Accident Case 2
A corroded bursting disc is due for inspection. An operating permit has been issued, but no device specific isolation sheet has been executed. The system takes only valve isolation, two of which are automatic valves. The system was not fully decompressed and remained at about 0.25 Barg.
As the maintenance technicians began to unscrew the flange bolts that held the bursting disc holder in place, there was a loud crash and they saw the bursting disc shoot out of the drain and hit the ground. The bursting disc has been partially detached from its holder and partially torn. Luckily no one was hurt.
There are serious flaws in the work permit system and the energy isolation program. Work permits should be issued after quarantine confirmation. In this case, single valve isolation alone is not enough; And there is no validity verification after the quarantine.