Hydraulic Accumulator
A hydraulic accumulator is the component that stores pressurized oil against a compressed nitrogen cushion and gives it back when needed. It damps pressure spikes, provides short term peak flow rate, and supplies energy to the pilot circuit when the pump stops. On mobile equipment, 0.5-5 liter diaphragm or bladder types are common.
The operating principle is gas compression: as oil enters, the nitrogen is compressed and energy is stored. The usable volume stored follows from the relationship between the pre-charge pressure and the highest and lowest working pressures of the system. Pre-charge is typically selected at 80-90% of the system minimum pressure.
- Spike damping: it absorbs the pressure surge created when a valve closes suddenly, extending hose and fitting life.
- Peak flow rate: it briefly feeds a fast movement that the pump cannot instantaneously keep up with.
- Safety: it must always be discharged before maintenance; the accumulator stays under pressure even when the system is shut down.
This last item is critical for field safety. On a machine fitted with electronic lever control, switching off the remote control or pressing Emergency Stop does not release the energy in the accumulator; the hydraulic side pressure must be relieved by a separate procedure.
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