The butterfly check valve is a common type of valve, mainly used to prevent the backflow of media in the pipeline system. Its working principle and design features make it very effective in many applications. The following are the main mechanisms of the butterfly check valve to prevent the backflow of media:
1. Basic structure and core sealing mechanism
The butterfly check valve is mainly composed of valve body, valve disc, valve stem, sealing ring and other components. Its core sealing mechanism is based on the cooperation between the valve disc and the valve seat. The valve seat is usually made of elastic sealing materials such as rubber and fluoroplastics, or metal surfacing hard alloy. The valve disc rotates around a fixed axis in the valve body.
When the medium flows forward, the medium pressure pushes the valve disc to rotate around the axis and open, the valve disc is separated from the valve seat, and the medium passes smoothly. Once the medium stops flowing or flows back, the valve disc quickly rotates and fits tightly to the valve seat under the action of gravity, medium reverse pressure and possible spring auxiliary force.
2. Dynamic closing process based on fluid mechanics
Forward flow stage: The dynamic pressure generated by the flow of the medium acts on the surface of the valve disc, forming a torque that opens the valve disc. This torque needs to overcome the friction resistance torque of the valve disc rotation, the resistance torque generated by the spring preload, and the resistance torque generated by the valve disc’s own gravity. When the opening torque generated by the dynamic pressure of the medium is greater than the sum of the above resistance torques, the valve disc opens and the medium passes smoothly.
Closing transition stage: When the medium flow rate decreases, such as when the water pump stops or the system pressure fluctuates, the positive force of the medium on the valve disc decreases, and the direction of the resultant force on the valve disc begins to change. At this time, the valve disc begins to rotate in the closing direction under the combined action of its own gravity, the medium backflow pressure, and the spring force.
Fully closed stage: As the valve disc continues to rotate, it eventually fits tightly with the valve seat.
3. Special structural design enhances anti-backflow performance
Eccentric structure optimization:
Double eccentric design: The valve stem not only deviates from the center of the valve disc, but also deviates from the center line of the pipeline. This structure makes the valve disc completely separate from the valve seat at the moment of opening, further reducing friction; when closed, the valve disc gradually squeezes toward the valve seat to form a good sealing effect, which is especially suitable for high temperature and high pressure conditions.
Auxiliary seal and damping device:
Elastic seal ring: A seal ring made of nitrile rubber (NBR), ethylene propylene rubber (EPDM) and other materials, installed on the valve seat or valve disc. When the valve disc is closed, the seal ring is compressed, filling the tiny gap to form a secondary seal.
Damping device: Some butterfly check valves are equipped with dampers, such as hydraulic dampers, spring dampers, etc. During the closing process of the valve disc, the damper controls the rotation speed of the valve disc to avoid water hammer caused by closing too quickly.
Conclusion
Butterfly check valves achieve efficient and reliable prevention of medium backflow through the synergy of structural design, application of fluid mechanics principles, special structural optimization and other aspects, meeting the needs of different industrial fields and complex working conditions. TWT Valve, as a Chinese non return valve manufacturer and supplier, is committed to producing high-quality check valves, such as high performance butterfly valves. If you have any questions, please feel free to contact us!