BOOT-PLUG 5000494 - Caterpillar

Illustration 1 g03880029
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
Illustration 2 g03880064
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 The return oil that flows through the slow return check valve is divided into two flow paths. A portion of the oil flows through inlet line (2) to hydraulic oil cooler (6). The oil flow from the hydraulic oil cooler flows to outlet line (5) and through return line (8) to the return filter in the hydraulic tank. The remainder of the return oil flows through bypass check valve (9).When the temperature of the return oil in inlet line (2) is very low, the viscosity of the oil is high. The flow resistance of the return oil in inlet line (2) is high. Thus, the pressure of the return oil is high.As a result of the high pressure of the return oil, bypass check valve (9) opens. Most of the return oil flows through bypass check valve (9) and return line (8) to the return filter in the hydraulic tank. The remainder of the oil flows through inlet line (2) to hydraulic oil cooler (6). Since a small amount of the return oil flows to the oil cooler, the temperature of the oil increases. As the oil temperature increases, the return oil pressure decreases. Bypass check valve (9) begins to close. A greater portion of the return oil flows to hydraulic oil cooler (6). Bypass check valve (9) maintains the hydraulic oil at the optimum operating temperature.