330D, 336D and 340D Excavators Hydraulic System – Accumulator (Pilot)

Illustration 1 g00681745

(5) Accumulator

(16) Line (pilot oil from pilot oil manifold)

(17) Mounting block

The accumulator stores pilot pressure oil for use at the main control valves. During some operations, the pilot system needs more oil because there is insufficient flow from the pilot pump. Accumulator (5) will provide pilot pressure oil to the pilot system when the pilot pump flow is inadequate. Insufficient supply of pilot oil flow to the pilot system may be caused by the following two reasons:

  • Implements are lowered while the engine is stopped and oil supply to the main control valves is stopped.

  • Combined operations

Illustration 2 g01230637


(5) Accumulator

(16) Line (pilot oil flow from pilot oil manifold to the mounting block for the accumulator)

(17) Mounting block

(18) Passage

(19) Inlet port

(20) Pressure oil chamber

(21) Vessel

(22) Bladder

(23) Gas chamber

(24) Passage

(25) Passage

(26) Passage

(27) Inlet port (pilot oil manifold)

(28) Passage

(29) Check valve

Pilot oil from the pilot filter enters inlet port (27) of the pilot oil manifold. Pilot oil flows through passage (28) and opens check valve (29). Pilot oil now flows through passages (24) and (26) to the pilot control valves (joysticks and travel levers/pedals).

The pilot oil also flows through passage (25) and line (16) to the mounting block for the accumulator. The pilot oil now flows through passage (18) and inlet port (19) into pressure oil chamber (20). The pilot oil acts against bladder (22) and the nitrogen gas in gas chamber (23) is compressed. Check valve (29) prevents a backflow of the stored oil in the accumulator. The stored oil is used for solely operating the stems of the main control valve.