Service braking
Under a service brake application is the process intended by the vehicle driver or an automatic traction and brake control (z. B. cruise control ) induced deceleration of a vehicle outside dangerous situations.
In the case of trams, the braking deceleration during service braking must not exceed 2.0 m / s 2 .
Railway air brake
On rail vehicles with compressed air brakes, a pressure of 5 bar is built up in the main air line (HLL) to release the brakes. By lowering this pressure by actuating the driver's brake valve , the brake can now be applied to different degrees. If the pressure in the main air line is reduced to 3.8 to 4.7 bar during the braking process, this is known as service braking. Depending on the design of the driver's brake valve, this pressure can be continuously variable or, for. B. in the brake valves of the types Knorr self-regulating , regulated to specified values.
Today, normal service braking takes place with a pressure reduction of up to 1 bar, whereby - thanks to the multi-release brake valves that are common today - the pressure in the HLL is increased again after the braking effect has started. In this way the delay of the train can be adjusted very well. Braking properly is particularly important for vehicles with disc brakes and plastic / composite brake blocks, as this is the only way the brakes can quickly reach operating temperature. This is particularly important when it is wet and snowy, as the water has to go in order to achieve an even braking effect.
The aim of service braking is the moderate deceleration of the vehicle in order to change its speed or to stop, and as such is usually initiated and withdrawn again by the driver. In rail vehicles with train control systems such as LZB or GNT , however, the on-board electronics can also trigger a service brake called forced service braking when the line's maximum speed is actually or expected to be exceeded, which, however, in contrast to the emergency braking, is automatically released again after the dangerous situation has been resolved.
Demarcation
If the pressure in the main air line is reduced to 3.5 bar during the braking process, this is referred to as full braking , in which the maximum possible deceleration is achieved. Because even with a further decrease in the main line pressure, there is no longer any increase in the brake cylinder pressure.
The emergency braking triggered by the driver in the event of a dangerous situation is characterized by a complete venting of the main air line to 0 bar and is not counted as service braking . The same applies to quick brakes initiated by the on- board electronics ( emergency braking ) or passengers ( emergency braking ).
Individual evidence
- ^ Association of German Transport Companies V. [VDV] (Hrsg.): Technical rules for the dimensioning and testing of the brakes of vehicles according to the regulation on the construction and operation of trams (BOStrab) - Technical rules for brakes - (TR Br) . December 19, 2008, 2.2.1 "Service braking", p. 9 ( vdv.de [PDF; 302 kB ]).
- ^ Association of German Transport Companies V. [VDV] (Hrsg.): Technical rules for the dimensioning and testing of the brakes of vehicles according to the regulation on the construction and operation of trams (BOStrab) - Technical rules for brakes - (TR Br) . December 19, 2008, 5 "Limits for braking", p. 27 , paragraph 3 ( vdv.de [PDF; 302 kB ]).
- ↑ The Swiss driving regulations speak of a service brake when lowering a maximum of 1 bar - once or in steps. ( Swiss Driving Service Regulations (FDV) A2016 Federal Office of Transport (FOT), July 1, 2016 (PDF; 3 MB). R 300.14, Section 2.4.1 Brakes )
- ↑ Minimum lowering of the first braking; for gray cast iron soles 0.4 to 0.5 bar, for passenger trains with disc brakes or plastic soles 0.5 to 0.8 bar, for freight trains with disc brakes or plastic soles 1 bar ( Swiss Driving Service Regulations (FDV) A2016 Federal Office of Transport (BAV), July 1, 2016 (PDF; 3 MB)) . R 300.14, Section 2.4.1 Brakes )