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.

Relief device sizing for liquid hydrogen tanks follow recognized standards such as CGA S1.3. The sizing criteria include a worst-case scenario of an engulfing fire with loss of vacuum integrity.

LH2 tanks are unlikely to BLEVE due to the vacuum insulation outer jacket (usually carbon or stainless steel) preventing direct impingement of fire onto the main pressure vessel, as well as the internal cryogenic contents maintaining the inner pressure vessel walls at a cooler temperature until the contents have been relieved by the relief devices.

While not required by Code, nearly all LH2 tank designs follow a best practice of having at least one non-reclosing relief device to better empty the tank of its contents during a fire.

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, these codes will not provide the sizing criteria nor anticipate all of the potential demand cases that might be imparted upon a vessel. 

In the US, the model fire codes require compliance with NFPA 2, which then references documents such as CGA S1.2 and CGA S1.3 for sizing criteria. These documents have been customized by the industrial gas business specifically for cryogenic fluids such as LH2. API Standard 520 “Sizing, Selection and Installation of Pressure-Relieving Devices in Refineries” of is also a helpful document to provide additional guidance. 

For LH2 storage tanks, usually the highest process demand is an engulfing fire with a loss of vacuum insulation to atmosphere. This failure mode can result in additional heat flux from air condensation in the annular space which must also be addressed. 

It is not required to proactively vent the contents of an LH2 tank when exposed to fire. Relief devices are required to prevent the accumulation of internal pressure to unsafe levels. Within the ASME BPV, this is 121% of Maximum Allowable Working Pressure for scenarios involving fire exposure. It is common practice, but not required, that at least one device be non-reclosing (e.g. a rupture disc) for both managing the high flow required as well as to relieve the contents of the tank. Reclosing relief devices will maintain pressure in a fire and are more likely to lead to a vessel rupture if the fire ultimately weakens the pressure vessel.

LH2 tanks are unlikely to BLEVE due to the vacuum insulation outer jacket (usually carbon or stainless steel) preventing direct impingement of fire onto the main pressure vessel, as well as the internal cryogenic contents maintaining the main pressure vessel walls at a cooler temperature until the contents have been relieved by the relief devices. 

These distances are based primarily on hydrogen piping releases and resultant vapor clouds and jet flames based on pipe diameter and pressure. It’s important to note that many facilities have issues such as confinement and congestion, so it may be applicable to apply contemporary engineering models to assess risk.