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 should be carefully executed at all high-temperature and high-pressure plants.
• A plant must pay close attention to both the chemical impacts and the mechanical impacts of an unexpected temperature rise during start-up operations.

Several factors are important for flange use in applications of this type. Bolting patterns/torque order need to be considered in engineering, training, stewardship, and maintenance aspects of the specific operations. Cold bolt torque requirements should be developed so hot bolting is not required or relied upon for start-up. Flange stress from an increased or decreased operating temperature needs to always be checked. Substantial industry knowledge and practice exist for flange use to ensure that such operations are conducted safely.

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.

Countermeasures

• Thorough control of component parts during the construction process is required.
• Bolts should be tightened equally and fully.
• A new support for distributing the weight of piping is installed.
• Thoroughness of checks after construction is going to be initiated.

Additional discussion about working with reactive metal-hydride materials in the laboratory can be found in the Lessons Learned Corner on this website and in the Hydrogen Safety Best Practices Manual.

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.

Hydrogen rises twice as fast as helium, at a speed of 45 mph. Therefore, unless a roof or some other structure contains the rising gas, the laws of physics prevent hydrogen from lingering near its point of production. It is unclear weather the room's ventilation system wasn't functioning properly, or if it wasn't designed properly; but in either case, battery charging facilities need to consult experienced engineering firms on proper location and design of hydrogen detection and exhaust systems. On-site Standard Operating Procedures also need to mandate periodic functional/operational tests.

Adequate ventilation of battery charging facilities is addressed in the Lessons Learned Corner on this website.

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 process should be required to ensure that the maintenance was performed according to the written specifications, and that the hydrogen system will continue to function as designed until the next scheduled maintenance activity.

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. Experienced consultants/engineers should be involved in the design of gas detection and ventilation systems before hydrogen cylinders are employed in any laboratory. Laboratories also need to develop a Standard Operating Procedure, requiring periodic maintenance on hydrogen systems to check fittings, valves, and all critical components to ensure proper functionality at all times.

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 should be reviewed by workers before maintenance activities are started. Training on mandatory compliance with the operations manual should be carried out for all staff involved in hydrogen plant operations and maintenance.

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 in pressure or vacuum systems.

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 began. Steam tracing was strengthened to prevent condensation of moisture.
3. The gusset was remodeled into a structure in which thermal expansion is not restricted.

Careful management oversight of startup procedures is necessary to avoid stress corrosion cracking from occurring in hydrogen piping, since it can result in a serious accident. The chlorine concentration can be high in industrial water, and it is desirable to avoid treatment using water with a high chlorine concentration.

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.
3. Although a valve stops a flow, it is necessary to consider potential leakage. A valve might leak due to fouling, solid material between seals, etc.

• 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 strengthened.
• All refineries with the same kind of desulfurization units should thoroughly check dead-end piping areas. They should also conduct a safety review of their operating and management procedures.
• If a very careful study is not done, safety aspects of remodeling projects might be disregarded, even if the initial purpose of remodeling is achieved.
• Dead-end piping is the cause of various problems, so careful attention to areas of dead-end piping is needed to ensure safe operation.

• 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 instrumentation to monitor the high-pressure hydrogen system.
• Confirm that temporary offices/facilities are not co-located with hazardous chemical storage sites.
• A procedure is now in place that requires a Job Hazard Analysis (JHA) to be done on unloading hydrogen and shared enterprise-wide.
• A competent plant employee must be present during all hydrogen unloading activities.

• A redundant safety circuit was put into service and the tank returned to normal operation after the failure. Both rupture discs were replaced and the tank was inspected.
• Important to note that the safety system functioned as intended. Most prevalent learning is that liquid air will form and fall off the vent stack due to very high flow of very cold gas when the relief systems are flowing at capacity. Liquid air may also splash off flanges or other pieces and will cause a small vapor cloud as it falls from the stack. Falling liquid air was mistaken for liquid hydrogen during the event.

Hazard analysis should consider potential leak locations, potential ignition sources in the vicinity, and the potential for accumulating flammable gases in that area.

Users should leak-check all cylinders upon installation. This event would have been avoided if personnel had followed internal procedures/requirements.

In the future, this mesoporous carbon material and ammonia borane:mesoporous carbon material will be handled under anaerobic conditions (glove box) to prevent further incidents.

No Lessons Learned, Specific Suggestions for Avoidance, or Mitigation Steps Taken.

• Unprotected hoses are susceptible to glass shards, abrasion, and burns during normal use. This leak was formed from a glass shard penetrating the tube wall.
• Flexible hoses require protective sheaves to avoid cuts, abrasions and burns during normal use. Hydrogen supplied workstations require emergency shut off valves that are readily accessible by operators and are removed from the normal usage point of the gas. A request has been submitted to facilities engineering to select an appropriate valve. Once this has been done a follow-up request to facilities will be made to install such a valve. Such corrective action will be implemented plant-wide.
• All existing hoses have been replaced. Weekly inspections during the units clean-up period has been requested of all glass workers. The hoses will be inspected for wear and burns. Flexible hoses on equipment have been replaced with stainless steel tubing where applicable.

This occurrence underscores the importance of appropriate design, equipment selection, and design review; the potential drawbacks of sharing utilities with other facilities; and the need to simplify [in this case, glove box atmosphere purification equipment/process] operations as much as possible.

1. There should have been greater awareness during the design and installation of the burn box regarding the static pressure limitations of the exhaust fan in relation to the anticipated static pressure buildup across the HEPA filter.
2. Monitoring the pressure drop across the HEPA filter is not a sufficient or reliable indicator of ventilation system performance (air flow). An air flow monitor incorporating a low-level alarm would have provided a reliable indication of ventilation system performance.

This occurrence underscores the importance of completing a hazard analysis for each different process. Non-safety-related systems or equipment may be used for purposes other than their primary purpose so long as potential hazards are identified and engineering and administrative controls are applied to eliminate or minimize them. The filling of lecture bottles seemed to fall within the safety envelope previously established for high-pressure testing; however, the rupture of a cylinder revealed an unanticipated potential to release an overfilled gas cylinder to laboratory personnel.

The risk of a serious fire occurring inside the chemistry laboratory hood from use of hydrogen gas and/or presence of a small quantity of hydrazine-hydrate was underestimated. Additional control measures were required to reduce the risk of fire and to ensure that consequences of an incipient fire were minimized.