Check Valve

1 Typical Usage
Check valves are used to block the pipe flow in one direction while permitting flow in the other direction. A typical application of a check valve is at the discharge of a pump. If the pump is idle on stand-by the check valve prevents reverse flow though this pump; the moment the pump start the flow can lift the check valve and go in the downstream direction. 

2 Primary Function

The primary function of a check valve is to prevent flow reversal. Check valves pass fluid freely in one direction and, if pressure reverses, close to stop flow in the other direction. Therefore, the principal force on the check valve is a water or steam hammer transient load.

3 Application Objectives

The major engineering concern in design and selection of check valves is to achieve, at normal flow condition, a low pressure drop across the valve, a reasonable wear rate on the valve element, and a stable operating mode. The design and selection of the check valve should also include the attainment of an acceptably low transient load and a tolerable leakage rate during and after valve closure.