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From industrial gas lines to household appliances, from wastewater treatment to pharmaceutical processing, from fuel pumps to air compressors, the functionality of check valves remains diverse, running the gamut through a myriad of liquid, gas, and slurry applications. Though check valves appear in a variety of forms, the fundamental premise of these units remains similar: a typically self-operated device that opens to allow flow in one direction but closes to prevent or limit flow in the reverse direction. Initial cost, basic familiarity, required maintenance, piping orientation, and process media all prove factors that can influence the selection of a particular style of the check valve. source:  yuandavalves.com Swing Check Valves The conventional swing check valve serves as one of the more widely recognized check valve varieties. This arrangement incorporates a circular disc whose face rests perpendicular to the flow path when in the closed position. The hinge at the top of the dis

Check valves are simple valves. They use forward flow to open the valve, then automatically close when flow stops, preventing reverse flow from making its way back through the valve. They don’t require power to function, and they don’t require a whole lot of attention or maintenance. They do get a lot of attention, however, when they slam. What causes the slam? A check valve relies on gravity and/or reverse flow to close completely. Opportunity for check valves to slam frequently occurs at pump shutdown. When a pump stops, gravity and reverse flow slam the check valve shut. Because fluid is non-compressible, it creates a pressure or shock wave (water hammer). The fluid continues to flow back and forth until friction losses cause the wave to settle. Slamming check valves cause serious pressure surges in a system that rattle pipes and damage equipment. Some people assume that’s just what check valves do. "No matter what, they’re going to slam." But that’s just not the case. Us