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| Illustration 1 | g03880029 |
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Compartment for the main control valve (return circuit) (typical example) (1) Main control valve (2) Line to the oil cooler inlet (3) Slow return check valve (4) Makeup line (makeup oil to swing motor) (5) Line from the oil cooler outlet (6) Hydraulic oil cooler (7) Hydraulic tank (8) Return line to the hydraulic tank (9) Bypass check valve | |
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| Illustration 2 | g03880064 |
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Slow return check valve and bypass check valve (2) Line to the oil cooler inlet (3) Slow return check valve (5) Line from the oil cooler outlet (6) Hydraulic oil cooler (8) Return line to the hydraulic tank (9) Bypass check valve (10) Check valve (11) Return port | |
Slow return check valve (3) is contained in check valve (10). Slow return check valve (3) is located between the main control valve and the hydraulic tank in the return circuit. The slow return check valve restricts the return oil flow. This restriction causes a pressure increase in return port (11) and makeup line (4).
If cavitation occurs in the swing motor, oil from return port (11) flows into makeup line (4). This makeup oil is supplied to the inlet port of the swing motor in order to prevent cavitation in the swing motor.
Note: For more information on the makeup operation, refer to System Operation, "Oil Makeup (Swing System)".
The return oil that flows through slow return check valve (3) is divided into two flow paths. A portion of the oil flows through inlet line (2) to hydraulic oil cooler (6). The cooled oil from the hydraulic oil cooler flows through outlet line (5) and through return line (8) to the return filter in the hydraulic tank. The remainder of the oil flows from slow return check valve (3) through bypass check valve (9), to the return filter in the hydraulic tank.