Sandbox (locomotive)
A sand spreader is a device used in rail vehicles which, with the aid of compressed air (about 8 bar) or blown through sand downpipes under the wheels or is scattered in front of the wheels on the rails by gravity sand from a storage container ( sandbox ) in order to increase the friction between wheel and rail. This is particularly important when ( as a result of wetness ) reduced friction ratio and strong train or braking forces makes sense to improve the traction or braking effect and to prevent slippage of the wheels ( skidding or sliding). The sand supply is such that it must be complemented usually only look up to look up.
For the operation of the sand sprinkler, it is very important that the brake sand is kept dry. With steam locomotives, the sandbox was therefore regularly on the vertex of the long boiler in a separate Sanddom where the sand was kept warm and dry through the boiler temperature. In modern vehicles, mostly an electric heating coil is installed in the sand reservoir that keeps the sand dry.
When braking sand sand comes with high strength due to a high proportion of quartz used. The sand should have a particle size of 0.8-1.6 mm according to TL 918 2243-5 or 0.71 to 1.6 mm according to BN 918 224 (see coarse sand ) and his lehmfrei. The sand supply is within the scope of the thesis to check on the vehicle and, if necessary replenish.
Operation of the sand-box
The operation of the sand-box is done from the cab of train vehicle. With steam locomotives operating on compressed air, mechanical linkage or cable was; the sand was then solely by the force of gravity on the sand tubes before both wheels of the axle to the rail. In modern locomotives the sands performed at a keystroke or automatically by the plain or anti-skid. For this, a solenoid valve is actuated, the compressed air from the main air reservoir line ( HBL) passes into a nozzle of the Sandungsvorrichtung and thereby causes the sand is blown through a tube or pipe under the wheels.
Is on slippery rails and expected soon that the wheels slide that appeal to skid devices or excessive slip occurs, the Sandungsvorrichtung must be operated in accordance with DB directive. But may on bridges, switches, hubs, sliding platforms, rail scales and in a range of stations of rail vehicles except in exigent circumstances, not be sanded, since the function more flexible and sensitive components could be affected by sands. For excessive sands should generally be avoided, since the crushed quartz sand can cause a poor contact between wheel and rail, and thus in electrical rail vehicles the flow of current ( drive current return and track-release ).
Hazards
Scattered at low speed braking sand can cause an insulating effect between wheel and rail in single -propelled traction vehicles. Through resulting faulty track circuits on electrical track circuits there have been repeated clashes. The Federal Railway Authority instructed the railway company to avoid at disc-braked locomotives the sands at speeds of 25 km / h (or less).
In his report of 20 August 2013, the German magazine Report Mainz near-accidents reported by the fact that the use of braking sand the electrical contact between wheel and rail disturbed and thus put it out of train control systems. For this reason, for example, the Swiss Federal Railways does not use sand for braking of locomotives.
On 1 August 2013 came in the Mainz main station to a near- collision of two S -Bahn trains. On September 24, 2013, the Federal Railway Authority said that the cause was too much braking sand on the tracks.
Similarly, it may, at the output of too much sand come to an upgrade (similar to sand rails ). This can especially lead to the track points to problems in which the sand can not slip sideways (eg crossings).
Not least of sand increases the friction between rail and wheel flange, which acts against the wheel flange lubrication; the reduced flange lubrication increases the risk of Aufkletterns.
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Due to the problems caused by sand, other methods such as are in the industry the free brushing the rails discussed.