The general design of check valves is made to keep fluids movement in one direction through a pipeline. The check valves come with a clapper that’s attached to a hinge and a clapper shift or pint that’s installed to the bottom of the bonnet within the body of the valve.
The clapper is rising and allows fluid to flow through the system in one direction. This causes the valve to open. If fluid pressure decreases or flow begins to reverse, the flapper is triggered to close to help maintain directional flow.
The degree at which the check valve will open depends on the flow rate of the system, or the quantity of fluid passing through. Increasing the flow of the fluid traveling through the pipeline, the check valve gets more opened. Usually, the full open position of a check valve is about 85 degrees depending on the type you’re using.