In industrial machinery, mobile equipment and automated production lines, the use of hydraulic pressure compensators helps the actuators operate stably under complex load conditions and reduces energy consumption. This article will introduce the functions, types and applications of hydraulic pressure compensators, helping you gain a comprehensive understanding.
What is a Hydraulic Pressure Compensator?
The hydraulic pressure compensator is an automatic control device that can respond to changes in system pressure. It is mainly composed of a valve body, a control valve core, and a preload spring mechanism.
The hydraulic pressure compensator automatically adjusts the opening degree of the valve by sensing the changes in the load pressure, thereby maintaining a stable output flow or limiting the maximum pressure of the system during pressure fluctuations.
The Function of the Hydraulic Pressure Compensator
Maintain the Stability of the Output Flow
The hydraulic pressure compensator can automatically adjust the throttle element according to the pressure changes of the load, so that the flow entering the hydraulic actuator remains stable when the pressure changes. A stable flow can avoid big fluctuations in the speed of the actuator caused by load changes, thereby achieving more precise motion.
Limit the Maximum Pressure of the System
When the system pressure reaches the preset upper limit, the hydraulic pressure compensator will regulate to avoid the pressure from continuing to rise beyond the safety limit. This can prevent the hydraulic pump from overloading, as well as damage to the pipelines and hydraulic components.
Reduce the Wear of Hydraulic Components
A hydraulic pressure compensator can reduce the impact load on hydraulic pumps, hydraulic valve groups, pipelines, and actuators during pressure fluctuations by adjusting the pressure and flow of the system. This helps to extend the service life of various components in the hydraulic system, while reducing maintenance frequency and costs.
Improve System Operational Efficiency
The hydraulic pressure compensator will automatically adjust its output when the system does not require continuous high-pressure operation. This on-demand adjustment reduces energy loss and improves system operating efficiency.
Coordination of Multiple Actuator Operations
For complex hydraulic systems with multiple execution circuits, the hydraulic pressure compensator can provide a stable flow rate for each circuit. This function can avoid interference with the operation of other circuits when the load of a certain circuit suddenly changes, keeping the coordinated operation of the entire system.
Types of Hydraulic Pressure Compensators
Classified by Application
Pump Pressure Compensator
This type of pressure compensator is usually integrated into the control mechanism of hydraulic pumps. It dynamically adjusts the pump displacement by sensing the pump outlet pressure and load feedback.
It will reduce the pump output when the pressure demand is low, and increase the output appropriately when the pressure demand rises. This can maintain stable output under dynamic loads, reducing the impact of system vibration and pressure fluctuations on pumps and pipelines.
These compensators are usually used in conjunction with variable displacement pumps.
Valve Pressure Compensator
This type of pressure compensator often works in conjunction with throttle valves, directional valves, etc. According to its structure and installation location, it can be classified into the following categories.
2‑Way Pressure Compensator
The 2-way pressure compensator has only two oil ports for oil inlet and outlet. It is often installed in series with the main throttle valve.
When the load pressure decreases and the flow rate increases, the 2-way pressure compensator will automatically close the valve port, increase resistance, and maintain a constant pressure difference through the main throttle port.
3‑Way Pressure Compensator
The 3-way pressure compensator has three oil ports: inlet, outlet, and return. It is connected in parallel with the main throttle valve and is usually located before the throttle valve. It can maintain a stable pressure difference at the main valve port.
In addition, when the output flow of the pump exceeds the set value, it can directly guide the excess hydraulic oil back to the oil tank through the return oil port. The 3-way pressure compensator is usually used for fixed-displacement pumps.
Pre-Compensation
Pre-compensation means that the pressure compensator is installed on the oil inlet side of the main control valve. It adjusts the pressure entering the main valve core according to the load pressure, keeping a constant pressure difference between the inlet and outlet of the main valve core.
But when multiple actuators work in parallel, it will not distribute the flow proportionally, and the low-pressure side actuator will first receive the flow.
Post-Compensation
Post-compensation refers to the pressure compensator installed on the outlet side of the main control valve. It adjusts the pressure difference after throttling by sensing the actual load pressure.
Post-compensation can achieve balanced flow distribution when multiple actuators are connected in parallel. For instance, when the pump flow is insufficient, the pressure compensator makes all the actuators in the circuit to distribute the flow proportionally. This is also known as flow sharing.
Classified by Control Settings
Fixed Pressure Compensator
The set pressure value of the fixed pressure compensator is fixed by an internal spring at the factory. You cannot adjust the pressure setting value when using it. Its structure is simple, compact, and it is highly reliable. Fixed pressure compensators are suitable for stable working conditions that do not require adjusting the set pressure.
Adjustable Pressure Compensator
The adjustable pressure compensator is equipped with adjustment mechanisms such as adjusting screws and knobs. You can change the set pressure or pressure difference by adjusting the preload of the regulating spring, so that your hydraulic system can adapt to different working conditions.
Load-Sensing Pressure Compensator
The load-sensing pressure compensator can adjust the compensation value according to the real-time signal of the load pressure. One end of it receives the actual working pressure from the actuator, and the other end receives the pump outlet pressure.
The load-sensing pressure compensator will continuously compare this pressure difference and maintain it at the value set by the spring. It is commonly used in complex hydraulic systems.
The Application of Hydraulic Pressure Compensators
Pressure-Compensated Flow Control Valves
The pressure-compensated flow control valve is a typical application of the pressure compensator in the hydraulic system. It is mainly used in hydraulic circuits where a stable flow needs to be maintained under pressure fluctuations.
Pressure-compensated flow control valves are usually installed on the inlet or return lines of hydraulic actuators. It makes the extension or rotation speed of the hydraulic actuator only determined by the set opening degree of the valve port, and is not affected by changes in external loads.
Pressure-Compensated Pump
Pressure compensated pump is the application of a pressure compensator in a hydraulic pump. It can dynamically adjust the displacement of the hydraulic pump according to changes in system load. The pressure compensation pump can avoid a large amount of energy loss caused by overflow of the quantitative pump under high pressure.
Engineering Machinery
Hydraulic pressure compensators are widely used in construction machinery such as excavators, loaders and cranes.
In the composite action of lifting the excavator boom and unloading the bucket, the hydraulic pressure compensator can balance the pressure distribution of each circuit, avoiding action lag caused by sudden load changes.
During the slewing and telescopic operations of the crane arm, the hydraulic pressure compensator can stabilize the operating speed of the actuator, keeping the safety of the lifting and transfer process of heavy objects.
Industrial Manufacturing
In the hydraulic mechanical grippers, rotating workbenches, lifting platforms and other actuators of automated production lines, hydraulic pressure compensators can control the operating speed and positioning accuracy of each actuator.
When multiple actuators work in parallel, the hydraulic pressure compensator prevents sudden changes in the load of a single actuator from interfering with the operation of other actuators, keeping the orderly operation of each process on the production line.
Mining
Hydraulic pressure compensators are commonly used in hydraulic protection circuits for crushers and braking circuits for mine hoists.
During the operation of the crusher, the hydraulic pressure compensator can automatically relieve pressure when encountering hard material impact, preventing equipment damage due to overload.
During the operation of the mine hoist, the hydraulic pressure compensator can stabilize the braking system pressure and improve the operational safety of the equipment.
Other Industry Applications
In the aerospace field, hydraulic pressure compensators can be used to control the hydraulic circuits of components such as aircraft landing gears and flaps.
In the petroleum and energy industry, hydraulic pressure compensators are also used in the hydraulic systems of equipment such as oil and gas extraction and drilling platforms.
FAQs
If a Hydraulic Pressure Compensator is Installed in the System, but the Action Speed of the Actuator Still Slows Down with Increasing Load, what could be the Possible Reasons?
This may be due to insufficient set pressure difference or spring failure of the compensator, which prevents it from maintaining sufficient valve opening to stabilize the pressure difference at both ends of the throttle.
Secondly, it could be that the system is not supplying enough oil. When the compensator attempts to open the valve to maintain the pressure difference, the flow output of the pump has reached its limit.
Finally, you can also check whether the installation direction or oil port connection of the hydraulic pressure compensator is correct.
Why does the Adjustment Accuracy of Hydraulic Pressure Compensators Decrease in Low Temperature Environments?
The low temperature environment will increase the viscosity of hydraulic oil and the flow resistance. This will slow down the movement speed of the valve core inside the compensator and cause a delay in response.
At the same time, low temperature may cause changes in the elastic modulus of the setting spring of the compensator, resulting in deviations in the pressure setting value and a decline in adjustment accuracy.
Will the Hydraulic Pressure Compensator Malfunction due to the Case Drain Pressure?
Yes. If the case drain pressure increases abnormally, it will cause the hydraulic pressure compensator to misjudge the system pressure, resulting in improper compensation adjustment. You need to keep the oil discharge pressure of the housing at a low level to avoid interference with the compensator.
What are the Special Requirements for Hydraulic Pressure Compensators in Deepwater Hydraulic Systems?
Deepwater hydraulic systems are subject to both external water pressure and internal oil pressure.
When using a hydraulic pressure compensator, it is necessary to consider the impact of external environmental pressure on pressure sensing and feedback signals. It needs to respond to internal pressure changes in the system and avoid being accidentally triggered by deepwater environmental pressure.
What is the Hysteresis of a Hydraulic Pressure Compensator?
Hysteresis refers to the difference between the pressure value that triggers the compensator action during the pressure rise process and the pressure value that resets during the pressure drop process.
This is mainly caused by the force of the spring and the frictional force of the valve core movement. The hysteresis is usually very small, within a few percentage points of the output peak.
Final Thoughts
The hydraulic pressure compensator can prevent interference caused by load fluctuations and environmental changes. It can also optimize system energy allocation and extend equipment lifespan.
The hydraulic pressure compensator is constantly being improved to adapt to more complex working conditions and higher control accuracy requirements. If you would like to know more about the hydraulic pressure compensator, please feel free to contact us.
