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Diaphragm Accumulators


Fluids are practically incompressible and cannot, therefore, store pressure energy. The compressibility of a gas is utilised in hydraulic accumulators for storing fluids. HYDAC diaphragm accumulators are based on this principle, using nitrogen as the compressible medium.

A diaphragm accumulator consists of a fluid section and a gas section with the diaphragm acting as the gas-proof screen.

The fluid section is connected to the hydraulic circuit so that the diaphragm accumulator draws in the fluid when the pressure increases and the gas are compressed. When the pressure drops, the compressed gas expands and forces the stored fluid into the circuit.

At the base of the diaphragm is a valve poppet. This shuts off the hydraulic outlet when the accumulator is completely empty and thus prevents damage to the diaphragm.


HYDAC diaphragm accumulators when fitted with a HYDAC Safety and Shut-off Block comply with the regulations of the Pressure Equipment Directive PED 97/23/EC and the German regulations on health & safety at work (Betr.Sich.V.).

See catalogue section: Safety and shut-off block SAF/DSV No. 3.551


  • design optimised for function and weight,
  • choice of installation positions,
  • no pressure differential between fluid side and gas side,
  • low-maintenance and long service life.


  • Nominal volume: 0.075 … 4 l,
  • Permitted operating pressure: 40 … 750 bar,
  • Elastomers: NBR, ECO, IIR, FKM (FPM) and others,
  • accumulator shell materials: carbon steel, stainless steel, aluminium and others.


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HYDAC Australia

HYDAC New Zealand

AUSTRALIA 1300 449 322

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