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What Is Butterfly Valve and Its Characteristics?

Butterfly valve, also known as flap valve, is a regulating valve with simple structure. Butterfly valves can be used for switch control of low-pressure pipeline media. The butterfly valve uses the disc or butterfly plate as a disc, which rotates around the valve shaft to open and close.

Butterfly valves can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. It mainly plays the role of cutting and throttling on the pipeline. The opening and closing part of the butterfly valve is a disc-shaped butterfly plate that rotates around its own axis in the valve body to achieve the purpose of opening and closing or adjustment.

The main features of the butterfly valve are: small operating torque, small installation space and light weight. Taking DN1000 as an example, the butterfly valve is about 2 T, while the gate valve is about 3.5 T, and the butterfly valve is easy to combine with various driving devices, and has good durability and reliability. The disadvantage of the rubber-sealed butterfly valve is that when it is used for throttling, cavitation will occur due to improper use, which will cause peeling and damage of the rubber seat, so how to choose it correctly depends on the requirements of the working conditions. The relationship between the opening of the butterfly valve and the flow rate basically changes linearly. If it is used to control the flow, its flow characteristics are also closely related to the flow resistance of the piping. For example, if two pipes are installed with the same valve diameter and form, but the loss coefficient of the pipes is different, the flow rate of the valves will also vary greatly. If the valve is in a state of large throttling, cavitation is prone to occur on the back of the valve plate, which may damage the valve. Generally, it is used outside 15°. When the butterfly valve is in the middle opening, the opening shape formed by the valve body and the front end of the butterfly plate is centered on the valve shaft, and the two sides form different states. The front end of the butterfly plate on one side moves along the direction of flowing water, and the other side moves against the direction of flowing water. Therefore, one side of the valve body and the valve plate form a nozzle-shaped opening, and the other side is similar to a throttle-shaped opening. The flow velocity on the nozzle side is much faster than that on the throttle side, and negative pressure will be generated under the valve on the throttle side, often The rubber seal will come off. The operating torque of the butterfly valve varies with the opening and the opening and closing direction of the valve. For horizontal butterfly valves, especially large-diameter valves, due to the water depth, the torque generated by the difference between the upper and lower heads of the valve shaft cannot be ignored. In addition, when an elbow is installed on the inlet side of the valve, a bias flow is formed and the torque will increase. When the valve is in the middle opening, the operating mechanism needs to be self-locking due to the action of the water flow torque.

Butterfly valve is a kind of valve which uses disc type opening and closing parts to turn back and forth about 90° to open, close or adjust the flow of medium. Butterfly valve not only has simple structure, small size, light weight, low material consumption, small installation size, small driving torque, easy and fast operation, but also has good flow regulation function and closing and sealing characteristics at the same time. One of the fastest valve varieties. Butterfly valves are widely used. The variety and quantity of its use are still expanding, and it is developing towards high temperature, high pressure, large diameter, high sealing, long life, excellent adjustment characteristics, and multi-function of a valve. Its reliability and other performance indicators have reached a high level.

The butterfly valve is usually less than 90° from fully open to fully closed. The butterfly valve and butterfly rod have no self-locking ability. In order to position the butterfly plate, a worm gear reducer should be installed on the valve rod. The use of the worm gear reducer not only enables the butterfly plate to have self-locking ability, makes the butterfly plate stop at any position, but also improves the operating performance of the valve. The characteristics of the industrial special butterfly valve: high temperature resistance, high applicable pressure range, large nominal diameter of the valve, the valve body is made of carbon steel, and the sealing ring of the valve plate is made of a metal ring instead of a rubber ring. Large-scale high-temperature butterfly valves are manufactured by welding steel plates and are mainly used for flue gas ducts and gas pipelines for high-temperature media.


Post time: Aug-09-2023