Optimierte Bremsnach steller im Betriebseinsatz.

Hamburger Hochbahn AG maintains and overhauls round about 800 metro cars in their own workshops with a high production depth. Especially the refurbishment of the bogies takes a high effort, the interval bases on the wheel profile wear and happens normally every 1.4 million km. There all bogie components are checked and if necessary overhauled, the only exception is the slack adjuster of the pneumatic brake actuator which has to be replaced already at 700.000 km. Reason for the early exchange of the slack adjuster is the operating mode of the modern metros. These trains use regenerative braking during normal service and the pneumatic brake is only used as a holding brake during standstill. Therefore the brake pads and the brake disc show nearly no wear and the automatic slack adjuster is hardly used. But this uncommon service leads to problems in the slack adjuster, because the mechanical parts are working on the same place for a very long time and then the mating areas of the friction coupling don't wear, but they are polished. This polished surface leads to low coefficients of friction and then the brake force would not be transferred in a reliable way, if the parts were not replaced before. The article shows how Hochbahn together with Knorr-Bremse SfS, the supplier of the pneumatic brake system, started a successful project with the target to increase the lifetime of the slack adjuster to minimum 1.4 million km (resp. 2 million load cycles). [ABSTRACT FROM AUTHOR]