Common check valve types！
A check valve is a valve whose opening and closing member is a circular disc and acts on its own weight and medium pressure to block the backflow of the medium. It is an automatic valve, also known as a check valve, check valve, return valve or isolation valve. There are several common check valves.
一、lifting check valve: vertical and horizontal. The shape of the body of the lift check valve is the same as that of the stop valve, so its fluid resistance is large. The valve disc slides along the vertical centerline of the valve body. When the medium flows downstream, the valve flap is opened by the thrust of the medium. When the medium stops flowing, the valve flap falls on the valve seat by hanging.
1. Vertical lift check valve. The direction of the medium inlet and outlet channels is the same as that of the valve seat channels, and its flow resistance is smaller than that of the straight-through type. Vertical lift check valve is installed in vertical pipeline.
2. Straight-through lifting check valve can only be installed in horizontal pipelines. Limited by installation requirements, commonly used in small diameter occasions DN <50.
二、Swing check valve: The disc of the swing check valve is disc-shaped and rotates around the rotation axis of the valve seat channel. Because the channel inside the valve is streamlined, the flow resistance is higher than that of the lift check valve. Small, suitable for small and medium caliber, low pressure large caliber pipes (large caliber occasions with low flow rate and infrequently changing flow). The sealing performance is not as good as the lifting type.
1. There are three types of swing check valves: single, double and multiple. These three types are mainly divided by the valve diameter. The purpose is to prevent the hydraulic shock when the medium stops flowing or flows backward. Single flap swing check valve is generally suitable for medium-caliber applications. When large-diameter pipelines use single-lobe swing check valves, in order to reduce water hammer pressure, it is best to use slow-closing check valves that reduce water hammer pressure. Double flap swing check valve is suitable for large and medium diameter pipelines. Wafer double flap swing check valve has a small structure and light weight, and is a fast-growing check valve. Multi-flap swing check valve is suitable for large diameter pipelines.
2. The installation position of the swing check valve is not limited. It can be installed on horizontal, vertical or inclined pipelines.
三、Butterfly check valve: straight type. The structure of butterfly check valve is similar to butterfly valve. Its structure is simple, flow resistance is small, and water hammer pressure is also small. Non-return valve with valve disc rotating around pin in valve seat. The disc check valve has a simple structure and can only be installed on a horizontal pipe, which has poor sealing performance.
四、Diaphragm check valve: There are many structural forms, all of which use diaphragms as opening and closing parts. Due to their good performance of water hammer, simple structure and low cost, they have developed rapidly in recent years. However, the operating temperature and pressure of the diaphragm check valve are limited by the diaphragm material.
The diaphragm check valve is suitable for pipelines that are prone to water hammer. The diaphragm can well eliminate the water hammer generated when the medium is flowing backward. It is generally used on low pressure and normal temperature pipelines, especially for tap water pipelines. Between -12--120 ℃, the working pressure is less than 1.6MPa, but the diaphragm check valve can achieve a larger diameter, and the maximum DN can reach more than 2000mm;