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

A rupture disc blew on a 20,000-gallon liquid hydrogen tank, causing the vent stack to exhaust cold gaseous hydrogen. Emergency responders were called to the scene. To stabilize the tank, the remaining hydrogen was removed from the tank except for a small volume in the heel of the tank that could not be removed manually. The tank vacuum was lost. Firemen sprayed the tank with water and directed a stream onto the fire exiting the vent stack. The water was channeled directly into the open vent stack, and the exiting residual hydrogen gas (between -423 F and -402 F) caused the water in the vent stack to freeze. The water freezing caused the vent stack to be sealed off, disabling the only exit for the cold hydrogen gas. After a time, the residual hydrogen gas in the tank warmed up, causing view more

The bulkhead between a liquid hydrogen tank and a liquid oxygen tank failed due to a series of events. Air services to the building were shut down for repairs and the facility had switched to an emergency nitrogen supply. Failure to switch back to service air when it became available, led to the mishap.

The emergency supply became depleted and two valves in the normal nitrogen purge system failed in the open position, releasing the high-pressure nitrogen gas from the manifold into the liquid hydrogen tank. The gas flow raised the liquid hydrogen tank pressure to 4.5 psig. That was sufficient to rupture the bulkhead wall.

Incident Synopsis
During development tests, a gaseous H2 test tank was over pressurized and ruptured. The tank dome was destroyed.

Cause
The pressure relief valves were set too high. In addition, the tank was not depressurized while being worked on. Safe distances, as required by the procedures for personnel safety, were not followed.

Incident Synopsis
While attempting to replace a rupture disk in a liquid H2 vessel, H2 gas was released and ignited. In fighting the fire, liquid N2 was sprayed onto a second liquid H2 vessel located nearby. This resulted in cracking of the outer mild steel vacuum jacket. The loss of the vacuum caused a rapid increase in pressure and rupture of the burst disk of the second vessel. H2 boiled off and was burned in the fire.

Cause
The rupture disk was being replaced with a load of liquid H2 in the vessel and no separating inerting gas. The H2-air mixture was probably ignited by static discharges. Rupture of the second vessel burst disk was caused by the low-temperature exposure of the mild steel vacuum jacket.

Incident Synopsis
During pressure testing of a H2 tank for investigation of quick-release manhole cover, the tank burst at a pressure between 60-67 psig. Flow regulators indicated peak pressure of 67 psig.

Cause
The tank was over pressurized. A mistake was made in interpreting the blueprint, believing the tank was designed to withstand 150 psig, yet the actual design limit was 50.7 psig.

Summary

A hydrogen generation plant experienced a fire and significant damage due to a concussive combustion event that started in a high-pressure hydrogen feed pipe.

System Description

A certain hydrogen plant is designed to continuously produce hydrogen at a purity of 99.75% and at a rate of 510 m3 per day. Hydrogen is produced in two banks of cells filled with a strong solution of caustic soda. Current is passed through the cells to produce hydrogen and oxygen. The oxygen is vented directly to the atmosphere, while the hydrogen is piped to the gasholder. The gasholder is a low-pressure storage vessel capable of storing 28 m3 of gas. It is constructed in two parts. The bottom section is a large round tank. The upper section is an inverted tank or bell that is view more

A fire occurred in a hydrogen storage facility. The fire was reported by an employee who saw the fire start after he had aligned valves at the hydrogen storage facility in preparation for putting the hydrogen injection system into service. The employee escaped injury because he was wearing fire-retardant protective clothing and was able to quickly scale a 7-foot-high fence enclosing the hydrogen area. The local fire brigade was dispatched and offsite fire fighting assistance was requested. Upon reaching the scene, the local fire department reported seeing a large hydrogen-fueled fire in the vicinity of the hydrogen tube trailer unit. The heat of the fire potentially endangered the nearby hydrogen storage tanks. The onsite fire department, with offsite fire fighting support, fought the view more

Hydrogen was stored in a plant in a 42 ½ ft diameter sphere made of 3/16 inch steel. The sphere was partitioned into two hemispheres by a neoprene diaphragm attached around the equator. Hydrogen was stored under the diaphragm, while the upper hemisphere contained air. An explosion-proof fan was situated in the upper portion of the sphere in order to provide a slight positive pressure on the top of the diaphragm.

When the plant was shut down for a local holiday, the fan on top of the hydrogen sphere was also stopped. During plant startup two days later, a violent explosion occurred in the sphere. The sphere shell was torn into many sections by the explosion, and some of the sections were propelled as far as 1,200 ft. Some of these sections struck flammable liquid storage tanks view more