V
1
p
1
V
0
p
0
V
2
p
2
Hydraulics
Bosch Rexroth AG
RE 50170/12.10 HAB
5
/18
The largest hydraulic pressure is not to exceed four times the
filling pressure as otherwise, the bladder elasticity is greatly
strained and excessive compression changes with consider-
able gas heating result:
The accumulator bladder service life is the longer the smaller
the difference between
p
1
and
p
2
. This, however, results in
the reduction in the corresponding degree of utilization of the
maximum storage capacity.
Application, mode of operation
Applications
Hydro-pneumatic accumulators offer versatile applications:
– Energy storage for saving pump drive power in systems
with intermittent operation.
– Energy reserve for emergencies, e.g. in case of hydraulic
pump failure.
– Compensation of leakage losses.
– Shock and vibration absorption in periodic vibrations.
– Volume compensation in case of pressure and tempera-
ture changes.
Mode of operation
Liquids are almost incompressible and are therefore not able
to store pressure energy. In hydro-pneumatic Rexroth accu-
mulators, the compressibility of a gas is used for the fluid stor-
age. You may
only
use nitrogen of cleanliness class 4.0!
N
2
= 99.99 vol. %
Charge
Pressures
In the accumulator calculation, the following pressures are of
vital importance:
p
0
= Gas filling pressure at room temperature
and drained fluid chamber
p
0
(
t
)
= Gas filling pressure at operating temperature
p
0
(
t
max
) = Gas filling pressure at max. operating temperature
p
1
= Minimum operating pressure
p
2
= Maximum operating pressure
In order to achieve the best utilization of the accumulator vol-
ume possible as well as long service life, compliance with the
following values is recommended:
p
0
(
t
max
) 0.9
p
1
(1)
p
2
4 •
p
0
(2)
Calculation
Charge
Discharge
Discharge
