We have discussed this many times: far too many employees fail to recognize the proper application of “pounds per square inch” (PSI). In my LOTO training, I spend 15 minutes explaining that even 1.0 PSI can be lethal. This case was brought about by poor planning and a LOTO failure, but it shows that even low PSI can be lethal.
On March 25, 2003, two employees were instructed to remove a cover plate from an electrical generator at a power generation plant. The hydrogen gas had been purged from the generator and replaced with air pressurized at approximately 40 psi. The generator was pressurized with air so the workers could perform a leak test on the system.
The cover plate was 11.5 inches thick and 19 inches in diameter. It was secured to the generator by 24 bolts, 21.5 inches long by 0.625 inches in diameter.
The two employees were informed that the cover plate needed to be removed to remove a balancing weight from the shaft. It would be used as a guide to manufacture additional weights.
The employees removed all 24 bolts while the system was under pressure. When the cover plate would not come loose, the employees got a pry bar and chisel to free it. They also reinstalled four (4) of the bolts to prevent the heavy plate from falling on their feet. One of the employees used a hammer and chisel to break the cover plate loose. When the plate was loosened, the air pressure stripped the bolts from their anchor points. The plate struck one of the employees, hurling him into the air. He came to rest on a concrete floor several feet away. The employee had been killed.
Source: https://www.osha.gov/ords/imis/accidentsearch.accident_detail?id=202064192