The Functions of Hydraulic Accumulators
The functions of hydraulic accumulators are quite varied. In general terms, a hydraulic accumulator works like a safety valve for the hydraulic system. To go into detail, the functions of hydraulic accumulators are as follows:
Emergencies
For example, during a power failure, the energy stored in the accumulators creates a working or closing stroke. An emergency circuit is shown in the figure below.
During a power failure, the spring causes valve (1) to close and return to its normal position. This connects the accumulator and the cylinder’s piston-rod side to each other.
The accumulator’s role here is to allow the piston rod to retract.

Compensating for oil leaks
Maintaining preload force in a hydraulic cylinder is only possible if losses caused by leaks are recovered back into the system. Accumulators are especially well suited for these situations.
The figure shows a leak-oil compensation circuit. As shown in the figure, leaked oil is pushed from the accumulators into the piston chamber.
When the pressure in the accumulator drops below a predetermined value, the pump kicks back in to refill the accumulator with fluid.

Emergency lubrication
To maintain the oil film layer in bearings, the bearing must be continuously supplied with lubricating oil. Lubrication points are under constant pressure.
If the lubrication oil pump fails, the accumulator keeps the pressure constant until the machine stops, or until the auxiliary pump in the circuit reaches the required pressure.

Shortening stroke time
In presses and drills, the longest and fastest approach strokes are needed in the shortest time for proper production. The actual working process, however, is carried out under low-speed, high-pressure conditions.
In light-duty operation, to achieve the desired high speed, pump I (the low-pressure pump), pump II (the high-pressure pump), and the accumulators all operate simultaneously.
As pressure rises toward the end of the desired stroke, check valve (A) closes. In this state, only pump II supplies fluid to the circuit, at low flow but high pressure. Meanwhile, pump I refills the accumulator.
Preventing system failures
A power failure occurring in the middle of a working cycle during production, before the cycle is complete, can lead to costly results.
In such cases, accumulators help ensure the incomplete cycle is finished.

Protection against pressure fluctuations
In many hydraulic systems, pressure fluctuations occur due to the hydraulic components used or to variable loads in the system (e.g., excavator bucket movement).
By using accumulators, components sensitive to pressure fluctuations (for example, hydraulic pumps) can be prevented from being damaged.

Damping pressure spikes caused by opening/closing events
When large volumes of fluid are rapidly delivered into the return line, pressure spikes occur. These spikes can damage oil coolers and return filters.
In addition, the sudden stopping of moving fluid in the line can cause damage to the valve, hose, and fittings. An example of this is an emergency shutdown situation.

Reducing shock and oscillation
In hydraulic systems, pressure fluctuations can occur in various processes, depending on the system, whenever fluid flow rate changes.
Variations within the hydraulic pump, spring-mass (pressure compensator) systems in valves, sudden connection of chambers at different pressure levels, short opening and closing times of shut-off and control valves, and distributor pumps switching in and out.

Balancing forces
Forces and displacements can be balanced using a hydraulic accumulator. Balancing forces is especially necessary in continuous-operation applications. For example, deformation in the material and the resulting variation in material residue can occur due to differing roller loads.
If the forces on the rollers are balanced, the rolled material’s strip thicknesses become uniform.
The figure shows a counterbalance circuit for a workpiece. Safety and shutoff valves, which can be mounted directly to the system, have been added to the circuit together with a suitable accumulator.
The features of this system are as follows:
1- Smooth balancing of forces, applying less load to the system frame
2- Gains from the counterweight, thereby reducing the weight and space needed for installation
Energy Storage Function
Hydraulic accumulators store pressurized oil in the system, providing extra energy during sudden load increases.
Reducing Pressure Fluctuations
Accumulators protect the system by smoothing out pressure fluctuations caused by pump pulsations.
Emergency Backup Power
Accumulators can supply backup energy so the system can keep running for a short time if the pump fails.
Related Questions
Hydraulic accumulators store pressurized oil in the system, providing extra energy during sudden load increases.
Accumulators protect the system by smoothing out pressure fluctuations caused by pump pulsations.
Yes, accumulators can supply backup energy so the system can keep running for a short time if the pump fails.
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