Check valve, also called as clack valve, non-return valve or one-way valve is a valve normally allows media (liquid or gas) to flow through it in only one direction. Check valve is two-port valve, which means that there are two openings in the body of check valve, one for media to enter and the other for media to leave. There are various types of check valve used in a wide variety of applications. Accordingly, most of check valves do not have any valve handle or stem. Plastic or metal can be used for bodies (external shells) of the check valve. Typically, check valve is designed for and can therefore be specified for a specific cracking pressure.
Based on structure, check valve is classified into lift check valve, swing check valve and butterfly check valve.
Based on materials, check valve is classified into cast iron check valve, brass check valve, stainless steel check valve, carbon steel check valve and forged steel check valve.
Based on connection, check valve is classified into threaded check valve, flanged check valve and welded check valve.