Pressure switch in hydrogen-powered train ensures safety

In a newly developed hydrogen train for local transport, a pressure switch from WIKA plays a crucial role. Within the scope of pressure monitoring, it performs the central safety function in the H2 supply system during the journey.
The advantages of hydrogen in rail transport are rather unknown to everyone. Even if the initial trains with H2 fuel cells are already in operation. They are powered by non-electrified railway lines and replace the diesel trains that were used before.
Cataclysmic predicated on carbon fibre composite technology
The tank capacity for the hydrogen must be adapted to the distances. Among WIKA?s customers has specialised in individual fuel storage systems for H2 vehicles. Their cylindrical tanks are based on carbon fibre composite technology. They’re therefore extremely robust and yet have a comparatively low weight compared to steel vessels.
Tanks of the type are also installed in the hydrogen-powered train mentioned at the beginning. This multiple-unit train, designed for commuting traffic, is filled with the hydrogen at a particular terminal. The tank pressure is 300 to 350 bar. While driving, it should be reduced to a single-digit value for the supply to the fuel cell. Focused is done with a pressure regulation unit downstream of the storage system.
Pressure switch in hydrogen-powered train switches the drive system off
Suitable for used in a new kind of hydrogen-powered train when it comes to safety ? the model PXA pressure switch from WIKA.
The pressure switch model PXA meets certain requirements of the hydrogen-powered train application. With the monitoring the of tank pressure and pressure regulation in the hydrogen-powered train, the customer uses the pressure switch model PXA for the safety function. The miniature instrument switches off the H2 propulsion system in two cases, depending on function:
if the tank is in danger of emptying
if the pressure becomes too high when the hydrogen is transferred to the propulsion system
Such an emergency protection may be realised with a pressure sensor and a software. But also for trains this solution would be very complicated. It is also rated with a higher risk of error when compared to a switch-based safety function.
SIL-3 approval made the case for its use
The customer didn’t decide on the model PXA because of its measurement quality alone. The pressure switch was also considered right for the duty in the hydrogen-powered train due to the SIL-3 suitability. It thus easily meets the safety-related market requirements for the H2 application (SIL-2).
Flameproof enclosure (?Ex d?) and compact design
The PXA has also been designed for ambient temperatures from -40 �C to +85 �C. Furthermore, the pressure switch has IECEx approval ?Ex d? (flameproof enclosure), that your customer requires as standard. An additional advantage of this instrument: The PXA could be easily built-into the storage system because of its extremely compact design.
Note
Further information on the subject of hydrogen and on the pressure switch model PXA are available on the WIKA website. In case you have any questions, your contact will gladly gelp you.
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