Must a hydrogen safety valve be a micro-popping type safety valve?
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A few days ago, some experts came and told us that micro-opening type valves can only be used for liquids; are there specific regulations for hydrogen safety valves, requiring the use of fully-opening type valves?
When selecting a hydrogen safety valve, it is not necessarily required to use a micro-opening or full-opening type of safety valve; what is more important is to properly design and configure the selected safety valve. The main difference between full-opening and micro-opening safety valves lies in their opening and closing mechanism. In a fully open safety valve, once the pressure reaches the set value, its valve disc opens completely immediately, allowing the pressure in the system to be released rapidly. In contrast, the disc of a slightly lifting type safety valve has a smaller opening and closing stroke, so it cannot open fully immediately; its opening and closing processes are relatively smoother and more stable. For liquid systems prone to pressure surges, micro-popping safety valves are often more suitable. However, as a gaseous substance, hydrogen may experience pressure changes more rapidly; therefore, the use of a full-open safety valve allows for faster release of excess pressure, preventing damage to the equipment due to overpressure. Furthermore, hydrogen has a low density and strong diffusivity; if the pressure release process is too slow, it may cause hydrogen to accumulate within the equipment, increasing the risk of explosion. But this does not mean that micro-poppet safety valves cannot be used; as long as they are properly designed and configured to meet the operational and safety requirements of hydrogen systems, they can indeed be utilized. To determine which type of safety valve to use, it is also necessary to consider the actual operating conditions, such as the pressure rating of the equipment, the flow rate of hydrogen, and the design of the safety discharge system. When making these decisions, relevant industry standards and regulations should be followed. .
According to clause 7.2.5.1.2 of GB/T 29729-2022 \"Basic requirements for the safety of hydrogen systems\", full-opening safety valves shall be used.
It is mainly determined based on the actual operating conditions, the hydrogen pressure level, and whether it is a liquid or a gas; generally, fluid proportionally controlled relief valves are used for gases (those suitable for the current operating conditions), while low-temperature safety valves are used for low-temperature liquids.
The high compression ratio of gases means that micro-acting valves cannot meet the requirements for rapid discharge in cases of overpressure. This requirement is specified not only in safety valve standards but also clearly outlined in the **TS technical specifications.