What Is A Butterfly Valve?
A butterfly valve, also known as a flap valve, is a regulating valve with a simple structure, which can be used for switching control of a low-pressure pipeline medium. of a valve.
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.

How Butterfly Valves Work?
The butterfly valve is a kind of valve that uses disc-type opening and closing parts to turn back and forth about 90° to open, close, or adjust the flow of the medium. Butterfly valve not only has a simple structure, small size, lightweight, low material consumption, small installation size, small driving torque, and 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. It’s reliability and other performance indicators have reached a high level.
With the application of chemically resistant synthetic rubber on butterfly valves, the performance of butterfly valves has been improved. Since synthetic rubber has the characteristics of corrosion resistance, erosion resistance, stable size, good resilience, easy forming, and low cost, synthetic rubber with different properties can be selected according to different application requirements to meet the working conditions of butterfly valves.
Because polytetrafluoroethylene (PTFE) has strong corrosion resistance, stable performance is not easy to age, a low friction coefficient, easy to shape, and stable size, and its comprehensive performance can be improved by filling and adding appropriate materials to obtain better strength and friction. Butterfly valve sealing materials with a lower coefficient overcome the limitations of synthetic rubber. Therefore, high molecular polymer materials represented by polytetrafluoroethylene and their filling-modified materials have been widely used in butterfly valves, thus improving the performance of butterfly valves. It has been further improved, and a butterfly valve with a wider temperature and pressure range, reliable sealing performance, and longer service life has been manufactured.
To meet the requirements of industrial applications such as high and low temperatures, strong erosion, and long life, metal-sealed butterfly valves have been greatly developed. With the application of high-temperature resistance, low-temperature resistance, strong corrosion resistance, strong erosion resistance, and high-strength alloy materials in butterfly valves, metal-sealed butterfly valves have been widely used in industrial fields such as high and low temperatures, strong erosion, and long life. Butterfly valves with large diameters (9~750mm), high pressure (42.0MPa), and wide temperature range (-196~606°C) appeared, which brought the technology of butterfly valves to a whole new level.
When the butterfly valve is fully opened, it has a small flow resistance. When the opening is between about 15°~70°, it can also perform sensitive flow control, so in the field of large-diameter regulation, the application of butterfly valves is very common.
Since the movement of the butterfly plate is wiping, most butterfly valves can be used for media with suspended solid particles. Depending on the strength of the seal, it can also be used for powdery and granular media.
Butterfly valves are suitable for flow regulation. Since the pressure loss of the butterfly valve in the pipe is relatively large, about three times that of the gate valve, when selecting a butterfly valve, the influence of the pressure loss on the pipeline system should be fully considered, and the strength of the butterfly plate to withstand the pressure of the pipeline medium when it is closed should also be considered. In addition, the limitation of the operating temperature of the elastic seat material at high temperatures must also be considered.
The structure length and overall height of the butterfly valve are small, the opening and closing speed is fast, and it has good fluid control characteristics. The structural principle of the butterfly valve is most suitable for making large-diameter valves. When the butterfly valve is required to be used for flow control, the most important thing is to correctly select the specification and type of the butterfly valve so that it can work properly and effectively.
Generally, butterfly valves are recommended for throttling, regulating control, and mud media where short structural length, fast opening and closing speed, and low-pressure cut-off (small pressure difference) are required. Butterfly valves can be selected for double-position adjustment, reduced-diameter channels, low noise, cavitation and vaporization, a small amount of leakage to the atmosphere, and abrasive media. Throttle adjustment under special working conditions, or working conditions that require strict sealing, severe wear, low temperature (cryogenic), and so on.
The Structure Of The Butterfly Valve
It is mainly composed of the valve body, valve stem, butterfly plate, and sealing ring. The valve body is cylindrical, with a short axial length and a built-in butterfly plate.
The Characteristics Of The Butterfly Valve
1. The butterfly valve has the characteristics of a simple structure, small size, lightweight, low material consumption, small installation size, rapid switching, 90° reciprocating rotation, and small driving torque. It is used to cut off, connect, and adjust the medium in the pipeline. Has good fluid control characteristics and shut-off sealing performance.
2. The butterfly valve can transport mud, and the liquid accumulated at the mouth of the pipe is the least. At low pressure, a good seal can be achieved. Good adjustment performance.
3. The streamlined design of the butterfly plate makes the loss of fluid resistance small, which can be described as an energy-saving product.
4. The valve stem is a through-rod structure, which has good comprehensive mechanical properties, corrosion resistance, and scratch resistance after quenching and tempering treatment. When the butterfly valve is opened and closed, the valve stem only rotates and does not move up and down. The packing of the valve stem is not easy to damage and the seal is reliable. It is fixed with the taper pin of the butterfly plate, and the protruding end is designed to prevent the valve stem from collapsing when the joint between the valve stem and the butterfly plate breaks accidentally.
5. The connection methods include flange connection, clamp connection, butt welding connection, and lug clamp connection.
The driving forms include manual, worm gear transmission, electric, pneumatic, hydraulic, electro-hydraulic linkage, and other actuators, which can realize remote control and automatic operation.
Advantage Of Butterfly Valves
1. The opening and closing are convenient and quick, labor-saving, and the fluid resistance is small, so it can be operated frequently.
2. Simple structure, small size, short structure length, small size, lightweight, suitable for large diameter valves.
3. It can transport mud, and the liquid accumulated at the pipe mouth is the least.
4. Under low pressure, good sealing can be achieved.
5. Good adjustment performance.
6. When fully open, the effective flow area of the valve seat channel is larger, and the fluid resistance is smaller.
7. The opening and closing torque is relatively small, because the butterfly plates on both sides of the rotating shaft are equal to the action of the medium, and the direction of the torque is opposite, so the opening and closing are relatively labor-saving.
8. The sealing surface material is generally made of rubber or plastic, so the low-pressure sealing performance is good.
9. Easy to install.
10. The operation is flexible and labor-saving, and manual, electric, pneumatic, and hydraulic methods can be selected.
Shortcoming Butterfly Valves
1. The working pressure and working temperature range are small.
2. Poor sealing.
Butterfly valves can be divided into offset plate type, vertical plate type, inclined plate type, and lever type according to the structure.
According to the sealing form, there are two types: soft seal type and hard seal type. The soft seal type is generally sealed with a rubber ring, and the hard seal type is usually sealed with a metal ring.
According to the connection type, it can be divided into flange connection and wafer connection; according to the transmission mode, it can be divided into manual, gear transmission, pneumatic, hydraulic, and electric.