Bladder Accumulators
Low Pressure

Fluids are practically incompressible and
cannot therefore store pressure energy.
The compressibility of a gas is utilised in
hydraulic accumulators for storing fluids.
HYDAC bladder accumulators are based
on this principle, using nitrogen as the
compressible medium.
A bladder accumulator consists of a
fluid section and a gas section with the
bladder acting as the gas-proof screen.
The fluid around the bladder is connected
to the hydraulic circuit so that the
bladder accumulator draws in fluid when
the pressure increases and the gas is
compressed. When the pressure drops,
the compressed gas expands and forces
the stored fluid into the circuit.
HYDAC bladder accumulators can be used
in a wide variety of applications, some of
which are listed below:
zzenergy storage
zzemergency operation
zzforce equilibrium
zzleakage compensation
zzvolume compensation
zzshock absorption
zzvehicle suspension
zzpulsation damping
See catalogue section:
zzHydraulic Dampers
No. 3.701

1.2.tDesign

HYDAC low pressure bladder accumulators
consist of a welded pressure vessel, a
flexible bladder with gas valve and a
hydraulic connection with check valve or a
perforated disc.
The table shows the different models
which are described in greater detail in the
pages that follow:
Designation
SB402.5 ... 50
SB4070 ... 220
SB35HB- 20 ... 50
SB16A- 100 ... 450
SB35A- 100 ... 450
SB16AH- 100 ... 450
SB35AH- 100 ... 450
1)t
2)t

Perm.
pressure
[bar] 2)
40
35
16
35
16
35

Volume

Q 1)

[l]
[l/s]
2.5 - 50
7
70 - 220 30
20 - 50 20
15
100 - 450
20

Q = max. flow rate of pressure fluid
Higher pressures on request

1.3.t Bladder material

The following elastomers are available as
standard:
zzNBR (acrylonitrile butadiene rubber,
perbunan),
zzIIR (butyl rubber),
zzFKM (fluoro rubber, Viton®),
zzECO (ethylene oxide epichlorohydrin
rubber).
The material must be selected according
to the particular operating fluid and
temperature.
When choosing the elastomer, allowances
must be made for the fact that the gas
can cool down to below the permitted
elastomer temperature if there are adverse
discharge conditions (high pressure ratio
p2/p0, high discharging velocity). This can
cause cold cracking in the elastomer.
The gas temperature can be calculated
using the HYDAC Accumulator Simulation
Program ASP.

1.5. tMounting position

HYDAC bladder accumulators can be
installed vertically, horizontally and at a
slant. When installing vertically or at a
slant, the oil valve must be at the bottom.
On certain applications listed below,
particular positions are preferable:
zzEnergy storage:
vertical,
zzPulsation damping:
any position from horizontal to vertical,
zzMaintaining constant pressure:
any position from horizontal to vertical,
zzPressure surge damping:
vertical,
zzVolume compensation:
vertical.
If the mounting position is horizontal
or at a slant, the effective volume and
the maximum permitted flow rate of the
operating fluid are reduced.
Bladder accumulators SB16A / SB35A and
SB16AH / SB35AH must only be installed
vertically with the gas side at the top.

1.6.tType of mounting

For strong vibrations and volumes above
1 litre, we recommend the use of HYDAC
accumulator supports or the HYDAC
accumulator mounting set.
See catalogue sections:
zzSupports for Hydraulic Accumulators
No. 3.502
zzACCUSET SB
No. 3.503

1.4.tCorrosion
protection

For operation with chemically aggressive
media, the accumulator shell can be
supplied with corrosion protection, such as
plastic coating on the inside or chemical
nickel-plating. If this is insufficient, then
stainless steel accumulators must be used.

E 3.202.2/03.12

1. t Description
1.1.tFunction

27