A shift supervisor received severe burns and later died after a flexible hose used to transfer hydrogen to the catalytic reformer was over-pressurised and caught fire.Hydrogen is supplied from three modules each consisting of 12 x 1m3 cylinders at 150 bar (2205 psig) pressure. Each cylinder is fitted with a needle valve and the twelve are connected together with steel tubing. Each module has a filling connection (with no pressure regulator) and a discharge connection equipped with a pressure regulator and a pressure safety relief valve set at 14 bars (206 psig) pressure.

The incident occurred during a temporary shutdown of the distillate hydro-treatement unit. The crude oil distillation units main column overhead product was pumped to a gasoline storage tank via the straight run gasoline rundown line. When restarting the distillate hydro-treatement unit, a valve in the start-up line to the high pressure separator branching off the crude oil distillation unit main column overhead product line was opened before the line to tank was closed.Hydrogen gas at a pressure of 30 bars consequently reached the tank, caused an overpressure and caused substantial damage.

The methanation reactor vessel was found to be deformed and had a 3-4 inch rupture at a position corresponding to the top of the catalyst bed. It is though that the incident was caused by ethylene entering the reactor. The ethylene reacted with hydrogen on the nickel catalyst, resulting in a very rapid release of energy. The corresponding temperature rise was sufficient to cause a ductile failure of the vessel.The proposed mechanism for the reaction is that ethylene vapour entered the methanation reactor via the cold box where there was a low pressure/high temperature following the trip.

A leak and fire occurred in a hydrogen compression section of a hydrocracker.

The explosion occurred in the ammonia/hydrogen separator of the ammonia reactor due to metallurgical problem.

The event affected the hydrocracker unit. A sudden release into a cracker compressor flare header destroyed a safety relief valve and damaged a sight glass on a liquid collection pot. As a consequence, release of hydrogen rich vapour to atmosphere occurred, necessitating a shut down of the iso-cracker.The damage was limited to that previously described, and there were no injuries. The cracker was returned to service four days later.

An explosion and fire occurred at a reciprocating recycle hydrogen compressor during commissioning of a new Diesel hydrotreatement Unit. It happened during the reactor pre-sulphidisation step, when the recycle gas contained 9000 ppm of H2S (hydrogen sulfide) and the pressure was at 940 psig (65 bar). The failure of retaining bolts on head-end suction valve unloader of recycle cylinder on compressor allowed release of process gas. Investigations revealed that the bolts failed due to material inappropriate to prevent sulfide stress cracking) and inadequate design for the service.

A leak of a flammable mixture of hydrocarbons and hydrogen from a ruptured pipeline caused an explosion and fire, killing one person and injuring forty six. Investigations into the incident found that emergency procedures were not followed.

Failure of a strainer allowed sand from brine filters to get into mercury cells in a chlorine plant. It appears that the sand obstructed flow and caused excessive hydrogen generation. An explosion occurred in the chlorine collection system.

A 7 inch thick reactor of a wide range hydrocracking unit being operated by computer at 2500 psi failed explosively due to localised heating. The blast caused widespread damage over a 300 yard radius including an adjoining catalytic cracker and crude pipe still where the roof of the control building collapsed. Other units were safely shut down from a blast resistant control building which sustained minor damage.