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.
A large, hydrogen-cooled generator is driven by steam turbines at a power station. During maintenance shutdowns, the hydrogen cooling loop in the generator is purged with carbon dioxide. After CO2 concentrations are measured with a densitometer to verify the complete removal of hydrogen, the generator is purged with air and the maintenance is performed.
During an inspection, three potential safety problems were identified concerning the location of a hydrogen storage facility. The hydrogen storage facility is located on a building's roof, which is made of 30-inch-thick reinforced concrete. The following potential safety problems were identified during the inspection:
Difficulties were experienced with two solenoid-operated globe valves in a charging system. When shut, the valves could not be reopened without securing all charging pumps. During a refueling outage, the two valves were disassembled and examined to determine the cause of the malfunction. It was found that disc guide assembly springs in both valves had undergone complete catastrophic failure. The springs, which initially had 25 coils, were found in sections of only 1-2 coils.
An offgas system mishap involved two explosions occurring within an interval of about 3 ½ hours. The first offgas explosion was reportedly caused by a welding operation on an air line adjacent to a hydrogen sensor line containing off gas. The welding arc initiated a detonation within the offgas piping. The detonation was contained by the piping system but blew out the water seal at the base of the vent stack.The second hydrogen explosion in this incident occurred in the stack base area.
A power plant reported a hydrogen leak inside an auxiliary building. The given plant was in cold shutdown at the time of the event. The discovery of this problem was as a result of an unassociated event involving the activation of a chlorine monitor in the control building. When additional samples indicated no chlorine gas, the shift supervisor ordered further investigation into other plant areas. Because there was no installed detection equipment, portable survey instruments were used to determine gaseous mixtures.
Description of Circumstances
An explosion at a coal-fired power plant killed one person and injured 10 others. The blast killed the delivery truck driver who was unloading compressed hydrogen gas, which is used to cool the plant's steam generators. Hydrogen deliveries are routine at the plant, occurring about once a week. Evidence pointed to the premature failure of a pressure-relief device (PRD) rupture disk, which had been repaired by the vendor six months prior to the explosion.
A five-pound CO2 cylinder being stored in a compressed gas storage cage at a power plant failed catastrophically and became a missile. The cylinder destroyed the storage cage, then struck one of six stationary hydrogen storage cylinders used as emergency make-up for the hydrogen supply system. One of the hydrogen cylinders was broken away from its mounts and moved 10 feet from its original location. The loss of this cylinder severed the manifold tubing, creating a leak path to the atmosphere for the remaining five hydrogen cylinders.