PLATE AS 2887878 - Caterpillar

Illustration 1 g00679536
Pilot Hydraulic System (1) Pendulum arm control valve (2) Pilot accumulator (3) Pilot oil filter (4) Implement control valve (5) Hydraulic oil tank (AA) Pilot pressure oil (BB) Pilot return oilWhen the engine is running, pump pressure oil flows to implement control valve (4). A pilot valve in the implement control valve reduces the pump pressure oil to approximately 3500 kPa (500 psi). Because the standby pressure of the implement pump is above 3500 kPa (500 psi), pilot pressure oil is always present when the engine is running.Note: The pilot pressure setting is not adjustable.The pilot oil flows through pilot oil filter (3) before flowing to the proportional solenoids. A bypass valve in the pilot oil filter opens if the filter becomes plugged with debris.The pilot oil then flows to pendulum arm control valve (1) and implement control valve (4). The proportional solenoids in the control valves control the flow of pilot oil to the valve spools. As the operator moves a joystick control a corresponding solenoid moves. As the joystick control is moved, the proportional solenoid valve will move a proportional amount. More oil will flow to the end of the valve spool. The valve spool will move a proportional amount.Accumulator (2) maintains pressure in the pilot hydraulic system when the engine is stopped. The accumulator allows an operator to lower the harvester head or the pendulum arms with the engine stopped. However, current must flow to the solenoids in order to activate the solenoids.