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Innotrans 2022

Air-free brake system with CAN

At the Innotrans 2022, Siemens Mobility showed its air-free brake system developed jointly with Liebherr. The device uses a 24-V power supply and a CAN interface to control the brake actuator.

First application in the Vienna metro trains: Braking by wire with the brake subsystem developed jointly by Siemens and Liebherr avoids piping, compressor, and valves (Source: Siemens Mobility)

Westinghouse invented the air-brake 153 years ago. This year, Siemens announced that the Mocomp air-free brake for rail vehicles is ready for serial production. This innovation was developed jointly by Siemens Mobility and Liebherr. An electro-hydraulic brake actuator provides the brake force for the brake system. Unlike the conventional pneumatic brake, with the air-free brake the control of the brake is electrical. This means all piping and all pneumatic components for controlling the brake can be eliminated.

The Mocomp air-free brake actuator is controlled via a CAN interface (Source: Siemens Mobility)

The brake actuator is integrated in the bogie in the same installation space and has the same mechanical interfaces as the conventional pneumatic brake caliper. This brake actuator meets the safety requirements up to SIL 4 (Safety Integrity Levels). It is derived from the technology that Liebherr developed for aerospace flight control actuation applications. Jens Lichterfeld from Siemens Mobility explained: “Using the air-free brake results in a number of benefits on car-level, including reduced weight and reduced effort for installation and commissioning of the brake system. In addition, installation space that was previously required for the air brake components can now be used for other subsystems. That’s extremely useful when it comes to vehicle development". In operation, efforts can be reduced in several areas like maintenance, train’s start-up time and shortening of headways.”

Siemens Mobility has applied the air-free brake technology for the first time on the X-Wagen metro project in Vienna (Austria). Robert Steinfelder said: “Wiener Linien will then be the first transit authority in the world to benefit from our brake system, both in conventional operation with a driver and later in automated operation on the new U5 Line.” The air-free brake is controlled via its CAN interface. The necessary hardware and software are integrated in the actuator.


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Siemens Mobility