Facility management confirmed that a hydrogen gas cylinder did not comply with the limiting condition for operation (LCO) for flammable gas control systems in the lab's safety requirements. Earlier erroneous calculations had shown that a release of the entire contents of the cylinder into the hood could not reach the lower flammability limit (LFL).
The facility manager determined that the LCO was applicable and immediately entered the action statement in the safety system, which required immediate termination of normal operations in the affected wing of the building. Because normal operations had already been terminated in the wing for HVAC maintenance, further efforts to terminate normal operations were not necessary. The hydrogen cylinder was removed from the hood, thus removing the out-of-specification condition and rendering the LCO not applicable. Removal of out-of-specification conditions is a valid action, regardless of whether it is specifically stated in the LCO. Following removal of the hydrogen cylinder, the facility exited the LCO.
The hydrogen cylinder was only a hazard inside the limited volume of the hood. The cylinder was removed from the hood and secured in the laboratory. All laboratory spaces in the facility were walked down to verify that there were no other flammable gas cylinders that had been improperly excluded from the requirements for a flammable gas control system. No other problems were found.
In the future, a policy will require verification of calculations performed for the hazard control plans by an independent engineer and will be included with the hazard control plan when it is submitted for approval. In order to clear up interpretation issues surrounding the safety policies and the use of a gas detection/shut off control system, the LCO will be simplified to require that any flammable gas source that could exceed the LFL in its respective volume be removed or replaced within an hour of discovery.
- Hydrogen Storage Equipment
- Gas cylinder
A flammable gas explosion is an analyzed hazard and gas detection/shut off is a safety significant control system that requires a limiting condition for operation (LCO). The rigor of the evaluation of flammable gas systems was inadequate. There was no independent calculation for the hydrogen cylinder and there was no report to document the findings of the evaluation. As a result, incorrect assumptions were made about the acceptability of the hydrogen cylinder. Calculations, independently verified by an engineer, must be included for processes involving a flammable gas and must accompany the hazard control plan for approval.