Check valves are flow monitoring device used in pipelines to prevent the backflow and ensuring the fluid flow in single direction.
Check Valve works on the principle of differential pressure. It means the check valve will only open if the upstream pressure is more than the downstream pressure. Moreover, if downstream pressure is more, the valve will close preventing back-flow. Closure can also be accomplished by the weight of the check mechanism, by a spring, or by a combination of all these means.
There are various types of check valves according to construction for e.g. swing check , dual plate check , ball check , diaphragm check , lift check , foot check etc. Dual plate check valve employs 2 springs loaded hinged on a central hinge pin. Dual plate check valves are designed according to API 594 & 6D, API 598 confirms the adequate testing requirements.
Axial flow check valves are specially designed to eliminate the water hammer effect; these valves consist of a centre guided stem-disc assembly along with a compression spring. This means the disc stays in the flow stream and the media flows around it and doesn’t require manual or automated assistance to operate. Design standard followed is according ASME B 16.34& API 6D. API 598& API 6D covers the testing parameters.