A hydraulic accumulator is essentially a type of energy storage device…
A pressure storage reservoir in which a non-compressible hydraulic fluid is held under pressure by an external source. The external source can be a spring, a raised weight, or a compressed gas.
Using a hydraulic accumulator enables a hydraulic system to: cope with extremes of demand using a less powerful pump; store power for intermittent duty cycles; provide emergency or standby power; respond more quickly to a temporary demand; smooth out pulsations compensate for leakage loss.
Common types of hydraulic accumulator are: piston, bladder and diaphragm.