Clamp Closes Itself Immediately After Being Opened; Clamp Looses Grip On The Pile - Dawson EMV-300 Operator's Instructions/Spare Parts List

7.5 Oil blowing out of the gearbox breather valve & the gear box is full of oil
The drive motor case seal has been blown, typically because the drain line pressure
has been exceeded – see also section 7.4.
The unit will need to be removed from the job site and repaired in a suitably
equipped workshop. The oil in the box will be a mixture of hydraulic and gear oils.
Once in the workshop drain the oil from the gearbox and inspect the oil for signs of
debris. If only the seal has blown out without any damage to the motor casting then
it may be possible to repair the motor with an authorised Volvo (VOAC) distributor,
change the gear oil and rebuild the unit.
If however, the motor casting has also been damaged in the area of the seal housing
it will be necessary to completely inspect the inside of the gearbox. Remove the
gearbox lid and inspect the gear teeth and inspect all bearings. Check the gears for
any signs of damage. Remove all bearing covers from the gearbox sides and inspect
the outer races for signs of grooves or any other contamination or damage – look at
the rollers in each bearing. The bearings and all running faces should be in perfect
condition, if not they will need to be replaced. Consult with the manufacturer at this
stage or one of their approved distributors – it is strongly recommended that the unit
be repaired by the manufacturer in order to ensure correct procedures and materials
are used for an effective repair.

7.6 Clamp closes itself immediately after being opened

This fault can only occur on older units prior to serial number 45-083 without the
reverse flow check valve fitted to the return motor port. It occurs when the D reg
check valve on the flow regulator becomes jammed shut. When opening the clamp
the drive motor can then rotate slowly. Once the control lever is released the motor
effectively becomes a pump, driven by the inertia of the eccentric weights in the
gearbox. Consequently the clamp can be driven closed again. Should this problem
occur Dawson could supply a reverse flow check valve as a fix.

7.7 Clamp looses grip on the pile

Check the condition of the Hard Jaws – see section 6.1.f.
The clamp can also loose grip on the pile when clamped, with the vibrator not
vibrating, if the check valve on the rear of the clamp cylinder has faulty/leaking seals
or it the clamp cylinder piston seals are damaged/worn.
Alternatively there may be insufficient system operating pressure if the sequence
valve setting has been adjusted down in order to attempt running on an unsuitable
excavator. Check the system operating pressure and excavator specifications.