It is characteristic of silver/zinc batteries to outgas both hydrogen and oxygen for several hours after discharge. Also, in the future, the battery should be properly secured inside the container.

Refueling operations need to be conducted in a careful and attentive manner, and operators need to be aware of the potential consequences of their actions.

The site needs to implement a good Operational and Readiness Inspection procedure. System inspection deficiencies need to be identified, and (if possible) reviewed by a second party before future tests are conducted. This inspection could include…

Proper bolt identification can prevent similar occurrences in the future. This can be achieved by simply painting the critical bolt heads a certain color (or by purchasing bolts with painted bolt heads). An explanation form should then be clearly…

Extra caution should be taken when working around elevated pressure storage tanks. Pressure relief valve settings should be checked and then verified by a second party if possible. Proper procedures need to be followed at all times.

• Facilities housing battery charging systems need to ensure the ventilation systems are operational, and delivering enough outdoor air to properly ventilate the enclosure.
• Operators need to be aware of safe practices and proper…

Normally hydrogen fires are not extinguished until the supply of hydrogen has been shut off due to the danger of re-ignition and explosion. During a gas leak/fire, it is important to shut off the source of the hydrogen if it is safe to do so. If…

Lessons Learned The site initiated the establishment of a field patrol and strengthened their onsite monitoring of mechanical equipment during a plant-wide temperature rise.

• Quantitative control of tightening torque on bolts…

Lessons Learned
Construction errors are difficult to detect once construction is complete. It is important to develop and use a systematic oversight process for minimizing construction errors during the construction process.

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Although a functional fire protection system would have helped to extinguish the fire, a properly installed hydrogen detection system, coupled with a properly designed ventilation system, could have prevented the incident altogether.

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Routine maintenance activities on pressurized hydrogen systems should be conducted per written design specifications. The procedures should provide detailed oversight regarding bolt, nut and fitting replacements or repairs. A formal review…

This incident emphasizes the need for proper gas detection and ventilation systems, as well as fire suppression systems, in laboratories using and storing hydrogen. This is especially true when open flame burners are in close proximity.…

Hazards should be eliminated to the extent possible rather than depending on workers to follow an operations manual.

Potassium carbonate draw-off operations should be improved, and the operations manual should be revised. The manual…

Fail-safe position of control valves in supply lines must be set correctly to prevent damage to pressure vessels.

Recommendation

Set all valves for fail safe operation (open or closed) according to needs before installation…

1. The dilution water for making a polythionic acid aqueous solution was changed from industrial water to pure water to lower the chlorine concentration in the piping.
2. Water that accumulated in the drain was removed before heating…

1. The plant tried to increase production and decrease workload, but failed to notice the potential negative outcomes of this change.
2. It is necessary to thoroughly simulate all potential negative outcomes of a change in procedures…

• Operation and management of the hydrodesulfurization unit should be strengthened to account for abnormal phenomena such as local corrosion.
• The safety review system for remodeling existing equipment and facilities should be…

• Verify that all PRDs contain fuse-backed adapters.
• Explore elimination of rupture disk PRDs and substitution of spring-style relief valves.
• Develop new hydrogen unloading procedure using a written checklist. * Add…

Investigation determined that internal galling has caused the failure rendering the needle valve unusable. The galling was caused by a stainless steel stem acting against a stainless steel seat. This failure mode had been observed before and the…

For the use of mechanical fittings in hydrogen service, administrative controls should be in place, as in this case, to ensure that leak testing is conducted on a regular basis. It should never be assumed that every fitting is tight. Additional…