A chemical plant experienced a valve failure during a planned shutdown for maintenance that caused hydrogen to leak from a valve and catch fire. Four chemical reactor chambers in series were being emptied of liquid using hydrogen gas as part of a maintenance procedure. Two heater valves were opened allowing 3000 psi hydrogen to flow in reverse direction to purge the reactor system for approximately 25 minutes. At completion of the purging process, a "light" thud was heard as the reactor empty-out valves are being closed. Smoky vapor was observed coming out of one of the reactor empty-out valves and the valve closing was stopped by the operator. The operator summoned a second operator for help at which time a second "loud" thud was heard with a much larger light and view more

In the fall of 2007, the operations team began a procedure (a written procedure was being followed) to sample the liquid hydrogen (LH2) storage vessels ("tanks"), and associated transfer system. This procedure was being performed to determine the conditions within the system, and if necessary, to purge the system of any excess gaseous hydrogen (GH2) in preparation for reactivation of the system. The system had not been used since 2003.

The LH2 storage system contains two (2) spherical pressure vessels of 225,000 gallons in volume, with a maximum working pressure (MAWP) of 50 psig. Eight-inch transfer piping connects them to the usage point. Operations began with activation of the burnstack for the LH2 storage area. Pneumatic gaseous nitrogen (GN2) systems in the view more