Butterfly valve open and close
the relationship between butterfly valve opening degree and flow is basically linear rate change. If it is used to control the flow, its flow characteristics also are related to matched pipe flow resistance, if the installed valve diameter, form of two pipelines are all the same, while the pipe loss coefficient is different, the valve flow will be much different.
If the valve in a significant throttle reduction state, the disc back is easy to cavitation, maybe damage the valve, generally used out of 15 °.
When butterfly valve is in the middle of opening, the body and the front end of disc formed opening shape uses shaft as the center, both sides forms complete different states, one side of disc front-end flows in direction of fluid, the other side flows upstream, so one side body and plate may form a nozzle-shaped openings, the other side similar to the orifice-shaped openings, the nozzle side flow rate is many times faster than the throttle side, while the throttle side valve will produce the negative pressure, often occur rubber sealing part off.
Butterfly valve operating torque values are different, due to different open and close opening, horizontal butterfly valve, especially the large-diameter valves, beacause of water depth, valve shaft up and down water head generated mement should be overlooked. In addition, when the valves entrance device is bending, forming a bias current, torque will increase. When the valve in the middle of the valve opening, due to the function of the water flow torque, operating actuators need to self-locking.
