A hydro-pneumatic accumulator is a device used specifically for storage of liquid under pressure. As liquids, for all practical purposes, are incompressible, this objective is achieved by utilizing the compressibility of gases.
A flexible rubber separator i.e., diaphragm is fitted into the accumulator shell.
An inert gas - nitrogen - is filled into the diaphragm through a pressure valve to a pressure P . The diaphragm expands,0 filling the entire volume V of the accumulator shell.0
When the system (circuit) pressure P is higher than the1 gas precharge pressure P , the liquid enters the shell and0 the diaphragm is compressed reducing the gas volume to V .1
Should the liquid pressure rise to P , the volume of gas2 reduces to V with an attendant rise in pressure, thus2 balancing the Liquid pressure.
A potential energy is now stored in the accumulator to be utilised whenever needed.