• Metal hydride materials of a composition which is not well characterized should be handled with procedures that assume a "worst case" for that class of materials, intermediates or precursors.
• Laboratory procedures should be in written form and should be adopted only after performing a safety vulnerability analysis and adopting appropriate risk mitigation steps.
• Working with small amounts of material does not provide assurance of safety.
• The method described to seal samples that are highly reactive upon exposure to air is not recommended. An alternative method, that is now being used for packaging aluminum hydride samples for offsite shipment is as follows: Aluminum hydride powders (0.5 g - 1.0 g) are sealed in glass bottles with a cap. The bottles are sealed in a thick plastic bag under Ar using a plastic bag sealer in the glove box. The sample bags are then removed from the glove box and sealed under vacuum in a much larger plastic bag using a vacuum sealer. The purpose of the large evacuated bag is to contain any evolved hydrogen gas if the material begins to decompose and the internal bottle & bag rupture. It is a good idea to calculate the maximum volume of H2 (at 1-atm) that could be released by the sample to determine if the outer bag is sufficiently large to contain the evolved gas. The package is then inserted into a cardboard box of sufficient volume (about 1-liter) to accommodate the expanded outer bag.

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.

• 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.

• Equipment that is designed to provide a safety barrier must be stringently tested upon installation.
• A procedure requiring annual testing of both excess flow valves, which includes proper seating for closure and proper flow, has been developed.

All safety devices worked as designed thereby protecting the environment and laboratory personnel. Researchers involved in the experiment acted properly and with the parameters set forth in operational procedures.

Follow up: Stops have been added to the apparatus to prevent the valves from being opened too far and exposing the 0-ring seals to damage.

Whenever a new program or organization is created, management should ensure that program interfaces and new responsibilities are clearly defined. Effective program integration is necessary to ensure that all responsibilities and requirements are implemented. Facility safety is the focus of review on hazard evaluation documentation that is provided to the facility by the reindustrialization program.

Following receipt of hydrogen tank accident analysis and other data, develop an approved corrective action plan, identify applicable facilities "surrounding" the building, and review and update the authorization basis documents for those facilities, as necessary.

Procedures will be revised to include specific information about hydrogen sensors and alarm controls. Caution will be added about sparks and flames in the fuel cell operation area. Workers will be cautioned that shunt resistors may reach high temperatures, shunt resistors should be kept away from gas tubing and other electrical wiring but near the fan; and shunt resistors should be checked periodically to assure that a good connection is made, thus preventing overheating. The procedure will also be revised to specify the proper hierarchy of emergency notification.

Workers should think twice about blowing out a fire, even if it is perceived as small. Serious injury can result even if the fire is relatively small. Flammable gases such as hydrogen and oxygen could provide additional fuel. It is important to document changes to an experiment through a formal change control process. On-the-Job training should be provided in several modes of communication. An electronic mail notification should not be the only and primary method of communication.

Management should ensure that a complete and thorough review of the previous work activities identified in the work package is performed at the pre-job briefing for the planned work. Work activities should be discontinued if any confusion exists concerning how to execute procedure steps. A process should be put in place to positively mark pipes that have been tested and retested to ensure proper identification when testing for acceptable levels of hydrogen.

This occurrence demonstrated the use of data by engineering to evaluate equipment problems. As the data changed, highlighting a problem with one-half inch PVC ball valves, the facility redesigned the valve extension and valve handle to prevent recurrence.

Valves for compressed gas service and for cryogenic liquid service are discussed in the Hydrogen Safety Best Practices Manual.

This occurrence highlights the need for ensuring work is organized and planned in a manner that is practical and efficient. The primary lesson learned from this occurrence is that personnel must be cognizant of the impact of their actions on other shifts. Planning with thought on potential consequences is necessary to ensure work activities are performed safely and the appropriate actions are taken as required.

Facilities should review their process systems to determine if they have valves installed that may be subject to this hazard. If so, facilities should conduct a detailed hazard analysis to determine the risk of valve failure. Detailed internal inspections may be necessary in order to identify high-risk valves. Facilities should consider replacing high-risk valves at the earliest opportunity with a blow-out-resistant design. If immediate valve replacement is impossible or impractical, facilities should consider immediately modifying the valves to prevent shaft blow-out. Valve manufacturers should be consulted in order to ensure that any modifications are safe.

A web-based resource developed by Sandia National Laboratories to provide data on hydrogen embrittlement of various materials is available at Technical Reference for Hydrogen Compatibility of Materials.

Cause and effect can sometimes be predicted by observing abnormal behavior even when the behavior is within specifications. Operators log equipment data and inform shift management when specifications are exceeded or when unusual equipment behavior is noted. Engineering establishes trending when patterned behavior is noted. Rotameter sample flow failures are too erratic to establish a cost effective preventive maintenance program. Predictive maintenance establishes a method to predict imminent failure based on symptoms that may be displayed during normal (within specification) operation. Operations and Engineering will continue to assess abnormal equipment behavior that may be within specification, and implement prediction methods, like trending, when applicable. Maintenance will implement annual rotameter inspection to aide in rotameter operational assessment.

1. Parallel-path design activities require an increased level of management oversight and control to mitigate the risks inherent in this process.
2. Schedule pressure cannot be allowed to compromise the integrity of the design process.
3. Turnover of personnel responsibilities that may be needed during the design process must be formal and controlled.