The butterfly valve is simple in structure, small in size, light in weight, and consists of only a few parts. Moreover, it can be opened and closed quickly by rotating 90°, and the operation is simple. At the same time, the valve has outstanding fluid control characteristics. When the butterfly valve is in the completely open position, the thickness of the butterfly plate is the only resistance when the medium flows through the valve body, so the pressure drop that occurs through the valve is small, so it has better flow control characteristics.
If the butterfly valve is required to be used for flow control, the first thing is to correctly select the size and type of the valve. The structure principle of the butterfly valve is particularly suitable for manufacturing large diameter valves. Butterfly valves are not only widely used in general industries such as petroleum, gas, chemical, and water treatment, but also used in cooling water systems in thermal power stations. The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline.
In the cylindrical passage of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, and the rotation point of view is between 0° and 90°. When the rotation reaches 90°, the valve is fully open. The handle of the butterfly valve handles the valve plate directly, and the switch is quick but difficult. The worm gear butterfly valve passes through the worm gear drive valve plate, which switches slowly but saves effort. Therefore, the handle butterfly valve is particularly difficult when the pressure in the pipe is high.
The butterfly valve commonly used in engineering is generally the worm gear butterfly valve. In addition to saving labor, its seal is better than that of the handle butterfly valve. Especially in the environment of high switching frequency, the service life is longer than that of the handle butterfly valve. Commonly used butterfly valves include wafer butterfly valves and flange butterfly valves. Wafer type butterfly valve uses double-head bolts to connect the valve between two pipe flanges; flange type butterfly valve has a flange on the valve, and bolts the two flanges of the valve to the pipe flange.
The butterfly valve has two sealing types: elastic seal and metal seal. Elastic sealing valve, the sealing ring can be inlaid on the valve body or attached to the periphery of the butterfly plate. Valves with metal seals generally have a longer life than valves with elastic seals, but it is difficult to achieve a complete seal. Metal seals can get used to higher operating temperatures, while elastic seals have the disadvantage of being restricted by temperature.