U.S. Department of Labor
Process: Surface Preparation and Preservation
Welding, Cutting, and Heating
During shipbuilding and ship repair activities involving welding, cutting, and heating, workers may be exposed to toxic fumes from metals such as lead, chromium, cadmium and zinc. Coatings applied to the metal surfaces of vessels or vessel sections may also contain toxic compounds that, when heated, release hazardous fumes. Manufacturers have made great progress in using alternative metals that meet structural requirements and reduce toxic fumes during hot work, and in using fewer toxic and flammable coatings. Despite these gains, the risk for adverse health effects such as damage to digestive, neurological, reproductive or respiratory systems in workers still exists and must always be evaluated. Subpart D of 29 CFR Part 1915 covers aspects of welding, cutting and heating, including ventilation, respiratory protection, and confined spaces (29 CFR 1915, Subpart D – Welding, Cutting, and Heating).
Before welding, cutting, or heating is performed on any surface covered by a preservative coating whose flammability is unknown, a competent person must test the substance to determine its flammability (29 CFR 1915.53(b)). If the substance is determined to be flammable or combustible, precautions must be taken to prevent its ignition by stripping the coating from the area to be heated (29 CFR 1915.53(c)).
In enclosed spaces where hot work will be performed toxic preservatives must be stripped for a distance at least four inches from the area where heat will be applied. Otherwise, workers must be protected by airline respirators meeting the requirements of 29 CFR 1915.154 (29 CFR 1915.53(d)(1)). Employers must post a fire watch during hot work where ignition may occur through spark, conduction, or radiation (29 CFR 1915.504(b)). Examples include:
- Slag, weld splatter, or sparks that might pass through an opening (1915.504(b)(1)).
- Failure to use fire-resistant guards, curtains, or flame-proof covers where combustible materials are located on or near decks, bulkheads, partitions, overheads, and within 35 feet of where hot work is performed (1915.504(b)(2) and (3)).
- Hot work conducted on or near insulation, combustible coatings, or sandwich-type construction that cannot be shielded, cut back, or removed, as well as where its construction has the potential for being reactive (1915.504(b)(4)).
- Combustible materials located adjacent to, or on the backside of the heated area (bulkheads, decks, overheads, or metal partitions), and have the potential for ignition (1915.504(b)(5)). A fire watch is also required where ignition may occur due to the close proximity of materials such as insulated pipes, coatings, combustible pipes, or cable runs (1915.504(b)(6) and ((7)).
A fire watch must also be posted when required by a competent person, Marine Chemist, or Coast Guard-authorized person (29 CFR 1915.504(b)(8)).
A competent person must test the atmosphere of any enclosed space where soft and greasy preservatives are present before hot work can begin (29 CFR 1915.53(e)(1)). Where explosive vapors (having flash points below 80 degrees Fahrenheit) are detected, no hot work may start until necessary measures are taken to ensure the work can be done safely (29 CFR 1915.53(e)(1)). For example, effective ventilation must be used where necessary to control atmospheric conditions to ensure that hot work can be performed safely. All motors and equipment used for mechanical ventilation must be grounded and designated explosion-proof, and fans equipped with nonferrous blades (29 CFR 1915.13(b)). Frequent tests to determine the concentration of solvent vapors must be conducted periodically by a competent person during welding, cutting, and heating operations (29 CFR 1915.53(f)).
Once it is determined that the atmosphere of the space is safe for entry and hot work, preservative coatings must be removed for a sufficient distance from the area to be heated to ensure that the temperature of the unstripped metal is not appreciably raised (29 CFR 1915.53(e)(2)). Flame or heat may not be used to remove soft or greasy preservative coatings, as this could result in the ignition of the substance or release of toxic vapors (29 CFR 1915.34(b)(2)).