Check valve, this is a special type of valve whose main function is to ensure that the medium (e.g. liquid or gas) can only flow in one direction, and as soon as the medium tries to flow in the opposite direction, the check valve stops it. This type of valve usually operates automatically and does not require manual operation.
When the medium flows in the permitted direction, the flap of the return valve opens automatically under fluid pressure, allowing the medium to pass through. And if the medium tries to flow in the opposite direction, then the fluid pressure and the weight of the valve flap itself will work together to make the valve flap tightly pressed on the valve seat, thus effectively cutting off the flow.
Back valve is mainly divided into two types: swing back valve and lift back valve.
Swing-back valves are designed like a door, with a hinge mechanism that allows the valve flap to rest freely against the sloping seat surface. To ensure that the valve flap closes accurately, the valve flap is designed to rotate enough so that it makes full contact with the seat. The valve flap can be made of metal, or leather, rubber or other synthetic materials can be added to the metal to improve sealing performance. When a swing back valve is fully open, there is little or no obstruction to fluid pressure, so the pressure drop through the valve is relatively small.
The flap of a lift-back valve, on the other hand, acts like a piston that sits on the seat sealing surface of the valve body. Except for the fact that the valve flap can be raised and lowered freely, the rest of the lift-back valve is very similar to a globe valve. As the medium flows, fluid pressure causes the valve flap to lift off the seat; if the medium tries to flow back, the flap falls back onto the seat, cutting off the flow. The valve flap can be made of metal, or a rubber gasket or ring can be added to the valve frame to improve sealing. However, because of the relatively narrow passageway of a lift-back valve, the pressure drop through it will be somewhat greater than that of a swing-back valve.
There are some common problems that may be encountered when using a return valve, such as a broken valve flap or backflow of media.
Flap breakage is usually caused by the media pressure before and after the return valve being in near equilibrium, causing the flap to slap against the valve seat frequently. If the valve flap is made of brittle materials (such as cast iron, brass, etc.), it is easy to be broken. In order to avoid this problem, you can choose to use a tough material made of valve flap.
Backflow of media may be due to damage to the sealing surface or entrapment of impurities. To solve this problem, you need to repair the sealing surface and clean out the impurities.
Hopefully this article will help you better understand how return valves work and how to solve common problems.