In the 1930s, the United States invented the butterfly valve, which was introduced to Japan in the 1950s, and was not widely used in Japan until the 1960s, while the promotion in China was just after the 1970s. At present, in the world, the general diameter is above DN300, the butterfly valve has gradually replaced the gate valve. Compared with the gate valve, the butterfly valve has a short opening and closing time, the operation is small moment, small installation space and light weight. Take DN1000 as an example, the butterfly valve is about 1.2T, while the gate valve is about 3T, and the butterfly valve is easily combined with various drive devices, with good durability and reliability.
The disadvantage of rubber sealing butterfly valve is that when using as a throttle, due to improper use, will produce gas corrosion, so that the rubber seat peeling, damage and other situations will occur. To this end, now the metal seal butterfly valve has been developed internationally, and the air erosion area has been reduced. In recent years, China has also developed the metal sealed butterfly valve and metal sealed rotating ball valve. In recent years, Japan has also developed the gas corrosion resistance, low vibration and low noise comb-shaped butterfly valve.
The life of the general sealing seat is, under normal circumstances, 5-10 years for rubber, and 30-50 years for metal. But how to choose correctly is according to the requirements of the working conditions.
The relationship between the opening degree of the butterfly valve and the flow rate is basically linear in proportion. If it is used to control the flow rate, its flow characteristics are also closely related to the flow resistance of the pipe distribution, such as the diameter and form of the two pipes to install the valve are all the same, and the pipe loss coefficient is different, the flow rate of the valve will also be very different.
If the valve is in a large throttle state, the back of the valve plate is prone to air corrosion, with the possibility of damaged valve, the valve is generally used outside 15 °.
Butterfly valve in the medium opening, the opening shape formed by the valve body and the front end of the butterfly plate is centered on the valve shaft, and different states are formed on both sides, the front of the butterfly plate on one side moves along the direction of running water, and the other side moves against the direction of flowing water. Therefore, one valve body and valve plate forms a nozzle opening, and the other side is like a throttle hole-shaped opening. The nozzle side is faster than the throttle side, and negative pressure under the throttle side valve, often appear rubber seal off.
The operating torque of the butterfly valve has different values due to the opening degree and the valve opening and closing direction. The horizontal butterfly valve, especially the large size valve, due to the water depth, the torque generated by the valve shaft and water head difference cannot be ignored. In addition, when the valve inlet side device bends, the deflection is formed, and the torque will increase. When the valve is in the middle opening degree, the operating mechanism needs to lock itself because the water flow torque works.
Post time: Dec-20-2021