This is a complicated subject. Thermally activated pressure relief devices can be an important safeguard for hydrogen vessels if properly designed and installed in accordance with code requirement. Requirements vary globally and often depend on the type of vessel and its intended service (e.g. mobile or stationary). However, as with any device, TPRD’s offer both advantages and disadvantages.…

Requirements for TPRD/PRD’s depend on the local regulations. Some jurisdictions require them, some do not. Others make them optional based on results of performance testing.

In most cases, it is not necessary to depressurize hydrogen systems in an emergency. Pressure vessels are usually isolated in an emergency. The best actions to assure safety during an emergency should be identified during the hazard analysis.

There are several levels of documents which can be used to assist with the design, sizing, selection, and installation of the pressure relief device settings for LH2 tanks. 

Pressure vessel design codes, such as the ASME Boiler and Pressure Vessel Code will provide minimum requirements for design of pressure vessels (including LH2 tanks), relief devices, and relief systems. However…

Several organizations published a paper together on this topic in 2017 (see attached). Based on comparisons with tests and CFD simulations, the following conclusions were drawn:

1. The gas concentration for vapor cloud explosion blast load calculations for H2 jets can be limited to approximately 10% to 75%. Note that testing for H2-air VCEs in congested environments has been performed…

Safety codes globally have a requirement to provide a positive means to isolate energy sources and hazardous substances prior to performing maintenance. For gaseous hydrogen systems, methods such as a blind flange, a double block valve arrangement or a double block and bleed valve arrangement can provide that positive isolation.

Installing a blind flange requires breaking the supply line…

There are two parts for such a system to be effective. First, the system would have to activate quickly enough to establish a water mist throughout the region of interest (i.e., region occupied by a flammable gas mixture) before it could be ignited. This is challenging in terms of timing, and the impact of spraying water inside an enclosure filled with equipment not designed to get wet can be…

Explosion testing with hydrogen should be utilized only where there is not an established alternative and then only by personnel experienced in such testing. 
Testing with hydrogen is always a challenge and needs to be approached carefully due to significant differences in properties between hydrogen and propane. Hydrogen can develop significantly higher overpressures and preliminary…

The Panel has not received such inquiries. Section 14.2 of NFPA 69 Standard for Explosion Prevention Systems covers foam and mesh requirements. NFPA 69 states in 14.3.4 that the tests shall be conducted with a flammable gas/air mixture with a fundamental burning velocity representative of the burning velocities of flammable vapors expected in the intended applications.

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