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…

Exhaust systems (sometimes referred to as ventilation systems) are used to exhaust hydrogen and air mixtures. Normally these are used to vent streams with less than flammable range hydrogen in air.

That is, hydrogen detectors trigger venting or the ventilation systems runs during all hydrogen operations. In these instances, low concentrations of hydrogen are expected, but deflagration is…

The deflagration pressure is dependent upon many variables.

However, some general concepts are:

1. Deflagration pressure is proportional to operating pressure
2. Deflagration pressure is inversely related to initial temperature
3. Deflagration pressure is based on concentration and H2/O2 ratio
4. In general, an internal deflagration is unlikely to exceed about a 10…

Liquid hydrogen will almost never accumulate in a vent system since vent systems are typically designed without insulation. The extremely cold liquid hydrogen temperature of -420 F.

Additionally, vent stacks on an LH2 tank are connected to the vapor phase of the tank. Only in a few rare instances will LH2 be entrained in the gas stream.

Accumulators are recommended at the bottom of…

1. Understand any reactions the hydrogen can add to what is being vented. For instance, O2/H2 vented in the same stack would not be a good idea.
2. Understand all the flow and operating parameters of the streams to ensure no back flow into the hydrogen system or vice versa.
3. Ensure the venting/flaring system can handle the hydrogen flow parameters.

Delayed ignition is a significant hazard for hydrogen releases, either intended or unintended. The primary concern is the overpressure and energy release created from a vapor cloud which could contain a significant quantity of hydrogen. The H2Tools Incidents database contains a number of examples of delayed ignition. 

When it is necessary or desirable to work on a part of a hydrogen system while another part of the system remains in operation or in standby condition. An example is a system with two compressors, where one is normally operating and the other acts as an installed spare. The two block valves are closed, and the bleed (vent) valve is open. This arrangement assures that any hydrogen leaking…

Applicable EU Directives frequently include the following:

·        Low Voltage - 2014/35/EU

·        Machinery - 2006/42/EC

·        Electromagnetic Compatibility - 2014/30/EU, EMC

·        Pressure Equipment - 2014/67/EU

·        Restriction of Hazardous…

There is currently a published ASME BPV Code Case describing pressure design requirements for pressure design of electrolyzers. If the Code Case is adopted by the jurisdiction where a new electrolyzer will be installed, the new electrolyzer will have to meet the requirements in the Code Case. The responsible ASME committee is working to revise the Code Case and intends to incorporate the Code…

The primary safety standards for applicable to this piping in the U.S. are ASME B31.3, B31.12, and NFPA 2. The editions used should be those adopted by the local jurisdiction. Design of an LH2 piping system should always be conducted and reviewed by engineers experienced in cryogenic piping design. The equipment should also be installed per NFPA 2 and NFPA 55. IT is recommended that the piping…