1. What is an accumulator
A hydraulic accumulator is a device that stores energy. In an accumulator, the stored energy is stored in the form of compressed gas, compressed springs, or lifted loads, applied to a relatively incompressible fluid.
Accumulators are very useful in fluid power systems to store energy and eliminate pulses. They can be used in hydraulic systems to reduce the size of fluid pumps by replenishing the pump’s fluid. Accumulators can be used in hydraulic systems to stabilize pressure changes when the fluid is affected by temperature increases and decreases. They can distribute pressurized fluids such as greases and oils.
2. Working principle of accumulator
(1) When liquid is under pressure, the change in volume (under constant temperature) is very small, so if there is no power source (that is, the replenishment of high-pressure liquid), the pressure of the liquid will drop rapidly.
(2) The elasticity of gas is much greater, because gas is compressible. In the case of large volume changes, gas can still maintain a relatively high pressure. Therefore, when the accumulator is replenishing the hydraulic oil of the hydraulic system, the volume of the liquid has changed, and the high-pressure gas can continue to maintain the pressure of the hydraulic oil, without the hydraulic oil in the container becoming smaller due to the replenishment of the hydraulic oil, resulting in a rapid loss of pressure of the hydraulic oil.
(3) As for nitrogen, the main reason is that nitrogen is stable in nature and does not have oxidation or reduction properties. This is very beneficial for maintaining the performance of hydraulic oil and does not cause oxidation/reduction degeneration of hydraulic oil! Nitrogen is pre-charged pressure and is installed in the accumulator’s air bag, which is separated from the hydraulic oil!
3. The main functions of accumulators
(1) As auxiliary power source
The actuators of some hydraulic systems are intermittent and have a very short total working time. Although the actuators of some hydraulic systems are not intermittent, their speeds vary greatly within a working cycle (or within a stroke). After installing an accumulator in such a system, a pump with lower power can be used to reduce the power of the main transmission, making the entire hydraulic system small in size, light in weight and cheap in price.
(2) As an emergency power source
For some systems, it is required that when the pump fails or the power is cut off (the oil supply to the actuator is suddenly interrupted), the actuator should continue to complete the necessary action. For example, for safety reasons, the piston rod of the hydraulic cylinder must be retracted into the cylinder. In this case, an accumulator of appropriate capacity is required as an emergency power source.
(3) Compensate for leakage and maintain constant pressure
For systems where the actuator does not move for a long time but needs to maintain a constant pressure, an accumulator can be used to compensate for leakage, thereby keeping the pressure constant.
(4) Absorbing hydraulic shock
Sudden reversal of the reversing valve, sudden stoppage of the hydraulic pump, sudden cessation of the movement of the actuator, or even the need for emergency braking of the actuator, etc., will cause the flow of liquid in the pipeline to change dramatically, resulting in shock pressure (oil shock). Although the system is equipped with a safety valve, it is still inevitable to produce a short-term surge and shock in pressure. This shock pressure often causes the instruments, components and sealing devices in the system to malfunction or even damage or pipeline rupture, and also causes obvious vibration in the system. If an accumulator is installed before the control valve or hydraulic cylinder shock source, this shock can be absorbed and mitigated.
(5) Absorbing pulsation and reducing noise
The pulsating flow of the pump will cause pressure pulsation, making the movement speed of the actuator uneven, generating vibration, noise, etc. By connecting an accumulator with sensitive response and small inertia in parallel at the outlet of the pump, the pulsation of flow and pressure can be absorbed and the noise can be reduced.
