Standard Interpretations - Table of Contents|
| Standard Number:||1910.179; 1910.179(k)(1)(ii); 1910.179(n)(4)|
October 21, 2003
Mr. Wade Samson
P.O. Box 568833
Orlando, FL 32856-8833
Dear Mr. Samson:
Thank you for your June 25 letter to the Occupational Safety and Health Administration (OSHA), regarding the tests associated with the trip setting of hoist limit switches described under OSHA's rule at 29 CFR 1910.179(k)(l)(ii). This letter constitutes OSHA's interpretation only of the requirements discussed, and may not be applicable to any questions not delineated within your original correspondence. We apologize for the delay in our response. Your scenarios, questions, and our responses are provided below:
Scenario: The OSHA rule at 29 CFR 1910.179(k)(1)(ii) states that, "The trip setting of hoist limit switches shall be determined by tests with an empty hook traveling in increasing speeds up to the maximum speed. The actuating mechanism of the limit switch shall be located so that it will trip the switch, under all conditions, in sufficient time to prevent contact of the hook or hook block with any part of the trolley."
Question: What is the interpretation of the wording "under all conditions" in the above paragraph?
Response: When OSHA first published its rules, it adopted several industry consensus standards, including the standards published by the American National Standards Institute (ANSI). Accordingly, OSHA adopted ANSI B30.2.0-1967, "Safety Code for Overhead and Gantry Cranes," the basis for the provisions covered under 29 CFR 1910.179. Therefore, the language, including the wording "under all conditions" found in 1910.179(k)(1)(ii) was originally part of the ANSI B30.2.0-1967 standard.
OSHA interprets the wording "under all conditions," described in Section 29 CFR 1910.179(k)(1)(ii), as all testing conditions for series of runs recommended by the manufacturer. In situations, in which the manufacturer's recommended testing conditions are not available, then OSHA interprets this phrase to mean all testing conditions (primarily the hook speeds) for the series of runs, each run at increasing hook speeds up to the maximum speed. Note that if the hoist has a single speed, then only one run is performed.
Scenario: If an employer, owner, or inspector of an overhead crane complies with the manufacturer's specifications and limitations applicable to the operation of cranes, the conditions which a hook block may trip an upper limit switch are minimal. All manufacturers of overhead cranes that I have contacted state that the hoist upper limit switch is a vertical trip device. For this reason, there are many warnings to crane operators on the dangers of side loads, swinging load blocks during hoisting, and using the hoist upper limit switch as an operational control.
How would OSHA cite and/or apply its rules on a failed upper limit switch resulting in a dropped load which causes personal injury or worse if: The crane manufacturer installed and tested the overhead crane prior to placing it in service? The employer inspected, tested, and maintained the crane per manufacturer's recommendations and regulatory agency standards. The employer trained, tested, and issues permits to crane operators. The crane operator involved in this incident admits to using the hoist upper limit switch as an operational control several times prior to the limit switch failure. The crane operator states that the sling being used this day was longer than normal which led to excessively swinging loads and difficulty clearing obstacles on the floor.
Question: What advice can OSHA give an employer or maintenance department to ensure compliance with the subject paragraph?
Response: The OSHA rule at 29 CFR 1910.179(n)(4)(i) requires that, "At the beginning of each operator's shift, the upper limit switch of each hoist shall be tried out under no load. Extreme care shall be exercised; the block shall be "inched" into the limit or run in at slow speed. If the switch does not operate properly, the appointed person shall be immediately notified." To insure compliance with this requirement, employers shall ensure at the beginning of each shift, that crane operators conduct the 1910.179(n)(4)(i) prescribed tests. Additionally, the OSHA rule at 29 CFR 1910.179(n)(4)(ii) states that, "The hoist limit switch which controls the upper limit of travel of the load block shall never be used as an operating control." If the crane operator you noted in your letters admits to using the hoist upper limit as an operational control, then the operator was violating the requirements contained in 1910.179(n)(4)(ii).
With respect to the operator's statement that, "the sling being used this day was longer than normal which led to excessively swinging loads and difficulty clearing obstacles on the floor," you should note that 29 CFR 1910.184 (copy attached) contains requirements for various types of slings. Since your letter did not specify the type of sling being used at the time of the incident you stated in your letter, OSHA cannot provide you with any additional information on this subject, other than suggesting you to review the