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Bladder Accumulators
High pressure
Fluids are practically incompressible and
cannot therefore store pressure energy.
The compressibility of a gas (nitrogen)
is utilised in hydraulic accumulators
for storing fluids. HYDAC bladder
accumulators are based on this principle.
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 and are
also available in different pressure ranges,
see catalogue sections:
zzBladder Accumulators Standard
No. 3.201
zzBladder Accumulators Low Pressure
No. 3.202
zzAccumulators
No. 3.000
1.2.t CONSTRUCTION
The high pressure bladder accumulator
consists of the pressure vessel, the flexible
bladder with gas valve and the hydraulic
connection with check valve.
1.2.1 t Shell material
The forged pressure vessel is seamless
and manufactured from high tensile
chrome molybdenum steel.
1.2.2t 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 used depends on the
particular operating medium 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.
1.3. t MOUNTING POSITION
AND TYPE OF
MOUNTING
Information on secure mounting positions
and mounting elements can be found in
the following catalogue sections:
zzBladder Accumulators Standard
No. 3.201
zzSupports for Hydraulic Accumulators
No. 3.502
zzACCUSET SB
No. 3.503
1.2.3t Corrosion protection
For operation with chemically aggressive
media, the accumulator shell can be
chemically nickel-plated internally or
supplied with a special plastic coating,
such as Duroplast.
For external corrosion protection the
accumulator can be supplied with an
epoxy resin finish specially for offshore
applications.
E 3.203.3/03.12
1. t Description
1.1.tFUNCTION
35
"
