I am communicating with a company that is exploring this technology for an application involving a mixture of flammable gases, including hydrogen.

In the case of fuel-rich mixtures like those in the question, the heat of combustion for the mixture should be calculated on the basis of the oxygen content of the mixture. The heat of combustion per mole oxygen is twice the heat of combustion per mole hydrogen, i.e., it is 286*2 kJ per mole O2. You should be able to do the calculations based on this reply.

The HSP is not familiar with this particular fitting or its potential application in H2 service but can offer engineering judgment. Many similar compression-type swaged fittings are used in H2 service. These fittings must be used within the manufacturer recommendations for pressure, temperature, and fluid service. Deformation is also introduced into stainless steel tubing in other ways, such…

The Panel considers two approaches to be acceptable. 

1. Stainless steel (corrosion resistant) lines embedded in concrete. This keeps the piping out of direct contact with the earth and provides a degree of physical protection from activities such as digging.
2. Lines enclosed within a PVC sleeve. The PVC sleeve would usually be directly buried but could also be embedded in…

It’s not clear if “mobile” in the question refers to vehicle fuel tanks, or vessels used for transportation of hazardous materials. 

1. If it’s a Type 4 vessel for transportation of hazardous materials, it will be built to a special permit that details the inspection requirements. Special permits vary but they are generally consistent on a 5-year requalification period, which also…

FCEVs usually contain only a minimal amount of hydrogen fuel pressure (several Mpa) to support getting the car on and off car carriers. Panel members are not aware of any hydrogen release incidents during vehicle loading and don’t know what the probability of such a leak is considering the loading operations. A risk assessment accounting for the probability of collisions as well as leaks from…

Generally speaking, the International Fire Code and NFPA 2 apply to non-transportation use of hydrogen. These are maturing quickly, with NFPA 2 currently having issued its most recent edition in 2023. Standards for both on-board LH2 tanks and LH2 tankers for bulk fuel transport are managed by the U.S. Department of Transportation (DOT) and are well established. DOT transport requirements for…

Hydrogen gas storage and fuel cell systems are typically closed systems with a variety of monitoring and control functions to prevent leaks. Please check with the bus manufacturer and authority having jurisdiction to verify this is acceptable per their direction. However, a good safety practice would be to minimize the time spent indoors for these activities. Hydrogen vehicles maintained in a…

Assuming this question relates to the roof of the enclosure, there are no design criteria on this topic to the Panel’s knowledge. The key to the design would be ensure that the exhaust ventilation inlet is located at the highest point and that there are no pockets that can capture hydrogen (restrict flow to the exhaust inlet).

Information on Toyota’s repair garage approach is available…

A best practice, even for small hydrogen vents, is to vent to a dedicated vent system outside the building where possible. Several international codes and standards can be used to provide guidance; the Panel recommends discussing the configuration with a local fire official to ensure their required standards are followed. In the U.S. NFPA 2, Hydrogen Technologies Code, has information in…