A swing check valve is a device that allows fluid to flow in one direction and prevents it from flowing in the opposite direction. Swing check valves are typically used as part of plumbing systems, but they can also be used as part of industrial processes, such as oil refining, chemical processing and others.
A swing check valve consists of a disc with two ports — an inlet port and an outlet port — connected to pipes or tubes. A spring attaches the disc to a movable arm, which connects it to a frame or other support structure. When fluid flows through the inlet port, the disc flips open so that it’s facing away from the flow. This allows fluid to pass through the valve unimpeded by any obstructions. As soon as pressure drops on one side of the check valve because there’s not enough fluid flowing through it, however, gravity pulls down on the disc so that it swings back around into its closed position again. This prevents any more fluid from passing through the valve until pressure builds up again on that side of it again.