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How to choose butterfly valve?

2023-08-21 15:34:28

Butterfly valve, also known as flap valve, is a simple structure of the regulating valve, can be used for low-pressure pipeline media switching control of the butterfly valve is the closing member (valve flap or butterfly plate) for the disc, rotating around the valve axis to achieve the opening and closing of a kind of valve.
The butterfly Valves can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, slurry, oil, liquid metals and radioactive media. Mainly in the pipeline to cut off and throttling role. Butterfly valve opening and closing member is a disc-shaped butterfly plate, rotating around its own axis in the valve body, so as to achieve the purpose of opening and closing or regulation.

Advantages of butterfly valve:

① Opening and closing convenient and rapid, energy saving, fluid resistance is small, can be frequently operated.

② Simple structure, small external dimensions, short structural length, small size, light weight, suitable for large calibre valves.

③ It can transport slurry and accumulate the least amount of liquid at the mouth of the pipeline.

④ Good sealing can be achieved under low pressure.

⑤ Good adjustment performance.

⑥ The effective flow area of the valve seat channel is larger when fully open, and the fluid resistance is smaller.

⑦ The opening and closing torque is small, due to the rotating shaft on both sides of the butterfly plate by the role of the medium is equal, and produce torque in the opposite direction, thus opening and closing more energy.

⑧ Sealing surface materials are generally used rubber, and plastic, so the low-pressure sealing performance is good.

⑨ Easy to install.

⑩ Flexible operation, can choose manual, electric, pneumatic, or hydraulic mode.

Concentric butterfly valve, double eccentric butterfly valve and three eccentric butterfly valve how to choose?
Butterfly valve structure on the different distinction between the four types of butterfly valves, respectively: concentric butterfly valve, single eccentric butterfly valve, double eccentric butterfly valve and three eccentric butterfly valve.
What is the concept of eccentricity? How to decide when to use concentric butterfly valve, when to use single eccentric butterfly valve, when to use double eccentric butterfly valve and triple eccentric butterfly valve?

eccentric butterfly valve
Here we do a specific analysis:

Concentric Butterfly Valve, Double Eccentric Butterfly Valve and Triple Eccentric Butterfly Valve Structural Diagrams

Concentric Butterfly Valve, Single Eccentric Butterfly Valve, Double Eccentric Butterfly Valve, and Triple Eccentric Butterfly Valve reflect in fact a process of opening and closing with more and more energy-saving, and less and less wear and tear of the sealing surface. The sealing and opening state of the butterfly valve is changed by setting the position of the rotating axis of the butterfly valve plate. Under the same conditions, the valve is subjected to more torque than one under each opening degree. The angle of rotation required to disengage the valve plate from the seal when the valve opens is one smaller than the other.

Concentric butterfly valve structure is characterized by the stem axis, butterfly plate center, and the valve body center in the same position. In general, in principle, we can use concentric butterfly valve will try to use concentric butterfly valve. Because of the concentric butterfly valve both structural and operational sealing requirements are not high, belonging to the conventional products. In order to overcome the extrusion, and scraping, to ensure the sealing performance, a concentric butterfly valve seat using rubber or PTFE and other elastic materials, is a soft seal butterfly valve. This makes the concentric butterfly valve in the use of the temperature limitations. To solve the problem of extrusion of concentric butterfly valve’s butterfly plate and valve seat, a single eccentric butterfly valve. Its structural feature is that the stem axis is off the center of the butterfly plate.

Concentric butterfly valve

The double eccentric butterfly valve is the most widely used. Its structural characteristics in the valve stem axis both deviated from the butterfly plate center and the valve body center. Deviated from the two central position so called double eccentric butterfly valve. Many double eccentric butterfly valves are line sealing, closing the sealing surface when the disc plate and the valve seat friction, sealing effect is delicious. It has the characteristics of a small area and large pressure. After the valve is opened, the butterfly plate can quickly detach from the valve seat, greatly eliminating the butterfly plate and the seat of the unnecessary excessive extrusion, and scraping phenomenon, reducing the opening distance, reducing wear and tear, and improving the life of the valve seat.

Three eccentric butterfly valves in the double eccentric butterfly valve based on the third eccentric, the shape of the sealing vice is not a positive cone, but an oblique cone. Mostly short distance force and face seal. The stem shaft of the triple eccentric butterfly valve is a three-section shaft structure, the two sections of this three-section shaft are concentric, while the center line of the central section of the shaft and the two ends of the axis deviate from the center distance, and the butterfly plate is mounted on the middle section of the shaft.
Such an eccentric structure makes the butterfly plate become double eccentric when it is in the fully open position. In contrast, it becomes single eccentric when the butterfly plate is rotated to the closed position.

double eccentric butterfly valve

Due to the role of the eccentric shaft, when close to the closing, the butterfly plate to the seat of the sealing cone a distance, the butterfly plate and the sealing sealing surface coincide to achieve a reliable sealing performance. It makes up for the contradiction that hard seal has poor sealing, and soft seal has good sealing effect but not high-temperature resistance.

Butterfly valve applicable occasions:
The butterfly valve is suitable for flow regulation. As the pressure loss of butterfly valve in the pipeline is relatively large, the sturdiness of the butterfly plate to withstand the pressure of the pipeline medium during closing should also be considered. In addition, it is also necessary to consider the limitations of the working temperature borne by the resilient valve seat material at high temperatures.

Butterfly valve structure length and overall height is small, fast opening and closing speed, and has good fluid control characteristics, butterfly valve structure principle is most suitable for the production of large diameter valves. When the butterfly valve is required to be used for flow control, the most important thing is to choose the correct size and type of butterfly valve so that it can work properly and effectively.

① In throttling, regulating control and slurry media, it is required to have short structure length and fast opening and closing speed (1/4 turn). Low-pressure cut-off (small differential pressure), the recommended choice of butterfly valve.

② In the two-position adjustment, indented ground channel, low noise, cavitation and cavitation phenomenon, a small amount of leakage to the atmosphere, with abrasive media, butterfly valves can be selected.

③ In the special conditions of throttling regulation, or require strict sealing, or wear and tear, low temperature (deep cold) and other conditions of use of butterfly valves, need to use a special design of metal sealing with regulating device, three eccentric or double eccentric special butterfly valves.

④ Butterfly valves are suitable for fresh water, sewage, seawater, salt water, steam, natural gas, food, medicine, oil and all kinds of acid and alkali and other pipelines which require complete sealing, zero leakage of gas test, high life expectancy, and the working temperature ranges from -10 degrees to 150 degrees.

⑤ Soft seal eccentric butterfly valve is suitable for bidirectional opening and closing and adjustment of ventilation and dust removal pipelines, and is widely used in metallurgy, light industry, electric power, petrochemical systems, such as gas pipelines and waterways.

⑥ Metal-to-metal line sealed double eccentric butterfly valve is suitable for city heating, gas supply, water supply and other gas, oil, acid and alkali pipelines, as a regulating and throttling device.

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