Hydrogen and pressure sensors ? What must be observed?

When pressure sensors touch hydrogen, this often results in difficulties. Unfortunately, I frequently notice in my own job that our customers have no idea of this ahead of use. For this reason they often do not even reveal that their medium contains hydrogen. We only find out when we receive a complaint. But why do we get yourself a complaint? How come especially hydrogen so critical to pressure sensors?
A simple rule is that a large number of metals become brittle when exposed to hydrogen. Hydrogen atoms that diffuse into the metal grid change the strength of the material. In the worst case, this results in cracks in the material. Or even to put it simply, the pressure sensor starts leaking or is totally destroyed. Regarding pressure sensors, specifically thin membranes required for measuring pressure play a decisive role. Atomic hydrogen can not only penetrate the metal, but additionally pass through it by diffusion.
This has several effects: When piezoresistive measuring principles are employed, it becomes critical if hydrogen reacts with the internal transmission medium or accumulates there. This initially only falsifies the measurement results, but can later on also lead to complete destruction of the sensor in individual cases. The addition of hydrogen also changes the instrumentation characteristics of the resistance structures of the measurement bridge of thin-film sensors. Despite being reversible, this technique results in a detuning of the bridge at least temporarily, resulting in a falsification of the measurement signal.
However, the effects described above occur in various materials differently. This means that the effects of hydrogen can be lowered substantially by selecting suitable materials.
Note
Insidious on our pressure sensors and on the subject of hydrogen can be found on the WIKA website. If you use hydrogen because the medium, your contact will gladly recommend an optimum solution for your application.

Leave a Comment