Butterfly valves control the flow of fluid in a pipe using a disc attached to a central shaft. This disc controls the amount of fluid passing through the valve by creating a variable orifice.
Butterfly valves can be classified according to the alignment of the flap relative to the valve body:
- Zero offsetbutterfly valve
- Single offset butterfly valve
- Double offset butterfly valve
- Triple offsetbutterfly valve
The early butterfly valve is the most traditional concentric butterfly valve(zero offset butterfly valve). Because it cannot withstand high temperature and high pressure and has large leakage, its application range is greatly restricted. In order to meet the requirements of various working conditions, butterfly valves have evolved from concentric to single offset butterfly valve, double offset butterfly valve and triple offset butterfly valve.
In this article, TWT,China would like to introduce to you buyers the development process of butterfly valve offsetity, and focus on the double offset butterfly valve.
Development of butterfly valve offsetity
Traditional concentric butterfly valve
The structural characteristics of concentric butterfly valves are that the axis of the valve stem, the center of the butterfly plate and the center of the body are in the same position, the structure is simple and easy to manufacture. The disadvantage is that the butterfly plate and valve seat are always pinched and scratched, which creates a lot of resistance and wears out quickly.
The first offsetity
In order to solve the problem of extrusion between the butterfly plate and the valve seat of the concentric butterfly valve, a single offset butterfly valve is produced. The structural feature is that the valve stem axis deviates from the center of the butterfly plate, so that the upper and lower ends of the butterfly plate are the butterfly is no longer the axis of rotation. Disperse and reduce excessive extrusion between the upper and lower ends of the butterfly plate and the valve seat. However, because the single offset structure only reduces but does not eliminate the scratching phenomenon between the butterfly plate and the valve seat to a certain extent during the entire valve switching process, its application scope is similar to that of the concentric butterfly valve, so it is not widely used.
The second offsetity
Based on the single offset butterfly valve, the double offset butterfly valve is currently widely used. The structural feature is that the valve stem axis deviates from the center of the butterfly plate and the center of the valve body.
The third offsetity
The third offsetity of the butterfly valve has made some essential changes: the sealing structure has been fundamentally changed, from position sealing to torque sealing. That is to say, it does not rely on the elastic deformation of the valve seat, but completely relies on the contact surface pressure of the valve seat to achieve the sealing effect. This sealing structure enables the triple-offset butterfly valve to achieve hard sealing level VI, achieving true zero leakage. At the same time, the triple offset butterfly valve uses a metal valve seat to achieve high temperature resistance. At this point in the development, the leakage and high temperature resistance problems of the butterfly valve have been finally solved.
Features of double offset butterfly valve
The double offset effect enables the butterfly plate to quickly separate from the valve seat after the valve is opened, greatly eliminating unnecessary excessive squeezing and scratching between the butterfly plate and the valve seat, reducing the opening resistance, reducing wear and tear on the valve seat. More durable. The scratching is greatly reduced, and it also gives the possibility of using a metal valve seat for the double offset butterfly valve, opening up its application in high temperature fields.
However, because the sealing principle is a positional sealing structure, that is, the sealing surface of the butterfly plate and the valve seat is in line contact, and the elastic deformation caused by the butterfly plate extruding the valve seat produces a sealing effect, so the requirements for the closing position are very high (especially for metal valves). valve seat), so the pressure-bearing capacity is still low.
In general, the double offset butterfly valve is already a type of butterfly valve with obvious advantages. The industry calls it a high-performance butterfly valve. TWT,China think this is a butterfly valve that is very worthy of buyers to consider purchasing,and provides high quality double offset butterfly valve.
Application of double offset butterfly valves
Double offset butterfly valves are widely used in fluid pipeline systems in water supply and drainage, sewage, construction, petroleum, chemical industry, textile, papermaking, hydropower, metallurgy, energy and other projects for regulation and interception.
Double offset butterfly valves are widely used in chemical industry systems, such as media control of conveying, stirring, filtration, dehydration and other equipment. In chemical equipment, double offset butterfly valves are mainly used to control the flow regulation and cut-off control of corrosive media, high temperature media, high pressure media, high viscosity media and media containing solid particles.