Dawson EMV-70 METRIC, Operator'S Instructions/Spare Parts List

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7.2 EMV clamp closes but the unit will not vibrate
7.2.1 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.
7.2.2 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.
7.2.3 Damaged sequence valve – remove and inspect but replace if in doubt using
new seals.
7.2.4 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
.
7.2.5 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 a result.
7.2.6 Remove the motor from the gearbox and test.
7.2.7 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!
7.2.8 Consult the manufacturer from section 7.2.5 onwards.
7.3 Unit will not run at the correct speed – “jumps around” or speed fluctuates.
7.3.1 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.
7.3.2 Check the setting of the flow regulator to ensure adequate flow is reaching
the drive motor.
7.3.3 Check the sequence valve pressure setting – see section 7.2.2. If this setting
is too close to the operating pressure the EMV will speed up then slow
down, speed up then slow down etc.
7.3.4 Check the gearbox oil level. If it is much higher than the sight glass the
motor shaft seal has probably blown – see section 7.4.
Sequence Valve
Cartridge with
Adjusting Screw
& Locknut Flow Regulator
Cartridge with
Adjusting Screw
& Locknut