Check valves also known as dual plate check valves are mechanical valves that permit gases and liquids to flow in only one direction, preventing process flow reversing.They are classified as one-way directional valves. Fluid flow in the desired direction opens the valve, while back flow forces the valve closed. The mechanics of check valve operation are not complicated.

A check valve allows fluid to flow through it in only one direction. Check valves are two-port valves,meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave.There are various types of check valves used in a wide variety of applications. Check valves work automatically and most don't need control by people or any external control.