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| Illustration 1 | g02175057 |
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Compartment for the main control valve (return circuit) (1) Main control valve (2) Inlet line to oil cooler (3) Slow return check valve (4) Makeup line (makeup oil to swing motor) | |
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| Illustration 2 | g02175077 |
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Slow return check valve and bypass check valve (2) Inlet line to oil cooler (3) Slow return check valve (5) Return port (return flow to return filter) (6) Return port (7) Check valve (8) Return line to bypass check valve (9) Bypass check valve (10) Hydraulic oil cooler | |
Slow return check valve (3) is contained in check valve (7). Slow return check valve (3) is located between the main control valves 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 (6) and makeup line (4).
If cavitation occurs in the swing motor, oil from return port (6) 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 flow through slow return check valve (3) is divided into two flow paths. A portion of the oil flows through inlet line (2) to the hydraulic oil cooler. The cooled oil from the hydraulic oil cooler flows through return line (8) and the return filter to the hydraulic tank. The remainder of the oil flow from slow return check valve (3) flows through bypass check valve (9) and the return filter to the hydraulic tank.