Check valves are simple devices that allow fluid media (gas, liquid or solids such as sand or slurry) to flow only one way. Typical check valve installations are found in industrial plants, automobiles, plumbing and ventilation systems. Usually, check valve are relatively inexpensive, compared to more accurate control valves. For a given application, the valve body must be able to contain the media and pressure, and the gate action must have a durable service life. Installing check valves is a matter of determining the correct flow direction for the media and ensuring proper fittings for the inlet and outlet port.
Installing the correct check valve for a particular process means knowing the media the valve will control. Caustic or abrasive media (lime slurries, acids, cement mixes, etc.) require a check valve resistant to severe corrosion; stainless steel or ceramic check valves work well for such applications. A check valve installed to control hot water flow in a plumbing installation can be made from PVC plastic, brass or steel. As long as the valve can handle the heat and pressure of a standard water line, it will work well.
Installing a check valve is similar in procedure to installing any other valve with one important distinction: direction. The valve must be installed in the media’s flow direction--nothing can move against a closed check valve gate. Check valve manufacturers include on the valve body an arrow indicating proper flow direction.
Incoming and outgoing lines can be connected using clamps, swage fittings (fittings using a collar around the line, with the fitting and the valve stem hydraulically compressed together) or threaded fittings.
Check valves work automatically to eliminate back flow in a process line. There's no need for manual operation--the valve can be installed in relatively inaccessible locations. Although other valve installations may require clearance for actuators, access to a manual valve shut off or other features, check valves require little maintenance.
If installed as a diversion valve to relieve excess pressure or heat, the check valve gate can be adjusted to respond to specific pressure settings. For example, a check valve can prevent a steam boiler from building up too much pressure or a car’s radiator from rupturing when the coolant fails: the check valve will divert the high pressure media away from the process and avoid catastrophic failure. When pressure and heat amounts remain within operating limits, the check valve will stay closed.