Dawson EMV 550, Owner'S Manual

Page: 28 / 63

EMV CLAMP CLOSES BUT THE UNIT WILL NOT VIBRATE
Check the base machine operating pressure and flow rate. If the pressure output of the excavator is too low
the EMV will not run at all. This is because the sequence valve pressure setting has to be overcome before
oil can pass to the drive motor.
Check the sequence valve setting by installing a pressure test gauge in the clamp close line and monitoring
the pressure at which the valve opens. Ensure this is set to 165 bar.
Damaged sequence valve – remove and inspect but replace if in doubt using new seals.
Motor failure or gearbox problem. Try connecting the two main oil supply lines directly to the hydraulic motor
ports and running the unit with low engine speed – effectively low oil flow rate. Caution - it will be easy to
over-speed the motor in this case because the flow regulator is now out of the circuit.
If the unit does not vibrate either the motor has become damaged or there is a fault with the gearbox.
Check the oil level in the gearbox to see that it has not become filled with hydraulic oil from the motor shaft
seal – in this case the unit usually runs very slowly unless metal fragments have become entrapped in the
transmission system as result. Consult the manufacturer.
Remove the motor from the gearbox and test.
As a last resort take the saddle assembly off the EMV and remove the gearbox lid for an internal inspection.
The gears, shafts and bearings should rotate freely.
Caution - pay attention to trapping body parts in the mechanism during inspection!
UNIT WILL NOT RUN AT THE CORRECT SPEED - “JUMPS AROUND” OR SPEED FLUCTUATES
Check that the base machine hydraulic output complies with the minimum specified for the unit. Specifically
check with the excavator supplier/manufacturer what system pressure is available on the bucket ram circuit
at 90 l/min.
Check the setting of the flow regulator to ensure adequate flow is reaching the drive motor.
Check the sequence valve pressure setting. If this setting is too close to the operating pressure the EMV will
speed up then slow down, speed up then slow down etc.
Check the gearbox oil level. If it is much higher than the sight glass the motor shaft seal has probably blown.
excavator mounted vibrator
28
continued - troubleshooting