Process: Fabricating and Repairing Large Structural Components

Description

Structural steel plates or aluminum plates are fabricated and assembled to form the ship or erection units. Erection units are assembled to form ships. Steel plates are replaced during repair and conversion work.

  • Steel plates may be cut to size in a shop, and then transferred to the ship where they are welded into place. The steel plate may first be tacked or spot-welded to secure its position before the entire perimeter is welded.1
    Alternatively, steel plate may be welded to form erection units that are later moved and assembled to form the ship.2
    Welding has mostly replaced drilling and hot riveting.3
  • Stainless steel is used extensively in building ships with nuclear propulsion and in cryogenic liquid container ships.3
    Lead (to provide radiation shielding) is used extensively in construction of nuclear-powered vessels and submarines.3
    Aluminum is being used more often as a structural material.
  • The trend is towards use of computer-driven cutting torches to cut structural steel for fabrication in shipbuilding, and to remove worn or damaged steel plates in ship repair and conversion.4,5
    Oxy-acetylene, oxy-propane, and oxy-butane cutting torches are used.3
    Hand cutting is used to remove surplus materials from erection units for proper fit.3
  • Steel plate may be treated by shot blasting, either using automatic machines, or, for small components, by hand. Angle steel "stiffeners" may be used to reinforce steel plates.
  • Portions of the ship that will be below the water line may be sand-blasted and painted before assembly into the hull.6
  • Commercial divers may make temporary emergency repairs to the underside of a hull while the ship remains afloat. For example, a diver may plug a damaged area with wooden wedges or by welding or bolting a double plate over the damaged area.7
Equipment
  • Sheet Metal Equipment - includes shear, brake, punch, saw, spot welding, grinder, and hand electrodes.4,5
  • Welding equipment - includes automatic welding equipment, heliarc, and aluminum oxy-acetylene submerged arc.4,5
    Argon arc welding is used for aluminum alloys.3
    Underwater welding equipment may be used for emergency repairs.
  • Cutting Equipment - includes oxy-acetylene, oxy-propane, and oxy-butane torches, circular and straight torches, automatic tracing machines, computer-driven cutting torches, and metal saws.3,4,5
Associated Hazards
  • Respiratory irritation and systemic poisoning from exposure to toxic fumes and particles during welding and cutting operations.
  • Thermal burns from welding operations - burns from hot slag or sparks are common injuries.8
  • Conjunctivitis from arc welding operations - also called "arc eye." Caused by ultraviolet radiation, this is a common problem during arc welding operations.9 A shield of argon gas can double the intensity of ultraviolet radiation.10
  • Drowning, injuries from falls - 70% of falls result from equipment failures of scaffolds and ladders.8
    For standards covering scaffolds, ladders and other working surfaces, see 29 CFR 1915, Subpart E. Drowning results from falls from staging, decks, and end and wings wall of dry docks. Work over and near water requires life jackets, but compliance is difficult to enforce.8
    For standards covering types and maintenance of lifesaving equipment, see 29 CFR 1915.158. For standards covering personal flotation devices, which references Coast Guard standards, 46 CFR 160 and 33 CFR 175.23, see 29 CFR 1915.158(a). OSHA has issued two instructions that concern falling hazards. OSHA instruction STD 03-10-006 [STD 3-10.6] covers restrictions on welding from float and ship scaffolds and clarifies a contradiction between 29 CFR 29 CFR 1926.451(w) and 29 CFR 1926.451(a)(18) by allowing welding from these scaffolds providing the supporting ropes are without flaws and of adequate size. OSHA instruction STD 1-11.2B concerns work platforms suspended from lattice or hydraulic crane booms, and clarifies 29 CFR 29 CFR 1926.550(b)(2) by allowing the use of such platforms only when the procedure is safer than alternative available work practices.
  • Exposure to ionizing radiation - workers can be exposed to radiation from x-rays and radioisotopes used when testing welds.3
  • Frost bite, hypothermia, heat exhaustion, heat cramps, dehydration from exposure to extreme weather (heat stress).
  • Loss of hearing from noise - noise is prevalent, especially reverberant noise during plating operations.3
  • Drowning, electrocution, decompression sickness among divers while making temporary underwater hull repairs - although diving depths are relatively shallow, rapid surfacing in an emergency can lead to decompression problems. Section 29 CFR 1910, Subpart T covers the standard for commercial diving operations. Electrocution is a hazard during arc-welding operations. For the standard covering welding and burning during a dive, see 29 CFR 1910.422(g).
References

1 Gloss, D.S. and M.G. Wardle. Introduction to Safety Engineering. New York: Wiley, 1984.

2 "Shipbuilding." McGraw-Hill Encyclopedia of Science and Technology (1977).

3 Burton, D. J. "Safety Information Profile: Ship Building & Repairing." National Institute for Occupational Safety and Health (NIOSH) Contract Report 210-78-130 (NTIS PB-84-154-749).

4 Best, A.M. "Ship building." Loss Control Engineering Manual (1975).

5 Best, A.M. "Ship repair or conversion." Loss Control Engineering Manual (1975).

6 Levine, M.S. and D. Schott. "Walk-through Survey Report at Bay Shipbuilding Corporation." Sturgeon Bay, WI., (December 13, 1978). National Institute for Occupational Safety and Health (NIOSH) Industry Wide Study Report IW/074.47 (NTIS PB-82-151-671).

7 JRB Associates. Economic Impact Study of the Commercial Diving Industry. OSHA, Contract No. J-9-F-2-0069, 1983.

8 Netterson, R.W. "Accident prevention in shipbuilding and repairing." Safety and Health in Shipbuilding and Ship Repair. Geneva: International Labour Office, 1972.

9 Haglind, O. "Occupational health in the shipbuilding industry." Safety and Health in Shipbuilding and Ship Repair. Geneva: International Labour Office, 1972.

10 "Welding and cutting." Accident Prevention Manual for Industrial Operations. 8th ed. National Safety Council (NSC), 1980.