Schematic of Main Hydraulic System
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| Illustration 1 | g02447006 |
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Shown with optional auxiliary hydraulic circuit (1) Swing motor (2) Stick cylinder (3) Travel motor (Left) (4) Blade cylinder (5) Burst valve (Blade) (6) Swivel (7) Changeover valve (8) Variable gauge cylinder (Track) (9) Travel motor (Right) (10) Swing boom cylinder (11) Bucket cylinder (12) Boom cylinder (13) Main control valve (14) Outer gear pump relief valve (15) Inner gear pump relief valve (16) Tandem gear pumps (17) Engine (18) Oil filter (19) Hydraulic tank | |
Pump Flow and Pressure Control System
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| Illustration 2 | g02449136 |
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(16) Tandem gear pumps
(17) Engine | |
This machine is driven and controlled by the following systems:
- The main hydraulic system provides oil to the boom cylinder, stick cylinder, bucket cylinder, blade cylinder, track cylinder, and swing boom cylinder. The main hydraulic system also provides oil to the travel motors and the swing motor.
Tandem gear pumps (16) are directly connected to the engine through a coupling.
The pumps are a fixed displacement gear pump. The pumps supply oil to main control valve (13).
When an operation is being performed, the main control valve directs pump oil to the respective cylinders (boom, stick, bucket, blade, track, and swing boom). When an operation is being performed, the main control valve also directs pump oil to the motors (swing and travel). The main control valve contains numerous valve stems, passages, check valves, relief valves, and orifices in order to carry out a single operation or a combined operation. The working pressure of the main hydraulic system is restricted by relief valve (14) and relief valve (15).
Reference: For more information on the main control valve, see Systems Operation, "Main Control Valve".
The output flow of the main pump is maximized at no load. As the load pressure increases during working conditions, the oil delivery pressure increases and the oil flow rate decreases. The hydraulic horsepower remains constant even though the delivery pressure and the flow rates change. The hydraulic horsepower is approximately identical to the engine horsepower.
When there is no load on the machine, pump oil flows through the main control valve to the hydraulic tank. When a load is applied to the machine, pump oil is divided at the main control valve. The oil is sent to the travel motor, the swing motor, and the cylinders.
Reference: For more information on the main pump, see Systems Operation, "Main Hydraulic Pump".