butterfly valve working condition selection
Butterfly valve also known as flap valve, is a simple structure of the control valve, but also can be used for low-pressure pipeline medium switch control. Butterfly valve refers to a kind of valve whose closing part (disc or disc) is a disc, which rotates around the valve shaft to open and close. It mainly plays the role of cutting off and throttling on the pipeline. The opening and closing part of butterfly valve is a disc-shaped butterfly plate, which rotates around its own axis in the valve body, so as to achieve the purpose of opening and closing or adjusting.
Butterfly valve is a kind of valve which uses the round butterfly plate as the opening and closing part and rotates with the valve stem to open, close and adjust the fluid channel. The butterfly plate of butterfly valve is installed in the diameter direction of pipeline. In the cylindrical channel of butterfly valve body, the disc-shaped butterfly plate rotates around the axis, and the rotation angle is between 0 ° and 90 ° and when the rotation reaches 90 ° the valve plate is fully open.
Butterfly valves are classified into concentric butterfly valve, single eccentric sealing butterfly valve, double eccentric sealing butterfly valve and three eccentric sealing butterfly valve.
Driving mode: manual, worm gear drive, pneumatic, electric, hydraulic, pneumatic and hydraulic linkage, electro-hydraulic linkage.
1、 Concentric butterfly valve: the structural characteristics of the butterfly valve are that the shaft center of the valve rod, the center of the butterfly plate and the center of the body are in the same position. The structure is simple and the manufacture is convenient. 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 and scraping, with large resistance distance and fast wear.
2、 Single eccentric butterfly valve: in order to solve the extrusion problem between the butterfly plate and the valve seat of concentric butterfly valve, the single eccentric butterfly valve is produced. Its structural feature is that the shaft center of the valve rod deviates from the center of the butterfly plate, so that the upper and lower ends of the butterfly plate no longer become the rotary axis, disperse and reduce the excessive extrusion between the upper and lower ends of the butterfly plate and the valve seat.
3、 Double eccentric butterfly valve: in the single eccentric butterfly valve on the basis of further improvement is currently the most widely used double eccentric butterfly valve. The structure feature is that the shaft center of the valve rod deviates from the center of the butterfly plate and the center of the body. The effect of double eccentricity makes the butterfly plate break away from the valve seat immediately after the valve is opened, which greatly eliminates the unnecessary excessive extrusion and scratch between the butterfly plate and the valve seat, reduces the opening resistance, reduces the wear and improves the service life of the valve seat.
4、 Three eccentric butterfly valve: to withstand high temperature, must use hard seal, but the leakage is large; to zero leakage, must use soft seal, but not high temperature. In order to overcome the contradiction of double eccentric butterfly valve, the third eccentricity (deviation from the center line of metal sealing surface) was carried out for butterfly valve.