Introduction to common types of check valves

The swing check valve is the most commonly used. It operates with a disc which swings on a hinge or a shaft. As inlet pressure increases, the disc swings off the valve seat and fluid is allowed to flow through the valve, and as inlet pressure decreases or there is backflow, the disc swings back to the seat to restrict the fluid flow.

This check valve offers minimal restriction to flow when open. When springs are not used to assist the valve in closing, the valves should be mounted to allow the disc to shut with gravity.

Dual plate check valves (butterfly check valve) are commonly used in industrial operations and refineries. They are compactly built and can handle huge fluid backflow that other weaker types of check valves will not handle.

These check valves have double metal plates and are lightweight, making them easy for installation, transport and storage. They are mostly designed as non-slam types and usually result in low fluid pressure losses.

The ball check valves use a spherically shaped ball to seal the valve. The ball is moved by a spring or acted upon by gravity. When the inlet pressure increases, the ball is pushed by the pressure away from the curved seat to allow the flow of fluid through the valve.

As the inlet pressure decreases or there is backflow, the disc shuts off the valve due to spring force or gravity.

Rubber Flapper Swing Check Valves feature a unique, simple design with only one moving part. The flapper does not swing from a hinge pin; it simply flexes open. The seat is on a 45° angle. The flapper travels 35° from open to closed, usually before column reversal can occur. It has non-slam characteristics. The valve requires no regular maintenance. Recommended for water, sewage, gas, oil and rubber lined for chemicals.