Operational principle:The relationship between the opening and flow of plastic ball valve basically changes in linear proportion. If used to control the flow, its flow characteristics and the pipe is also closely related to the flow resistance of the pipe, the valve diameter and form of the two pipelines are all the same, and the pipeline loss coefficient is different, the valve flow will be very different. If the valve is in a large state of throttle range, the back of the valve plate is prone to air erosion, there is a possibility of damage to the valve, are generally used outside 15. Plastic ball valve in the medium opening, the valve body and the butterfly front opening shape of the valve shaft as the center, on both sides to complete different state, one side of the butterfly front along the direction of the upstream water, therefore, one side of the valve body and valve form like nozzle opening, on the other side of the throttle hole opening, nozzle side is faster than throttle side flow rate, and throttle side valve will produce negative pressure, often appear rubber seal fall off.
PVC Ball Valve and the butterfly lever themselves have no self-locking ability, in order to locate the butterfly plate, the worm gear reducer should be installed on the valve lever. The worm gear reducer can not only make the butterfly plate have self-locking ability and stop at any position, but also improve the operation performance of the valve. Plastic Union Ball Valve operating torque, due to the opening degree and valve opening direction of the different values, horizontal ball valve, especially the large diameter valve, due to the water depth, the valve shaft, water head difference produced by the torque can not be ignored. In addition, the valve inlet side of the device elbow, the formation of deflection, the torque will increase. When the valve is in the middle opening, the operating mechanism needs to self-lock due to the water flow moment.
Plastic ball valve structure is simple, only composed of a few parts, material consumption saving; small volume, light weight, small installation size, small drive torque, small operation, easy and fast, only rotate 90 can quickly open and close; and also has good flow regulation function and close sealing characteristics, in the use of large and medium caliber, medium and low pressure field, plastic ball valve is the dominant valve form. When the Flange Ball Valve is in the fully open position, the thickness of the butterfly plate is the resistance when the medium flows through the valve body, so the pressure drop generated through the valve is very small, so it has good flow control characteristics. Ball valve has elastic seal and metal seal two sealing types. Elastic seal valve, seal ring can be embedded on the valve body or attached to the butterfly plate periphery. Valves with metal seals generally last longer than elastic valves, but it is difficult to seal completely. Metal seals can adapt to high working temperatures, while elastic seals are temperature-limited defective. If ball valves are required to be used as a flow control, the main thing is to correctly select the size and valve type. The structure principle of the UPVC Ball Valve is especially suitable for making large diameter valves. Ball valve is not only widely used in oil, gas, chemical industry, water treatment and other general industries, but also used in the cooling water system of thermal power station.