Butterfly valve technical knowledge

Butterfly valve (butterflyvalve) refers to the closure (disc or butterfly plate) for the disc, around the valve shaft rotation to achieve the opening and closing of a valve, the main cut and throat in the pipeline. Butterfly valve opening and closing parts is a disc-shaped disc, in the valve body around its own axis of rotation, so as to achieve the purpose of opening or closing or adjustment. Butterfly valve fully open to the whole is usually less than 90 °, butterfly valve and butterfly rod itself does not have self-locking ability, in order to butterfly plate positioning, to install the worm on the stem reducer. The use of worm reducer, not only can make the disc with self-locking ability, so that the butterfly plate to stop at any position, but also improve the valve operating performance.

The characteristics of industrial butterfly valve can be high temperature, suitable pressure range is also high, the valve nominal diameter, the valve body made of carbon steel, valve plate sealing ring with metal ring instead of rubber ring. Large-scale high-temperature butterfly valve made of steel welding, mainly used for high-temperature media, smoke duct and gas pipeline.

The knowledge of butterfly valve in the course of application

In the 1930s, the United States invented the butterfly valve, introduced into Japan in the 1950s, and was widely adopted in Japan in the 1960s, and it was after the 1970s. At present the world generally more than DN300 mm butterfly valve has gradually replaced the gate valve. Butterfly valve and gate valve compared to open and close time is short, the operation is small, small installation space and light weight. To DN1000, for example, butterfly valve about 2T, while the gate valve is about 3.5T, and the butterfly valve with a variety of drive devices, with good durability and reliability.

Rubber seal butterfly valve is used for throttling, due to improper use will produce cavitation, so that rubber peeling off, damage and so on. In recent years, China has also developed a metal seal butterfly valve, in recent years, Japan has also developed anti-cavitation, low vibration, low noise comb teeth butterfly valve. In recent years, China has also developed a metal seal butterfly valve.

General seal seat life under normal circumstances, rubber 15 years - 20 years, metal 80 years - 90 years. But how to choose the right will be based on work conditions.

The relationship between the opening degree of the butterfly valve and the flow rate is basically linearly proportional. If used to control the flow, the flow characteristics and piping flow resistance is also closely related, such as the two pipe installation valve caliber, form the same, and the pipeline loss coefficient is different, the valve flow difference will be great.

If the valve is in a larger state of throttle, the back of the valve plate prone to cavitation, the possibility of damage to the valve, are generally used in 15 ° outside.

When the butterfly valve is in the opening degree, the opening shape of the valve body and the front end of the butterfly plate is centered on the valve shaft, and the two sides are formed in different states. The front side of the butterfly plate is moving in the direction of the downstream water, Therefore, the side of the valve body and the valve plate to form a nozzle-like opening, the other side of the throttle-like openings, the nozzle side than the throttling side of the flow rate faster, and throttle side of the valve will produce negative pressure, often There will be rubber seal off.

Butterfly valve operating torque, due to opening and valve opening and closing direction of different values vary, horizontal butterfly valve, especially large diameter valve, due to water depth, the valve shaft, the head of the difference between the torque can not be ignored. In addition, the valve inlet side of the elbow device, the formation of bias, the torque will increase. When the valve is in the middle opening, the operating mechanism needs to be self-locking due to the working torque of the water.

Valve model preparation method, valve number description

Valve type should usually indicate the valve type, drive mode, connection form, structural characteristics, nominal pressure, sealing surface material, body material and other elements. Valve model of the standardization of the valve design, selection, distribution, provides a convenient. Today, the type of valve and the type of material more and more, the valve model is also more and more complex. Although China has a unified model of the valve model, but gradually can not meet the needs of the development of the valve industry. At present, the valve manufacturers generally use a unified numbering method; can not use a unified number method, the production plant according to their own situation to develop a number method.