• 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.

In this case, failure to recognize a run of tubing still maintaining pressure could have been avoided if such information was provided in a safety briefing. Knowledge of any job is the utmost importance in promoting and maintaining a safe working environment.

Facilities should Issue instructions to appropriate personnel to establish the standard practice for hydrostatic & pneumatic pressure testing.

The set up configuration of a tubing/piping run for a hydrostatic pressure test must be carefully reviewed to ensure that means are provided to immediately shutoff pressure and safely and completely relieve pressure. Under no circumstances should a Swagelok fitting or any other fitting be used as a vent valve. Equipment should be utilized for its intended purpose only.

This incident highlights the need to ensure that the performance of special procedures does not place facility equipment in a condition that could lead to entry into a LCO.

Installation

1. Fittings need to be visually inspected to insure ferules are in place and correctly positioned prior to swageing.
2. Research staff are responsible for communicating system specifications [gas type, Maximum Allowable Working Pressure(MAWP)] and testing requirements to service provider.
3. Lines that run through ceilings and chases should be pressure-tested at the MAWP of the materials of that line.

Commissioning

1. System owners/users should specify QA requirements such as leak testing and service providers/installers must provide appropriate documentation.
2. System owners/users should document that they have accepted work.
3. The system owner is responsible for tracking, through safety documentation such as IOPS or SOPs, system modifications and procedural changes. Use of safety documentation prevents off normal events that could arise through staff turnover.

Best practices related to fittings and joints in compressed hydrogen gas piping systems are discussed in the Hydrogen Safety Best Practices Manual.

The practice of making gas mixtures in the laboratory should be eliminated, and gas mixtures with a known low hydrogen concentration should be purchased for use. The concentration of hydrogen used should be such that it is not possible to form an explosive mixture on dilution with air (i.e., hydrogen concentration less than 4% after mixing with air from a leak, damage to the chamber, or inadvertent admission of air to the chamber). A gas monitor with a built-in alarm should be purchased and installed to continuously monitor both hydrogen and oxygen concentrations in the chamber, and to provide visible and audible indication of any problems. The manufacturer’s instructions and manuals should be closely followed. All users should be fully trained in the use of the equipment, and should be fully conversant with the potential hazards and how to manage the associated risks. Hydrogen use in anaerobic chambers is discussed in the Lessons Learned Corner on this website.

After this accident, a safety inspection team was organized. An investigation of this incident and an inspection of all other experimental equipment was conducted by the team. As a result of this inspection, the heaters are now hard-wired to the temperature controllers. Follow-ups on the remainder of the team's findings for all other experimental equipment have not yet been completed.

When performing maintenance evolutions, proper work control processes must be in place to insure that process systems are adequately prepared, remain in a safe energy state during the maintenance evolution, and are properly restored afterwards.

This occurrence points to the importance of gathering and organizing all applicable administrative controls and other commitments prior to commencing work. It also re-emphasizes the importance of attention to detail, not only by the person responsible, but also by anyone confirming compliance.

The primary lesson learned was that the active hydrogen facility and existing operating procedure, at the time of the accident, were sound. While this now has been determined, the previous form(s) of this system, associated documentation, and accident history did not provide sufficient basis to assume continued safe operation. The review of furnace operation subsequent to this accident now provides a basis to evaluate the safe operation of furnace #4 as well as other similar facilities.

The failure to apply the appropriate procedure suggests the need for either additional administrative controls and/or periodic refresher training.

Some hydride materials (e.g., sodium alanates) may be rapidly exothermic, even pyrophoric, if exposed to water or humid air or slowly exothermic, even pyrophoric, if exposed to oxygen. Reactive materials, including fine metal powders, should be handled (as in this incident) in an inert atmosphere such as a glove box. The protocol for handling these materials should be incorporated into a standard operating procedure and appropriate safety training conducted for laboratory personnel, including guest staff.

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.

The manager in charge acknowledged that, while he made relatively recent modifications to the high-pressure gas storage side of the system and had directed a major rebuilding of various units, the moderate-pressure interconnecting system (the source of the problem) remained essentially in its original condition. He acknowledged waiting for safety definitions in the Safety Manual and thereby letting improvements be delayed. He supported the decision to have an independent engineering review after the second incident, pointing out that this essential step assisted in defining the actual root cause and led to more constructive and long-range corrective actions.