulfide may form in high-temperature, high-pressure units. Excessive contact time and/or temperature will create coking. Precautions need to be taken when unloading coked catalyst from the unit to prevent iron sulfide fires. The coked catalyst should be cooled to below 120 degrees F before removal, or dumped into nitrogen-inerted bins where it can be cooled before further handling. Special antifoam additives may be used to prevent catalyst poisoning from silicone carryover in the coker feedstock.
Health
Because this is a closed process, exposures are expected to be minimal under normal operating conditions. There is a potential for exposure to hydrogen sulfide or hydrogen gas in the event of a release, or to ammonia should a sour-water leak or spill occur. Phenol also may be present if high boiling-point feedstocks are processed. Safe work practices and/or appropriate personal protective equipment may be needed for exposures to
(For III:2-17, Click Here
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
chemicals and other hazards such as noise and heat; during process sampling, inspection, maintenance, and turnaround activities; and when handling amine or exposed to catalyst.
ISOMERIZATION
Isomerization converts n-butane, n-pentane and n-hexane into their respective isoparaffins of substantially higher octane number. The straight-chain paraffins are converted to their branched-chain counterparts whose component atoms are the same but are arranged in a different geometric structure. Isomerization is important for the conversion of n-butane into isobutane, to provide additional feedstock for alkylation units, and the conversion of normal pentanes and hexanes into higher branched isomers for gasoline blending. Isomerization is similar to catalytic reforming in that the hydrocarbon molecules are rearranged, but unlike catalytic reforming, isomerization just converts normal paraffins to isoparaffins.
There are two distinct isomerization processes, butane (C(4)) and pentane/hexane (C(5)/C(6)). Butane isomerization produces feedstock for alkylation. Aluminum chloride catalyst plus hydrogen chloride are universally used for the low-temperature processes. Platinum or another metal catalyst is used for the higher-temperature processes. In a typical low-temperature process, the feed to the isomerization plant is n-butane or mixed butanes mixed with hydrogen (to inhibit olefin formation) and passed to the reactor at 230-340 degrees F and 200-300 psi. Hydrogen is flashed off in a high-pressure separator and the hydrogen chloride removed in a stripper column. The resultant butane mixture is sent to a fractionator (deisobutanizer) to separate n-butane from the isobutane product.
Pentane/hexane isomerization increases the octane number of the light gasoline components n-pentane and n-hexane, which are found in abundance in straight-run gasoline. In a typical C(5)/C(6) isomerization process, dried and desulfurized feedstock is mixed with a small amount of organic chloride and recycled hydrogen, and then heated to reactor temperature. It is then passed over supported-metal catalyst in the first reactor where benzene and olefins are hydrogenated. The feed next goes to the isomerization reactor where the paraffins are catalytically isomerized to isoparaffins. The reactor effluent is then cooled and subsequently separated in the product separator into two streams: a liquid product (isomerate) and a recycle hydrogen-gas stream. The isomerate is washed (caustic and water), acid stripped, and stabilized before going to storage.
SAFETY AND HEALTH CONSIDERATIONS
Fire Protection and Prevention
Although this is a closed process, the potential for a fire exists should a release or leak contact a source of ignition such as the heater.
Safety
If the feedstock is not completely dried and desulfurized, the potential exists for acid formation leading to catalyst poisoning and metal corrosion. Water or steam must not be allowed to enter areas where
Table III:2-15. ISOMERIZATION PROCESSES _____________________________________________________________________ Feedstock From Process Typical products... To n-Butane Various Rearrange- Isobutane.......... Alkylation n-Pentane processes ment Isopentane......... Blending n-Hexane Isohexane.......... Blending Gas................ Gas Plant _____________________________________________________________________
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
(For III:2-18, Click Here
(For III:2-19, Click Here
hydrogen chloride is present. Precautions are needed to prevent HCl from entering sewers and drains.
Health
Because this is a closed process, exposures are expected to be minimal during normal operating conditions. There is a potential for exposure to hydrogen gas, hydrochloric acid, and hydrogen chloride and to dust when solid catalyst is used. Safe work practices and/or appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as heat and noise, and during process sampling, inspection, maintenance, and turnaround activities.
POLYMERIZATION
Polymerization in the petroleum industry is the process of converting light olefin gases including ethylene, propylene, and butylene into hydrocarbons of higher molecular weight and higher octane number that can be used as gasoline blending stocks. Polymerization combines two or more identical olefin molecules to form a single molecule with the same elements in the same proportions as the original molecules. Polymerization may be accomplished thermally or in the presence of a catalyst at lower temperatures.
The olefin feedstock is pretreated to remove sulfur and other undesirable compounds. In the catalytic process the feedstock is either passed over a solid phosphoric acid catalyst or comes in contact with liquid phosphoric acid, where an exothermic polymeric reaction occurs. This reaction requires cooling water and the injection of cold feedstock into the reactor to control temperatures between 300 degrees and 450 degrees F at pressures from 200 psi to 1,200 psi. The reaction products leaving the reactor are sent to stabilization and/or fractionator systems to separate saturated and unreacted gases from the polymer gasoline product.
NOTE: In the petroleum industry, polymerization is used to indicate the production of gasoline components, hence the term "polymer" gasoline. Furthermore, it is not essential that only one type of monomer be involved. If unlike olefin molecules are combined, the process is referred to as "copolymerization." Polymerization in the true sense of the word is normally prevented, and all attempts are made to terminate the reaction at the dimer or trimer (three monomers joined together) stage. However, in the petrochemical section of a refinery, polymerization, which results in the production of, for instance, polyethylene, is allowed to proceed until materials of the required high molecular weight have been produced.
SAFETY AND HEALTH CONSIDERATIONS
Fire Prevention and Protection
Polymerization is a closed process where the potential for a fire could occur due to leaks or releases reaching a source of ignition.
Safety
The potential for an uncontrolled exothermic reaction exists should loss of cooling water occur. Severe corrosion leading to equipment failure will occur should water make contact with the phosphoric acid, such as during water washing at shutdowns. Corrosion may also occur in piping
Table III:2-16. POLYMERIZATION PROCESS _____________________________________________________________________ Feedstocks From Process Typical products To Olefins Cracking Unification High octane Gasoline processes naphtha blending Petrochem. Petrochemical feedstocks Liquefied petro. Storage gas _____________________________________________________________________
manifolds, reboilers, exchangers, and other locations where acid may settle out.
Health
Because this is a closed system, exposures are expected to be minimal under normal operating conditions. There is a potential for exposure to caustic wash (sodium hydroxide), to phosphoric acid used in the process or washed out during turnarounds, and to catalyst dust. Safe work practices and/or appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat, and during process sampling, inspection, maintenance, and turnaround activities.
(For III:2-20, Click Here
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
ALKYLATION
Alkylation combines low-molecular-weight olefins (primarily a mixture of propylene and butylene) with isobutene in the presence of a catalyst, either sulfuric acid or hydrofluoric acid. The product is called alkylate and is composed of a mixture of high-octane, branched-chain paraffinic hydrocarbons. Alkylate is a premium blending stock because it has exceptional antiknock properties and is clean burning. The octane number of the alkylate depends mainly upon the kind of olefins used and upon operating conditions.
SULFURIC ACID ALKYLATION PROCESS
In cascade type sulfuric acid (H(2)SO(4)) alkylation units, the feedstock (propylene, butylene, amylene, and fresh isobutane) enters the reactor and contacts the concentrated sulfuric acid catalyst (in concentrations of 85% to 95% for good operation and to minimize corrosion). The reactor is divided into zones, with olefins fed through distributors to each zone, and the sulfuric acid and isobutanes flowing over baffles from zone to zone.
The reactor effluent is separated into hydrocarbon and acid phases in a settler, and the acid is returned to the reactor. The hydrocarbon phase is hot-water washed with caustic for pH control before being successively depropanized, deisobutanized, and debutanized. The alkylate obtained from the deisobutanizer can then go directly to motor-fuel blending or be rerun to produce aviation-grade blending stock. The isobutane is recycled to the feed.
HYDROFLUORIC ACID ALKYLATION PROCESS
Phillips and UOP are the two common types of hydro-fluoric acid alkylation processes in use. In the Phillips process, olefin and isobutane feedstock are dried and fed to a combination reactor/settler system. Upon leaving the reaction zone, the reactor effluent flows to a settler (separating vessel) where the acid separates from the hydrocarbons. The acid layer at the bottom of the separating vessel is recycled. The top layer of hydrocarbons (hydrocarbon phase), consisting of propane, normal butane, alkylate, and excess (recycle) isobutane, is charged to the main fractionator, the bottom product of which is motor alkylate. The main fractionator overhead, consisting mainly of propane, isobutane, and HF, goes to a depropanizer. Propane with trace amount of HF goes to an HF stripper for HF removal and is then catalytically defluorinated, treated, and sent to storage. Isobutane is withdrawn from the main fractionator and recycled to the reactor/settler, and alkylate from the bottom of the main fractionator is sent to product blending.
The UOP process uses two reactors with separate settlers. Half of the dried feedstock is charged to the first reactor, along with recycle and makeup isobutane. The reactor effluent then goes to its settler, where the acid is recycled and the hydrocarbon charged to the second reactor. The other half of the feedstock also goes to the second reactor, with the settler acid being recycled and the hydrocarbons charged to the main fractionator. Subsequent processing is similar to the Phillips process. Overhead from the main fractionator goes to a depropanizer. Isobutane is recycled to the reaction zone and alkylate is sent to product blending.
Table III:2-17. ALKYLATION PROCESS _____________________________________________________________________ Feedstocks From Process Typical products....To Petroleum gas Distillation Unification High octane or cracking gasoline...........Blending Olefins Cat. or hydro n-Butane & Stripper or cracking propane...........blender Isobutane Isomerization _____________________________________________________________________
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
(For III:2-21, Click Here
(For III:2-22, Click Here
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
Alkylation units are closed processes; however, the potential exists for fire should a leak or release occur that allows product or vapor to reach a source of ignition.
Safety
Sulfuric acid and hydrofluoric acid are potentially hazardous chemicals. Loss of coolant water, which is needed to maintain process temperatures, could result in an upset. Precautions are necessary to ensure that equipment and materials that have been in contact with acid are handled carefully and are thoroughly cleaned before they leave the process area or refinery. Immersion wash vats are often provided for neutralization of equipment that has come into contact with hydrofluoric acid. Hydrofluoric acid units should be thoroughly drained and chemically cleaned prior to turnarounds and entry to remove all traces of iron fluoride and hydro-fluoric acid. Following shutdown, where water has been used the unit should be thoroughly dried before hydrofluoric acid is introduced.
Leaks, spills, or releases involving hydrofluoric acid or hydrocarbons containing hydrofluoric acid can be extremely hazardous. Care during delivery and unloading of acid is essential. Process unit containment by curbs and drainage and isolation so that effluent can be neutralized before release to the sewer system should be considered. Vents can be routed to soda-ash scrubbers to neutralize hydrogen fluoride gas or hydrofluoric acid vapors before release. Pressure on the cooling water and steam side of exchangers should be kept below the minimum pressure on the acid service side to prevent water contamination.
Some corrosion and fouling in sulfuric acid units may occur from the breakdown of sulfuric acid esters or where caustic is added for neutralization. These esters can be removed by fresh acid treating and hot-water washing. To prevent corrosion from hydrofluoric acid, the acid concentration inside the process unit should be maintained above 65% and moisture below 4%.
Health
Because this is a closed process, exposures are expected to be minimal during normal operations. There is a potential for exposure should leaks, spills, or releases occur. Sulfuric acid and (particularly) hydrofluoric acid are potentially hazardous chemicals. Special precautionary emergency preparedness measures and protection appropriate to the potential hazard and areas possibly affected need to be provided. Safe work practices and appropriate skin and respiratory personal protective equipment are needed for potential exposures to hydrofluoric and sulfuric acids during normal operations such as reading gauges, inspecting, and process sampling, as well as during emergency response, maintenance, and turnaround activities. Procedures should be in place to ensure that protective equipment and clothing worn in hydrofluoric acid activities are decontaminated and inspected before reissue. Appropriate personal protection for exposure to heat and noise also may be required.
SWEETENING AND TREATING PROCESSES
Treating is a means by which contaminants such as organic compounds containing sulfur, nitrogen, and oxygen; dissolved metals and inorganic salts; and soluble salts dissolved in emulsified water are removed from petroleum fractions or streams. Petroleum refiners have a choice of several different treating processes, but the primary purpose of the majority of them is the elimination of unwanted sulfur compounds. A variety of intermediate and finished products, including middle distillates, gasoline, kerosene, jet fuel and sour gases are dried and sweetened. Sweetening, a major refinery treatment of gasoline, treats sulfur compounds (hydrogen sulfide, thiophene and mercaptan) to improve color, odor and oxidation stability. Sweetening also reduces concentrations of carbon dioxide.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Treating can be accomplished at an intermediate stage in the refining process, or just before sending the finished product to storage. Choices of a treating method depend on the nature of the petroleum fractions, amount and type of impurities in the fractions to be treated, the extent to which the process removes the impurities, and end-product specifications. Treating materials include acids, solvents, alkalis, oxidizing, and adsorption agents.
ACID, CAUSTIC, or CLAY TREATING
Sulfuric acid is the most commonly used acid treating process. Sulfuric acid treating results in partial or complete removal of unsaturated hydrocarbons, sulfur, nitrogen, and oxygen compounds, and resinous and asphaltic compounds. It is used to improve the odor, color, stability, carbon residue, and other properties of the oil. Clay/lime treatment of acid-refined oil removes traces of asphaltic materials and other compounds improving product color, odor, and stability. Caustic treating with sodium (or potassium) hydroxide is used to improve odor and color by removing organic acids (naphthenic acids, phenols) and sulfur compounds (mercaptans, H(2)S) by a caustic wash. By combining caustic soda solution with various solubility promoters (e.g., methyl alcohol and cresols), up to 99% of all mercaptans as well as oxygen and nitrogen compounds can be dissolved from petroleum fractions.
DRYING AND SWEETENING
Feedstocks from various refinery units are sent to gas treating plants where butanes and butenes are removed for use as alkylation feedstock, heavier components are sent to gasoline blending, propane is recovered for LPG, and propylene is removed for use in petrochemicals. Some mercaptans are removed by water-soluble chemicals that react with the mercaptans. Caustic liquid (sodium hydroxide), amine compounds (diethanolamine) or fixed-bed catalyst sweetening also may be used. Drying is accomplished by the use of water absorption or adsorption agents to remove water from the products. Some processes simultaneously dry and sweeten by adsorption on molecular sieves.
SULFUR RECOVERY
Sulfur recovery converts hydrogen sulfide in sour gases and hydrocarbon streams to elemental sulfur. The most widely used recovery system is the Claus process, which uses both thermal and catalytic-conversion reactions. A typical process produces elemental sulfur by burning hydrogen sulfide under controlled conditions. Knockout pots are used to remove water and hydrocarbons from feed gas streams. The gases are then exposed to a catalyst to recover additional sulfur. Sulfur vapor from burning and conversion is condensed and recovered.
HYDROGEN SULFIDE SCRUBBING
Hydrogen sulfide scrubbing is a common treating process in which the hydrocarbon feedstock is first scrubbed to prevent catalyst poisoning. Depending on the feedstock and the nature of contaminants, desulfurization methods vary from ambient temperature-activated charcoal absorption to high-temperature catalytic hydrogenation followed by zinc oxide treating.
Table III:2-18. SWEETENING AND TREATING PROCESSES _____________________________________________________________________ Feedstocks From Process Products........ To Gases Various Treatment Butane & butene...Alkylation Finished Propane, products distillates......Storage Intermediates Gasoline..........Blending Propylene.........Petrochemical _____________________________________________________________________
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
(For III:2-23, Click Here
(For Figure III:2-23 Molecular Sieve Drying and Sweetening, see printed copy)
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
The potential exists for fire from a leak or release of feedstock or product. Sweetening processes use air or oxygen. If excess oxygen enters these processes, it is possible for a fire to occur in the settler due to the generation of static electricity, which acts as the ignition source.
Health
Because these are closed processes, exposures are expected to be minimal under normal operating conditions. There is a potential for exposure to hydrogen sulfide, caustic (sodium hydroxide), spent caustic, spent catalyst (Merox), catalyst dust and sweetening agents (sodium carbonate and sodium bicarbonate). Safe work practices and/or appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat, and during process sampling, inspection, maintenance, and turnaround activities.
UNSATURATED GAS PLANTS
Unsaturated (unsat) gas plants recover light hydrocarbons (C(3) and C(4) olefins) from wet gas streams from the FCC, TCC, and delayed coker overhead accumulators or fractionation receivers. In a typical unsat gas plant, the gases are compressed and treated with amine to remove hydrogen sulfide either before or after they are sent to a fractionating absorber where they are mixed into a concurrent flow of debutanized gasoline. The light fractions are separated by heat in a reboiler, the offgas is sent to a sponge absorber, and the bottoms are sent to a debutanizer. A portion of the debutanized hydrocarbon is recycled, with the balance sent to the splitter for separation. The overhead gases go to a depropanizer for use as alkylation unit feedstock.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Table III:2-19. UNSAT GAS PLANT PROCESS
_____________________________________________________________________
Feedstock From Process Typical products... To
Gas Oils FCC,TCC, Treatment Gasoline.............Recycle or treating
Delayed Gases................Alkylation
coker
_____________________________________________________________________
HEALTH AND SAFETY CONSIDERATIONS
Fire Prevention and Protection
The potential of a fire exists should spills, releases, or vapors reach a source of ignition.
Safety
In unsat gas plants handling FCC feedstocks, the potential exists for corrosion from moist hydrogen sulfide and cyanides. When feedstocks are from the delayed coker or the TCC, corrosion from hydrogen sulfide and deposits in the high pressure sections of gas compressors from ammonium compounds is possible.
Health
Because these are closed processes, exposures are expected to be minimal under normal operating conditions. There is a potential for exposures to amine compounds such as monoethanolamine (MEA), diethanolamine (DEA) and methyldiethanolamine (MDEA) and hydrocarbons. Safe work practices and/or appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat, and during process sampling, inspection, maintenance, and turnaround activities.
AMINE PLANTS
Amine plants remove acid contaminants from sour gas and hydrocarbon streams. In amine plants, gas and liquid hydrocarbon streams containing carbon dioxide and/or hydrogen sulfide are charged to a gas absorption tower or liquid contactor where the acid contaminants are absorbed by counterflowing amine solutions (i.e., MEA, DEA, MDEA). The stripped gas or liquid is removed overhead, and the amine is sent to a regenerator. In the regenerator, the acidic components are stripped by heat and reboiling action and disposed of, and the amine is recycled.
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
The potential for fire exists where a spill or leak could reach a source of ignition.
Safety
To minimize corrosion, proper operating practices should be established and regenerator bottom and reboiler temperatures controlled. Oxygen should be kept out of the system to prevent amine oxidation.
Health
Because this is a closed process, exposures are expected to be minimal during normal operations. There is potential for exposure to amine compounds (i.e., monoethanolamine, diethanolamine, methyldiethanolamine), hydrogen sulfide and carbon dioxide. Safe work practices and/or appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat, and during process sampling, inspection, maintenance and turnaround activities.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SATURATE GAS PLANTS
Saturate gas plants separate refinery gas components including butanes for alkylation, pentanes for gasoline blending, LPGs for fuel, and ethane for petrochemicals. Because sat gas processes depend on the feedstock and product demand, each refinery uses different systems, usually absorption-fractionation or straight fractionation. In absorption-fractionation, gases and liquids from various refinery units are fed to an absorber-deethanizer where C(2) and lighter fractions are separated from heavier fractions by lean oil absorption and removed for use as fuel gas or petrochemical feed. The heavier fractions are stripped and sent to a debutanizer, and the lean oil is recycled back to the absorber-deethanizer. C(3)/C(4) is separated from pentanes in the debutanizer, scrubbed to remove hydrogen sulfide, and fed to a splitter where propane and butane are separated. In fractionation sat-gas plants, the absorption stage is eliminated.
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
There is potential for fire if a leak or release reaches a source of ignition such as the unit reboiler.
Safety
Corrosion could occur from the presence of hydrogen sulfide, carbon dioxide, and other compounds as a result of prior treating. Streams containing ammonia should be dried before processing. Antifouling additives may be used in absorption oil to protect heat exchangers. Corrosion inhibitors may be used to control corrosion in overhead systems.
Health
Because this is a closed process, exposures are expected to be minimal during normal operations. There is potential for exposure to hydrogen sulfide, carbon dioxide, and other products such as diethanolamine or sodium hydroxide carried over from prior treating. Safe work practices and/or appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat, and during process sampling, inspection, maintenance, and turnaround activities.
ASPHALT PRODUCTION
Asphalt is a portion of the residual fraction that remains after primary distillation operations. It is further processed to impart characteristics required by its final use. In vacuum distillation, generally used to produce road-tar asphalt, the residual is heated to about 750 degrees F and charged to a column where vacuum is applied to prevent cracking.
Asphalt for roofing materials is produced by air blowing. Residual is heated in a pipe still almost to its flash point and charged to a blowing tower where hot air is injected for a predetermined time. The dehydrogenization of the asphalt forms hydrogen sulfide, and the oxidation creates sulfur dioxide. Steam, used to blanket the top of the tower to entrain the various contaminants, is then passed through a scrubber to condense the hydrocarbons.
A third process used to produce asphalt is solvent deasphalting. In this extraction process, which uses propane (or hexane) as a solvent, heavy oil fractions are separated to produce heavy lubricating oil, catalytic cracking feedstock, and asphalt. Feedstock and liquid propane are pumped to an extraction tower at precisely controlled mixtures, temperatures (150-250 degrees F), and pressures of 350-600 psi. Separation occurs in a rotating disc contactor, based on differences in solubility. The products are then evaporated and steam stripped to recover the propane, which is recycled. Deasphalting also removes some sulfur and nitrogen compounds, metals, carbon residues, and paraffins from the feedstock.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Table III:2-20. SOLVENT DEASPHALTING PROCESS _____________________________________________________________________ Feedstock From Process Typical products.... To Residual Vacuum tower Treatment Heavy lube oil........Treating or lube blending Atmospheric Asphalt Storage or tower shipping Reduced Deasphalted oil.......Hydrotreat & crude catalytic cracker Propane...............Recycle _____________________________________________________________________
SAFETY AND HEALTH CONSIDERATIONS
Fire Protection and Prevention
The potential for a fire exists if a product leak or release contacts a source of ignition such as the process heater. Condensed steam from the various asphalt and deasphalting processes will contain trace amounts of hydrocarbons. Any disruption of the vacuum can result in the entry of atmospheric air and subsequent fire. In addition, raising the temperature of the vacuum tower bottom to improve efficiency can generate methane by thermal cracking. This can create vapors in asphalt storage tanks that are not detectable by flash testing but are high enough to be flammable.
Safety
Deasphalting requires exact temperature and pressure control. In addition, moisture, excess solvent, or a drop in operating temperature may cause foaming, which affects the product temperature control and may create an upset.
Health
Because these are closed processes, exposures are expected to be minimal during normal operations. Should a spill or release occur, there is a potential for exposure to residuals and asphalt. Air blowing can create some polynuclear aromatics. Condensed steam from the air-blowing asphalt process may also contain contaminants. The potential for exposure to hydrogen sulfide and sulfur dioxide exists in the production of asphalt. Safe work practices and/or appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat, and during process sampling, inspection, maintenance, and turnaround activities.
HYDROGEN PRODUCTION
High-purity hydrogen (95-99%) is required for hydro-desulfurization, hydrogenation, hydrocracking, and petrochemical processes. Hydrogen, produced as a by-product of refinery processes (principally hydrogen recovery from catalytic reformer product gases), often is not enough to meet the total refinery requirements, necessitating the manufacturing of additional hydrogen or obtaining supply from external sources.
In steam-methane reforming, desulfurized gases are mixed with superheated steam (1,100-1,600 degrees F) and reformed in tubes containing a nickel base catalyst. The reformed gas, which consists of steam, hydrogen, carbon monoxide, and carbon dioxide, is cooled and passed through converters containing an iron catalyst where the carbon monoxide reacts with steam to form carbon dioxide and more hydrogen. The carbon dioxide is removed by amine washing. Any remaining carbon monoxide in the product stream is converted to methane.
Steam-naphtha reforming is a continuous process for the production of hydrogen from liquid hydrocarbons and is, in fact, similar to steam-methane reforming. A variety of naphthas in the gasoline boiling range may be employed, including fuel containing up to 35% aromatics. Following pretreatment to remove sulfur compounds, the feedstock is mixed with steam and taken to the reforming furnace (1,250-1,500 degrees F) where hydrogen is produced.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Table III:2-21. STEAM REFORMING PROCESS
_____________________________________________________________________
Feedstock From Process Typical products... To
Desulfurized Various Decomposition Hydrogen............. Processing
refinery gas treatment Carbon dioxide....... Atmosphere
units Carbon monoxide...... Methane
_____________________________________________________________________
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
The possibility of fire exists should a leak or release occur and reach an ignition source.
Safety
The potential exists for burns from hot gases and superheated steam should a release occur. Inspections and testing should be considered where the possibility exists for valve failure due to contaminants in the hydrogen. Carryover from caustic scrubbers should be controlled to prevent corrosion in preheaters. Chlorides from the feedstock or steam system should be prevented from entering reformer tubes and contaminating the catalyst.
Health
Because these are closed processes, exposures are expected to be minimal during normal operating conditions. There is a potential for exposure to excess hydrogen, carbon monoxide, and/or carbon dioxide. Condensate can be contaminated by process materials such as caustics and amine compounds, with resultant exposures. Depending on the specific process used, safe work practices and/or appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat, and during process sampling, inspection, maintenance, and turnaround activities.
BLENDING
Blending is the physical mixture of a number of different liquid hydrocarbons to produce a finished product with certain desired characteristics. Products can be blended in-line through a manifold system, or batch blended in tanks and vessels. In-line blending of gasoline, distillates, jet fuel, and kerosene is accomplished by injecting proportionate amounts of each component into the main stream where turbulence promotes thorough mixing. Additives including octane enhancers, metal deactivators, anti-oxidants, anti-knock agents, gum and rust inhibitors, detergents, etc. are added during and/or after blending to provide specific properties not inherent in hydrocarbons.
HEALTH AND SAFETY CONSIDERATIONS
Fire Prevention and Protection
Ignition sources in the area need to be controlled in the event of a leak or release.
Health
Safe work practices and/or appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat; when handling additives; and during inspection, maintenance, and turnaround activities.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
LUBRICANT, WAX, AND GREASE MANUFACTURING PROCESSES
Lubricating oils and waxes are refined from the residual fractions of atmospheric and vacuum distillation. The primary objective of the various lubricating oil refinery processes is to remove asphalts, sulfonated aromatics, and paraffinic and isoparaffinic waxes from residual fractions. Reduced crude from the vacuum unit is deasphalted and combined with straight-run lubricating oil feedstock, preheated, and solvent-extracted (usually with phenol or furfural) to produce raffinate.
WAX MANUFACTURING PROCESS
Raffinate from the extraction unit contains a considerable amount of wax that must be removed by solvent extraction and crystallization. The raffinate is mixed with a solvent (propane) and precooled in heat exchangers. The crystallization temperature is attained by the evaporation of propane in the chiller and filter feed tanks. The wax is continuously removed by filters and cold solvent-washed to recover retained oil. The solvent is recovered from the oil by flashing and steam stripping. The wax is then heated with hot solvent, chilled, filtered, and given a final wash to remove all oil.
LUBRICATING OIL PROCESS
The dewaxed raffinate is blended with other distillate fractions and further treated for viscosity index, color, stability, carbon residue, sulfur, additive response, and oxidation stability in extremely selective extraction processes using solvents (furfural, phenol, etc.). In a typical phenol unit, the raffinate is mixed with phenol in the treating section at temperatures below 400 degrees F. Phenol is then separated from the treated oil and recycled. The treated lube-oil base stocks are then mixed and/or compounded with additives to meet the required physical and chemical characteristics of motor oils, industrial lubricants, and metal working oils.
GREASE COMPOUNDING
Grease is made by blending metallic soaps (salts of long-chained fatty acids) and additives into a lubricating oil medium at temperatures of 400-600 degrees F. Grease may be either batch-produced or continuously compounded. The characteristics of the grease depend to a great extent on the metallic element (calcium, sodium, aluminum, lithium, etc.) in the soap and the additives used.
SAFETY AND HEALTH CONSIDERATIONS
Fire Protection and Prevention
The potential for fire exists if a product or vapor leak or release in the lube blending and wax processing areas reaches a source of ignition. Storage of finished products, both bulk and packaged, should be in accordance with recognized practices.
While the potential for fire is reduced in lube oil blending, care must be taken when making metal-working oils and compounding greases due to the use of higher blending and compounding temperatures and lower flash point products.
Table III:2-22. LUBRICATING OIL AND WAX MANUFACTURING PROCESSES _____________________________________________________________________ Feedstock From Process Typical products.. To Lube Vacuum tower, Treatment Dewaxed raffinate.....Lube blend solvent or compound feedstock dewaxing, Grease hydrotreating compounding and solvent Wax....................Storage or additives extraction, shipping etc. _____________________________________________________________________
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Safety
Control of treater temperature is important as phenol can cause corrosion above 400 degrees F. Batch and in-line blending operations require strict controls to maintain desired product quality. Spills should be cleaned and leaks repaired to avoid slips and falls. Additives in drums and bags need to be handled properly to avoid strain. Wax can clog sewer or oil drainage systems and interfere with wastewater treatment.
Health
When blending, sampling, and compounding, personal protection from steam, dusts, mists, vapors, metallic salts, and other additives is appropriate. Skin contact with any formulated grease or lubricant should be avoided. Safe work practices and/or appropriate personal protection may be needed for exposures to chemicals and other hazards such as noise and heat; during inspection, maintenance, and turnaround activities; and while sampling and handling hydrocarbons and chemicals during the production of lubricating oil and wax.
E. OTHER REFINERY OPERATIONS _____________________________________________________________________
HEAT EXCHANGERS, COOLERS, AND PROCESS HEATERS
HEATING OPERATIONS
Process heaters and heat exchangers preheat feedstocks in distillation towers and in refinery processes to reaction temperatures. Heat exchangers use either steam or hot hydrocarbon transferred from some other section of the process for heat input. The heaters are usually designed for specific process operations, and most are of cylindrical vertical or box-type designs. The major portion of heat provided to process units comes from fired heaters fueled by refinery or natural gas, distillate, and residual oils. Fired heaters are found on crude and reformer preheaters, coker heaters, and large-column reboilers.
COOLING OPERATIONS
Heat also may be removed from some processes by air and water exchangers, fin fans, gas and liquid coolers, and overhead condensers, or by transferring heat to other systems. The basic mechanical vapor-compression refrigeration system, which may serve one or more process units, includes an evaporator, compressor, condenser, controls, and piping. Common coolants are water, alcohol/water mixtures, or various glycol solutions.
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
A means of providing adequate draft or steam purging is required to reduce the chance of explosions when lighting fires in heater furnaces. Specific start-up and emergency procedures are required for each type of unit. If fire impinges on fin fans, failure could occur due to overheating. If flammable product escapes from a heat exchanger or cooler due to a leak, fire could occur.
Safety
Care must be taken to ensure that all pressure is removed from heater tubes before removing header or fitting plugs. Consideration should be given to providing for pressure relief in heat-exchanger piping systems in the event they are blocked off while full of liquid. If controls fail, variations of temperature and pressure could occur on either side of the heat exchanger. If heat exchanger tubes fail and process pressure is greater than heater pressure, product could enter the heater with downstream consequences. If the process pressure is less than heater
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
pressure, the heater stream could enter into the process fluid. If loss of circulation occurs in liquid or gas coolers, increased product temperature could affect downstream operations and require pressure relief.
Health
Because these are closed systems, exposures under normal operating conditions are expected to be minimal. Depending on the fuel, process operation, and unit design, there is a potential for exposure to hydrogen sulfide, carbon monoxide, hydrocarbons, steam boiler feed-water sludge, and water-treatment chemicals. Skin contact should be avoided with boiler blowdown, which may contain phenolic compounds. Safe work practices and/or appropriate personal protective equipment against hazards may be needed during process maintenance, inspection, and turnaround activities and for protection from radiant heat, superheated steam, hot hydrocarbon, and noise exposures.
STEAM GENERATION
HEATER AND BOILER OPERATIONS
Steam is generated in main generation plants, and/or at various process units using heat from flue gas or other sources. Heaters (furnaces) include burners and a combustion air system, the boiler enclosure in which heat transfer takes place, a draft or pressure system to remove flue gas from the furnace, soot blowers, and compressed-air systems that seal openings to prevent the escape of flue gas. Boilers consist of a number of tubes that carry the water-steam mixture through the furnace for maximum heat transfer. These tubes run between steam-distribution drums at the top of the boiler and water-collecting drums at the bottom of the boiler. Steam flows from the steam drum to the superheater before entering the steam distribution system.
HEATER FUEL
Heaters may use any one or combination of fuels including refinery gas, natural gas, fuel oil, and powdered coal. Refinery off-gas is collected from process units and combined with natural gas and LPG in a fuel-gas balance drum. The balance drum provides constant system pressure, fairly stable Btu-content fuel, and automatic separation of suspended liquids in gas vapors, and it prevents carryover of large slugs of condensate into the distribution system. Fuel oil is typically a mix of refinery crude oil with straight-run and cracked residues and other products. The fuel-oil system delivers fuel to process-unit heaters and steam generators at required temperatures and pressures. The fuel oil is heated to pumping temperature, sucked through a coarse suction strainer, pumped to a temperature-control heater, and then pumped through a fine-mesh strainer before being burned.
In one example of process-unit heat generation, carbon monoxide boilers recover heat in catalytic cracking units as carbon monoxide in flue gas is burned to complete combustion. In other processes, waste-heat recovery units use heat from the flue gas to make steam.
STEAM DISTRIBUTION
The distribution system consists of valves, fittings, piping, and connections suitable for the pressure of the steam transported. Steam leaves the boilers at the highest pressure required by the process units or electrical generation. The steam pressure is then reduced in turbines that drive process pumps and compressors. Most steam used in the refinery is condensed to water in various types of heat exchangers. The condensate is reused as boiler feedwater or discharged to wastewater treatment. When refinery steam is also used to drive steam turbine generators to produce electricity, the steam must be produced at much higher pressure than required for process steam. Steam typically is generated by heaters (furnaces) and boilers combined in one unit.
FEEDWATER
Feedwater supply is an important part of steam generation. There must always be as many pounds of water entering the system as there are pounds of steam leaving it. Water used in steam generation must be free of
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
contaminants including minerals and dissolved impurities that can damage the system or affect its operation. Suspended materials such as silt, sewage, and oil, which form scale and sludge, must be coagulated or filtered out of the water. Dissolved gases, particularly carbon dioxide and oxygen, cause boiler corrosion and are removed by deaeration and treatment. Dissolved minerals including metallic salts, calcium, carbonates, etc., that cause scale, corrosion, and turbine blade deposits are treated with lime or soda ash to precipitate them from the water. Recirculated cooling water must also be treated for hydrocarbons and other contaminants.
Depending on the characteristics of raw boiler feedwater, some or all of the following six stages of treatment will be applicable:
- (1) Clarification (2) Sedimentation (3) Filtration (4) Ion exchange (5) Deaeration (6) Internal treatment HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
The most potentially hazardous operation in steam generation is heater startup. A flammable mixture of gas and air can build up as a result of loss of flame at one or more burners during light-off. Each type of unit requires specific startup and emergency procedures including purging before lightoff and in the event of misfire or loss of burner flame.
Safety
If feedwater runs low and boilers are dry, the tubes will overheat and fail. Conversely, excess water will be carried over into the steam distribution system and damage the turbines. Feedwater must be free of contaminants that could affect operations. Boilers should have continuous or intermittent blowdown systems to remove water from steam drums and limit buildup of scale on turbine blades and superheater tubes. Care must be taken not to overheat the superheater during startup and shut-down. Alternate fuel sources should be provided in the event of loss of gas due to refinery unit shutdown or emergency. Knockout pots provided at process units remove liquids from fuel gas before burning.
Health
Safe work practices and/or appropriate personal protective equipment may be needed for potential exposures to feedwater chemicals, steam, hot water, radiant heat, and noise, and during process sampling, inspection, maintenance, and turnaround activities.
PRESSURE-RELIEF AND FLARE SYSTEMS
PRESSURE-RELIEF SYSTEMS
Pressure-relief systems control vapors and liquids that are released by pressure-relieving devices and blow-downs. Pressure relief is an automatic, planned release when operating pressure reaches a predetermined level. Blowdown normally refers to the intentional release of material, such as blowdowns from process unit startups, furnace blowdowns, shutdowns, and emergencies. Vapor depressuring is the rapid removal of vapors from pressure vessels in case of fire. This may be accomplished by the use of a rupture disc, usually set at a higher pressure than the relief valve.
SAFETY RELIEF VALVE OPERATIONS
Safety relief valves, used for air, steam, and gas as well as for vapor and liquid, allow the valve to open in proportion to the increase in pressure over the normal operating pressure. Safety valves designed primarily to release high volumes of steam usually pop open to full capacity. The overpressure needed to open liquid-relief valves where large-volume discharge is not required increases as the valve lifts due to increased spring resistance. Pilot-operated safety relief valves, with up to six times the capacity of normal relief valves, are used where tighter
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
sealing and larger volume discharges are required. Nonvolatile liquids are usually pumped to oil-water separation and recovery systems, and volatile liquids are sent to units operating at a lower pressure.
FLARE SYSTEMS
A typical closed pressure release and flare system includes relief valves and lines from process units for collection of discharges, knockout drums to separate vapors and liquids, seals, and/or purge gas for flashback protection, and a flare and igniter system which combusts vapors when discharging directly to the atmosphere is not permitted. Steam may be injected into the flare tip to reduce visible smoke.
PRESSURE RELIEF HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
Vapors and gases must not discharge where sources of ignition could be present.
Safety
Liquids should not be discharged directly to a vapor disposal system. Flare knockout drums and flares need to be large enough to handle emergency blowdowns. Drums should be provided with relief in the event of over pressure.
Pressure relief valves must be provided where the potential exists for overpressure in refinery processes due to the following causes:
- (1) Loss of cooling water, which may greatly reduce pressure in condensers and increase the pressure in the process unit.
- (2) Loss of reflux volume, which may cause a pressure drop in condensers and a pressure rise in distillation towers because the quantity of reflux affects the volume of vapors leaving the distillation tower.
- (3) Rapid vaporization and pressure increase from injection of a lower boiling-point liquid including water into a process vessel operating at higher temperatures.
- (4) Expansion of vapor and resultant over-pressure due to overheated process steam, malfunctioning heaters, or fire.
- (5) Failure of automatic controls, closed outlets, heat exchanger failure, etc.
- (6) Internal explosion, chemical reaction, thermal expansion, or accumulated gases.
Maintenance is important because valves are required to function properly. The most common operating problems are listed below.
- (1) Failure to open at set pressure, because of plugging of the valve inlet or outlet, or because corrosion prevents proper operation of the disc holder and guides.
- (2) Failure to reseat after popping open due to fouling, corrosion, or deposits on the seat or moving parts, or because solids in the gas stream have cut the valve disc.
- (3) Chattering and premature opening, because operating pressure is too close to the set point.
Health
Safe work practices and/or appropriate personal protective equipment may be needed to protect against hazards during inspection, maintenance, and turnaround activities.
WASTEWATER TREATMENT
Wastewater treatment is used for process, runoff, and sewerage water prior to discharge or recycling. Wastewater typically contains hydrocarbons,
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
dissolved materials, suspended solids, phenols, ammonia, sulfides, and other compounds. Wastewater includes condensed steam, stripping water, spent caustic solutions, cooling tower and boiler blowdown, wash water, alkaline and acid waste neutralization water, and other process-associated water.
PRETREATMENT OPERATIONS
Pretreatment is the separation of hydrocarbons and solids from wastewater. API separators, interceptor plates, and settling ponds remove suspended hydrocarbons, oily sludge, and solids by gravity separation, skimming, and filtration. Some oil-in-water emulsions must be heated first to assist in separating the oil and the water. Gravity separation depends on the specific gravity differences between water and immiscible oil globules, which allows free oil to be skimmed off the surface of the wastewater. Acidic wastewater is neutralized using ammonia, lime, or soda ash. Alkaline wastewater is treated with sulfuric acid, hydrochloric acid, carbon dioxide-rich flue gas, or sulfur.
SECONDARY TREATMENT OPERATIONS
After pretreatment, suspended solids are removed by sedimentation or air flotation. Wastewater with low levels of solids may be screened or filtered. Flocculation agents are sometimes added to help separation. Secondary treatment processes biologically degrade and oxidize soluble organic matter by the use of activated sludge, unaerated or aerated lagoons, trickling filter methods, or anaerobic treatments. Materials with high adsorption characteristics are used in fixed-bed filters or added to the wastewater to form a slurry which is removed by sedimentation or filtration. Additional treatment methods are used to remove oils and chemicals from wastewater. Stripping is used on wastewater containing sulfides and/or ammonia, and solvent extraction is used to remove phenols.
TERTIARY TREATMENT OPERATIONS
Tertiary treatments remove specific pollutants to meet regulatory discharge requirements. These treatments include chlorination, ozonation, ion exchange, reverse osmosis, activated carbon adsorption, etc. Compressed oxygen is diffused into wastewater streams to oxidize certain chemicals or to satisfy regulatory oxygen-content requirements. Wastewater that is to be recycled may require cooling to remove heat and/or oxidation by spraying or air stripping to remove any remaining phenols, nitrates, and ammonia.
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
The potential for fire exists if vapors from wastewater containing hydrocarbons reach a source of ignition during treatment.
Health
Safe work practices and/or appropriate personal protective equipment may be needed for exposures to chemicals and waste products during process sampling, inspection, maintenance, and turnaround activities as well as to noise, gases, and heat.
COOLING TOWERS
Cooling towers remove heat from process water by evaporation and latent heat transfer between hot water and air. The two types of towers are crossflow and counterflow. Crossflow towers introduce the airflow at right angles to the water flow throughout the structure. In counterflow cooling towers, hot process water is pumped to the uppermost plenum and allowed to fall through the tower. Numerous slats or spray nozzles located throughout the length of the tower disperse the water and help in cooling. Air enters at the tower bottom and flows upward against the water. When the fans or blowers are at the air inlet, the air is considered to be forced draft. Induced draft is when the fans are at the air outlet.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
COOLING WATER
Recirculated cooling water must be treated to remove impurities and dissolved hydrocarbons. Because the water is saturated with oxygen from being cooled with air, the chances for corrosion are increased. One means of corrosion prevention is the addition of a material to the cooling water that forms a protective film on pipes and other metal surfaces.
HEALTH AND SAFETY CONSIDERATIONS
Fire Prevention and Protection
When cooling water is contaminated by hydrocarbons, flammable vapors can be evaporated into the discharge air. If a source of ignition is present, or if lightning occurs, a fire may start. A potential fire hazard also exists where there are relatively dry areas in induced-draft cooling towers of combustible construction.
Safety
Loss of power to cooling tower fans or water pumps could have serious consequences in the operation of the refinery. Impurities in cooling water can corrode and foul pipes and heat exchangers, scale from dissolved salts can deposit on pipes, and wooden cooling towers can be damaged by microorganisms.
Health
Cooling-tower water can be contaminated by process materials and by-products including sulfur dioxide, hydrogen sulfide, and carbon dioxide, with resultant exposures. Safe work practices and/or appropriate personal protective equipment may be needed during process sampling, inspection, maintenance, and turnaround activities; and for exposure to hazards such as those related to noise, water-treatment chemicals, and hydrogen sulfide when wastewater is treated in conjunction with cooling towers.
ELECTRIC POWER
Refineries may receive electricity from outside sources or produce their own power with generators driven by steam turbines or gas engines. Electrical substations receive power from the utility or power plant for distribution throughout the facility. They are usually located in nonclassified areas, away from sources of vapor or cooling-tower water spray. Transformers, circuit breakers, and feed-circuit switches are usually located in substations. Substations feed power to distribution stations within the process unit areas.
Distribution stations can be located in classified areas, providing that classification requirements are met. Distribution stations usually have a liquid-filled transformer and an oil-filled or air-break disconnect device.
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
Generators that are not properly classified and are located too close to process units may be a source of ignition should a spill or release occur.
Safety
Normal electrical safety precautions including dry footing, high-voltage warning signs, and guarding must be taken to protect against electrocution. Lockout/tagout and other appropriate safe work practices must be established to prevent energization while work is being performed on high-voltage electrical equipment.
Health
Safe work practices and/or the use of appropriate personal protective equipment may be needed for exposures to noise, for exposure to hazards during inspection and maintenance activities, and when working around transformers and switches that may contain a dielectric fluid which requires special handling precautions.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
GAS AND AIR COMPRESSORS
Both reciprocating and centrifugal compressors are used throughout the refinery for gas and compressed air. Air compressor systems include compressors, coolers, air receivers, air dryers, controls, and distribution piping. Blowers are used to provide air to certain processes. Plant air is provided for the operation of air-powered tools, catalyst regeneration, process heaters, steam-air decoking, sour-water oxidation, gasoline sweetening, asphalt blowing, and other uses. Instrument air is provided for use in pneumatic instruments and controls, air motors and purge connections.
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
Air compressors should be located so that the suction does not take in flammable vapors or corrosive gases. There is a potential for fire should a leak occur in gas compressors.
Safety
Knockout drums are needed to prevent liquid surges from entering gas compressors. If gases are contaminated with solid materials, strainers are needed. Failure of automatic compressor controls will affect processes. If maximum pressure could potentially be greater than compressor or process-equipment design pressure, pressure relief should be provided. Guarding is needed for exposed moving parts on compressors. Compressor buildings should be properly electrically classified, and provisions should be made for proper ventilation.
Where plant air is used to back up instrument air, interconnections must be upstream of the instrument air drying system to prevent contamination of instruments with moisture. Alternate sources of instrument air supply, such as use of nitrogen, may be needed in the event of power outages or compressor failure.
Health
Safe work practices and/or appropriate personal protective equipment may be needed for exposure to hazards such as noise and during inspection and maintenance activities. The use of appropriate safeguards must be considered so that plant and instrument air is not used for breathing or pressuring potable water systems.
MARINE, TANK CAR, AND TANK TRUCK LOADING and UNLOADING
Facilities for loading liquid hydrocarbons into tank cars, tank trucks, and marine vessels and barges are usually part of the refinery operations. Product characteristics, distribution needs, shipping requirements, and operating criteria are important when designing loading facilities. Tank trucks and rail tank cars are either top- or bottom-loaded, and vapor-recovery systems may be provided where required. Loading and unloading liquefied petroleum gas (LPG) require special considerations in addition to those for liquid hydrocarbons.
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
The potential for fire exists where flammable vapors from spills or releases can reach a source of ignition. Where switch-loading is permitted, safe practices need to be established and followed. Bonding is used to equalize the electrical charge between the loading rack and the tank truck or tank car. Grounding is used at truck and rail loading facilities to prevent flow of stray currents. Insulating flanges are used on marine dock piping connections to prevent static electricity buildup and discharge. Flame arrestors should be installed in loading rack and marine vapor-recovery lines to prevent flashback.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Safety
Automatic or manual shutoff systems at supply headers are needed for top and bottom loading in the event of leaks or overfills. Fall protection such as railings are needed for top-loading racks where employees are exposed to falls. Drainage and recovery systems may be provided for storm drainage and to handle spills and leaks. Precautions must be taken at LPG loading facilities not to overload or overpressurize tank cars and trucks.
Health
The nature of the health hazards at loading and unloading facilities depends upon the products being loaded and the products previously transported in the tank cars, tank trucks, or marine vessels. Safe work practices and/or appropriate personal protective equipment may be needed to protect against hazardous exposures when loading or unloading, cleaning up spills or leaks, or when gauging, inspecting, sampling, or performing maintenance activities on loading facilities or vapor-recovery systems.
TURBINES
Turbines are usually gas- or steam-powered and are typically used to drive pumps, compressors, blowers, and other refinery process equipment. Steam enters turbines at high temperatures and pressures, expands across and drives rotating blades while directed by fixed blades.
HEALTH AND SAFETY CONSIDERATIONS
Safety
Steam turbines used for exhaust operating under vacuum should have safety relief valves on the discharge side, both for protection and to maintain steam in the event of vacuum failure. Where maximum operating pressure could be greater than design pressure, steam turbines should be provided with relief devices. Consideration should be given to providing governors and overspeed control devices on turbines.
Health
Safe work practices and/or appropriate personal protective equipment may be needed for noise, steam and heat exposures, and during inspection and maintenance activities.
PUMPS, PIPING AND VALVES
Centrifugal and positive-displacement (i.e., reciprocating) pumps are used to move hydrocarbons, process water, fire water, and wastewater through piping within the refinery. Pumps are driven by electric motors, steam turbines, or internal combustion engines. The pump type, capacity, and construction materials depend on the service for which it is used.
Process and utility piping distribute hydrocarbons, steam, water, and other products throughout the facility. Their size and construction depend on the type of service, pressure, temperature, and nature of the products. Vent, drain, and sample connections are provided on piping, as well as provisions for blanking.
Different types of valves are used depending on their operating purpose. These include gate valves, bypass valves, globe and ball valves, plug valves, block and bleed valves, and check valves. Valves can be manually or automatically operated.
HEALTH AND SAFETY CONSIDERATIONS
Fire Protection and Prevention
The potential for fire exists should hydrocarbon pumps, valves, or lines develop leaks that could allow vapors to reach sources of ignition. Remote sensors, control valves, fire valves, and isolation valves should be used to limit the release of hydrocarbons at pump suction lines in the event of leakage and/or fire.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Safety
Depending on the product and service, backflow prevention from the discharge line may be needed. The failure of automatic pump controls could cause a deviation in process pressure and temperature. Pumps operated with reduced or no flow can overheat and rupture. Pressure relief in the discharge piping should be provided where pumps can be overpressured. Provisions may be made for pipeline expansion, movement, and temperature changes to avoid rupture. Valves and instruments that require servicing or other work should be accessible at grade level or from an operating platform. Operating vent and drain connections should be provided with double-block valves, a block valve and plug, or blind flange for protection against releases.
Health
Safe work practices and/or appropriate personal protective equipment may be needed for exposure to hazards such as those related to liquids and vapors when opening or draining pumps, valves, and/or lines, and during product sampling, inspection, and maintenance activities.
TANK STORAGE
Atmospheric storage tanks and pressure storage tanks are used throughout the refinery for storage of crudes, intermediate hydrocarbons (during the process), and finished products. Tanks are also provided for fire water, process and treatment water, acids, additives, and other chemicals. The type, construction, capacity and location of tanks depends on their use and materials stored.
HEALTH AND SAFETY CONSIDERATIONS
Fire Prevention and Protection
The potential for fire exists should hydrocarbon storage tanks be overfilled or develop leaks that allow vapors to escape and reach sources of ignition. Remote sensors,control valves, isolation valves, and fire valves may be provided at tanks for pump-out or closure in the event of a fire in the tank, or in the tank dike or storage area.
Safety
Tanks may be provided with automatic overflow control and alarm systems, or manual gauging and checking procedures may be established to control overfills.
Health
Safe work practices and/or appropriate personal protective equipment may be needed for exposure to hazards related to product sampling, manual gauging, inspection, and maintenance activities including confined-space entry where applicable.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
F. BIBLIOGRAPHY ________________________________________________________________________
American Petroleum Institute. 1971. Chemistry and Petroleum for
- Classroom Use in Chemistry Courses. Washington, D.C.: American Petroleum Institute.
__________. 1973. Industrial Hygiene Monitoring Manual for
- Petroleum Refineries and Selected Petrochemical Operations. Manual 2700-1/79-1M. Washington, D.C.: American Petroleum Institute.
__________. 1980. Facts About Oil. Manual 4200-10/80-25M.
- Washington, D.C.: American Petroleum Institute.
__________. 1990. Management of Process Hazards. RP 750.
- Washington, D.C.: American Petroleum Institute.
__________. 1990. Inspection of Piping, Tubing, Valves and
- Fittings. RP 574. Washington, D.C.: American Petroleum Institute.
__________. 1991. Inspection of Fired Boilers and Heaters. RP 573.
- Washington, D.C.: American Petroleum Institute.
__________. 1992. Inspection of Pressure Vessels. RP 572.
- Washington, D.C.: American Petroleum Institute.
__________. 1992. Inspection of Pressure Relieving Devices. RP
- 576. Washington, D.C.: American Petroleum Institute.
__________. 1994. Fire Protection in Refineries. Sixth Edition.
- RP 2001. Washington, D.C.: American Petroleum Institute.
Armistead, George, Jr. 1950. Safety in Petroleum Refining and
- Related Industries. New York: John G. Simmons & Co., Inc.
Exxon Company, USA. 1987. Encyclopedia for the User of Petroleum
- Products. Lubetext D400. Houston: Exxon Company, USA.
Hydrocarbon Processing. 1988. Refining Handbook. Houston: Gulf
- Publishing Co.
__________. 1992. Refining Handbook. Houston: Gulf Publishing Co.
IARC. [No date given.] Occupational Exposures in Petroleum
- Refining. IARC Monographs, Volume 45.
Kutler, A. A. 1969. "Crude distillation." Petro/Chem Engineering.
- New York: John G. Simmonds & Co., Inc.
Mobil Oil Corporation. 1972. Light Products Refining, Fuels
- Manufacture. Mobil Technical Bulletin, 1972. Fairfax, Virginia:
- Mobil Oil Corporation.
Parmeggiani, Luigi, Technical Editor. 1983. Encyclopaedia of
- Occupational Health and Safety. Third Edition. Geneva:
- International Labour Organization.
Shell International Petroleum Company Limited. 1983. The Petroleum
- Handbook. Sixth Edition. Amsterdam: Elsevier Science Publishers B.V.
Speight, James G. 1980. The Chemistry and Terminology of Petroleum.
- New York: Marcel Dekker, Inc.
Vervalin, Charles H., Editor. 1985. Fire Protection Manual for
- Hydrocarbon Processing Plants. Volume 1, Third edition. Houston:
- Gulf Publishing Co.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
APPENDIX III:2-1. GLOSSARY _____________________________________________________________________
ABSORPTION The disappearance of one substance into another so that the absorbed substance loses its identifying characteristics, while the absorbing substance retains most of its original physical aspects. Used in refining to selectively remove specific components from process streams.
ACID TREATMENT A process in which unfinished petroleum products such as gasoline, kerosene, and lubricating oil stocks are treated with sulfuric acid to improve color, odor, and other properties.
ADDITIVE Chemicals added to petroleum products in small amounts to improve quality or add special characteristics.
ADSORPTION Adhesion of the molecules of gases or liquids to the surface of solid materials.
AIR FIN COOLERS A radiator-like device used to cool or condense hot hydrocarbons; also called fin fans.
ALICYCLIC HYDROCARBONS Cyclic (ringed) hydrocarbons in which the rings are made up only of carbon atoms.
ALIPHATIC HYDROCARBONS Hydrocarbons characterized by open-chain structures: ethane, butane, butene, acetylene, etc.
ALKYLATION A process using sulfuric or hydro-fluoric acid as a catalyst to combine olefins (usually butylene) and isobutane to produce a high-octane product known as alkylate.
API GRAVITY An arbitrary scale expressing the density of petroleum products.
AROMATIC Organic compounds with one or more benzene rings.
ASPHALTENES The asphalt compounds soluble in carbon disulfide but insoluble in paraffin naphthas.
ATMOSPHERIC TOWER A distillation unit operated at atmospheric pressure.
BENZENE An unsaturated, six-carbon ring, basic aromatic compound.
BLEEDER VALVE A small-flow valve connected to a fluid process vessel or line for the purpose of bleeding off small quantities of contained fluid. It is installed with a block valve to determine if the block valve is closed tightly.
BLENDING The process of mixing two or more petroleum products with different properties to produce a finished product with desired characteristics.
BLOCK VALVE A valve used to isolate equipment.
BLOWDOWN The removal of hydrocarbons from a process unit, vessel, or line on a scheduled or emergency basis by the use of pressure through special piping and drums provided for this purpose.
BLOWER Equipment for moving large volumes of gas against low-pressure heads.
BOILING RANGE The range of temperature (usually at atmospheric pressure) at which the boiling (or distillation) of a hydrocarbon liquid commences, proceeds, and finishes.
BOTTOMS Tower bottoms are residue remaining in a distillation unit after the highest boiling-point material to be distilled has been removed. Tank bottoms are the heavy materials that accumulate in the bottom of storage tanks, usually comprised of oil, water, and foreign matter.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
BUBBLE TOWER A fractionating (distillation) tower in which the rising vapors pass through layers of condensate, bubbling under caps on a series of plates.
CATALYST A material that aids or promotes a chemical reaction between other substances but does not react itself. Catalysts increase reaction speeds and can provide control by increasing desirable reactions and decreasing undesirable reactions.
CATALYTIC CRACKING The process of breaking up heavier hydrocarbon molecules into lighter hydrocarbon fractions by use of heat and catalysts.
CAUSTIC WASH A process in which distillate is treated with sodium hydroxide to remove acidic contaminants that contribute to poor odor and stability.
CHD UNIT See Hydrodesulfurization.
COKE A high carbon-content residue remaining from the destructive distillation of petroleum residue.
COKING A process for thermally converting and upgrading heavy residual into lighter products and by-product petroleum coke. Coking also is the removal of all lighter distillable hydrocarbons that leaves a residue of carbon in the bottom of units or as buildup or deposits on equipment and catalysts.
CONDENSATE The liquid hydrocarbon resulting from cooling vapors.
CONDENSER A heat-transfer device that cools and condenses vapor by removing heat via a cooler medium such as water or lower-temperature hydrocarbon streams.
CONDENSER REFLUX Condensate that is returned to the original unit to assist in giving increased conversion or recovery.
COOLER A heat exchanger in which hot liquid hydrocarbon is passed through pipes immersed in cool water to lower its temperature.
CRACKING The breaking up of heavy molecular-weight hydrocarbons into lighter hydrocarbon molecules by the application of heat and pressure, with or without the use of catalysts.
CRUDE ASSAY A procedure for determining the general distillation and quality characteristics of crude oil.
CRUDE OIL A naturally occurring mixture of hydrocarbons that usually includes small quantities of sulfur, nitrogen, and oxygen derivatives of hydrocarbons as well as trace metals.
CYCLE GAS OIL Cracked gas oil returned to a cracking unit.
DEASPHALTING Process of removing asphaltic materials from reduced crude using liquid propane to dissolve nonasphaltic compounds.
DEBUTANIZER A fractionating column used to remove butane and lighter components from liquid streams.
DE-ETHANIZER A fractionating column designed to remove ethane and gases from heavier hydrocarbons.
DEHYDROGENATION A reaction in which hydrogen atoms are eliminated from a molecule. Dehydro-genation is used to convert ethane, propane, and butane into olefins (ethylene, propylene, and butenes).
DEPENTANIZER A fractionating column used to remove pentane and lighter fractions from hydrocarbon streams.
DEPROPANIZER A fractionating column for removing propane and lighter components from liquid streams.
DESALTING Removal of mineral salts (most chlorides, e.g., magnesium chloride and sodium chloride) from crude oil.
DESULFURIZATION A chemical treatment to remove sulfur or sulfur compounds from hydrocarbons.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
DEWAXING The removal of wax from petroleum products (usually lubricating oils and distillate fuels) by solvent absorption, chilling, and filtering.
DIETHANOLAMINE A chemical (C(4)H(11)O(2)N) used to remove H(2)S from gas streams.
DISTILLATE The products of distillation formed by condensing vapors.
DOWNFLOW Process in which the hydrocarbon stream flows from top to bottom.
DRY GAS Natural gas with so little natural gas liquids that it is nearly all methane with some ethane.
FEEDSTOCK Stock from which material is taken to be fed (charged) into a processing unit.
FLASHING The process in which a heated oil under pressure is suddenly vaporized in a tower by reducing pressure.
FLASH POINT Lowest temperature at which a petroleum product will give off sufficient vapor so that the vapor-air mixture above the surface of the liquid will propagate a flame away from the source of ignition.
FLUX Lighter petroleum used to fluidize heavier residual so that it can be pumped.
FOULING Accumulation of deposits in condensers, exchangers, etc.
FRACTION One of the portions of fractional distillation having a restricted boiling range.
FRACTIONATING COLUMN Process unit that separates various fractions of petroleum by simple distillation, with the column tapped at various levels to separate and remove fractions according to their boiling ranges.
FUEL GAS Refinery gas used for heating.
GAS OIL Middle-distillate petroleum fraction with a boiling range of about 350-750 degrees F, usually includes diesel fuel, kerosene, heating oil, and light fuel oil.
GASOLINE A blend of naphthas and other refinery products with sufficiently high octane and other desirable characteristics to be suitable for use as fuel in internal combustion engines.
HEADER A manifold that distributes fluid from a series of smaller pipes or conduits.
HEAT As used in the Health Considerations sections of this document, heat refers to thermal burns for contact with hot surfaces, hot liquids and vapors, steam, etc.
HEAT EXCHANGER Equipment to transfer heat between two flowing streams of different temperatures. Heat is transferred between liquids or liquids and gases through a tubular wall.
HIGH-LINE OR HIGH-PRESSURE GAS High-pressure (100 psi) gas from cracking unit distillate drums that is compressed and combined with low-line gas as gas absorption feedstock.
HYDROCRACKING A process used to convert heavier feedstocks into lower-boiling, higher-value products. The process employs high pressure, high temperature, a catalyst, and hydrogen.
HYDRODESULFURIZATION A catalytic process in which the principal purpose is to remove sulfur from petroleum fractions in the presence of hydrogen.
HYDROFINISHING A catalytic treating process carried out in the presence of hydrogen to improve the properties of low viscosity-index naphthenic and medium viscosity-index naphthenic oils. It is also applied to paraffin waxes and microcrystalline waxes for the removal of undesirable components. This process consumes hydrogen and is used in lieu of acid treating.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
HYDROFORMING Catalytic reforming of naphtha at elevated temperatures and moderate pressures in the presence of hydrogen to form high-octane BTX aromatics for motor fuel or chemical manufacture. This process results in a net production of hydrogen and has rendered thermal reforming somewhat obsolete. It represents the total effect of numerous simultaneous reactions such as cracking, polymerization, dehydrogenation, and isomerization.
HYDROGENATION The chemical addition of hydrogen to a material in the presence of a catalyst.
INHIBITOR Additive used to prevent or retard undesirable changes in the quality of the product, or in the condition of the equipment in which the product is used.
ISOMERIZATION A reaction that catalytically converts straight-chain hydrocarbon molecules into branched-chain molecules of substantially higher octane number. The reaction rearranges the carbon skeleton of a molecule without adding or removing anything from the original material.
ISO-OCTANE A hydrocarbon molecule (2,2,4-trimethylpentane) with excellent antiknock characteristics on which the octane number of 100 is based.
KNOCKOUT DRUM A vessel wherein suspended liquid is separated from gas or vapor.
LEAN OIL Absorbent oil fed to absorption towers in which gas is to be stripped. After absorbing the heavy ends from the gas, it becomes fat oil. When the heavy ends are subsequently stripped, the solvent again becomes lean oil.
LOW-LINE or LOW-PRESSURE GAS Low-pressure (5 psi) gas from atmospheric and vacuum distillation recovery systems that is collected in the gas plant for compression to higher pressures.
NAPHTHA A general term used for low boiling hydrocarbon fractions that are a major component of gasoline. Aliphatic naphtha refers to those naphthas containing less than 0.1% benzene and with carbon numbers from C(3) through C(1)6. Aromatic naphthas have carbon numbers from C(6) through C(16) and contain significant quantities of aromatic hydrocarbons such as benzene (greater than 0.1%), toluene, and xylene.
NAPHTHENES Hydrocarbons (cycloalkanes) with the general formula C(n)H(2n), in which the carbon atoms are arranged to form a ring.
OCTANE NUMBER A number indicating the relative antiknock characteristics of gasoline.
OLEFINS A family of unsaturated hydrocarbons with one carbon-carbon double bond and the general formula C(n)H(2n).
PARAFFINS A family of saturated aliphatic hydrocarbons (alkanes) with the general formula C(n)H(2n+2).
POLYFORMING The thermal conversion of naphtha and gas oils into high-quality gasoline at high temperatures and pressure in the presence of recirculated hydrocarbon gases.
POLYMERIZATION The process of combining two or more unsaturated organic molecules to form a single (heavier) molecule with the same elements in the same proportions as in the original molecule.
PREHEATER Exchanger used to heat hydrocarbons before they are fed to a unit.
PRESSURE-REGULATING VALVE A valve that releases or holds process-system pressure (that is, opens or closes) either by preset spring tension or by actuation by a valve controller to assume any desired position between fully open and fully closed.
PYROLYSIS GASOLINE A by-product from the manufacture of ethylene by steam cracking of hydrocarbon fractions such as naphtha or gas oil.
PYROPHORIC IRON SULFIDE A substance typically formed inside tanks and processing units by the corrosive interaction of sulfur compounds in the
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
hydrocarbons and the iron and steel in the equipment. On exposure to air (oxygen) it ignites spontaneously.
QUENCH OIL Oil injected into a product leaving a cracking or reforming heater to lower the temperature and stop the cracking process.
RAFFINATE The product resulting from a solvent extraction process and consisting mainly of those components that are least soluble in the solvents. The product recovered from an extraction process is relatively free of aromatics, naphthenes, and other constituents that adversely affects physical parameters.
REACTOR The vessel in which chemical reactions take place during a chemical conversion type of process.
REBOILER An auxiliary unit of a fractionating tower designed to supply additional heat to the lower portion of the tower.
RECYCLE GAS High hydrogen-content gas returned to a unit for reprocessing.
REDUCED CRUDE A residual product remaining after the removal by distillation of an appreciable quantity of the more volatile components of crude oil.
REFLUX The portion of the distillate returned to the fractionating column to assist in attaining better separation into desired fractions.
REFORMATE An upgraded naphtha resulting from catalytic or thermal reforming.
REFORMING The thermal or catalytic conversion of petroleum naphtha into more volatile products of higher octane number. It represents the total effect of numerous simultaneous reactions such as cracking, polymerization, dehydrogenation, and isomerization.
REGENERATION In a catalytic process the reactivation of the catalyst, sometimes done by burning off the coke deposits under carefully controlled conditions of temperature and oxygen content of the regeneration gas stream.
SCRUBBING Purification of a gas or liquid by washing it in a tower.
SOLVENT EXTRACTION The separation of materials of different chemical types and solubilities by selective solvent action.
SOUR GAS Natural gas that contains corrosive, sulfur-bearing compounds such as hydrogen sulfide and mercaptans.
STABILIZATION A process for separating the gaseous and more volatile liquid hydrocarbons from crude petroleum or gasoline and leaving a stable (less-volatile) liquid so that it can be handled or stored with less change in composition.
STRAIGHT-RUN GASOLINE Gasoline produced by the primary distillation of crude oil. It contains no cracked, polymerized, alkylated, reformed, or visbroken stock.
STRIPPING The removal (by steam-induced vaporization or flash evaporation) of the more volatile components from a cut or fraction.
SULFURIC ACID TREATING A refining process in which unfinished petroleum products such as gasoline, kerosene, and lubricating oil stocks are treated with sulfuric acid to improve their color, odor, and other characteristics.
SULFURIZATION Combining sulfur compounds with petroleum lubricants.
SWEETENING Processes that either remove obnoxious sulfur compounds (primarily hydrogen sulfide, mercaptans, and thiophens) from petroleum fractions or streams, or convert them, as in the case of mercaptans, to odorless disulfides to improve odor, color, and oxidation stability.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SWITCH LOADING The loading of a high static-charge retaining hydrocarbon (i.e., diesel fuel) into a tank truck, tank car, or other vessel that has previously contained a low-flash hydrocarbon (gasoline) and may contain a flammable mixture of vapor and air.
TAIL GAS The lightest hydrocarbon gas released from a refining process.
THERMAL CRACKING The breaking up of heavy oil molecules into lighter fractions by the use of high temperature without the aid of catalysts.
TURNAROUND A planned complete shutdown of an entire process or section of a refinery, or of an entire refinery to perform major maintenance, overhaul, and repair operations and to inspect, test, and replace process materials and equipment.
VACUUM DISTILLATION The distillation of petroleum under vacuum which reduces the boiling temperature sufficiently to prevent cracking or decomposition of the feedstock.
VAPOR The gaseous phase of a substance that is a liquid at normal temperature and pressure.
VISBREAKING Viscosity breaking is a low-temperature cracking process used to reduce the viscosity or pour point of straight-run residuum.
WET GAS A gas containing a relatively high proportion of hydrocarbons that are recoverable as liquids.
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
SECTION V: CHAPTER 1
HOSPITAL INVESTIGATIONS: HEALTH HAZARDS
A. INTRODUCTION _________________________________________________________________________
_________________________________________________________________
| | | A. Introduction......................................V:1-1 | | | | B. Typical Hazards and Health Effects................V:1-2 | | | | C. Investigative Guidelines..........................V:1-2 | | | | D. Sampling Methods..................................V:1-4 | | | | E. Controls and Prevention...........................V:1-5 | | | | F. Bibliography......................................V:1-9 | | | | Appendix V:1-1. Biological Agents--Blood and Body | | Fluids..........................................V:1-11 | | | | Appendix V:1-2. Chemical Agents.......................V:1-12 | | | | Appendix V:1-3. Physical Agents.......................V:1-14 | |_________________________________________________________________|
INCIDENCE AND CAUSAL FACTORS
As of 1988, 4% of the total U.S. work force was employed by hospitals. The National Safety Council (NSC) reports that hospital employees are 41% more likely to need time off due to injury or illness than employees in other industries.
In a survey of 165 clinical laboratories in Minnesota showed that the most frequent type of injuries were needle sticks (63%) followed by cuts and scrapes (21%).
Hospital workers frequently report stress, as a predisposing factor for accidents.
Sprains and strains (often representing low back injury) were the most common type of workers compensation claim in 1983 as reported by the Bureau of Labor Statistics. See Chapter VI:1 for more information.
GUIDANCE
In 1988, NIOSH published Guidelines for Protecting the Safety and Health of Health Care Workers, the American Association of Critical-Care Nurses has published a handbook on the occupational hazards encountered in the critical care environment, and the NSC has a Safety Guide for hospital environments.
The hazards of exposure to waste anesthetic gases, cytotoxic drugs, and blood-borne diseases such as hepatitis and HIV/AIDS, are the subject of NIOSH criteria documents and OSHA policy statements.
OSHA Instruction TED 1.15 September 22, 1995 Office of Science and Technology Assessment
B. TYPICAL HAZARDS AND HEALTH EFFECTS _________________________________________________________________________
This chapter covers hospital or health care facility-specific employee hazards. Biological, chemical and physical agents presenting potential exposure to health care employees are reviewed in Appendices V:1-1 through V:1-3. These lists are not inclusive.
C. INVESTIGATIVE GUIDELINES _________________________________________________________________________
HOSPITAL RECORDS
Hospital's OSHA 200 Log versus employee medical clinic care of employees-is there a possible trend in injuries and illnesses related to typical hazards?
If available, check the hospital's safety program records and facility-enabling or operation equipment licenses, e.g., NRC radioisotope and radiation-source license.
HOSPITAL SAFETY PROGRAM
Note any previous health and safety inspections by local health departments, fire departments, regulatory or accreditating agencies, such as the Joint Commission on Accreditation of Healthcare Organizations (JCAHO), College of American Pathologists (CAP), and the American Osteopathic Association (AOA).
The policies and procedures should outline the training that all employees must receive. General hospital training should include fire and electrical safety, infection control procedures, and the hazard communication program.
The policies and procedures should also delineate appropriate personnel and methods for preparation, mixing, application, storage, removal, and disposal of any hazardous agents.
Emergency procedures should include provisions for fires, chemical or radioactive spills, extensive blood or body fluid spills, release of compressed, toxic, and corrosive gases, or power failure.
A safety committee and/or infection control committee should be established within the hospital. Periodic inspection and monitoring is the responsibility of the safety committee.
Immunizations, other than the mandatoryvaccination for Hepatitis B, should be offered to personnel at risk.
All electrical equipment used in the hospital must be approved for safety by Underwriters Laboratory (UL) or another OSHA approved body.
Biosafety cabinets should be labeled and certified by the manufacturer and/or a safety officer. The cabinets should be placed in the room at a position where doors, windows, and traffic flow will not create turbulence at the face of the cabinet.
WALKAROUND
INFORMAL INTERVIEWS
The worker interviews should concentrate on compliance with appropriate policies and procedures.
The employee should be able to verbalize what actions to take in the event of an emergency, i.e., accidental chemical or radioactive spill.
The employee should be aware of the hazards of the products with which he or she works.
- OSHA Instruction TED 1.15 September 22, 1996 Office of Science and Technology Assessment
Observe the employees' lifting practices.
Walk-around Inspection for health hazards.
Table V:1-1 contains a suggested area checklist.
SCREENING SAMPLES
All samples is based on the CSHO's professional judgment.
TABLE V:1-1. WALKAROUND INSPECTION FOR HEALTH HAZARDS _____________________________________________________________________________ | Area To check | | | | Every Area Floor slippriness | | Adequate marking of hazards and chemical labelling | | Handling of infectious and chemical wastes | | Spill and emergency procedures | | Use of appropriate personal protective equipment | | Adequate hand-washing facilities | | Presence of impervious containers for needles and | | other sharp objects | | Where equipped, the aerator and local exhaust | | ventilation for ethylene oxide sterilizers, along | | with any sampling or vapor badge records | | Where equipped, the steam autoclave drain should be free | | of debris | | Electrical equipment and wiring must meet electrical | | standards | | | | Pharmacy Availability of a class II type A or B biological | | safety cabinet for mixing chemotherapeutic drugs | | Accurate, clear labels on all drugs, chemicals, and | | biologicals | | | | Laboratory Uncluttered work areas, clear ventilation slots, and | | properly labeled ductwork in laboratory hoods and | | biological safety cabinets | | Specimen handling | | Use of pipettes (no mouth pipetting) | | Gas cylinder placement and storage | | Maintenance records for laboratory hoods and other | | equipment | | Centrifuge tubes with caps | | Food should never be stored in refrigerators with lab | | specimens | | Readily detectable vapors, funes, or dust | | Laser or radiation hazards | | | | Operating room Handling of waste anesthetic gases Air conditioning and | | humidity (should be about 50%) Static electricity control | | | | Radiation area Level of radiation Maintenance and radiation logs | |_____________________________________________________________________________|
- OSHA Instruction TED 1.15 September 22, 1995 Office of Science and Technology Assessment
D. SAMPLING METHODS _________________________________________________________________________
When sampling, it is important to ensure that it is a typical day, i.e., normal exposure time.
Bioaerosols can be evaluated using the ACGIH Bioaerosol Committee's Guidelines. These guidelines contain information on sampling, analysis, and recommendations for remedial actions. Hospital infection control personnel should assist in bioaerosol determinations, as this is nonroutine sampling and is specific for preidentified organisms. Specialized bioaerosol sampling equipment is available through the OSHA Health Response Team.
Some of the most commonly found chemicals, e.g., formaldehyde, xylene, halothane, and acrylamide, can be screened using detector tubes.
For nitrous oxide, passive monitors can be used to monitor exposures as stated in OSHA Method No. ID-166.
Specific sampling for chemical agents, such as ethylene oxide, methyl methacrylate, ribavirin, nitrous oxide, halothane, and other waste anesthetic gases, can be found in the Chemical Information Manual.
LASERS
Lasers are calibrated by the manufacturer, but the laser system must be checked prior to each procedure and during extended procedures. Classifications of lasers must coincide with actual measurement of output (See Figure V:1-1). Generally, measurements are required when the manufacturer's information is not available, when the laser system has not been classified or when alterations have been made to the laser system that may have changed its classification. Measurements should only be made by personnel trained in laser technology.
Records of alignment and power density can be checked against the manufacturer's equipment specifications.
Maximum Permissible Exposure (MPE) values to the eyes and skin are given in tables 5, 6, and 7 of the ANSI standard (Z136.1-1986) as well as the ACGIH standard. Requirements for measurements and criteria for calculating the MPEs are given in secion 8 and 9 of the ANSI standard.
Figure V:1-1. Laser Classifications.
__________________________________________________________________________
| |
| Class 1 The least-hazardous class. Considered incapable of providing |
| damaging levels of laser emissions. |
| |
| Class 2 Applies only to visible laser emissions and may be viewed |
| directly for time periods of less than or equal to 0.25 |
| seconds, which is the aversion response time. |
| |
| Class 3a Dangerous under direct or reflected vision. These lasers are |
| restricted to the visible electromagnetic spectrum. |
| |
| Class 3b May extend across the whole electromagnetic spectrum and are |
| hazardous when viewed intrabeam. |
| |
| Class 4 The highest-energy class of lasers, also extending across the |
| electromagnetic spectrum. This class of laser presents |
| significant fire, skin, and eye hazards. |
|__________________________________________________________________________|
- OSHA Instruction TED 1.15 September 22, 1995 Office of Science and Technology Assessment
workers administering pentamidine.(67) Similar monitoring for ribavirin has found concentrations as high as 316 mcg/m(3). (31)
OCCUPATIONAL EXPOSURE: BIOLOGICAL EVIDENCE OF ABSORPTION
URINARY MUTAGENICITY
Falck et al. were the first to note evidence of mutagenicity in the urine of nurses who handled cytotoxic drugs.(26) The extent of this effect increased over the course of the work week. With improved handling practices, a decrease in mutagenic activity was seen.(27) Researchers have also studied pharmacy personnel who reconstitute antineoplastic drugs. These employees showed increasingly mutagenic urine over the period of exposure; when they stopped handling the drugs, activity fell within two days to the level of unexposed controls.(5,76) They also found mutagenicity in workers using horizontal laminar flow BSCs that decreased to control levels with the use of vertical flow containment BSCs.(76) Other studies have failed to find a relationship between exposure and urine mutagenicity.(25) Sorsa(99) summarizes this information and discusses the factors, such as differences in urine collection timing and variations in the use of PPE, which could lead to disparate results. Differences may also be related to smoking status; smokers exposed to CDs exhibit greater urine mutagenicity than exposed nonsmokers or control smokers suggesting contamination of the work area by CDs and some contribution of smoking to their mutagenic profile.(9)
URINARY THIOETHERS
Urinary thioethers are glutathione conjugated metabolites of alkylating agents which have been evaluated as an indirect means of measuring exposure. Workers who handle cytotoxic drugs have been reported to have increased levels compared to controls and also have increasing thioether levels over a 5-day work week.(44,48) Other studies of nurses who handle CDs and of treated patients have yielded variable results which could be due to confounding by smoking, PPE, and glutathione-S-transferase activity.(11)
URINARY METABOLITES
Venitt assayed the urine of pharmacy and nursing personnel handling cisplatin and found platinum concentrations at or below the limit of detection for both workers and controls.(112) Hirst found cyclophosphamide in the urine of two nurses who handled the drug documenting worker absorption.(35) (Hirst also documented skin absorption in human volunteers by using gas chromatography after topical application of the drug.) Urinary pentamidine recovery has also been reported in exposed health care workers.(94)
OCCUPATIONAL EXPOSURE: HUMAN EFFECTS
CYTOGENETIC EFFECTS
A number of studies have examined the relationship of exposure to CDs in the workplace to chromosomal aberrations. These studies have looked at a variety of markers for damage, including sister chromatid exchanges (SCE), structural aberrations (e.g., gaps, breaks, translocations), and micronuclei in peripheral blood lymphocytes. The results have been somewhat conflicting. Several authors found increases in one or more markers.(74,75,80,113) Increased mutation frequency has been reported as well.(17) Other studies have failed to find a significant difference between workers and controls.(99,101) Some researchers have found higher individual elevations(28) or a relationship between number of drugs handled and SCEs.(8) These disparate results are not unexpected. The difficulties in quantitating exposure have resulted in different exposure magnitudes between studies; workers in several negative studies appear to have a lower overall exposure.(101) In addition, differences in the use of PPE and work technique will alter absorption of CDs and resultant biologic effects.
OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
Finally, techniques for SCE measurement may not be optimal. A recent study that looked at correlation of phosphoramide-induced SCE levels with duration of anticancer drug handling found a statistically significant correlation coefficient of 0.63.(66)
Taken together, the evidence indicates an excess of markers of mutagenic exposure in unprotected workers.
REPRODUCTIVE EFFECTS
Reproductive effects associated with occupational exposure to CDs have been well documented. Hemminki et al.(32) found no difference in exposure between nurses who had spontaneous abortions and those who had normal pregnancies. However, the study group consisted of nurses who were employed in surgical or medical floors of a general hospital. When the relationship between CD exposure and congenital malformations was explored, the study group was expanded to include oncology nurses, among others, and an odds ratio of 4.7 was found for exposures of more than once per week. This observed odds ratio is statistically significant. Selevan et al.(89) found a relationship between CD exposure and spontaneous abortion in a case-control study of Finnish nurses. This well designed study reviewed the reproductive histories of 568 women (167 cases) and found a statistically significant odds ratio of 2.3. Similar results were obtained in another large case-control study of French nurses,(102) and a study of Baltimore area nurses found a significantly higher proportion of adverse pregnancy outcomes when exposure to antineoplastic agents occurred during the pregnancy.(85) The nurses involved in these studies usually prepared and administered the drugs. Therefore, workplace exposure of these groups of professionals to such products has been associated with adverse reproductive outcomes in several investigations.
OTHER EFFECTS
Hepatocellular damage has been reported in nurses working in an oncology ward; the injury appeared to be related to intensity and duration of work exposure to CDs.(96) Symptoms such as lightheadedness, dizziness, nausea, headache, and allergic reactions have also been described in employees after the preparation and administration of antineoplastic drugs in unventilated areas.(22,86) In occupational settings, these agents are known to be toxic to the skin and mucous membranes, including the cornea.(69,82)
Pentamidine has been associated with respiratory damage in one worker who administered the aerosol. The injury consisted of a decrease in diffusing capacity that improved after exposure ceased.(29) The onset of bronchospasm in a pentamidine-exposed worker has also been reported.(22) Employees involved in the aerosol administration of ribavirin have noted symptoms of respiratory tract irritation.(55) A number of medications including psyllium and various antibiotics are known respiratory and dermal sensitizers. Exposure in susceptible individuals can lead to asthma or allergic contact dermatitis.
D. WORK AREAS _________________________________________________________________________
Risks to personnel working with HDs are a function of the drugs' inherent toxicity and the extent of exposure. The main routes of exposure are: inhalation of dusts or aerosols, dermal absorption, and ingestion. Contact with contaminated food or cigarettes represents the primary means of ingestion. Opportunity for exposure to HDs may occur at many points in the handling of these drugs.
PHARMACY OR OTHER PREPARATION AREAS
In large oncology centers, HDs are usually prepared in the pharmacy. However, in small hospitals, outpatient treatment areas, and physicians' offices they have been prepared by physicians or nurses without appropriate engineering controls and protective apparel.16,20 Many
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- ____________________________________________
- |Section II | | | |HEALTH HAZARDS | | | |CHAPTER 1: POLYMER MATRIX MATERIALS: | | ADVANCED COMPOSITES | | | |CHAPTER 2: INDOOR AIR QUALITY | | | |CHAPTER 3: VENTILATION INVESTIGATION | | | |CHAPTER 4: HEAT STRESS | | | |CHAPTER 5: NOISE MEASUREMENT | | | |CHAPTER 6: LASER HAZARDS | | | |CHAPTER 7: PETROLEUM REFINING | | PROCESSES | | | | | | | |____________________________________________|
- OSHA Instruction TED 1.15 CH-1 May 24, 1996 Office of Science and Technology Assessment
- ____________________________________________
- | | |SECTION III | | | |SAFETY HAZARDS | | | |CHAPTER 1: OILWELL DERRICK STABILITY: | | GUYWIRE ANCHOR SYSTEMS | | | |CHAPTER 2: LEGIONNAIRES' DISEASE | | | |CHAPTER 3: PRESSURE VESSEL | | GUIDELINES | | | |CHAPTER 4: INDUSTRIAL ROBOTS AND | | ROBOT SYSTEM SAFETY | | | | | | | |____________________________________________|