Bladder accumulators, piston accumulators and diaphragm accumulators

Accumulators for Offshore Hydraulic applications with special coatings or stainless steel up to 690bar.

HYDAC has also acquired QHP Hydraulics in the UK.

HYDAC Accumulator Technology can reflect on over 45 years' experience in research & development, design and production of Hydac accumulators. Bladder, piston, diaphragm and metal bellows accumulators from HYDAC together form an unbeatable range and as components or units, support hydraulic systems in almost all sectors.

The main applications of our accumulators are:

  • Energy storage
  • Emergency and safety functions
  • Damping of vibrations, fluctuations, pulsations (pulsation damper), shocks (shock absorber) and noise (silencer)
  • Suction flow stabilisation
  • Media separation
  • Volume and leakage oil adjustment
  • Weight equalization
  • Energy recovery
  • Using accumulators improves the performance of the whole system and specifically this has the following benefits:
  • Improvement in the functions, Increase in service life, Reduction in operating and maintenance costs, Reduction in pulsations and noise.

Basic criteria, such as:

  • Design pressure
  • Design temperature
  • Fluid displacement volume
  • Discharge/ Charging velocity
  • Fluid
  • Acceptance specifications
  • Mounting options are important parameters required for sizing the correct accumulator.

In addition, the knowledge developed by our accumulator specialists will help to select the right type of accumulator. The comprehensive range of HYDAC accessories simplifies installation and maintenance according to the specification.

Note: Australian range may differs from the catalogue and data-sheet available on the website.


  • What is a hydraulic accumulator?

    Hydraulic accumulators are closed pressure vessels designed to store then discharge pressurised fluids.

    A hydraulic accumulator consists of a fluid section and a gas section with a gas-proof separation element between them.

    The fluid section of the accumulator is connected to the hydraulic circuit so that as the hydraulic system pressure increases the gas is compressed. When the pressure drops, the compressed gas expands and forces the stored fluid into the circuit.

    What are some of the most common applications for HYDAC’s hydraulic accumulators?

    According to HYDAC, some of the most common applications for hydraulic accumulators are:

    • energy storage,
    • emergency and safety functions
    • damping of vibrations, fluctuations, pulsations (pulsation damper), shocks (shock absorber) and noise (silencer)
    • volume and leakage oil adjustment, and
    • energy recovery

    Each of these varied applications may require specialist knowledge in order to select and configure the correct accumulator.

    What are the most common types of accumulators?

    Hydraulic accumulator types are defined by the gas-proof separation element.

    The most common hydraulic accumulators are diaphragm, bladder and piston. Metal bellows accumulators are available but are less common in the Australian market.

    Each hydraulic accumulator type is available in different sizes and can be selected for specific applications.

    What gas should I use to pre-charge an accumulator?

    Hydraulic accumulators must be pre-charged with an inert gas, typically nitrogen (Class 4.0, filtration < 3μm). Compressed air or oxygen should never be used due to risk of explosion.

    For energy storage applications, the pre-charge pressure must be less than or equal to 90 per cent of the minimum operating pressure of the hydraulic system.

    Contact HYDAC if gases other than nitrogen are used or for information regarding pre-charge pressure for different applications.

    What are some of HYDAC’s safety considerations for accumulators?

    Hydraulic accumulators are subject to high pressures; therefore no welding, soldering or mechanical work can be carried out on them.

    HYDAC recommends that all hydraulic accumulators have a dedicated relief valve and a method of isolating and bleeding the accumulator as this will ensure the correct and safe application.

    What are the main differences between a diaphragm and bladder-type accumulator?

    Hydraulic accumulator types are defined by their gas-proof separation element. The most common hydraulic accumulators are diaphragm and bladder in the Australian market. Each hydraulic accumulator type is available in different sizes and can be selected for specific applications.

    Diaphragm accumulators are usually not repairable and typically small in size, ranging from 0.075L to 4L.

    Bladder accumulators are the most common accumulator type and typically range between 0.5L to 200L.

    Are diaphragm or bladder accumulators repairable?

    Due to the nature of diaphragm accumulators typically being a weld-type design, they are not repairable.

    However the bladder accumulators are serviceable and repairable and spare components such as bladders, poppet valves and anti-extrusion rings etc. are readily available.

    Do hydraulic accumulators need to meet any certifications, approvals or regulations?

    Hydraulic accumulators in Australia are designed and constructed in accordance with AS1210 and are subject to AS/NZS 3788 when in service.

    For more information, click here to watch HYDAC’s webinar

    For additional information please see the Accumulator Technology Product Catalogue or contact

    How can you determine if a vessel is a pressure vessel?

    The determination of whether a vessel is a pressure vessel can be made using visual and numerical methods outlined in the AS1210 design code.