308C CR Excavator Hydraulic System – Accumulator (Pilot)

Illustration 1 g00868533

Pilot oil manifold (partial view)

(1) Gas chamber

(2) Accumulator

(3) Bladder

(4) Bowl

(5) Oil chamber

(6) Pilot oil manifold

(7) Inlet manifold

(8) Passage

(9) Port

(10) Check valve

(11) Passage

Illustration 2 g00868527

Pilot manifold

(2) Accumulator

(9) Port

Pilot oil flows through the pilot filter and through port (9) of pilot oil manifold (6). The pilot oil opens check valve (10) and flows through passage (8) to the hydraulic activation control valve. Pilot oil then flows to the pilot control valves.

Accumulator (2) provides oil to the pilot line as makeup oil. During combined operations, the pilot system needs more oil because there is not enough flow from the pilot pump. When implements are lowered with the engine stopped, makeup oil supply is provided by the accumulator.

The accumulator stores hydraulic pressure oil by taking advantage of the compressibility of nitrogen gas in gas chamber (1) .

The pilot pump oil in port (9) opens check valve (10) and oil flows into oil chamber (5) through inlet port (7). The pilot oil pressure acts against bladder (3) and the nitrogen gas in chamber (1) is compressed.

Check valve (10) is located in the passage that is connected to inlet port (9). The check valve prevents oil from flowing back to port (9). Oil from accumulator (2) flows through passage (11). This oil is used to shift the main control valve stems.