FILM-INSTRUCTION 3209835 - Caterpillar

Illustration 1 g01146938
(1) Tilt pilot control valve (2) Lift pilot control valve (3) Float valve (4) Right main control valve (5) Spool for lowering (6) Left main control valve (7) Screen (8) Relief valve (9) Spool for tilting (10) Case drain filter (11) Left implement pump (12) Makeup valve (13) Tandem implement pump (14) Right implement pump (15) Makeup and vent valve (16) Spool for lifting (17) Line relief and makeup valve (18) Hydraulic tankThe main hydraulic system has two fixed displacement pumps (11) and (14), and one tandem pump (13) . The pumps pull hydraulic oil from hydraulic tank (18). There is a case drain filter (10) for each pump. Oil from the case drain filters flows back to the hydraulic tank.From the implement pumps, the oil flows through screens (7). The oil then travels to main relief and check valves (8). The main relief valves maintain an oil pressure of 32800 400 kPa (4750 58 psi). The check valve prevents oil from flowing back to the pumps when the pressure in the system is higher than the pump outlet pressure.The oil then flows to the main control valves (4) and (6). The main control valve controls the flow of the oil to the lift cylinders and to the tilt cylinders. The oil then flows to tank (18) when the lift and tilt spools are in the neutral position.The lift circuit will be explained. The tilt circuit functions similarly.Hydraulic System in Hold
When the pilot control valves are in HOLD, pilot oil to the main control valves is blocked and the oil in the main control valve housings is drained to hydraulic tank (18). The spools in the main control valves are centered. Oil from the four pumps will flow through the opened centered control valves and the oil will flow back to the tank. Oil that is in the lift cylinders and in the tilt cylinders is blocked.Hydraulic System in LIFT Position
When the lift pilot control valve is moved to the RAISE position and the raise prevention solenoid is turned off, the pilot oil is sent to the main control valve. The passage to the head end of the