WIRE A. 4K6520 - Caterpillar

The main control valve is located in the hydraulic system between the main pumps and actuators (cylinders and motors). Depending on the machine operation, the oil flow from right pump (37), left pump (36) and pilot pump (38) to the hydraulic circuits are controlled by the operation of each component in the main control valve. By this control, the speed and direction of the cylinders and the motors can be controlled and adjusted. The pump delivery pressure can be controlled and adjusted.The main control valve includes right body (40) and left body (41). The main control valve is coupled together with bolts in order to make one assembly.
Right travel control valve (6), grapple control valve (7), control valve (8), boom I control valve (10) and stick II control valve (11) are located in right body (40). Hydraulic oil from the right pump is delivered through inlet port (34), center bypass passage (9) and return port (1) to hydraulic tank (39). In addition, the following components are located in right body (40) .
Line relief valve (29) (head end of the grapple cylinder) and line relief valve (30) (grapple cylinder rod end) limit the pressure in the grapple circuit due to external forces.
When the joysticks and/or travel levers/pedals are in the NEUTRAL position, or when the joysticks and/or travel levers/pedals are partially moved from the NEUTRAL position, negative flow control relief valve (15) and negative flow control orifice (16) decrease the pump flow.
Line relief valve (28) (boom cylinder rod end) is located on the right body.
Boom regeneration valve (27) supplies return oil from the head end of the boom cylinders to the rod end of the boom cylinders when the boom is lowered.
Load check valves (26) are part of the following control valves: grapple control valve (7), control valve (8), boom I control valve (10) and stick II control valve (11) .
Straight travel control valve (12), left travel control valve (24), swing control valve (23), stick I control valve (19) and boom II control valve (17) are located in left body (41). Hydraulic oil from the left pump is delivered through inlet port (33), center bypass passage (22) and return port (1) to hydraulic tank (39). In addition, the following components are located in left body (41) .
Line relief valve (20) (stick cylinder rod end) is located on the left body.
When the joysticks and/or travel levers/pedals are in the NEUTRAL position, or when the joysticks and/or travel levers/pedals are partially moved from the NEUTRAL position, negative flow control relief valve (13) and negative flow control orifice (14) decrease the pump flow.
Stick regeneration valve (2) supplies return oil from the head end of the stick cylinder to the rod end of the stick cylinder during the STICK IN function.
Stick unloading valve (18) reduces the back pressure in the head end of the stick cylinder during the stick in function.
Load check valves (3) are part of the following control valves: swing control valve (23) and stick I control valve (19) .
Main relief