Hydrogen Meets Gold

Martijn Smit
01. November 2022

Hydrogen is not only a trending topic but also a booming market. The Hydrogen Technology Expo in Bremen ist just one of many hydrogen trade fairs currently being organized. A team of experts from KELLER was also there.

«The exhibition was very well attended. Among other things, the visitors took the opportunity to find out about KELLER’s special pressure sensors for hydrogen applications. We exhibited our gold-plated OEM pressure sensors, ATEX-certified pressure transmitters and our normal pressure and level transmitters», Martijn Smit elaborates. 

 

What is actually special about the pressure sensors for hydrogen applications?

KELLER manufactures isolated piezoresistive pressure sensors, for type of pressure measurements invented by our company founder Hannes W. Keller. The great advantage of the piezoresistive measuring principle is its high stability. The chip that measures the pressure is installed in an oil-filled cylinder and sealed by a steel diaphragm. This ensures the best possible isolation. 

The piezoresistive pressure sensor is also considered one of the most stable for hydrogen applications. Without additional actions, however, an oil-filled sensor can also have a disadvantage. Under certain circumstances, hydrogen molecules can split into two hydrogen atoms at higher temperatures. These atoms are smaller than the pores of the steel membrane. This allows the atoms to penetrate through the membrane into the oil chamber of the pressure sensor. In the oil chamber, they fuse again to form a hydrogen gas molecule (H2), which leads to offset errors due to the expansion. Offset is called the signal deviation of the target value. After all it must be considered that medium is gas. The phenomenon described is called "permeation". 

For this reason, KELLER uses gold-plated steel membranes for hydrogen pressure sensors. Gold has much smaller pores than stainless steel. The hydrogen can hardly penetrate the gold layer. This defusing action, together with fully welded sensors without internal seals, confirms KELLER's competence and strength in the pressure sensor market, also for hydrogen applications. The typical pressure ranges for applications with hydrogen are from 0...2 bar to 0...1000 bar. KELLER offers exactly the right sensors for these applications. In addition, the hydrogen pressure sensors are compatible with the EC79 standard for automotive applications. 

A tour of the trade fair showed KELLER’s leading position. Attendees easily found KELLER instruments throughout the exhibition, including an impressive display by Pressure Control Solutions wherein KELLER’s gold diaphragm design was employed in their specially-made Series 39X digital differential pressure transmitter. PCS uses this instrument to control processes at less than 30 mbar. See KELLER and OCS in action at: https://www.youtube.com/shorts/7_zvUBvjzKc 

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