In a industrial gas plant, an employee had to disconnect a multi-element gas container (MEGC) containing silane (SiH4, pyrophoric gas) below 8 bar. The employee first performed the MEGC purge cycle. He performed another task and then resumed the disconnect sequence. He then mistook the MEGC and disconnected the one next to it by mistake. The one next to it was full of silane and is used in production at 9 bar. The silane began to leak and ignited as soon as the lyre clamp’s nut was loosened. The safety system was triggered in a matter of seconds after flames were detected: the gas supply was cut off to stop the leak, and the deluge fire protection system was activated to cool down the tubes. The employee, suffering from first degree burns to his hand, was taken care of by the firefighters.

The inquiry showed that the employee, who was qualified and had 20 years of experience, was not wearing the PPE recommended for operations involving the connection/disconnection of silane. The MEGC in used had not been locked out. The MEGC to be disconnected, emptied and purged of all residual pressure, had not been appropriately identified. This type of event (container error) had not been taken into account in the workstation’s risk analysis.

The operator reminded its employees of the instructions for wearing PPE. The victim was ordered to undergo a new cycle of training and authorisation, and the connection/disconnection procedure was modified. The interruption of the procedure is prohibited except in an emergency. Two persons equipped with PPE, including 1 with the proper authorisation, should be present during the critical connection/disconnection phases. The risks associated with this workstation were reviewed to take human error into account.

Finally, the MEGCs’ lockout/tagout systems were improved: installation of front/rear signalling on the MEGCs according to their status (in use or disconnected), installation of a position indicator (open/closed) on the manual valves of the manifold on each container, installation of a remote luminous indicator upon the pneumatic activation of the utility valve towards the connection of the lyre to be disconnected, and implementation of a connection/disconnection check-list with a double-checking system.