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Most hydraulic parts, like pumps, valves, motors, and actuators, may be familiar to you, but there is another crucial part called a “accumulator.” An accumulator is a container that stores, sustains, and recovers pressure, as the name suggests.
Every time a fluid is moving, hydraulic systems experience pressure drops and energy losses. Find out more about these things called “accumulators.” Why do we need them, what are they, and how do they function?
What Is a Hydraulic Accumulator?
As we all recall from middle school science, as the volume of a container is filled with less material, the empty space must be filled with air. Compressed gas is used in accumulators to fill the empty space, but since we don’t want the compressed gas to mix with the hydraulic fluid, there is typically a bladder inside the accumulator to keep the two separate. An accumulator is essentially a vessel with a bladder and gas inside of it so that as the bladder fills with pressurized hydraulic fluid, the gas inside the vessel compresses. The compressed gas pushes the fluid out of the accumulator when the fluid inside is released.
Preloading the accumulator means that a minimum pressure is needed for fluid to enter the accumulator. Preloading may be accomplished using weights, gas, or springs. There are diaphragm, bladder, and piston accumulators. Similar to a battery or capacitor, an accumulator stores energy, but why would we want to do so with pressurized hydraulic fluid?
Storing Pressurized Hydraulic Fluid
Similar to the reasons for storing electrical energy, there are a few reasons to want to store pressurized hydraulic fluid.
Reducing Pulsating Fluid Systems
One explanation is systems where the hydraulic fluid may pulse. I used to operate a device that examined diesel fuel injectors. The pressurized fluid behind the injector would experience a slight decrease in pressure as it fired fluid, simulating the rapid opening and closing of a water tap. The system’s sensors shook and had inconsistent readings due to the injector’s high speed. Since this was a testing device, accuracy in pressure readings was crucial,. And the injectors required a steady source of pressure. The system’s ability to compensate for the injector-caused pressure drop was no longer dependent on the pump thanks to the addition of an accumulator. The accumulator was able to replace the pressure lost by the injector fast enough that the sensor barely detected a change in pressure.
Compensating for Pressure Drop in Actuators
The importance of accumulators in hydraulic motion control systems, where the actuators expand at a high rate, is a similar example. Since the pump is unable to provide an infinite flow rate, the pressure in the system will decrease as the actuator’s volume increases. This causes the system response time to slow down, which is unacceptable for many systems. The accumulator offers the flow capability to maintain a more constant system pressure, resulting in a much more dependable system response.
Allowing for Thermal Expansion
To allow for fluid expansion is another justification. Some hydraulic systems operate in dangerously remote areas that may become very hot,. And the pressurization process for hydraulic fluid also raises the fluid’s temperature. The volume of the fluid increases as the temperature rises,. And if there is no space for the fluid to expand within the system, the pressure within the system could lead to a rupture. By allowing extra pressure to fill the accumulator, accumulation devices can be used to absorb this thermal expansion. The pressurized fluid from the accumulator can then be returned to the system after the temperature has dropped.
Where Are Accumulators Located?
The location of an accumulator can change depending on what it does. For instance, an accumulator that stores energy for use in an emergency might be placed apart from the rest of the system and pressurized just once. The accumulator can kick into action in an emergency or when the pump isn’t working properly, helping to maintain pressure in the system. Similar to an accumulator, the typical pressure tank found in residential water systems merely permits the pump to run on a less frequent cycle rather than continuously whenever water is needed, as opposed to operating in an emergency situation.
Place the accumulator very close to the pump’s output if you’re trying to quiet the pump’s pulsations and reduce noise. The accumulator would always be filled with fluid, which would dampen any vibrations the pump might otherwise cause. You should keep the accumulator on the high-pressure side of the system because it stores energy. The best location for a piston-style accumulator to dampen pulsations is close to the sources of those pulsations.
Hydraulic Accumulator Maintenance
Depending on the type of accumulator you have, they are simple machines with few moving parts. Due to the fact that accumulators are pressure vessels just like compressed gas cylinders,. Maintaining one can be hazardous and may call for a specialized third-party inspection. The various pre-charge techniques introduce various maintenance practices. The nitrogen gas in the gas pre-charge accumulators may need to be checked and topped off. The pre-charge gas will need to be vented and replaced. If an internal inspection is necessary or if valves need to be replaced. Never use oxygen or compressed air as the pre-charge gas, and always adhere to the manufacturer-recommended maintenance schedule.
Accumulator in a Hydraulic System
The flow of fluid to various system components is controlled by a hydraulic control system. Since the fluid is typically piped directly into and out of the accumulator,. The majority of accumulators don’t need any direct input signals from the control system. The control system must at least be aware of the accumulator’s presence. Because some systems may need to open a valve at the accumulator when necessary.
Accumulators are useful tools for storing hydraulic energy and reducing pulsations in the hydraulic system. An accumulator is not necessary for all hydraulic systems, but if yours is noisy or vibrates, making it difficult to read gauges and sensors,. Or if you need to keep pressure while the pump is off, an accumulator might be able to help.