FITTING GP 2734920 - Caterpillar

Schematic of Main Hydraulic System
Illustration 1 g02189955
(1) Swing motor (2) Travel motor (Left) (3) Travel motor (Right) (4) Swing boom cylinder (5) Stick cylinder (6) Bucket cylinder (7) Boom cylinder (8) Blade cylinder (9) Swivel (10) Main control valve (11) Pilot control valve (Boom and Bucket) (12) Pilot control valve (Swing and Stick) (13) Pilot control valve (Blade) (14) Pilot pump (15) Main pump (16) Oil cooler (17) Pilot manifold (18) Pilot Control Valve (Travel) (19) Pilot control valve (Swing boom) (20) Hydraulic tank (21) Oil filter Pump Flow and Pressure Control System
Illustration 2 g01210074
Pump compartment (14) Pilot pump (15) Main pumpThis machine is driven and controlled by the following systems:
The main hydraulic system provides oil to the boom cylinder, stick cylinder, bucket cylinder, blade cylinder, and swing boom cylinder. The main hydraulic system also provides oil to the travel motors and the swing motor.
The pilot hydraulic system provides oil to the control circuit.Main pump (15) is directly connected to the engine through a coupling. The main pump is constructed as a single body with one main outlet. The pump is a variable displacement piston pump. The pistons are arranged in a common cylinder block. The main pump supplies oil to the main control valve.When an operation is being performed, the main control valve directs pump oil to the respective cylinders (boom, stick, bucket, blade, and swing boom) and/or motors (swing and travel). The main control valve contains numerous valve stems, passages, check valves, relief valves, and orifices in order to carry out a single operation or a combined operation. The working pressure of the main hydraulic system is restricted by the main relief valve.ReferenceFor more information on the main control valve, see Systems Operation, "Main Control Valve".The output flow of the main pump is maximized at no load. As the load pressure increases during working conditions, the oil delivery pressure increases and the oil flow rate decreases. The hydraulic horsepower remains constant even though the delivery pressure and the flow rates change. The hydraulic horsepower is approximately identical to the engine horsepower.When there is no load on the machine, pump oil flows through the main control valve to the hydraulic tank. When a load is applied to the machine, pump oil is divided at the main control valve. The oil is sent to the travel motor, the swing motor, and the cylinders.ReferenceFor more information on the main pump, see Systems Operation, "Main Hydraulic Pump".The pilot pump (14) is a gear type pump that is connected to the rear of the main pump.