Operating Principle and Advantages and Disadvantages of Butterfly Valve

The butterfly valve opening and closing piece is a disc-shaped butterfly plate, which rotates around its own axis in the body of the valve, thus achieving the opening and closing or regulating of the valve is called the butterfly valve. Butterfly valves are usually less than 90 degrees open and closed. Butterfly valves and butterfly rods do not have self-locking force. In order to locate the butterfly plate, worm gear reducer should be installed on the valve stem. The use of worm gear reducer can not only make butterfly plate have self-locking ability, make butterfly plate stop at any position, but also improve the operation performance of the valve.

Industrial butterfly valves are characterized by high temperature resistance, high pressure range, large nominal diameter, carbon steel body and metal ring instead of rubber ring. Large high temperature butterfly valve is welded by steel plate, mainly used for flue gas duct and gas pipeline of high temperature medium. Concentric butterfly valve The structural characteristics of this butterfly valve are that the axis of the stem, the center of the butterfly plate and the center of the body are in the same position. The utility model has the advantages of simple structure and convenient manufacture. The common rubber lined butterfly valve belongs to this type.

The disadvantage is that the butterfly plate and valve seat are always in the state of extrusion, scratch, large resistance distance and fast wear and tear. In order to solve the problem of extrusion between butterfly plate and seat of concentric butterfly valve, a single eccentric butterfly valve is produced. Its structural feature is that the axis of the stem deviates from the center of the butterfly plate, so that the lower end of the butterfly plate is no longer the center of rotation, and the excessive extrusion between the lower end of the butterfly plate and the seat is reduced.

Double eccentric butterfly valve is the most widely used double eccentric butterfly valve, which is further improved on the basis of single eccentric butterfly valve. The structure features that the axis of the valve stem deviates from both the center of the butterfly plate and the center of the body. The effect of double eccentricity enables the butterfly plate to detach from the valve seat immediately after the valve is opened, greatly eliminating unnecessary over-extrusion and scratch between the butterfly plate and the valve seat, reducing the opening resistance, reducing wear and tear, and improving the service life of the valve seat. 

Tri-eccentric butterfly valve must be high temperature resistant, must use hard seal, but the leakage is large; to zero leakage, must use soft seal, but not high temperature resistant. In order to overcome the contradiction of double eccentricity butterfly valve, the third eccentricity of butterfly valve was carried out. Butterfly valve is a kind of valve which uses circular butterfly plate as opening and closing parts and rotates with the stem to open, close and adjust the fluid passage.

Butterfly valves not only have simple structure, small volume, light weight, less material consumption, small installation size, small driving moment, simple and rapid operation, but also have good flow regulation function and closing and sealing characteristics. Butterfly valves are the dominant valve form in large, medium and low pressure applications. With the application of anti-corrosion synthetic rubber and polytetrafluoroethylene, the performance of butterfly valves has been improved and satisfied with different working conditions.

 Turbine butterfly valve

In recent ten years, metal-sealed butterfly valves have developed rapidly. With the application of high temperature, low temperature, strong corrosion resistance, strong erosion resistance and high strength alloy materials in butterfly valves, metal-sealed butterfly valves have been widely used under high temperature, low temperature and strong erosion conditions, and partially replaced globe valves, gate valves and ball valves.

Butterfly valve advantages:

1. Butterfly valve opening and closing is convenient, fast, labor-saving, fluid resistance is small, and can be operated frequently.

2. Butterfly valve has simple structure, small volume and light weight.

3. Butterfly valves can transport mud and store the least liquid at the mouth of the pipeline.

4. The butterfly valve can achieve good sealing under low pressure.

5. The butterfly valve has good regulation performance.


Butterfly valve disadvantage:

1. Small range of pressure and working temperature of butterfly valve.

2. Butterfly valve has poor sealing.

3. Butterfly valves can be divided into offset plate type, vertical plate type, inclined plate type and lever type. According to the sealing form, it can be divided into denser ones.

4. Sealing type and hard sealing type. Soft seal is usually sealed by rubber ring, while hard seal is usually sealed by metal ring.

5. According to connection type, it can be divided into flange connection and clamp connection. According to transmission mode, it can be divided into manual, gear transmission, pneumatic, hydraulic and electric.

Post time: Oct-14-2019

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