CV4 mit Labom H2 Siegel
H2 vergoldete Membran im Anschnitt

ZIMMERLI: Labom Serie PASCAL CV4 Druckmessumformer mit vergoldeter Membrane für Wasserstoffanwendungen

We are pleased to present this product range of our long-standing partner Labom in more detail here.

HYDROGEN PERMEATION THROUGH STAINLESS STEEL

The hydrogen molecule decomposes into hydrogen atoms on the surface of metals.

These can diffuse through metals. The hydrogen migrates through the tetra- and octahedral gaps of the metal lattice. On the other side, the molecules reunite. The overall process is called permeation.
The permeation rate depends on temperature, pressure and material. 

RELEVANCE FOR PRESSURE MEASUREMENT TECHNOLOGY

Diaphragm seals have a thin metal membrane on the process side.
The pressure is transmitted to the sensor via the diaphragm and a filling liquid, usually oil. If hydrogen penetrates the membrane, it dissolves in the oil.
If the saturation is exceeded, the hydrogen beads out when the pressure is relieved and leads to measurement errors such as zero point shift.

SOLUTION

Depending on the process conditions, a diaphragm seal with a diaphragm, also internal (with the Ci4 series), made of hydrogen-resistant stainless steel or a gold-plated diaphragm can be used.

Our partner Labom has scientifically investigated the effect of permeation and has developed a tool to calculate hydrogen permeation and dissolution in the diaphragm seal oil.

For this, we need information from the plant operator on temperature, pressure and hydrogen content. This is used to calculate how long the service life of the unit would be for different configurations. Among other things, the temperature is decisive for this, as there is a strong temperature dependency - Labom has therefore also given special consideration to this aspect in the calculation formula according to Arrhenius' approach. The service life is calculated from the totality of these results.

We can play with that: Is a stainless steel membrane enough to get ten years of service life, for example?

Or do we need a gold coating and if so, what thickness of coating makes sense?

We and our partner Labom will be happy to assist you with our expertise in the field of hydrogen and look forward to hearing from you.

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