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 the gas 1 precharge pressure P , the liquid enters the shell and the 0 diaphragm is compressed reducing the gas volume to V .1 Should the liquid pressure rise to P , the volume of gas 2 reduces to V with an attendant rise in pressure, thus 2 balancing the Liquid pressure.