Check valve

A check valve, or non-return valve, prevents reverse flow by ensuring that fluid can only flow in one direction along a pipeline. It can be installed, for example, in the discharge lines of pumps operating in parallel (see Parallel operation) (where at least one pump is not running) to prevent both reverse flow of fluid handled and the resulting turbine mode operation (see Reverse runaway speed).

While check valves can basically be used in any installation position, gravity-dependent designs need to be installed taking into account the effect of gravity.

Examples of check valves are lift check valves, swing check valves and diaphragm check valves (see also Valve).

Swing check valves are mainly used for medium and large nominal diameters while lift check valves are often installed in smaller diameter pipes.