A metal hydride storage system was refilled using compressed hydrogen in a closed lab environment. The tank system is an in-house development and is optimized for high hydrogen storage density and use with an air-cooled fuel cell. The system is equipped with a pressure relief valve that opens gradually at 35 bar to protect the tank from overpressure conditions. The tank itself is designed to adsorb 400 g of hydrogen at a pressure less than 15 bar.
An operation to increase the pressure within a hydrogen tube-trailer to 6000 psig was in progress when a burst disk failed at approximately 5200 psig and hydrogen was released. A vent line attached to the burst disk was not sufficiently anchored and bent outward violently from the thrust of the release over an approximate 4-inch moment arm, causing considerable damage to the adjacent vent system components. The operation is conducted with personnel present, but fortunately no one was in proximity when the burst disk failed.
Hydrogen was released near the ground when the vent line from a 13,000-gallon liquid hydrogen storage vessel suffered damage from unusually high winds. The toppled vent line did not shear or tear, but sustained a kink that restricted hydrogen flow and created a back pressure on the vessel relief system.
Repair efforts were hampered by the potential for cold hydrogen gas, a flammability hazard, in the work area. Shut off or redirection of the hydrogen was not possible, and variable breezes made set up of safe zones uncertain. A protocol had not been prepared for this scenario.
An isolated vehicle hydrogen tank needed to be de-fueled, but the standard operating procedure could not be followed because the tank was inoperable and had to be manually vented with a special tool. This intentional release of hydrogen was done outside an R&D facility, but it unintentionally activated two sensors on vehicle bay gas detectors (at 20% LFL) in the adjacent indoor facility. Although each person involved in this activity was qualified to perform the work, the circumstances at the time were unusual.
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.
A researcher was using numerous compressed gases in his lab. To facilitate reconfiguring his experimental apparatus, he installed "quick-disconnect" fittings on flexible tubing connected to his compressed gas cylinders/regulators. He also fitted all of the equipment that needed gas with complementary "quick-disconnect" fittings.
A hydrogen explosion and fire occurred in the benzene unit of a styrene plant in a large petrochemical complex. The unit was being restarted following a scheduled maintenance shutdown. The explosion followed the release of about 30 kilograms of 700-psig hydrogen gas from a burst flange into a compressor shed. Two men were killed and two others were injured. If it had not been a holiday, the death toll and injuries would probably have been much worse.
A fire occurred in a continuous-feed autoclave system (fixed-catalyst-bed tubular reactor) when the rupture disc released, discharging hot oil, oil distillates, and hydrogen gas out a vent pipe into the autoclave cell. The flammable mixture was discharged directly into the cell because there was no system in place to catch or remotely exhaust the autoclave contents. The oil and gas ignited in a fireball that, in turn, ignited nearby combustibles (cardboard and paper), causing a sustained fire. The hydrogen gas and autoclave system were shutoff immediately.
A partial pressure sensor for an automated gas environment system (AGES) was not functioning correctly for pure hydrogen flow. While personnel were troubleshooting the problem, a burst disk ruptured resulting in a leak of hydrogen gas and actuation of a flammable gas alarm.