561N Pipelayer Hydraulic System Caterpillar

The hydraulic oil tank is located at the rear of the machine to the right of the fuel tank. The tank is sealed in order to prevent contamination. A screen is located in filler tube (2) in order to catch loose debris. Main oil filter assembly (1) is a part of the hydraulic tank assembly.

Illustration 1	g00784928
(1) Main Oil Filter Assembly (2) Filler Tube (3) Return port for the distribution manifold for the cooling oil (4) Suction Port (5) Manifold for the return lines (6) Filter Element (7) Screen (8) Bypass Valve Spring (9) Bypass Valve (10) Inlet Passage

Oil from the manifold for return lines enters the tank through return port (5). The oil flows through passage (10) to the inside of filter element (6). The filter stops any debris that is in the oil.

If the filter element becomes full of debris, the restriction causes a pressure increase outside the filter element. The pressure increase causes bypass valve (9) to move against spring (8). This allows the oil to pass through screen (7) and flow directly to the tank. Screen (7) removes the larger particles of debris.

Correct maintenance must be used in order to ensure that filter element (6) does not become full of debris.