It varies slightly due to different density of LH2 at different temperatures, but a gallon of LH2 at atmospheric pressure (0 psig) is ~113 SCF of H2. The expansion ratio is about 840:1. In metric units, a liter of LH2 at atmospheric pressure (0 MPa) would expand to about 840 liters of STP of gaseous pressure.

The National Fire Protection Association (NFPA), the Compressed Gas Association (CGA), and the Society of Fire Protection Engineers (SFPE)   represent the U.S. fire protection and engineering community, and these organizations publish handbooks and standards/guidelines that describe the properties of hydrogen. There are many other organizations and documents that provide similar…

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.

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…

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. 

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.

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.

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.