Check valve refers to the opening and closing member for the circular valve and by its own weight and media pressure to produce action to block the backflow of the medium of a valve. It belongs to the automatic valve category, also known as a check valve, backflow valve, or isolation valve.
What are the common types of check valves?
Lift check valve
It has a large fluid resistance. The valve flap slides along the vertical centerline of the valve body. When the media flow, the valve flap by the media thrust to open, when the media stop flowing, the valve flap by the self-hanging landing on the valve seat.
1、Vertical lift type check valve. Its media import and export channel direction and the seat channel direction are the same, its flow resistance is smaller than the straight-through type. A vertical lift check valve is installed in the vertical pipeline.
2, a straight-through lift check valve can only be installed in the horizontal pipeline. Restricted by the installation requirements, commonly used in small diameter occasions DN <50.
Swing check valve
Swing check valve flap is disc-shaped, rotating movement around the axis of the valve seat channel, because the valve channel is streamlined, the flow resistance of the lift check valve is small, suitable for small diameter, low-pressure large diameter pipeline (low flow rate and flow do not often change the large diameter occasions). Sealing performance is not as lift type.
1, the swing check valve is divided into single-valve type, double-valve type, and more than half of type three, these three forms are mainly divided by the valve caliber, the purpose is to prevent the media to stop flowing or backflow, weakening the hydraulic impact. The single-valve swing check valve is generally suitable for medium-caliber occasions.
Large diameter pipeline selection of single swing check valve, in order to reduce water hammer pressure, it is best to use the water hammer pressure can reduce the slow-closing check valve. The double-valve swing check valve is suitable for large and medium-diameter pipelines. Clamp double swing check valve structure is small, lightweight, and is faster development of check valve; multi-flap swing check valve for large diameter pipeline.
2, swing check valve installation location is not limited, it can be installed in the horizontal, vertical, or inclined pipeline.
Three, butterfly check valve: straight through. The structure of the butterfly check valve is similar to the butterfly valve. Its structure is simple, the flow resistance is smaller, and the water hammer pressure is also smaller. The valve flap rotates around the pin inside the valve seat check valve. Disc check valve structure is simple, can only be installed in the horizontal pipeline, and the seal is poor.
Diaphragm check valve:
There are a variety of structural forms, all using the diaphragm as the opening and closing parts, due to its good waterproof hammer performance, simple structure, and low cost, in recent years developed faster. But the diaphragm check valve temperature and pressure by the diaphragm material restrictions.
The diaphragm check valve is suitable for easy-to-produce water strikes on the pipeline, the diaphragm can well eliminate the water strikes generated by the media backflow, it is generally used in low-pressure room temperature pipelines, especially for water pipelines, the general medium working temperature between -12 – 120 ℃, working pressure <1.6MPa, but the diaphragm check valve can be larger diameter, DN can reach a maximum of 2000mm or more.