GEAR-RING 8P6222 - Caterpillar

Illustration 1 g02921617
Hydraulic schematic for the steering system
(1) Steering cylinder
(2) Steering cylinder
(3) Implement and steering solenoid valve
(4) Portable hydraulic pump quick connect coupler
(5) Brake accumulator charging valve
(6) Steering cylinder crossover relief valve
(7) Steering cylinder crossover relief valve
(8) Parking brake solenoid valve
(9) Steering control valve
(10) Secondary steering pump
(11) Spool
(12) Line to braking system
(13) Line to parking brakes
(14) Portable hydraulic pump quick connect coupler
(15) Check valve
(16) Steering system pressure tap
(17) Secondary steering diverter valve
(18) Primary steering flow switch
(19) Steering neutralizer valve
(20) Oil cooler
(21) Check valve
(22) STIC steering pilot valve
(23) Line from implement lift circuit
(24) Pilot oil filter
(25) Steering neutralizer valve
(26) Selector and pressure control valve
(27) Dual pilot check valve
(28, 29) Check valve
(30) Pilot system pressure tap
(31) Pilot relief valve
(32) Breaker relief valve
(33) Secondary steering flow switch
(34) Hydraulic oil temperature sensor
(35) Hydraulic oil level sensor
(36) Hydraulic filters
(37) Hydraulic tank
(38) Pilot and braking pump
(39) Steering pump Note: Illustration 1 shows a machine with the secondary steering system.Note: Machines without the secondary steering system will not have secondary steering pump (9), secondary steering diverter valve (17), primary steering flow switch (18) and secondary steering flow switch (33).The steering pilot circuit controls the movement of spool (11) in steering control valve (9).With the engine running, oil is drawn from hydraulic tank (37) by pilot and braking pump (38). Pilot and braking pump (38) supplies pilot oil through check valve (15) to brake accumulator charging valve (5). Pilot oil from the brake accumulator charging valve flows through pilot oil filter (24) to pilot relief valve (31).Pilot relief valve (31) maintains the pilot system at a constant pressure. Pilot relief valve (31) relieves excess pilot system pressure through a line to hydraulic tank (37).Pilot oil flows through check valve (29) to selector and pressure control valve (26). Selector and pressure control valve (26) will not allow alternate oil to flow into the pilot oil system.When pilot oil is not available, alternate oil from the lift cylinders will flow into the pilot system through selector and pressure control valve (26). When oil is not available from the lift cylinders, oil from steering control valve (9) will flow into the pilot system through selector and pressure control valve (26).Oil from the pilot system flows to implement and steering solenoid valve (3). Implement and steering solenoid valve (3) when de-energized prevents pilot oil flowing to STIC steering pilot valve (22) and the implement pilot circuit.When implement and steering solenoid valve (3) is energized, pilot oil flows to STIC steering pilot valve (22). When a turn is made using the STIC steering control lever, STIC steering pilot valve (22) routes pilot oil through dual pilot check valve (27). Pilot oil flows to steering neutralizer valve (19) for a right turn, or steering neutralizer valve (25) for a left turn. Pilot oil flows from the steering neutralizer valve to spool (11) in steering control valve (9). The pilot oil pressure causes spool (11) to move. When spool (11) moves, high-pressure oil from steering pump (39) flows to steering cylinders (1) and (2).Pilot