Check Valves

Check valves, also known as Non-Return valves or NRV, are designed so that pipe or tube medium is able to run freely in one direction only. The pressure of the fluid passing through the line opens the valve, while any reversal of flow will close the valve immediately.

There are several types of Check valve, the most common of which is the swing type. A basic swing type Check valve consists of a body, a bonnet, a disk that is connected to a hinge, and a seat of either metal or elastomer. When there is flow in the line, the disk is pushed away from the seat and the hinge opens, thus opening the valve. When there is no flow, the hinge closes and the disk seals against the seat. Swing Check valves are used only in the horizontal position.

In Tilting Disk design, a spring-loaded, dome-shaped disc floats in the valve port, with medium flowing over both the bottom and top of the disk surfaces. When forward flow pressure reduces, the spring force quickly closes the valve. Designed to overcome some of the weaknesses of conventional swing type Check valves, the tilting disk enables the valve to open fully and remain steady at lower flow rates, and quickly close when flow stops. Tilting disk Check valves are available in wafer and lug type design.

Lift Check valves have a piston or ball that is used as a disk, which when closed, is perfectly set on the seat with full contact. When flow enters below the seat, pressure raises the piston or ball from the seat, thus opening the valve. When flow stops or reverses, backflow and gravity force the piston or ball downward to set on the seat and close the valve. Lift Check valves are best used in horizontal or vertical lines with upward flow, and are particularly suitable for high-pressure / high-velocity service, providing superior leak-tight characteristics to typical swing Check valves.

Dual Plate Check valves, also known as Wafer Check valves, have a disk split into two halves which fold towards the center line with forward flow, and fold closed with reverse flow. Popular in low-pressure liquid and gas service, these lightweight and compact valves are particularly useful when space and convenience are important.

Stop Check valves are a blend of Lift Check and Globe valves, used as either a traditional Check valve or as an isolation valve. The Stop Check valve can be closed with the help of a stem which is not connected to the valve disc during normal operation, making it possible to use it as a regular Check. The stem, when required, is used to hold the disk against the seat, just like a Globe valve. Stop Check valves are available in wye, angle and tee patterns.

James Duva, Inc. offers a full line of Check Valves, in many material grades, built by manufacturers you trust.