Bomag BW 156 D-3, Service Manual

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Service Training
BW 156/177 D-3/PD-3 - E 9 -
BW 178/179 D-3/PD-3
The output torque raises with increasing pressure difference between low and high pressure side in the
closed circuit.
Changing the flow direction of the oil will also change the sense of rotation of the vibration motor.
When switching the vibration on the motor must first start to move the resting vibration shaft. This
resistance causes a hydraulic starting pressure, which is limited to 365 bar by the corresponding high
pressure relief valve. Once the vibrator shaft has reached its final speed, the pressure will drop to a
value between 100 and 150 bar (operating pressure). The value of the operating pressure mainly
depends on the condition of the ground (degree of compaction, material etc.).
• Hard ground = High operating pressure
• Loose ground = Low operating pressure
Fig. 8 Circuit diagram of vibration motor
1 Vibration motor
2 Flushing valve
3 Flushing pressure relief valve