Komatsu 930E-2 Shop Manual page 451

HOIST CIRCUIT OPERATION
The following information describes the basic hoist
system circuit as shown in Figure 7-1. Detailed com-
ponent operation is outlined under the individual com-
ponent descriptions.
Hydraulic fluid is supplied by a tank (1) located on the
left frame rail. The tank's service capacity is approxi-
mately 250 gal. (947 l). Hydraulic oil is routed to a
tandem gear type pump (2). A second pump, coupled
to the rear of the hoist pump, supplies oil for the
steering and brake systems. The pumps are driven by
an accessory drive at the end of the traction alternator.
Hoist pump output is directed to a pair of high pressure
filters (3), mounted to the inboard side of the fuel tank.
1. Hydraulic Tank
2. Hoist Pump
3. High Pressure Filter
4. Hoist Pilot Valve
5. Hoist Limit Solenoid
L07023
HOIST CIRCUIT
FIGURE 7-1. HOIST CIRCUIT SCHEMATIC
6. Pilot Operated Check Valve
7. Hoist Valve
8. Brake Cooling Oil Supply (Front)
9. Brake Cooling Oil Supply (Rear)
10. Hoist Cylinder
Hoist Circuit
Hydraulic oil from the hoist filters is directed to the hoist
valve (7), mounted above the pumps.
The hoist valve directs oil to the body hoist cylinders
(10) for raising and lowering of the dump body. Hoist
valve functions are controlled by the operator through
the lever connected to the hoist pilot valve (4) located
in the hydraulic components cabinet. A hoist limit
solenoid (5) located in the bleeddown manifold shifts
the hoist valve out of POWER UP before the hoist
cylinders extend to their maximum physical limit.
When the hoist valve is in the HOLD or FLOAT posi-
tion, hoist circuit oil flows to the front (8) and rear (9)
service brakes, cooling the wet disc brakes during
truck operation.
Hydraulic hoses deteriorate with
age and use. Prevent possible mal-
functions by inspecting all hoses
periodically. Replace any hose
showing wear, damage or deterio-
ration.
11. Quick Disconnect
12. Overcenter Manifold
13. Check Valve
14. Counterbalance Valve
15. Bleeddown Manifold
L7-1