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| Illustration 1 | g02921617 |
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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 (10), secondary steering diverter valve (17), primary steering flow switch (18) and secondary steering flow switch (33).
The high-pressure circuit provides the high-pressure oil for steering cylinders (1) and (2).
With the engine running, oil is drawn from hydraulic tank (37) by steering pump (39). Steering pump (39) supplies oil to steering control valve (9). Oil supplied to steering control valve (9) flows through spool (11).
When pilot oil moves spool (11), the oil from steering pump (39) is directed to steering cylinder (1) and steering cylinder (2). When turning right, the oil flows to the rod end of steering cylinder (2) and to the head end of steering cylinder (1). When turning left, the oil flows to the head end of steering cylinder (2) and the rod end of steering cylinder (1).
When a turn is made, oil is displaced from steering cylinders (1) and (2). Oil returns through spool (11) and steering control valve (9) to hydraulic oil cooler (20). The return oil flows through hydraulic oil cooler (20) and hydraulic filters (36) to hydraulic tank (37).
Hydraulic oil cooler (20) has a bypass orifice. Cold oil or a blocked oil cooler causes the oil to flow through the bypass orifice and return to hydraulic tank (37).
Steering cylinder crossover relief valves (6) and (7) prevent excessive pressure in steering cylinders (1) and (2). The pressure could develop if one of the tires hits an object.