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Small improvements, big impact—optimising butterfly valve connecting bolts

Release time:

Sep 22,2025

Butterfly valves, as components of piping system pass and flow control, have been widely used in many fields such as petroleum, chemical, metallurgy and hydropower. Commonly used butterfly valves generally use soft seal structure, through the retainer ring  fixes the sealing ringin on the valve seat or disc . This structure of the butterfly valve, the retainer ring fitting screws in the valve flow path in direct contact with the fluid medium, by the fluid movement and pipeline vibration and other impacts, after a period of time may lead to screw off, seal failure, affecting the operation of the equipment safety.

Improvement of The Connection Structure of Butterfly Valve's Disc and Sealing Ring's Retainer Ring

    1. Overview

    Butterfly valves, as components of piping system pass and flow control, have been widely used in many fields such as petroleum, chemical, metallurgy and hydropower. Commonly used butterfly valves generally use soft seal structure, through the retainer ring  fixes the sealing ringin on the valve seat or disc . This structure of the butterfly valve, the retainer ring fitting screws in the valve flow path in direct contact with the fluid medium, by the fluid movement and pipeline vibration and other impacts, after a period of time may lead to screw off, seal failure, affecting the operation of the equipment safety.

    2. Analyses

   In order to prevent loosening of the fitting screws of the valve sealing ring retainer ring and the butterfly plate, the retainer ring is equipped with a set screw for anti-loosening. According to the design requirements, after the fitting screws have finished connecting the retainer ring, tighten the set screws to achieve the anti-loosening of the fitting screws. The connection form has a simple structure and is easy to assemble, but it is difficult to ensure that the fitting screw of retainer ring and set screw do not fall off when the piping system is used for a long period of time. When the tightening torque is small, the fitting screw is easily affected by vibration and falls off. When the tightening torque is large, it is easy to cause screw damage.

    3. Improvements

   (1) To prevent the fitting screw from loosening and falling off, the set screw is replaced with a stop screw and a slot is added at the bottom of the screw. The stop screw is mounted on the retainer ring and does not need to be removed during operation.

   (2) In order to prevent the fitting screw from falling off, a stop washer is added to the bottom of the fitting screw, and the screw is fixed with four claws on the washer, and the screw cannot be rotated, so as to realise anti-loosening. When valve maintenance requires removal of the fitting screws, simply separate the four claws of the lockwashers to operate. The head of the improved stop screw is mounted in the middle of the butterfly disc and the retainer ring to avoid loosening and dislodging of the screw. The fitting screws are protected from loosening and dislodging by the tension provided by the locking screws and by the restriction of the stop washers.

    4. Test verification

   Screw anti-loosening test was carried out after improving the connection structure of butterfly disc sealing ring. The test results showed that the pre-revised structure was correct in terms of design principle, but could not avoid the risk of screw dislodgement caused by insufficient tightening torque of the anti-loosening screw. Relying on the protective effect of the thread locking sealant can prevent the screw from loosening and falling off, but due to the structure of the screw is in direct contact with the fluid medium, the use of screw locking sealant can not play a long-term protection effect. After improvement, relying on mechanical anti-loosening method can effectively avoid screw loosening and falling off.

    5. Conclusion

    After the improved of butterfly disc sealing structure , the connection of the retainer ring  screw is reliable, reasonable structure, service life improved to meet the needs of the working conditions, received good results.

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