Function of a Check Valve in a Hydraulic System
The primary function of a check valve in a hydraulic system is to allow fluid to flow in one direction only while blocking the flow in the opposite direction.
Working Principle of a Check Valve
When fluid enters through port p1, the pressure at p1 overcomes the pressure at port p2 acting on the valve core, along with the spring force and friction between the valve core and the valve body, pushing the valve core open and allowing fluid to flow from p1 to p2, achieving forward flow. Conversely, when pressure oil enters from port p2, the valve core is pressed tightly against the valve seat by the combined action of the liquid pressure at p2 and the spring force, blocking the fluid flow and achieving reverse flow cutoff.
Main Performance Indicators of a Check Valve
Minimum Forward Opening Pressure
The minimum forward opening pressure (Pa) is the smallest pressure required in the inlet chamber to just open the valve core. For a check valve with a zero outlet pressure, the minimum forward opening pressure can be derived using the force balance condition of the valve core:
Pa > (Ft + Ff + G) / A
Where:
Pa: Minimum forward opening pressure (MPa)
Ft: Spring force (N)
Ff: Frictional force on the valve core (N)
G: Weight of the valve core
A: Area of the valve seat (m²)
The minimum forward opening pressure varies according to the application. For the same check valve, different opening pressures can be achieved by replacing the spring. For example, if the check valve is only used to control unidirectional fluid flow, a spring with low stiffness is selected, requiring an opening pressure of only 0.03-0.05 MPa. However, if used as a backpressure valve in a hydraulic system, a stiffer spring is used, resulting in an opening pressure of 0.2-0.6 MPa.
Pressure Loss
This loss includes the pressure loss due to the spring force, frictional force, and fluid flow. To minimize pressure loss, a check valve with a low opening pressure should be selected.
Reverse Leakage
A high-performance check valve should have no leakage or only minimal leakage in the reverse direction. When the system requires high pressure retention, a valve with low leakage should be selected.
Applications of Check Valves
Placed at the outlet of a hydraulic pump to prevent hydraulic shock from affecting pump operation.
Installed between different oil circuits to prevent interference due to different pressures or flow rates.
Used as a backpressure valve in hydraulic systems to improve the stability of actuators.
Combined with flow and pressure valves to form a check valve assembly.
Considerations for Using Check Valves
When selecting a check valve, in addition to choosing the appropriate opening pressure, the flow rate during operation should match the valve’s rated flow. If the flow rate is much lower than the rated flow, the check valve may vibrate. The smaller the flow, the higher the opening pressure, and the more air in the oil, the more likely vibration will occur.
The M-SR..KE…1XJ/ type plug-in check valve is used to allow oil to flow freely from one direction only.
The spring inside keeps the valve core in a closed state.
M-SR…KE… 1XJ/ plug-in check valve valve mainly includes:
(1) Valve sleeve
(2) Valve core
(3) Spring seat
(4) Spring
The check valve has a conical valve structure with low pressure loss
It is mainly used at the outlet of the pump as a back pressure valve and bypass valve.
Common Issues with M-SR Check Valves
Valve cannot fully close
Possible Cause: Foreign objects causing the cone valve core to stick.
Delayed valve opening or closing
Possible Cause: Valve core sticking, often due to spring failure.
Valve vibration or noise
Possible Causes: Unstable flow, improper installation causing excessive fluid impact.
Internal or external leakage
Possible Causes: Aging or damaged seals, loose valve body or joints, damaged valve seat, or valve core surfaces.
Solutions to Common M-SR Check Valve Issues
Clean or replace internal valve components.
Replace springs or seals.
Optimize hydraulic oil quality.
Regular maintenance and inspection can prevent common issues and extend the service life of the M-SR check valve.
FAQ on Common Issues with M-SR Check Valves
To help troubleshoot and resolve issues with the M-SR check valve, here are some common questions and answers:
What should I do if the M-SR check valve generates noise during operation?
Answer: The noise may be caused by unstable fluid flow, excessive flow rate, or vibration of internal valve components. You can check if the valve is securely installed, ensure stable fluid flow, and inspect for any loose or worn components. If necessary, reduce the fluid flow rate or replace the damaged parts.
Why does the M-SR check valve fail to open at low pressure?
Answer: This issue could be due to an overly strong spring or a failed spring, resulting in a high opening pressure. It could also be caused by high-viscosity hydraulic oil or a clogged valve core. You can check and adjust the spring strength, use hydraulic oil with appropriate viscosity, or clean the valve core.
How can I prevent the M-SR check valve from sticking?
Answer: The key to preventing sticking is to keep the hydraulic system clean and regularly maintain the valve. Use high-quality hydraulic oil, change the oil periodically, and clean the filters to prevent contaminants from entering the valve. Ensure the valve is well-lubricated to prevent sticking due to friction.
What should I do if the M-SR check valve frequently leaks externally?
Answer: External leakage is typically caused by aging or damaged seals, or by loose connections on the valve body or joints. It is recommended to inspect and replace the seals, ensure the connections are tight, and, if necessary, check for cracks or damage in the valve body and repair or replace it.
How should the M-SR check valve be maintained?
Answer: Regular maintenance includes cleaning the valve body, checking the condition of seals and springs to ensure there is no wear or aging, and periodically replacing the hydraulic oil to keep the system clean. You can also perform periodic tests to ensure the valve’s opening and closing pressures meet design requirements.
conclusion
This translation covers the main functions, working principles, performance indicators, application scenarios, and common issues related to the check valves as described in the document.
