To allow media flow in one direction, check valves are used. They need one inlet and one outlet, and that they ought to be utilized in the right orientation for correct practicality. Since they solely enable flow in one direction, they're additionally known as “non-return” or ‘one-way” valves.
Since they solely enable flow in one direction, they forestall flow by either utilizing a spring or back-pressure to shut the valve, therefore, they are doing not need a user. they're usually employed in applications that can’t have flow because of the chance of flow damaging instrumentality or if it'd contaminate the media upstream.
Check valves require a pressure differential to function properly. Flow moves from high pressure to low pressure. Therefore, if the high pressure is on the inlet side of the check valve it will move through the check valve properly.
The pressure differential needs to be high enough to open the valve, which is called the “cracking pressure”. This pressure is specific to the check valve size and design. When the inlet pressure is no longer higher than the outlet pressure (back pressure) or the cracking pressure, then the valve closes.
Depending on the valve design, different methods are used to close the orifice from utilizing springs, conical shape with a ball, or simply utilizing the back-flow pressure. The orientation for installation is crucial due to them being one-way valves. Typically, there is an arrow to show the proper flow orientation.