Hydraulics
9803/3280 Issue 1
Component Location
Component Key:
T Hydraulic Tank
P1 Hydraulic Pump (main section)
P2 Hydraulic Pump (secondary section)
1B Hose - High Pressure Carry Over
3 Loader Valve Block
4 Excavator Valve
5 Auxiliary Valve
6 Return Line Filter (inside hydraulic tank)
7 Steer Circuit Priority Valve
13 Return Line Check Valve
26 Hydraulic Oil Cooler
62 Hydraclamp exhaust hose
Neutral Circuit Description
Fixed Flow - Double Pump
Oil is drawn from the hydraulic tank T by the
hydraulic pump. The pump has two sections, P1
and P2.
The hydraulic pump is mounted on the rear of the
gearbox and is driven by the engine via a
driveshaft.
Oil from the larger section P1 flows direct to the
loader valve 3. Oil from pump section P2, flows to
steering priority valve 7, and in neutral circuit flows
through the priority valve to the auxiliary valve 5
and then to join the flow from P1 at the loader
valve.
From the loader valve neutral gallery, oil flows via a
high pressure carry-over line 1B to the excavator
valve 4.
Some of the exhaust oil flows directly back to the
tank through an in-tank filter 6, and some of the
exhaust oil returns to tank via the hydraulic oil
cooler 26.
To help prevent excavator dipper ram and loader lift
ram cavitation, there is a check valve 13 fitted to
the return line. The check valve raises
approximately 5 bar (75 lbf/in
2
) of pressure in the
line, which improves the operation of the respective
anti-cavitation valves.
On sideshift machines only, hydraclamp exhaust
hose 62 is fitted. The hose connects the
hydraclamp spool directly into the exhaust circuit.
This prevents the clamps from ‘locking-up’ when
the sideshifting operation is required.
3 - 4 3 - 4
Basic System Operation
Section E Section E
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