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This is an impossible question to answer without greater understanding of the quantities of hydrogen involved, the types of vessels involved, and the atmospheric conditions. Several companies offer software to model such releases. It’s important to note that there is a high probability of ignition either during the vessel rupture or from nearby ignition sources.

Category: Properties
Keywords: Properties, Dispersion, Storage

Vaporization of a trapped volume of LH2 will lead to significant increase in pressure due to the very large expansion ratio as the liquid converts to gas. Relief devices are required since the pressure increase is likely to be far in excess of the pressure rating of the system. When vaporized as part of a flowing process, pressure will not increase. As the LH2 is warmed, it undergoes a phase…

Category: Properties
Keywords: Properties, Vaporization

A pressure of 600 kPa (87 psi) is relatively moderate, so the combustion properties are similar to those at atmospheric pressure where the autoignition temperature of hydrogen is 585°C. 

Category: Properties
Keywords: Properties, Auto-Ignition, Flammability

H2-air flammability limits vary with temperature  . The H2-air lower flammability limit is virtually the same as the H2-O2 lower limit. However, the H2-O2 upper flammability limit increases substantially to about 95% at room temperature and gets even higher at elevated temperatures.

Category: Properties
Keywords: Properties, Flammability, Oxygen, Pressure, Temperature

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.

Category: Properties
Keywords: Properties, Heat of Combustion

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…

Category: Explosions
Keywords: Explosion, Mitigation, Prevention Water Spray

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…

Category: Explosions
Keywords: Explosion, Testing, Burning Velocity

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.

Category: Explosions
Keywords: Explosion, NFPA 69, Foam, Mesh, Prevention

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

Category: Explosions
Keywords: Explosion, Prevention, Foam, Mesh

No, but it is always necessary to determine the possibility of an adverse chemical reaction with the particular material being used for the mesh.

Category: Explosions
Keywords: Explosion, Prevention, Foam, Mesh
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