Hydraulic Accumulator Basics

Accumulators are devices used to store fluid power to do the following:

  • 1. Store power for intermittent duty cycles thus economizing pump drive power
  • 2. Provide emergency or standby power
  • 3. Compensate for leakage loss
  • 4. Dampen pulsations and shocks of a periodic nature

Principals of Operation

Most hydraulic systems require variable and intermittent flow rates. Energy can be saved by using the accumulator as a storage device to accept pump output flow when system demand is low and supplement output when demand is high.

Most accumulator designs are based on the principle that gas is compressible and oil is nearly incompressible. Assume an inert gas, such as nitrogen, is contained under pressure in a vessel. If hydraulic fluid is pumped into that vessel at a higher pressure than that of the original gas, the nitrogen compresses as its Accumulator Basics - Circuitpressure rises to that of the fluid being pumped. This increase in gas pressure is proportional to the decrease in volume.

The vessel now contains energy in that the volume of hydraulic fluid, stored against the pressure of compressed nitrogen gas, if released, will quickly be forced out of the vessel under the pressure of the expanding gas.

Hydro-pneumatic accumulators with the gas separated from the liquid by a piston, diaphragm or bladder are by far the most common type.

To prevent auto ignition at high pressures, always use an inert gas such as dry nitrogen or helium.

Accumulator Basics - 3 Types