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The water vapor cloud formed from venting cold hydrogen gas from a liquid hydrogen tank will vary in size depending upon atmospheric conditions including ambient temperature and humidity. There is not a direct relationship between the water vapor cloud and the flammable cloud of hydrogen, but it’s often used as a proxy.
Initially upon release, it is possible that H2 vapor from…
Liquid hydrogen is much less likely to pool than liquified natural gas (LNG) due to its low heat of vaporization. Very large facilities are often equipped with methods to enhance vaporization, such as crushed stone under tanks, as well as diversion systems to allow liquid hydrogen to spill and boil off in a safe area. Care needs to be taken that diversion systems do not create a hazardous…
By definition, liquid hydrogen can BLEVE, but this is highly unlikely. Liquid hydrogen is stored in a double wall tank with vacuum insulation. This protects the primary pressure vessel from direct impingement and the very cold liquid provides self-cooling of the vessel walls. Tanks are also equipped with redundant pressure relief systems that are sized for fire exposure.
Underground storage tanks can be either installed in a vault or directly buried. Both offer additional
protection from external impact and fire, but each has unique challenges. Vaults must be properly
ventilated and designed to not create an explosion or asphyxiation risk. Direct burial vessels should not
have any underground leak points and must be protected from corrosion. Both…
This can be a complex problem and response to insulation failure should be considered in the emergency response guidelines and procedures.
First, a tank with an insulation failure may boil off at an elevated rate which applicable codes build into the relief device and vent system design.
Second, ice and oxygen enriched liquefied air can form where inadequately insulated surfaces…
This is not an easy question since many factors influence how much hydrogen can be transferred from one vessel at a higher pressure to another one at a lower pressure and the rate at which it can be transferred. The pressure in the higher vessel will fall while that in the lower vessel will rise as gas is transferred, so the flow rate will typically slow down and eventually stop as the…
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…
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