CHANNEL 1W9127 - Caterpillar

Illustration 1 g01387640
Location of hoist control valve (1) Outlet to the hydraulic tank (2) Inlet for pump oil (3) Low pressure relief valve (4) High pressure relief valve (5) Hoist proportioning solenoid for SNUB, FLOAT and LOWER (6) Hoist proportioning solenoid for RAISE (7) Outlet to the brake cooling system (8) Brake oil cooler relief valve
Illustration 2 g01334377
Hoist hydraulic system schematic (1) Outlet to the hydraulic tank (2) Inlet for pump oil (3) Low pressure relief valve (4) High pressure relief valve (5) Hoist proportioning solenoid for SNUB, FLOAT and LOWER (6) Hoist proportioning solenoid for RAISE (7) Outlet to the brake cooling system (8) Brake oil cooler relief valve (9) Hydraulic tank (10) Brake and pilot pump section (11) Brake cooling and hoist pump section (12) Pilot oil pressure reducing valve (13) Hoist, brake, and pilot gear pump (14) Check valve (15) Pilot oil filter (16) Line to the steering pilot circuit and parking brake circuit (17) Pilot oil line to the hoist control valve (18) Hoist control valve (19) Stem (20) Dump spool (21) Directional spool (22) Actuators (23) Centering springs (24) Outlet to the rod end of the hoist cylinders (25) Outlet to the head end of the hoist cylinders (26) Hoist cylindersOil flows from brake and pilot pump section (10) of the gear pump through check valve (14) to pilot oil pressure reducing valve (12). Pilot oil pressure reducing valve (12) maintains a constant pilot oil pressure to the parking brake, and to the steering and hydraulic pilot circuits. From the pilot oil pressure reducing valve, the oil flows through pilot oil filter (15). This oil flow is then split.Some of the oil is sent to the steering pilot circuit and to the parking brake circuit through line (16). The rest of the oil goes to hoist control valve (18) through line (17). This oil is used as pilot oil for hoist proportioning solenoid (5) and hoist proportioning solenoid (6). Pilot oil is always present at both ends of directional spool (21) .The hoist proportioning solenoids are used to drain the pilot oil from the ends of directional spool (21), which then allows the spool to move.Oil flows from brake cooling and hoist pump section (11) of the gear pump through line (2) to hoist control valve (18). The hoist control valve will send pump oil to one of two locations. When the dump body is being raised or lowered, the hoist cylinders receive the oil. If the hoist is not being used, the oil flows to the oil cooling system for the brakes.Brake oil cooler relief valve (8) limits the pressure in line (7) to the brake oil cooler. Brake oil cooler relief valve (8) will vent oil to hydraulic tank (9), when the pressure in line (7) is too high.Low pressure relief valve (3) limits the pressure