AP-655C and BG-2255C Asphalt Pavers Drag Conveyor and Auger Conveyor Systems Caterpillar

Location and Function

Illustration 1	g00936127
(1) Charge pump

Charge pump (1) is located on the upper pump stack.

The upper and lower piston pumps for the drag conveyors share the same charge pump.

The charge pump performs the following functions:

• Replaces oil lost through lubrication of the internal components

• Replaces oil lost through internal leakage.

• Replaces oil that is sent to the hydraulic oil cooler.

• Provides charge oil for the upper and lower pump stacks

Note: Correct charge pressure must be maintained under all conditions of operation in order to maintain the performance of the pump controls.

Operation and Oil Flow

Illustration 2	g00936140
(1) Charge pump (2) Line to upper pump stack (3) Line from hydraulic tank (4) Charge filter (5) Line to cooler bypass manifold (6) Line to lower pump stack (AA) Charge pressure (AB) Sump (AC) Activated components

Charge pump (1) draws oil from the hydraulic oil tank. Oil is drawn through a suction screen that is in the tank. The charge pressure oil is sent to charge filter (4). Charge pressure oil will then go to the upper pump stack and the lower pump stack. If the filter is plugged, the internal relief valve in the charge filter will direct oil to the oil cooler bypass manifold. The charge pump is a gear pump that produces a flow of 23 cc (1.4 in³) for each revolution of the pump.