Pressure switch in hydrogen-powered train ensures safety

In a newly developed hydrogen train for local transport, a pressure switch from WIKA plays an essential role. Within the scope of pressure monitoring, it performs the central safety function in the H2 supply system during the journey.
Some great benefits of hydrogen in rail transport are rather unknown to everyone. Even if the initial trains with H2 fuel cells already are in operation. They are powered by non-electrified railway lines and replace the diesel trains which were used before.
Tanks 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 yet have a comparatively low weight in comparison to steel vessels.
Tanks of the type are also installed in the hydrogen-powered train mentioned at the beginning. Scary -unit train, created for commuting traffic, is filled with the hydrogen at a particular terminal. The tank pressure is 300 to 350 bar. While driving, it must be reduced to a single-digit value for the supply to the fuel cell. That 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 the 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, with regards to the function:
if the tank is at risk of emptying
if the pressure becomes too high once the hydrogen is used in the propulsion system
This emergency protection may be realised with a pressure sensor and a software. But for trains this solution will be very complicated. Additionally it is rated with an increased risk of error when compared to a switch-based safety function.
SIL-3 approval made the case for its use
The customer did not decide on the model PXA due to the 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 in addition has been created for ambient temperatures from -40 �C to +85 �C. Furthermore, the pressure switch has IECEx approval ?Ex d? (flameproof enclosure), which the customer requires as standard. An additional benefit of this instrument: The PXA could be easily integrated 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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