The relationship between opening and flow rate of plastic ball valves varies linearly. If it is used to control flow, its flow characteristics are closely related to the flow resistance of piping. For example, the caliber and form of valves installed in two pipes are identical, and the flow rate of valves varies greatly with different loss coefficients of pipes.
If the valve is in a larger throttling range, the back of the valve plate is prone to cavitation, which may damage the valve, generally used outside 15 degrees.
When the plastic ball valve is in the middle opening, the shape of the opening formed by the valve body and the front end of the butterfly plate is centered on the valve shaft, and the two sides form different states. The front end of the butterfly plate on one side moves in the direction of downstream water and the other side moves in the direction of countercurrent water. Therefore, one side of the valve body and the valve plate forms a nozzle-like opening, the other side is similar to the orifice-shaped opening, and the flow speed of the nozzle side is faster than that of the throttle side. Negative pressure will be generated under the flow side valve, and rubber seals will often fall off.