Gaseous hydrogen can be stored forever as long as the system integrity is maintained. However, liquid hydrogen is “use it or lose it” and will boil from system heat leak and build pressure unless it is used or vented. This is not usually an issue for continuous use or low-pressure applications which can use hydrogen gas pressure directly from the tank.  

For intermittent or high…

An annual inspection of safety devices is recommended. Testing requirements will be based on the type of device and a quantified risk analysis. Typical replacement or function testing of relief valves is between 5 and 10 years depending on the application within the industrial gas industry. Rupture discs are not tested but are frequently replaced on an interval based on manufacturer…

Based on the question, it’s not clear if the reference to stress corrosion cracking (SCC) has been proven or is only suspected. It can be difficult to identify the nature of the cracks (SCC vs H2 embrittlement without analysis and microscopy). In addition, the question does not mention that the cylinders contain hydrogen gas, but it’s assumed since it was submitted to the Panel. 

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It depends on the service. Variables include disk design, corrosion resistance, number of cycles, and how to close the operating pressure is to the rupture disc set pressure. One approach is to ask the manufacturer for their recommendation. Typical practice for U.S. Department of Transportation vessels and discs is to replace them at the tube requalification (i.e., every 5 to 10 years in the U…

The answer could be no devices at all, just a TPRD, just a PRD, or both. It depends on the potential overpressure scenarios identified during a hazard assessment. TPRDs typically are not used on ASME pressure vessels since they are not ASME compliant devices and since  system siting provides protection from engulfing fires. However, TPRDs are frequently used in portable applications for…

In most cases, it is not necessary to depressurize hydrogen systems in an emergency. Pressure vessels are usually isolated in an emergency. The best actions to assure safety during an emergency should be identified during the hazard analysis.

In the U.S., liquid hydrogen fueling stations and dispensing equipment are addressed within NFPA 2, Chapter 11. Dispensing is covered within Section 11.3. When liquefied hydrogen is used as the supply for high pressure gaseous fueling, then Chapter 10 of NFPA 2 would apply.
ISO standards are also being developed for global LH2 fueling protocols.
 

If liquid hydrogen usage is sufficiently high at the fueling station, there may be no need to vent any boiloff generated from the LH2 storage tank. Boil-off gas should be minimized through system design, but where needed, the boil-off hydrogen along with any other hydrogen released must be vented through a local vent stack which is constructed to safely vent the hydrogen in accordance with CGA…