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OSHA Occupational Safety and Health Administration
U.S. Department of Labor

Process: Hot Work

 

Hazard: Burns and Shocks

CASE HISTORY

A worker was assigned to weld an attachment to a stanchion. As it was "only a stanchion" and not a tank or large void he assumed there should be no problem. After all the supervisor didn't mention any special precautions. And so he began the job. Shortly into the work, an explosion ripped the stanchion apart causing second and third degree burns to the workers neck and chest. Shrapnel from the explosion also struck the welder causing additional injuries.

test hole

test hole in stanchion

tester

Competent person testing similar stanchion

testing confirmed-inspection

Inspection / testing confirm that welding won't cause an explosion

Analysis and Preventive Measures

The welder knew that before hot work was done on structural voids that a competent person is required to test for flammable liquids or vapors. His assumption that this was only a stanchion that did not and had never contained any flammable material was flawed. Corrosion on the inside of the stanchion was the culprit in this case. Corrosion of metal can produce hydrogen gas. When this occurs inside a hollow non-vented void over time, a potentially explosive condition can occur. OSHA standard 29 CFR 1915.54 specifically addresses welding cutting and heating on hollow metal containers and structures. The standard requires that, in all cases, a competent person inspect and, if necessary, test structural voids (including stanchions and railings), before hot work is performed. This requirement must be strictly adhered to. Supervisors assigning hot work on structural voids should be certain that the worker is aware of the requirement and ensure that it is complied with no matter how small or seemingly safe the job. A contributing cause in this accident was that the employer's training program for welders did not satisfactorily explain all of the hazards associated with performing hot work on hollow structures. While hot work on tanks and voids that may have contained flammables was discussed in detail, the natural formation of hydrogen from metal corrosion in pipes and other hollow containers was not addressed.

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