What are the classifications of butterfly valves?

Butterfly valves, also known as flap valves, are commonly used in pipelines transporting various corrosive and non corrosive fluid media in engineering systems such as furnaces, coal gas, natural gas, liquefied petroleum gas, hot and cold air, chemical smelting, etc. They are used to regulate and cut off the flow of media.

The working principle of butterfly valves

Butterfly valve is a type of valve that uses a circular butterfly plate as the opening and closing element and rotates with the valve stem to open, close, and regulate the fluid channel. The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline.

In the cylindrical channel of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, with a rotation angle between 0 ° and 90 °. When it rotates to 90 °, the valve is fully open. By changing the deflection angle of the disc, the flow rate of the medium can be controlled.

Classification of Butterfly Valves

What are the classifications of butterfly valves?

1、 Concentric butterfly valve

The structural feature of this butterfly valve is that the valve stem axis, butterfly plate center, and body center are in the same position. Simple structure and convenient manufacturing. The common rubber lined butterfly valve belongs to this category.

The disadvantage is that the butterfly plate and valve seat are always in a squeezing and scraping state, with a large resistance distance and fast wear.

2、 Single eccentric butterfly valve

To solve the squeezing problem between the butterfly plate and valve seat of the concentric butterfly valve, a single eccentric butterfly valve was developed. Its structural feature is that the axis of the valve stem deviates from the center of the butterfly plate, so that the upper and lower ends of the butterfly plate no longer become the rotation axis, dispersing and reducing the excessive compression between the upper and lower ends of the butterfly plate and the valve seat.

3、 Double eccentric butterfly valve

On the basis of the single eccentric butterfly valve, the most widely used double eccentric butterfly valve is further improved and formed. Its structural feature is that the valve stem axis deviates from both the center of the butterfly plate and the center of the body.

The double eccentricity effect allows the butterfly plate to quickly detach from the valve seat after the valve is opened, greatly eliminating unnecessary excessive compression and scraping between the butterfly plate and the valve seat, reducing the opening resistance distance, reducing wear, and improving the service life of the valve seat.

What are the classifications of butterfly valves?

4、 Triple eccentric butterfly valve

To withstand high temperatures, a hard seal must be used, but the leakage is large; To achieve zero leakage, a soft seal must be used, but it is not resistant to high temperatures. To overcome the contradiction of the double eccentric butterfly valve, a third eccentricity (deviation from the centerline of the metal sealing surface) was carried out on the butterfly valve.

Its structural feature is that while the axis position of the double eccentric valve stem is eccentric, the conical axis of the butterfly plate sealing surface is skewed towards the main cylindrical axis. That is to say, after the third eccentricity, the sealing section of the butterfly plate is no longer a true circle, but an ellipse.

The biggest feature of the third eccentricity is that it fundamentally changes the sealing structure, no longer position sealing, but torque sealing; It is not relying on the elastic deformation of the valve seat, but completely relying on the contact surface pressure of the valve seat to achieve the sealing effect.