What is a swing check valve?

[freemexy]

A swing type check valve is mounted with a disc that swings on a hinge or shaft. The disc swings off the seat to allow forward flow and when the flow is stopped, the disc swings back onto the seat to block reverse flow. The weight of the disc and the return flow has an impact on the shut-off characteristics of the valve.

Often a lever and weight or a lever and spring are mounted to achieve optimum performance. Swing check valves with lever and weight are appropriate for installations with an increased risk of water hammer at standard velocities. Swing check valves with lever and external spring are suitable for high pressure, insufficient back pressure and high flow velocities.

An important thing to be aware of when installing a swing check valve is, that it is not completely maintenance free since the disc needs to be cleaned once in a while. Furthermore, a lever is often mounted to enable visual check. Therefore, swing check valves are often installed where personnel is present.

AVK swing check valves are designed with focus on easy access to maintenance. By unscrewing a few bolts the bonnet assembly including hinge and disc can be removed from the body, and maintenance can be performed.

The light-weight disc of EPDM rubber with lip sealing and steel insert requires a minimum of force to open and close the valve. The disc is mounted in a nylon bushing, which allows it to move slightly both horisontally and vertically to close completely tight also in case of minor impurities in the seat. The seat is placed in a 20° angle providing tightness even at low backpressure. The hinge is made of acid-resistant stainless steel and is firmly tightened around the shaft with bolts to eliminate play and thus to ensure durability. Where limited space is available, the hinge can be placed in reverse position.

When mounted with lever and weight, the swing check valves in small dimensions offer the possibility of priming by moving the lever manually. The weight is adjustable on the lever to achieve a soft closing against the seat as well as an optimum closing speed to prevent water hammer. A guard covering the lever and weight is available as an extra safety, as it eliminates the risk of injuries. The guard is available with limit switches for remote monitoring.