Bladder Accumulators

“All our accumulators are dispatched without pre-charge. A pre-charge incurs additional cost. For more information contact us on or call us on 03 9272 8900.”

Bladders accumulators are hydropneumatic accumulators with a flexible bladder. Therefore, this flexible bladder serves as a separate element between a compressible gas cushion and the operating fluid.

To begin with, HYDAC bladder accumulators possess either a welded or a forged pressure vessel, the accumulator bladder and the armatures for the gas-side and fluid-side connection. In addition to the standard construction design, custom designs for special application cases are also available. This is particularly the case for very high discharge velocities (e.g. up to 100 l/s) and pressures (e.g. up to 1,000 bar).

  • Nominal volume: 0.5 ... 450 l,
  • Permitted operating pressure: up to 1,000 bar
  • Also, standard elastomers: NBR, ECO, IIR, FKM (FPM)
  • Accumulator shell materials: carbon steel, stainless steel, aluminium
  • A high discharge speed
  • No pressure differential between fluid side and gas side,
  • Also, a compact, low-maintenance
  • And a high charging and discharge frequencies
  • Videos
  • Software


  • 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