41
TROUBLESHOOTING
TROUBLESHOOTING CHART FOR SLOW CYLINDER SPEED
Slow cylinder speed.
Operating pressure
okay. 3,625 psi (250
bar) minimum.
Carrier flow setting is
low.
Check flow output of
attachment hydraulic
circuit at 1000 psi
(69 bar).
Adjust control valve
flow adjustment of
carrier
Repair or replace the
carrier's pump
Check attachment
cylinder packing.
Replace if required.
Slow cylinder speed.
Operating pressure
not okay. Less than
3,625psi (250 bar)
Carrier relief set too
low. Set below 3,800
psi (262 bar).
Measure the
excavator circuit
relief valve pressure
with the shut-off
valve closed.
Adjust or replace the
carrier's circuit relief
valve.
Attachment
counterbalance
valve cartridge.
Check the
counterbalance
valve cartridge for
tightness
Tighten the
counterbalance
valve cartridge.
Check the o-rings
and backup rings of
the counterbalance
valve cartridge.
Replace the o-rings
and backup rings of
the counterbalance
valve cartridge.
NOTE: If additional assistance is required, call the NPK Service Department at 1-800-
225-4379.
JAW DRIFT
1. Some drift may be experienced depending on the Demo Grab’s position.
2. Acceptable drift may occur over a number of minutes.
3. Rapid drift may indicate a problem with the Demo Grab’s cylinder, rotary joint
assembly or the carrier’s hydraulic circuit.
TO DETERMINE IF THE JAW DRIFT IS OCCURING FROM A
BAD CYLINDER OR THE CARRIER
1. Remove the hoses from the joint fittings on the outside of the Demo Grab’s frame
and close the shut-off valves on the carrier.
2. Cap the joint fittings (#12 JIC).
If the jaw drifts, the problem is coming from the Demo Grab’s cylinder or rotary joint
assembly. If no drift occurs, the problem is in the carrier’s main control valve. Drift
due to the carrier’s main control valve internal leakage, may be inherent to the
carrier and may not be solvable.
To Next Page
Loading...