1. Overview of Check Valve

Check valve, this type of valve, its core function is to allow the medium to flow only in one direction while preventing its reverse flow. This type of valve usually has the characteristic of automatic operation. When pressure is applied to the fluid in one direction, the valve disc will open to allow flow; When the fluid attempts to flow in the opposite direction, the fluid pressure and the self weight of the valve disc will work together, causing the valve disc to tightly adhere to the valve seat, thereby completely cutting off the flow.

◇ Working principle

A check valve only allows one-way flow of the medium, and its valve disc opens when flowing downstream and tightly fits the valve seat to cut off flow when flowing upstream.

◇ Swing check valve

Swing check valve is one of the common types of check valves, characterized by a hinge mechanism and a valve disc resembling a gate. This design ensures that the valve disc can freely rest on the inclined valve seat surface and has sufficient swing space to achieve comprehensive valve seat contact. In addition, the material selection of the valve disc is flexible, and metal, leather, rubber or synthetic materials can be selected according to the performance requirements. In the fully open state, the fluid pressure of the swing check valve is almost unobstructed, so the pressure drop through the valve is relatively small.

◇ Lift check valve

Another common type of check valve is the lift check valve. Its characteristic is that the valve disc is directly seated on the sealing surface of the valve seat on the valve body. When fluid pressure acts on the valve disc, it will lift off the sealing surface of the valve seat; When the medium flows back, the valve disc will automatically fall back onto the valve seat, cutting off the flow. Similarly, the material selection for the valve disc of the lift check valve also has diversity, which can be a fully metal structure or a form of embedding rubber pads or rubber rings on the valve disc frame. It should be noted that although the flow restriction of the lift check valve is relatively small, the pressure drop through the valve is relatively large.

2. Common faults and solutions

Next, we will explore common faults that may occur during the use of check valves and corresponding solutions. The handling of these faults is crucial for ensuring the stable operation of the check valve.

◇ Valve disc damage

The reason for valve disc damage is usually due to the approximately balanced and constantly changing pressure of the medium before and after the check valve, resulting in frequent collisions between the valve disc and the valve seat. Especially for valve discs made of brittle materials such as cast iron, brass, etc., they are more prone to damage in this environment. To prevent this situation, it is recommended to use check valves with resilient valve discs.

◇ Reverse flow of medium

The reasons for medium backflow may involve multiple aspects, including but not limited to the following:

① Damaged sealing surface; ② Impurities are trapped. By repairing the sealing surface and removing impurities, it is possible to effectively prevent the backflow of the medium.