Butterfly valve refers to a valve in which the closing part (disc or butterfly plate) is a disc that rotates around the valve shaft to open and close. It is mainly used for 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. The butterfly valve is usually less than 90° from fully open to fully closed. The butterfly valve and butterfly rod have no self-locking ability. In order to position the butterfly plate, a worm gear reducer should be installed on the valve rod. The use of the worm gear reducer not only enables the butterfly plate to have self-locking ability, makes the butterfly plate stop at any position, but also improves the operating performance of the valve.
The industrial special butterfly valve is characterized by high temperature resistance, high applicable pressure range, large nominal diameter of the valve, the valve body is made of carbon steel, and the sealing ring of the valve plate is replaced by a metal ring instead of a rubber ring. Large-scale high-temperature butterfly valves are manufactured by welding steel plates and are mainly used for flue gas ducts and gas pipelines for high-temperature media.
The advantages of butterfly valves are as follows:
1. The opening and closing is convenient and quick, labor-saving, and the fluid resistance is small, so it can be operated frequently.
2. Simple structure, small size and light weight.
3. It can transport mud, and there is less liquid accumulated at the mouth of the pipeline.
4. Under low pressure, good sealing can be achieved.
5. Good adjustment performance.
The disadvantages of butterfly valves are as follows:
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, it can be divided into two types: relatively sealed type and hard sealed 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.
The installation and maintenance of butterfly valves should pay attention to the following:
1. When installing, the disc should stop at the closed position.
2. The opening position should be determined according to the rotation angle of the butterfly plate.
3. For butterfly valves with bypass valves, the bypass valves should be opened before opening.
4. It should be installed according to the installation instructions of the manufacturer. For heavy butterfly valves, a firm foundation should be set up.