Shanghai Siken Industries Inc.

Web:  www.siken-inc.com

Email:info@siken-inc.com

 

 

A hydraulic accumulator is a pressure storage reservoir (a type of energy storage device) that holds incompressible hydraulic fluid under pressure applied by an external source of mechanical energy.

 

The external source is typically a compressed gas (most commonly nitrogen), a spring, a raised weight, or occasionally an engine. Compressed-gas (hydro-pneumatic) accumulators are by far the most common type today.

 

How it works

Hydraulic fluid is nearly incompressible, while gas is compressible. In a typical gas-charged accumulator:

•  A flexible barrier (bladder, diaphragm, or floating piston) separates the hydraulic fluid from a pre-charged volume of inert gas (usually nitrogen).

•  The gas is pre-charged to a pressure typically around 80–90% of the system’s minimum working pressure.

•  When system pressure rises above the pre-charge, fluid enters the accumulator and compresses the gas, storing potential energy.

•  When system pressure drops, the compressed gas expands and forces the stored fluid back into the circuit.

This allows the device to store and release pressurized fluid on demand, much like a rechargeable battery stores and releases electrical energy.

Main types

•  Bladder accumulators: A flexible rubber bladder holds the gas; fluid surrounds it. Fast response, good for shock absorption and high flow rates.

•  Piston accumulators: A free-floating piston separates gas and fluid sides. Suitable for larger volumes and higher pressures; more durable but with some friction/hysteresis.

•  Diaphragm accumulators: A flexible diaphragm separates the chambers. Compact and economical, typically for smaller volumes.

•  Less common modern variants include spring-loaded or weight-loaded designs (the latter were used historically in large fixed installations like dock machinery).

Primary functions and benefits

Hydraulic accumulators are used to:

•  Store energy and supplement pump flow during peak demand (allowing a smaller pump).

•  Absorb shocks, pressure spikes, and pump pulsations (smoothing system operation and reducing noise/vibration).

•  Maintain system pressure during leaks, temperature changes, or when the pump is off.

•  Provide emergency or auxiliary power.

•  Improve overall efficiency, reduce component wear, and enable faster response to temporary demands.

 

They are widely used in industrial machinery, mobile equipment (construction, agriculture), presses, injection molding, marine systems, and many other fluid-power applications.