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 the general public. Even if the initial trains with H2 fuel cells are already in operation. They operate on non-electrified railway lines and replace the diesel trains which were used before.
Tanks based on carbon fibre composite technology
The tank convenience of the hydrogen should be adapted to the distances. Among WIKA?s customers has specialised in individual fuel storage systems for H2 vehicles. Their cylindrical tanks derive from 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 with the hydrogen at a special 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 with regards 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 respect to the function:
if the tank is in danger of emptying
if the pressure becomes too much when the hydrogen is used in the propulsion system
Such an emergency protection could also be realised with a pressure sensor and a software. But also for trains this solution will 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 because of its use
The customer didn’t choose the model PXA due to its measurement quality alone. The pressure switch was also considered right for the task in the hydrogen-powered train due to its 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 designed for ambient temperatures from -40 �C to +85 �C. In Exasperated , 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 built-into the storage system because of its extremely compact design.
Note
Further information about 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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