1. All samples with potential for hydrogen buildup should be limited to ground shipment only. (This shipment was by ground and air. If this incident were to have happened in an airplane, the consequences may have been worse.)

2. All samples must be properly labeled before shipping. Hazard label warnings need to be located on the outside of the shipment package.

3. The following safety information should be included with the shipment: the material safety data sheet (MSDS), applicable standard operating procedures (SOPs), and detailed information for the safe handling of the materials.

4. Improper labeling can result in improper handling and storage. Lack of proper labels allowed the sample to be delivered to an office rather than a laboratory, where the material can be properly handled and stored in an approved location.

5. For hazardous material shipments, do not ship material in quantities beyond what is needed by the receiver. Lesser material quantities lead to reduced risks in the event of a failure. In this incident, the analysis only required 0.1-0.2 gram of material, but 5 grams of the material were shipped. The receiver suggests that future sample sizes for this analysis be limited to a maximum of 0.5 gram (10% of what was shipped in this incident).

6. Samples that have the potential for hydrogen generation should use a pressure-rated container with the following features:

    a.  Head space to contain the maximum possible gas release from the sample below the container's maximum safety pressure limit.

    b.  Pressure relief mechanism (such as a release valve) that can be slowly opened within a glove box to safely equalize any pressure build-up.

    c.  Outer shell capable of containing any flying debris. A secondary metal container outside the pressure-rated container is suggested as a possible solution for containing potential flying debris.

7. Sealed glass containers should not be used to store samples that could generate pressure over time. These types of glass containers are not rated for pressure. Capped glass vials, bottles, or metal cans are alternate options to consider.

8. Safe transport and handling procedures for these types of materials need to be followed. The receiver requested that all shipments from the shipper of this sample be stopped until safety concerns from this incident are addressed.

9. Store these types of materials in proper approved storage. MSDSs should be available either locally or at a central location.

10. If a sample shipment lacks proper documentation, treat it as potentially hazardous until proper documentation is obtained.

11. DO NOT become comfortable with handling these types of aluminum hydride materials. Routine handling of these samples without problems can lull users into shortcuts that could result in more damaging results than this incident. If this incident had happened with personnel present, there was a potential for personnel injury.

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.

1. A hydrogen tube pressure indication system needs to be developed that is robust enough to withstand an accident, indicates hydrogen pressure regardless of valve position, and would be visible from a safe distance during an accident situation. Hydrogen system pressure is very important in determining incident response actions. Centralizing the system pressure indicators on a highly visible information panel located in a protected area of the hydrogen cylinder package is a possible solution to increase visibility.
2. Hydrogen valves should have a visible means to show that they are in the closed position. A highly visible lock or pin that can only be used when the valves are closed may help guarantee valve closure prior to transport. If the valve positions are visible, an operating procedure could be added that requires a final valve line-up check just prior to transport trailer departure.
3. Hydrogen cylinders grouped together and secured for transport as packaged assemblies should be designed for potential accident conditions. The package tie-down system should be designed with adequate safety margins to assure that hydrogen cylinder packages remain secured to the transport trailer under adverse conditions. However, the package design should assume that the package might fall from a moving transport vehicle and impact the ground, but the hydrogen cylinders should still be contained within the package. A program to test hydrogen cylinder packages under hypothetical accident conditions would be useful for developing designs that could be certified to survive potential accident conditions.

1. Increased structural protection is needed at the back of a hydrogen tube trailer to protect the vulnerable hydrogen systems components in this location (valves, pressure-indicating devices, manifolds, piping) in case of an accident. Side protection is especially important.
2. A system of designated lifting features is needed on hydrogen tube trailers to aid in accident recovery operations if the trailer is overturned or requires lifting. Typically, these types of accidents require the use of a crane for moving and lifting hydrogen tube trailers using lifting devices like slings. These lifting features should be designed to lift the hydrogen tube trailer with a full load of hydrogen cylinders and located at protected points. The current method for tube trailer lifting using slings around the hydrogen tube trailer at undefined locations and assumed centers of gravity is more hazardous and less safe.

1. A hydrogen tube pressure indication system needs to be developed that is robust enough to withstand an accident, indicates hydrogen pressure regardless of valve position, and would be visible from a safe distance during an accident situation. Hydrogen system pressure is very important in determining incident response actions. Centralizing the system pressure indicators on a highly visible information panel located in a protected area of the tube trailer is a possible solution to increase visibility. Fragile manometers should be replaced with more robust instruments and associated piping/components that can survive accident situations. Finally, pressure indications in all areas of the hydrogen system are desired, but especially the internal hydrogen tube pressure. System pressure components should be designed so that hydrogen pressure in the tubes is measured even when valves are closed and tubes are isolated.
2. Increased structural protection is needed at the back of the hydrogen tube trailer to protect the vulnerable hydrogen systems components in this location (e.g., valves, pressure-indicating devices, manifolds, piping) in case of an accident. More robust components (especially the pressure-indicating manometers) and better support/tie-down to the tube trailer of the hydrogen pressure components may be beneficial.
3. Hydrogen valves should have a visible means to show that they are in the closed position. A highly visible lock or pin that can only be used when the valves are closed may help guarantee valve closure prior to transport. If the valve positions are visible, an operating procedure could be added that requires a final valve line-up check just prior to hydrogen tube trailer departure.
4. The hydrogen tubes need more fire protection/heat shielding at their location on the tube trailer, especially as related to the key fire load sources (combustible material) at the tire and fuel/oil locations. Local shielding, both at the fire source and at the protected destination, should be considered to provide the best method for reducing flame impingement and thermal loading/impact on the hydrogen tubes and associated components during a fire. Consideration should also be given to hydrogen tubes and components designed for higher pressures and greater fire resistance.

• Replace the existing copper and carbon steel hydrogen pipeline with ¾-inch schedule 40 stainless steel.
• Reroute the new hydrogen line in the preferred location.
• Locate new hydrogen shut-off valves in a more convenient location.
• Remove all abandoned underground hydrogen lines.
• Continue to confer with the local fire department on the new piping system design until the project is completed.

The uncontrolled release of hydrogen occurred as a result of the rupture of the No. 6 hydrogen storage tube’s burst disc. This disc failed in response to being overloaded by mechanical stresses developed as water expanded and formed ice while in direct contact with the burst disc. It was the degraded condition of the vent cap (defective equipment) that enabled water to access the burst disc.

• As a corrective action, eliminate burst discs from hydrogen storage assembly. Redesign venting system for the pressure relief valves to prevent or inhibit moisture build up and allow moisture drainage.

The investigation uncovered two instances where the supplier was in possession of information ("safety data") that, if successfully conveyed to plant management and subsequently acted upon, would have prevented or reduced the chance of occurrence of the subject incident. Specifically, the hydrogen supplier found ice in a vent pipe, and was aware that the vent caps were cracked (recall the cracks were painted). Had a requirement existed for this information to be communicated to the plant, then plant management would have had the opportunity to evaluate and potentially influence the supplier's maintenance and operations program.As a corrective action, contract documents for the hydrogen and nitrogen supplies will be modified to stipulate the following:

• Suppliers of potentially hazardous equipment will provide plant management, for acceptance purposes, with written documentation describing the supplier’s preventive maintenance program.
• The supplier shall provide the plant representative with a copy of a preventive maintenance report upon the completion of each PM check performed by the supplier. The supplier shall expeditiously rectify any identified deficiency.
• Plant management will recommend to the Manager of Corporate Safety and Health that the above contract document modifications are implemented corporate wide.

Recommendation 1 - Overhaul and replace the diaphragms on all cells showing low-purity results. Check on a routine basis the individual cell purity levels to monitor the deterioration of performance of individual cells. Certain contaminants are produced as a result of the process that settle to the bottom of the cells. These contaminants, particularly magnetite, can block the water makeup ports and the drain valves. This was found to be the case on 6 makeup ports and on most drain valves. The blocked drain valves made it very difficult to clean the cells and to unblock the makeup ports.

Recommendation 2 - Replace the existing low-purity (LP) purity analyzer with a fail-safe model that ensures the vent valve is opened under the conditions described above. Carry out a risk assessment of the current LP purity analyzers to determine the level of risk associated with a loss of sample flow.

Recommendation 3 - Fit hydrogen purity analyzers that fail safe either between the stages of the compressor or immediately after the compressor. Carry out a risk assessment of the current LP and HP purity analyzers to determine the level of risk associated with a loss of sample flow failure.

Recommendation 4 - Fit pot-type water seals with open trough water makeup as a replacement for the existing U-tube and pot-type seals The original design drawings for the gasholder show the inlet and outlet pipes extend 50 mm above the water line. The actual measured extension was less than 20 mm. Small variations in the level control could allow water to enter the lines.

Recommendation 5 - The building is fitted with partially closed-in ends that can trap the gas under the roof. The current construction standard for this type of facility is to have the storage banks in an open area rather than inside a building of any kind. Any leakage will then quickly disperse into the atmosphere and not form an explosive mixture. This is not practicable at the current plant, but improvements are possible.

Recommendation 6 - Remove the end sheeting from the building to increase ventilation.

Recommendation 7 - Conduct an investigation into the feasibility of establishing a gas-up station away from the hydrogen generation plant, possibly near the CO2 plant, to allow the units to be gassed from transportable pallets in an emergency.

In the future, refining, petrochemical, and chemical industries need to review material verification programs to ensure that the maintenance procedures include sufficient controls and positive material identification (PMI) testing to prevent improper material substitutions in hazardous process systems.

Human Factors Based Design 
Designers should consider the entire process system life cycle, including planned maintenance, to avoid piping configurations that allow critical alloy piping components to be interchanged with non-compatible piping components.

Positive Material Verification Programs 
In-situ alloy steel material verification using x-ray fluorescence or non-destructive material testing is an accurate, inexpensive, and fast PMI test method. Facility owners, operators, and maintenance contractors should ensure that the verification program requires PMI testing, such as specified in API Recommended Practice 578, or other suitable verification process, for all critical-service alloy steel piping components that are removed and reinstalled during maintenance.

At a minimum, piping components and their respective locations should be tagged or marked before removal, and the correct installed location should be verified after reinstallation.

The accident proves that under special circumstances, the potential hazard connected with unforeseen microbial gas formation and accumulation should not be neglected. Thus, to avoid new accidents at the paper mill described above, the tower has now been equipped with a high-capacity fan for dilution of possible gases with air. Precautions are also taken to reduce the microbial contamination.

The lesson to pass on is that ventilation is critical in UPS battery rooms. Great care should be taken to ensure that the ventilation system is operational and brings in enough outdoor air to properly ventilate the enclosure.

Electrical safety interlocks should also be considered, which would isolate the batteries from their power supply, not allowing the batteries to charge if the ventilation system isn't working properly.

It is imperative that the battery room designers pay close attention to the design of ventilation systems and electrical safety interlocks. There are lots of good (and bad) ways to design and install battery rooms and critical ventilation systems. If designers do not have experience designing UPS battery rooms, experienced consultants should be contacted to ensure a safe and effective design.

In addition, internal management procedures need to be developed which analyze operation of such systems. As in this case, the entire data center was removed and the UPS system was no longer needed. The UPS system should have been decommissioned when the data center was removed. A good management-of-change procedure would have uncovered this problem before it became an incident.

More information on management of change can be found in the Lessons Learned Corner and also in the Hydrogen Safety Best Practices Manual.

Hydrogen distribution lines should be designed and carefully inspected to ensure process equipment in the area is correctly and safely installed. Equipment subject to vibration should not be placed in contact with hydrogen lines or with other equipment.

If equipment is moved or rearranged, the hydrogen system should be re-inspected as per the above.

This event illustrates the importance of adequately planning and communicating work. Procedures should cover all types of equipment that will be utilized. Work packages should clearly describe the equipment that will be used and the surrounding environment. Workers should be aware of potential hazards and un­known configurations before they begin work. Job hazard analyses should identify all situations that could pose a hazard to workers.

• Attentiveness to proper procedure would have prevented this incident.
• This incident also underscores is the need for rigorous training on hydrogen properties and behavior, not only for the operators of fueling equipment but also for emergency responders and the general public. The physical and chemical characteristics of hydrogen are different from those of fossil fuels and must be communicated, understood, and accounted for in hydrogen handling and use.

• 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.

Now, when conducting a sulfur deprivation test, vessels are ventilated to prevent over pressurization and safely facilitate the release of excess hydrogen.

This incident led to several changes in procedure:

• The purity of any gas bottle connected is double-checked. The practice outlined in the SOP requires confirming the content of the cylinder via the cylinder label prior to connection to the glove box. Increased attention is now paid during training of new staff members to ensure that this procedure is well understood.
• The vacuum pump is kept off so that the dilute gas will mix with the hydrogen
• Alarms are set at 10% hydrogen and at 300 ppm oxygen.
• A new SOP has been written.

• One needs to take extreme care with both new and supposedly spent hydride samples; the spent materials may contain pockets of unoxidized alanates that could react violently when being transferred.
• Work with small samples so if something does go wrong, the possibility of serious injury is low.
• The lab believes that the slow exposure to room air is the greatest concern.

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.

• Valve packing on ammonia tanks should be checked on a regular basis.
• If an ammonia smell becomes noticeable, the tank should be returned to the supplier.

Incident investigation findings for corrective actions were:
1. Install a valve after the regulator as an added precaution.
2. Clean the coupler at the end of the hydrogen delivery tube after each use to ensure that any catalyst residue has been removed.

1. Flexible tubing should be secured so it cannot get dislodged during operations.
2. Fume hoods where hydrogen is used should not be made of combustible materials. 3. Preventative maintenance should be performed on equipment on a regular basis to ensure that is is in good working condition.