Check valves prevent reverse flow of fluids and gases within a pipeline system. They are designed to allow fluid to flow one way through the pipeline. Due to the simple design, check valves generally operate without automation or human interaction and instead rely on the flow velocity of the fluid to open and close. How do they work? Check valves are flow sensitive and rely on the line fluid to open and close. The internal disc allows flow to pass forward, which opens the valve. The disc begins closing the valve as forward flow decreases or is reversed, depends on the design. Construction is normally simple with only a few components such as the body, seat, disc and cover. Check Valve types There are several types of check valves for just about any application. Some of the more popular types include:● Ball● Dual plate ● Double door● Spring assisted inline● Nozzle● Piston or lift ● swing checks As with other types of valves, speciality check valves can be found for special applications.Check valves are found in just about any type of facility from industrial plants and homes.