General Description - Doosan DX140R Shop Manual

GENERAL DESCRIPTION

The accumulator is a gas-charged storage device designed to
hold a reserve quantity of hydraulic fluid under pressure.
Accumulators are used in hydraulic circuits in much the same
way that condensers (or capacitors) are used to collect, store
and maintain electrical charge in a circuit.
In a hydraulic circuit, minor variations or lags in pump output that
might otherwise cause unsteady or irregular operation are made
up from the supply of pressurized oil in the accumulator.
Reference
Number
1
2
3
4
Accumulators are solidly constructed to resist the high operating
pressures of the fluids they contain. There are only three main
moving parts: a plug at the top allows precharging or expelling
gas from the compressible, precharged upper chamber; a valve
assembly at the bottom of the accumulator for passing hydraulic
fluid in and out, and an elastic diaphragm to separate the two
chambers. The flexible diaphragm changes shape to conform to
the changing pressures and volumes of the two fluids in the
upper and lower chambers.
There are six possible positions the diaphragm can be in and
they are as follows:
1. With no gas charge in the upper chamber 0 bar (0 psi,
empty) and no oil in the bottom 0 bar (0 psi, dry) the elastic
diaphragm hangs loosely.
2. When the prepressure charge of gas (usually nitrogen) is
introduced through the port at the top of the accumulator,
the diaphragm expands to maximum size. The valve button
in the center of the diaphragm pushes into the fluid
opening in the bottom chamber, sealing off the lower valve.
If the pressure of the gas charge exceeds system oil
pressure, no fluid enters the accumulator. The button also
keeps the diaphragm from protruding into the lower valve
opening.
NOTE: Precharge pressure is referred to as the "P1"
pressure. The accumulator manufacturer's "P1"
rated pressure should be stamped or marked on
the accumulator's rating plate. Annual checks of
actual precharge pressure should be made by
tapping a hydraulic pressure gauge (and 3-way
adapter coupling) into the valve on the bottom
of the accumulator.
Accumulator
Page 6
Description
Screw Plug
Steel Pressure Vessel
Diaphragm
Fluid Valve
1
2
3
4
Figure 1
Pressure Fluid
2
1
4 5
Figure 2
ARS1790L
Nitrogen
3
6
ARS1800L
SP000028