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 benefits of hydrogen in rail transport are rather unknown to the general public. Even if the first trains with H2 fuel cells already are in operation. They are powered by non-electrified railway lines and replace the diesel trains that were used before.
Tanks predicated on carbon fibre composite technology
The tank convenience of the hydrogen must be adapted to the distances. One of WIKA?s customers has specialised in individual fuel storage systems for H2 vehicles. Their cylindrical tanks are based on carbon fibre composite technology. They are therefore extremely robust yet have a relatively low weight in comparison to steel vessels.
Tanks of the type are also installed in the hydrogen-powered train mentioned in the beginning. This multiple-unit train, designed for commuting traffic, is filled up 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. This is done via 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 type of hydrogen-powered train with regard 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 client uses the pressure switch model PXA for the safety function. The miniature instrument switches off the H2 propulsion system in two cases, with respect to the function:
if the tank is in danger of emptying
if the pressure becomes too high when the hydrogen is transferred to the propulsion system
This emergency protection may be realised with a pressure sensor and a software. But also for trains this solution would be very complicated. Additionally it is rated with a higher risk of error than a switch-based safety function.
SIL-3 approval made the case for its use
The customer didn’t choose 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 its SIL-3 suitability. Grounded meets the safety-related market requirements for the H2 application (SIL-2).
Flameproof enclosure (?Ex d?) and compact design
The PXA has also been created for ambient temperatures from -40 �C to +85 �C. In addition, the pressure switch has IECEx approval ?Ex d? (flameproof enclosure), that your customer requires as standard. A further advantage of this instrument: The PXA could be easily integrated into the storage system because of its extremely compact design.
Note
Further information about hydrogen and on the pressure switch model PXA can be found on the WIKA website. In case you have any questions, your contact will gladly gelp you.
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