Installed where air is to flow in only one direction. Typically, from the pump to the tank. Valve closes when pump stops preventing air to flow from tank back to pump. This pre vents damage to pump valves and maintains air pressure in tank.
A valve that permits flow of liquid through a hose or pipe in one direction but prevents a return flow. Uses include the prevention of backflow on uphill hose lays, loss of prime with centrifugal pumps and chemical contamination in fire chemical mixing systems.
A one-way (nonreturn) valve whereby fluids pass in one direction only; the valve closes when the pressure causing flow stops or back pressure closes the valve, See also ball valve; gate valve; nonrising-stem valve; plug valve; pressure-control valve; pressure-reducing valve pressure-regulating valve; rising-stem valve, thermal-relief valve.
A two-way directional valve that allows free flow in one direction and blocks flow in the other direction. Check valves can act as either directional or pressure control apparatuses. ( http://www.check-valves.net)
A check valve is a mechanical device, a valve, that normally allows fluid (liquid or gas) 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.