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| Illustration 1 | g00537511 |
(1) Main relief valve (2) Main control valve (3) Valve spool for lift cylinder (4) Check valve (5) Lift cylinder (6) Valve spool for tilt cylinder (7) Tilt cylinder (8) Pilot valve (oil manifold) (9) Pilot/brake pump (10) Implement pump (11) Fan drive pump (12) Steering pump (13) Hydraulic oil pump (A) Line to the hydraulic brake system (B) Steering pilot line (C) Line from transmission pump (D) Line for the steering system (E) Line for the fan drive system | |
Note: This hydraulic system is for the 825G Soil Compactor. The main hydraulic system for 826G Landfill Compactor is similar.
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| Illustration 2 | g00660452 |
(5) Lift cylinder. (7) Tilt Cylinder. (14) Stabilizer. | |
The 825G Soil Compactor has only one tilt cylinder on the right side of the machine as standard equipment. A stabilizer is provided on the left side of the machine.
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| Illustration 3 | g00660465 |
(5) Lift cylinder. | |
The 826G Landfill Compactor has only a lift cylinder as standard equipment.
Reference: For additional information about the hydraulic system for the 826G Landfill Compactor, refer to the hydraulic schematic in the Service Manual module System Operations, "General Infomation".
The main hydraulic system is made up of the following components: implement pump (10), main relief valve (1), main control valve (2), implement cylinders (4) and (7) and hydraulic oil tank (13) .
Implement Pump
Implement pump (13) supplies the high pressure oil that operates the implement cylinders. Oil flows from implement pump (10) to main relief valve (1). The oil will then flow to main control valve (2). The main control valve controls the direction of oil flow to each cylinder. Main control valve (2) will also control the amount of oil to each cylinder.
Main Relief Valve
Main relief valve (1) controls the pressure in the main hydraulic system. Main relief valve (1) opens when the oil pressure from the implement pump (10) to the implement cylinders rises above the relief pressure setting. The relief pressure setting is 24100 ± 172 kPa (3500 ± 25 psi) for the main hydraulic system.
Main Control Valve
Main control valve (2) is made up of two individual control valves that are stacked together. Main relief valve (1) is also considered to be part of the main control valve. Each individual control valve is used in order to control the flow of oil for a particular cylinder.
Lift valve spool (3) has four positions: RAISE position, HOLD position, LOWER position and FLOAT position.
In the RAISE position, high pressure oil flows to the head end of the lift cylinder. In the HOLD position, all of the oil flow returns to the hydraulic oil tank. In the LOWER position, high pressure oil flows to the rod end of the lift cylinder.
When the lift control lever in the cab is placed in the FLOAT position the lift valve spool moves to the FLOAT position. A float valve in the pilot valve (oil manifold) (12) opens in order to allow the blade to rest on the ground.
Tilt valve spool (6) has three positions: TILT LEFT position, HOLD position and TILT RIGHT position. When tilt valve spool (6) moves to the TILT LEFT position, high pressure oil will flow through tilt valve spool (6) and into the head end of the tilt cylinder. Oil from the rod end of the tilt cylinder flows through the tilt valve spool, and then back to the hydraulic oil tank.
In the HOLD position, all of the oil flow returns to the hydraulic oil tank. When the tilt valve spool moves to the TILT RIGHT position, high pressure oil flows through the tilt valve spool. The oil flows to the rod end of the tilt cylinder. Oil from the head end of the tilt cylinder flows through the tilt valve spool, and then back to the hydraulic oil tank.