A significant hydrogen leak occurred during refueling of the onboard hydrogen storage tank of a fuel cell-powered lift truck while it was completely depowered. The in-tank shutoff solenoid valve had recently been replaced, and this was the initial refueling event after the replacement. The fuel zone access panel was removed to allow constant visual leak checking with Snoop leak-detection fluid. The event occurred during the final pressure testing of the repaired system when an O-ring failed at approximately 4500 psi, releasing the entire contents of the hydrogen tank in about 10 minutes. The dispenser hose/nozzle was immediately disconnected, and the leak location was quickly isolated to the tank/valve interface. A 30-foot boundary around the lift truck was cleared of personnel and view more
Hydrogen alarms went off in a research laboratory and the fire department was called, but no hydrogen leak was detected. The hydrogen system was leak-checked with helium and found to be leak-free except for a very small leak in the manifold area. The manifold leak was fixed, but because of its small size, it was not thought to be the likely source for the hydrogen alarm trigger. While hydrogen was removed from the system for leak-testing, the hydrogen alarm went off again, and again the fire department responded. There was no hydrogen present in the system to trigger this alarm. Other sources within the building were checked to see what may have set off the alarm, but none were found. One research area uses small amounts of hydrogen, but laboratory logs indicate that none was being view more
During maintenance on a breakaway fitting, a review of the pressure rating of the adapter fitting connecting the pipe to the breakaway found the adapter to be under rated for the design pressure. While the male straight-thread side of the "standard" fitting was rated to 7700 psig, the female compression-tube end of the same fitting was rated to only 4900 psig. The adapter was replaced with a fitting of increased wall thickness meeting the design pressure rating.
Within the International Space Station (ISS) oxygen generator, an increase in differential pressure across a pump supplying return water to a PEM electrolyzer fuel cell stack had persisted over a 4-month period and was approaching the shut-off limit for the system. This decrease in performance was suspected to be caused by water-borne catalyst fines containing platinum black and Teflon®* binder materials, shed by the fuel cell stack, and accumulated within the pump's inlet filter. Maintenance in the field was required.
The system had been designed for factory maintenance, and no contingency had been planned to handle field maintenance for such a circumstance. An initial assessment of hazards for the proposed filter maintenance raised the concern that opening the water line view more
An instrument engineer at a hydrogen production facility was arresting the hydrogen leakage in tapping a pressure transmitter containing 131-bar hydrogen gas. The isolation valve was closed and the fittings near the pressure transmitter were loosened. The pressure dropped from 131 bar to 51 bar. The fitting was further loosened (though very little); the instrument tube slipped out of the ferrule and got pulled out of the fitting. With the sudden release of the 51-bar hydrogen, there was a loud pop (like a fire cracker) and the spark-proof tool was observed to have black spot on it. The volume of the hydrogen gas released was small, since it was in the tapping line only.
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:
Leakage of hydrogen gas from the storage facility in proximity to the air intakes of the building's ventilation system may introduce a flammable or explosive gas mixture into the enclosure. Because the hydrogen storage facility, containing four 8,000-scf hydrogen tanks at up to 2,450 psig, is Seismic Category II, a seismic event may result in a hydrogen leak. Furthermore, the pressure relief valves in the hydrogen facility exhaust downward to within 6 view more
During a facility walk-through, it was noted that a combustible gas (hydrogen) monitoring system installed in a furnace room was inoperable (the system had been unplugged). This system is used to detect and warn facility employees of an explosive or flammable environment. An explosive or flammable environment can only occur if there is a leak in the system, which would not be expected to occur during normal operations. When the system was reactivated, no leaks were indicated.
The incident had the following three causes:
A procedure describing administrative controls necessary to ensure safe operations in the area should have been developed and implemented prior to disabling the hydrogen monitoring system.
The hydrogen monitor was not hard-wired, which allowed it view more
A process area alarm activated. The alarm was caused by an instrument channel located above a reaction vessel off-gas system final HEPA filter canister, which indicated 25% of the lower explosive limit (LEL) for hydrogen. Since the only source of hydrogen is from the reaction vessel during the reaction of sodium with concentrated sodium hydroxide, the immediate actions were to shutdown the reaction process and place the facility in a safe condition.
The root cause was inadequate or defective design. Had the pre-filter drains been vented to outside the building, no hydrogen could accumulate in the process area. The corrective action for this is to complete an Engineering Task Authorization (ETA) to install a sample/drain collection system with loop seals to prevent any release of view more
A facility replaced the copper tubing used for hydrogen distribution, with stainless steel tubing. This was done to address a fire protection concern related to the solder on the copper tubing being susceptible to heat, melting, and releasing a flammable gas. The facility maintenance personnel completed the replacement, noted the pressure on the hydrogen bottle, and left the building. When the maintenance person returned on the following day, s/he noticed the pressure on the hydrogen bottle had dropped 500 psi overnight, indicating a leak in the system. S/he notified the appropriate facility personnel and together they began to determine why the hydrogen had dropped 500 psi overnight. The hydrogen line originates at a manifold, which is part of a glove box atmosphere purification view more