What is Hydro Pneumatic Accumulator?

The accumulator are pressure storage reservoir in which non compressible fluids are stored under pressure.

Accumulators are connected to pump discharge lines for compensating for loss of fluid pressure in the hydraulic circuit.

Hydro Pneumatic Accumulators

They are used for

  1. Emergency operation

  2. pulsation Damping


  1. Bladder type accumulator

  2. Diaphragm type accumulator

3.Piston type accumulator

Bladder Accumulator

Fluids are not in compressible and cannot store pressure energy, but gas can be compressed so it is used for storing fluids in accumulator.The accumulator consists of a shell. The shell consist of fluid section and gas section.

The gas section has a bladder which is filled with nitrogen gas. Surrounding the bladder is the fluid.The bladder can be expanded and compressed for storing and releasing the fluid.

The fluid section is connected to the hydraulic section i.e poppet valve for drawing the fluid into the accumulator when the fluid pressure is higher and compresses the bladder with gas.so the fluid is stored inside the accumulator.when the fluid pressure in the line drops the bladder expands and forces the stored fluid in the hydraulic circuit with the pump flow.


The accumulator bladder is pre pressurised with nitrogen gas upto 2.3bar. The bladder gas pressure is set 70% to 80 %of the hydraulic circuit pressure.

Diaphragm type accumulator

These accumulators have a rubber plate or diaphragm as the separating element. This element is welded or screwed together between two spherical shells (or compartments).

The compartment above the diaphragm is filled with nitrogen. The compartment below is directly connected to the hydraulic circuit. Diaphragm accumulators are useful if the required fluid storage capacity is low (i.e. 4 litres or less).

Diaphragm accumulators have most of the advantages of bladder-type units, but can handle gas compression ratios of up to 8:1. However, they are limited to smaller volumes, and their performance can sometimes be affected by gas permeating across the diaphragm.


Special Equipment are available to check the pressure of the nitrogen and it should be check once per year. If nitrogen pressure is high it can be reduced. By using mobile nitrogen charging devices the pressure can be added or refilled