How does a hydraulic accumulator improve system efficiency and performance?

A hydraulic accumulator increases performance and efficiency by storing the energy of pressurized fluids and then releasing it upon demand. This allows a smaller pump to handle the highest load, smooths out the pulsations and pressure spikes as well as maintains pressure throughout power losses, and also reduces the energy wasted from over-sizing the pump to handle short bursts of high flow. In real terms it means lower energy costs, more time between components, more quiet operation, and a system that reacts quicker to changes in load. Below, we discuss precisely how accumulators can provide these benefits and how they can be integrated into a properly designed hydraulic circuit.

What exactly does a hydraulic accumulator do?

A hydraulic accumulator is a vessel that holds hydraulic fluid at pressure by using compressed gas (typically nitrogen) or a spring or a piston with a weight to store energy. The most popular industrial kind is called a piston or bladder accumulator in which nitrogen gas is compressed on one side when fluid is pushed into while expanding to force fluid out once pressure decreases.

Imagine it as an accumulator that can be recharged to store hydraulic energy. This pump "charges" the accumulator during times of low demand while it "discharges" that stored energy instantaneously when the system requires the flow to increase or pressure. This basic principle is what is the basis of nearly every efficiency improvement that is associated with the accumulators.

The most effective ways to improve the efficiency of accumulators

1. Reduced size of the pump and motor load

A lot of hydraulic systems are designed around demand for peak or instantaneous demands instead of average demand. A pump that requires an extremely high flow for just two seconds in 60 seconds still requires engineers to put in an engine that can handle the high flow even if it is not used for the remainder of the time.

An accumulator alters the equation. The pump can be made more closely to the flow required by charging the accumulator during low or idle periods. If the demand for peak hours is the accumulator, it provides the additional flow immediately and is able to supplement the pump. This permits a smaller motor and less power output, as well as less power consumption throughout the time.

2. Cutting energy consumption during idle periods

In systems where the actuator holds an object (a clamp or press platen or an elevator table) in the past, the pump must be running in order to prevent internal leakage. This wastes energy by producing heat. If an accumulator is installed in holding circuits, a pump will be shut off or unloaded after the accumulator is fully filled, and the accumulator is the only one to maintain system pressure. The pump will only kick back in if the accumulator's pressure is to a certain threshold.

This strategy of unloading the pump is among the most efficient ways to improve the efficiency of the design of fluid power systems, specifically when it comes to clamping, holding, and stamping processes, where dwell time makes up a large part of the process.

3. Absorbing shocks and pressure spikes

Rapid valve changes and sudden load shifts, as well as the reversal of cylinder direction, can cause tension spikes and hydraulic shock (sometimes known as the water hammer of the hydraulic system). These spikes strain hoses, fittings, and seals, as well as pumps, increasing wear while increasing the chance of catastrophic breakdown.

An appropriately sized accumulator functions as a cushion, taking the pressure spike when the gas charge shrinks to take in the sudden pressure increase. This safeguards downstream components and lessens mechanical stress that can reduce component service duration.

4. Pulsation of the Dampening Pump and Noise

Pumps with positive displacement, particularly gear and piston pumps, naturally cause pressure ripples as every pumping element is completed with its stroke. If left unamped, this pulsation creates noise and vibration, as well as fatigue in piping and fittings.

Small accumulators that are placed near the outlet of the pump act as pulsation dampeners, reducing the flow and waveform of pressure. This results in more quiet operation and less vibration-related wear on the components that are connected, which is especially important for mobile equipment and in precision manufacturing settings in which noise and vibration control are important.

5. Power for backup and emergency power

In applications that require safety, like control systems for steering, brake circuits, or emergency actuator retracting, an accumulator will provide the volume of fluid needed for a safe shutdown sequence in the event that the pump loses power or the primary mover is shut down unexpectedly. This is a safety and performance benefit, as well as a cost-saving one, as it ensures that vital functions are still in operation even if there is no active pump output.

6. Compensation for thermal expansion and leakage

In the course of time, and also across temperature fluctuations, the hydraulic fluid volume shifts, and internal leakage leads to the loss of pressure gradually in a closed circuit. Accumulators can automatically compensate by providing small amounts of fluid to keep an appropriate pressure, thus reducing your frequency for pump cycles and resulting wear and tear on the pump components as well as electrical contactors.

Benefits of performance beyond energy savings

Although energy efficiency is usually the main benefit, the accumulation of accumulators can also boost the overall performance of the system in a variety of ways:

• Accelerate cycle times because the accumulator boosts pump flow in times of peak demand; actuators are able to move more quickly than a pump by itself could allow, thereby reducing the cycle time of production equipment.
• Better response: Systems react faster to demands for flow speed because the stored power is released immediately without having to wait until the pumps get up and running.
• Reduction in heat production Pump cycling is less frequent, and lower relief valve activation results in less heat being generated, which eases the burden on cooling systems and helps keep fluid viscosity as well as lubricity within the optimal levels.
• Longer life of components The smoother profile of pressure and less shock loading translate into longer service lives of hoses, seals, and pump parts, which reduce the cost of maintenance over time.

In the places where accumulators are frequently used,

Accumulators are used extensively in:

• Equipment for stamping and press, to provide high-flow bursts of air in the stroke of a press
• Injection molding equipment, to ensure rapid clamping and quick response to injection
• Mobile equipment, for example, suspension, steering, and brake systems
• Circuits for clamping and holding for pump unloading during dwell times
• Pumps that are used to dampen the sound of noisy-sensitive or precise applications.
• Backup systems for emergency situations, where secure shutdowns require the storage of hydraulic energy

Selection and sizing considerations

The efficiency gains mentioned above are dependent on the correct size and type of accumulator. Insufficiently sized accumulators will not provide meaningful flow aid, and oversized units will add cost and footprint. The most important factors are

• The required volume is dependent on the duration and flow during the event that is causing peak demand
• Precharge pressure is usually set at a certain percent of the minimum operating pressure
• Accumulator type that has bladder accumulators, which are favored for the absorption of shock and pulsation, and piston accumulators being favored for higher volume and high-cycle applications.
• Operating temperature range, since gas precharge pressure is temperature-sensitive

Collaboration with an engineer or supplier to correctly calculate these parameters, you can ensure that the accumulator functions as it was intended instead of becoming a neglected or oversized component.

1. What is the primary function of a hydraulic accumulator?

Its main function is to store pressured hydraulic fluid and then release the energy upon demand so that the system can be able to meet pressure or flow demands without over-sizing the pump.

2. What is the best way to make it possible to save energy in a system?

It helps conserve energy through allowing unloading of the pump to occur during the duration of a hold or a dwell and by allowing engineers to set up an encapsulated pump that is smaller than average and not peak demand.

3. What is the difference between a piston and a bladder?

A bladder accumulator makes use of a flexible rubber bladder to separate fluid and gas, which is perfect for shock absorption and the dampening of pulsation. A piston accumulator utilizes the sliding piston and typically can handle larger volumes and greater cycle speeds.

4. Can an accumulator substitute for the hydraulic pump completely?

An accumulator does not add the output of the pump and stores the power generated by the pump. It is unable to produce flow by itself and has to be recharged regularly via the pump.

5. How often should the precharge accumulator pressure be monitored?

The precharge pressure should be checked on a regular basis at maintenance intervals at least every year, as gas precharges can fluctuate due to seal permeation or temperature fluctuations and reduce the efficiency of the accumulator when not monitored.