Bomag BW 156 D-3, Service Manual

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Service Training
BW 156/177 D-3/PD-3 - D 16 -
BW 178/179 D-3/PD-3
Flushing valve
Fig. 11 Cross-section of flushing valve
1 Flushing spool
2 Flushing pressure relief valve
The flushing valves are integrated in the axle drive motor, or on DH/PDH machines, also in the drum
drive motor. In case of a pressure increase in one of the two sides of the closed circuit the flushing
valves have the function to flush a certain quantity of oil out of the low pressure side.
The valve is operated by the pressure difference between the two sides of the closed circuit (A and B).
If the pressure in one side is higher than in the other, this pressure will move the valve out of neutral
position against the neutral setting spring. Oil can now flow out of the low pressure side. This oil flows
through a thermostat valve back to the tank. The flushed out oil quantity is immediately replaced by oil
entering from the charge circuit through the corresponding boost check valve (part of the multi-function
valve).
In this way the closed travel circuit is permanently supplied with cool and filtered oil and the temperature
household of the hydraulic system is maintained at a permissible level.
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