Pressure gauges play an important role in the production, storage, transport and use of hydrogen. In almost all applications, they monitor the pressure at measuring locations that require on-site indications without the need for external energy, or serve as a backup for electronic systems. As an alternative energy source in combatting climate change, hydrogen – H2 – has promising potential, but poses some challenges for measurement technology. Christopher Ott BEng – Product Management, WIKA Alexander Wiegand SE & Co. KG, here looks at what this means for the use of pressure gauges.
Hydrogen is the smallest molecule. It therefore quickly penetrates many materials (permeation) or causes embrittlement. For this reason, stainless steel pressure gauges with wetted parts made of 316L are most suitable for hydrogen applications, especially in the high-pressure range. For example, the WIKA models 23x.30 and 23x.50 serve well. This is because selected austenitic steels, such as 316L, are resistant to embrittlement by H2.
Permeation in pressure gauges
Permeation by hydrogen plays only a minor role in pressure gauges, in contrast to electronic pressure measuring instruments or diaphragm seals where the hydrogen that diffuses into the instruments can falsify the measuring result. Such effects can be ruled out with pressure gauges as a result of the measuring principle. Nevertheless, in the event of permeation over a long period of time, hydrogen can escape through the measuring element into the case of the pressure gauge. Due to the case design (plastic components, among other things), a concentration equalisation then takes place during normal operation. It is therefore always recommended to use the pressure gauge in a ventilated environment.
In most applications, H2 occurs in gaseous form and is usually exposed to pressures of between 60 bar (initial bottling) and 1 000 bar (filling stations). The EN 837-2 user standard for the selection and installation of pressure gauges recommends pressure gauges in safety version, at least level S2, for gases and pressures > 25 bar. With stainless steel pressure gauges, however, the safety versions S1 (like the WIKA model 23x.50) and S3 (WIKA model 23x.30) are the market standard.
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