An explosion occurred in an electrolysis system in a commercial facility. Electrolysis of a potassium hydroxide solution is used to produce hydrogen for a hydrogenation processes. The circular electrolysis cells are 1.5 m in diameter and 25 mm thick. Design current for the electrolyzer is 6,000 amps at 1.78 volts. Operating temperature and pressure is 70-90 °C and 435 psig. Hydrogen and oxygen product gases are separated from the electrolyte in separating drums. The system had been operating at the plant for 13 years prior to the explosion.
A facility experienced a major fire in its Resid Hydrotreater Unit (RHU) that caused millions of dollars in property damage. One employee sustained a minor injury during the emergency unit shutdown and there were no fatalities.
The RHU incident investigation determined that an 8-inch diameter carbon steel elbow inadvertently installed in a high-pressure, high-temperature hydrogen line ruptured after operating for only 3 months. The escaping hydrogen gas from the ruptured elbow quickly ignited.
On a given day personnel were removing a blind hub that had been used to temporarily isolate a portion of a gaseous hydrogen system. As a result of a sudden release of 2,800 psig gaseous nitrogen, sand and debris kicked up from the concrete pad and caused minor injury to two technicians.
During the investigation, it was found that:
Incident SynopsisDuring shipping preparation operations, out-gassed hydrogen/oxygen from a recently discharged silver/zinc battery in a hermetically sealed drum was ignited. Ignition was caused by a spark generated by the scraping of the battery against the side of the drum. An explosion occurred, blowing the lid from the drum, charring desiccant bags within the drum, and causing other damage.CauseThe cause of the incident was inadequate handling/transporting/storage techniques. The battery was placed in the drum too soon after discharge.
NaAlH4 powder mixed with hexane was placed in two metal trays and dried by placement in a glove box antechamber under vacuum. After several days, the trays were moved into the glove box main chamber. As the powder in one of the trays was being transferred to a container involving scraping of a metal sieve and metal milling balls with a metal spatula, a portion of the powder in the tray spontaneously reacted rapidly, creating a pressure pulse which cracked the window at the back of the glove box.
A technician was welding a cable suspended over a stainless steel H2 instrument line. During the welding process, two holes were accidentally burned through the hydrogen tubing. The operator heard a hissing sound and closed the valve, but the hydrogen had already ignited and it burned his hand while he was feeling for a leak.
A short during welding caused the pinholes in the tubing containing the gaseous H2.
A H2 air explosion occurred near a H2 compressor, located outside. Gaseous H2 had been released from a vent stack when a relief valve was actuated. The source of ignition was not known, but considerable damage was inflicted onto the system by the ensuing fire and explosion. Following the explosion, the shut-off valves were closed and the system was vented.
During transfer of liquid H2 from a commercial tank trailer to a receiving vessel, a leak developed in a bayonet fitting at the trailer/facility connection. The leak produced liquid H2 spray which enveloped the rear of the truck where the hand-operated shutoff valve was located. Emergency trained personnel, wearing protective clothing, except for proper shoes, entered the area and shut off the flow control valve. Reentry personnel suffered frost bite of their feet when shoes became frozen to the water-wetted rear deck of the truck.
Hydrogen Fire due to the Installation of an Incorrectly Sized Gasket at a Solvent Manufacturing Plant
During start-up operation of a high-temperature, high-pressure plant using hydrogen, hydrogen gas leaked from the flange of a heat exchanger and a fire occurred. The leakage occurred for two reasons:
Insufficient tightening torque control was carried out during hot-bolting and an unbalanced force was generated across the bolts.
A temperature rise was induced across the heat exchanger as a result of a revamping activity, during a turnaround shutdown.