- Home
-
Resources
- Center for Hydrogen Safety
- Hydrogen Fuel Cell Codes and Standards
- Learnings & Guidance
- Paper & References
- Web-based Toolkits
- Workforce Development
- Contact
- About H2Tools
Disclaimer: The Lessons Learned Database includes the incidents that were voluntarily submitted. The database is not a comprehensive source for all incidents that have occurred.
1. Management must ensure that operating decisions are not based primarily on cost and production. Performance goals and operating risks must be effectively communicated to all employees. Facility management must set safe, achievable operating limits and not tolerate deviations from these limits. Risks of deviation from operating limits must be fully understood by operators. Also, management must provide an operating environment conducive for operators to follow emergency shutdown procedures when required.
2. Process instrumentation and controls should be designed to consider human factors consistent with good industry practice. Hydroprocessing reactor temperature controls should be consolidated with all necessary data available in the control room. Some backup system of temperature indicators should be used so that the reactors can be operated safely in case of instrument malfunction. Each alarm system should be designed to allow critical emergency alarms to be distinguished from other operating alarms.
3. Adequate supervision is needed for operators, especially to address critical or abnormal situations. Supervisors need to ensure that all required procedures are followed. Supervisors should identify and address all operating hazards and conduct thorough investigation of deviations to determine root causes and take corrective action. Equipment and job performance issues related to operating incidents should be corrected by management.
4. Facilities should maintain equipment integrity and discontinue operation if integrity is compromised. Hydroprocessing operations especially need to have reliable temperature monitoring systems and emergency shutdown equipment. Equipment should be tested regularly and practice emergency drills should be held on a regular basis. Maintenance and instrumentation support should be available during start up after equipment installation or major maintenance.
5. Management must ensure that operators receive regular training on the unit process operations and chemistry. For hydrocrackers, this should include training on reaction kinetics and the causes and control of temperature excursions. Operators need to be trained on the limitations of process instruments and how to handle instrument malfunctions. Facilities need to ensure that operators receive regular training on the use of the emergency shutdown systems and the need to activate these systems.
6. Management must develop written operating procedures for all phases of hydrocracker operations. The procedures should include operating limits and consequences of deviation from the limits. The procedures should be reviewed regularly and updated to reflect changes in equipment, process chemistry, and operation. As appropriate, the procedures should be updated to include recommendations from process hazard analysis and incident investigations.
7. Process hazard analysis must be based on actual equipment and operating conditions that exist at the time of the analysis. The analysis should include the failure of critical operating systems, such as temperature monitors or emergency operating systems. A Management of Change review should be conducted for all changes to equipment or processes, as necessary, and should include a safety hazard review of the changes.
More information on management of change can be found in the Lessons Learned Corner and also in the Hydrogen Safety Best Practices Manual.
Additional details regarding probable causes and lessons learned can be found in Attachment 2.
The following corrective actions have been taken:
1. Evaluate any change in normal procedures or conditions for storage of aluminum hydride products. In this case, the aluminum hydride material was typically stored at -35°C in the glove box freezer. However, due to a change in glove boxes, this was no longer an option. Since commercially available aluminum hydride compound is shipped in glass bottles at room temperature, it was assumed that this was considered safe handling. The vial was stable for 6 weeks before the near miss occurred.
2. Limit aluminum hydride materials to small quantities as needed for immediate use. Larger samples have the potential to caused more damage.
3. Do not store aluminum hydride materials for extended periods of time and promptly dispose of any remaining material after use.
4. In-process aluminum hydride material should be stored at lower temperatures (i.e., in a freezer) and in an air-free contained environment (i.e., inside an air-free glove box) to reduce or slow decomposition into volatile materials (e.g., hydrogen, aluminum metal, and similar). In this case, if the aluminum hydride material had been stored in air, it is likely that a fire may have started.
5. Store aluminum hydride material in plastic containers instead of sealed glass containers to avoid catastrophic failure of containment. In this case, it is likely that the decomposition process of the aluminum hydride compound slowly built up pressure sufficient to destroy the glass vial.
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 packing in the flow control valve should be replaced periodically. A planned investigation will determine the optimum time period for packing replacement.
More information on management of change can be found in the Lessons Learned Corner and also in the Hydrogen Safety Best Practices Manual.
The following recommended actions were identified:
The importance of purging hydrogen piping and equipment is discussed in the Lessons Learned Corner on this website.
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. 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.
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.
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:
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.
We are the leaders in the building industries and factories. We're word wide. We never give up on the challenges.