Check valves are probably the most misunderstood valves ever invented. If you mention check valves to most plant personnel, the typical response is “they don’t work.” In fact, those personnel may well have taken out the internals or re-piped the system to avoid check valves. In other words, these valves are the least popular valve in use today.
Simply put, a check valve allows flow in one direction and automatically prevents back flow (reverse flow) when fluid in the line reverses direction. They are one of the few self-automated valves that do not require assistance to open and close. Unlike other valves, they continue to work even if the plant facility loses air, electricity, or the human being that might manually cycle them.
Check valves are found everywhere, including the home. If you have a sump pump in the basement, a check valve is probably in the discharge line of the pump. Outside the home, they are found in virtually every industry where a pump is located.
Like other valves, check valves are used with a variety of media: liquids, air, other gases, steam, condensate, and in some cases, liquids with fines or slurries. Applications include pump and compressor discharge, header lines, vacuum breakers, steam lines, condensate lines, chemical feed pumps, cooling towers, loading racks, nitrogen purge lines, boilers, HVAC systems, utilities, pressure pumps, sump pumps, wash-down stations, and injection lines.
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