2. RETURN CIRCUIT 3.0 220F3CI01 All oil from each actuator returns to the hydraulic tank through the control valve. The bypass check valves are provided in the return circuit. The setting pressure of bypass check valves are 1.5 kgf/cm 2 (21 psi ) and 3.0 kgf/cm 2 (43 psi ). Usually, oil returns to the hydraulic tank from the left side of control valve through oil cooler. When oil temperature is low, viscosity becomes higher and flow resistance increases when passing through the oil cooler. The oil pressure exceeds 3.0 kgf/cm 2 (43 psi ), the oil returns directly to the hydraulic tank, resulting in the oil temperature being raised quickly at an appropriate level.
When the oil cooler is clogged, the oil returns directly to the hydraulic tank through bypass check valve (1). The full-flow filter and bypass relief valve are provided in the hydraulic tank. The oil from right and left side of control valve is combined and filtered by the return filter. A bypass relief valve is provided in the full-flow filter. When the filter element is clogged, the bypass relief valve opens at 1.5 kgf/cm 2 (21 psi ) differential pressure. 3-4