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The working principle and classification of check valve

Release time:

Jun 21,2024

Check valve is a kind of valve used to control the flow of media, it has the important role of preventing the backflow of media and protecting the safety of equipment. Its working principle is to rely on the medium itself pressure and spool weight to achieve the opening and closing state, when the medium flows into the valve in the specified direction, the flow pressure over the opening pressure of the check valve, the disc will be pushed open under the action of the fluid pressure, the media is smoothly flowing。

Check valve is a kind of valve used to control the flow of media, it has the important role of preventing the backflow of media and protecting the safety of equipment. Its working principle is to rely on the medium itself pressure and spool weight to achieve the opening and closing state, when the medium flows into the valve in the specified direction, the flow pressure over the opening pressure of the check valve, the disc will be pushed open under the action of the fluid pressure, the media is smoothly flowing， Conversely, when the pipeline medium backflow, the valve will be pushed to the sealing seat under the fluid pressure, the valve is closed, meanwhile it cuts off the flow of media in the pipeline.

According to the different structure, check valve can be roughly divided into four kinds: lift check valve, swing check valve, butterfly check valve and diaphragm check valve:

1, lift check valve: it is the check valve that its disc does lifting movement along the center line of the valve seat, compared with other types of check valves, lift check valve's stroke is the shortest, and thus lift check valve may be a fast closed valve. However, if dirt enters the disc's motion guiding mechanism, the disc may be jammed or close too slowly. In addition, if used with viscous media, the movement of the disc in its guides may be slowed.

Silent check valve is also a kind of lift check valve.

2、Swing check valve: the valve disc is disc-shaped and the valve disc rotates around a fixed shaft outside the seat channel. Swing check valve consists of the valve body, valve cover, valve disc and valve stem; valve channel is streamlined, it has small fluid resistance. the check valve sealing ring is formed with flexible graphite packing or stainless steel under the high-temperature and high-pressure, it is through the media pressure to press the seal to achieve sealing, so the higher the media pressure the better the sealing is.

3, butterfly check valve: the shape is similar to the butterfly valve, its seat is tilted, the valve shaft is installed horizontally, and is located in the valve channel center line above, so that the lower part of the disc area under the shaft is larger than the upper part. When the medium stops flowing or backflow, the butterfly plate rotates to the valve seat by its own weight and the action of backflow medium. The structure of this check valve is simple, but the sealing is poor. Butterfly check valve is usually used for the occasion that swing check valve cannot meet the requirements.

4、Diaphragm check valve: there are a variety of structural forms, they are using the diaphragm as the opening and closing parts, due to its water hammer performance, simple structure, low cost, the diaphragm check valve develops very fast in recent years, but the using temperature and pressure the diaphragm check valve are limited by the diaphragm material. Diaphragm check valve is suitable for easy to produce water hammer pipe, the diaphragm can be very good to eliminate the water hammer When the medium flows backwards, it is generally used in low-temperature and normal temperature pipeline, especially suitable for water pipeline. The maximum caliber can reach above DN2000mm.

The above types of check valves in the form of connection can be divided into threaded connection, flange connection, welded connection and clamped connection. A description of the valve connections can be found in    https://www.successmach.com/news_details/18.html

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