The plastic butterfly valve is connected to the pipeline system in the following ways:

Butt welding connection: The outer diameter of the valve connection part is equal to the outer diameter of the pipe, and the end face of the valve connection part is opposite to the end face of the pipe for welding;

Socket bonding connection: the valve connection part is in the form of a socket, which is bonded to the pipe;

Electrofusion socket connection: the valve connection part is a socket type with an electric heating wire laid on the inner diameter, and it is electrofusion connection with the pipe;

Socket hot-melt connection: the valve connection part is in the form of a socket, and it is connected with the pipe by hot-melt socket;

Socket bonding connection: The valve connection part is in the form of a socket, which is bonded and socketed with the pipe;

Socket rubber sealing ring connection: The valve connection part is a socket type with a rubber sealing ring inside, which is socketed and connected with the pipe;

Flange connection: The valve connection part is in the form of a flange, which is connected with the flange on the pipe;

Thread connection: The valve connection part is in the form of thread, which is connected with the thread on the pipe or pipe fitting;

Live connection: The valve connection part is a live connection, which is connected with pipes or fittings.

A valve can have different connection modes at the same time.

working principle:

The relationship between the opening of the plastic butterfly valve and the flow rate basically changes linearly. If it is used to control flow, its flow characteristics are also closely related to the flow resistance of the piping. For example, two pipelines are installed with the same valve diameter and form, but the pipeline loss coefficient is different, and the flow rate of the valve will also be very different.

If the valve is in a state with a large throttle range, the back of the valve plate is prone to cavitation, which may damage the valve. Generally, it is used outside 15°.

When the plastic butterfly 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 are formed to complete different states. The front end of the butterfly plate on one side moves in the direction of the flow of water, and the other side is against the direction of the flow. Therefore, one side of the valve body and the valve plate form a nozzle-like opening, and the other side is similar to a throttle opening. The nozzle side has a much faster flow rate than the throttle side, and negative pressure will be generated under the throttle side valve. Rubber seals often fall off.

Plastic butterfly valves and butterfly rods have no self-locking ability. For the positioning of the butterfly plate, a worm gear reducer must be installed on the valve rod. The use of a worm gear reducer can not only make the butterfly plate self-locking and stop the butterfly plate at any position, but also improve the operating performance of the valve.

The operating torque of the plastic butterfly valve has different values ​​due to the different opening and closing directions of the valve. The horizontal butterfly valve, especially the large-diameter valve, due to the depth of water, the torque generated by the difference between the upper and lower water heads of the valve shaft cannot be ignored. In addition, when the elbow is installed on the inlet side of the valve, a bias flow is formed, and the torque will increase. When the valve is in the middle opening, the operating mechanism needs to be self-locking due to the action of the water flow torque.

The plastic butterfly valve has a simple structure, consisting of only a few parts, and saves material consumption; small size, light weight, small installation size, small driving torque, simple and rapid operation, only need to rotate 90° to quickly open and close; and At the same time, it has good flow adjustment function and closing and sealing characteristics. In the application field of large and medium caliber, medium and low pressure, the butterfly valve is the dominant valve form. When the butterfly valve is in the fully open position, the thickness of the butterfly plate is the only resistance when the medium flows through the valve body, so the pressure drop generated by the valve is small, so it has better flow control characteristics. 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. The metal seal can adapt to higher working temperature, while the elastic seal has the defect of being limited by temperature. If the butterfly valve is required to be used as a flow control, the main thing is to correctly select the size and type of the valve. The structure principle of the butterfly valve is especially suitable for making 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 of thermal power stations.　The commonly used butterfly valves include wafer type butterfly valves and flange type butterfly valves. Wafer butterfly valves are connected between two pipe flanges with stud bolts. Flanged butterfly valves are equipped with flanges on the valve. The flanges on both ends of the valve are connected to the pipe flanges with bolts. The strength performance of the valve refers to the ability of the valve to withstand the pressure of the medium. The valve is a mechanical product that bears internal pressure, so it must have sufficient strength and rigidity to ensure long-term use without cracking or deformation.

With the application of anti-corrosion synthetic rubber and polytetrafluoroethylene, the performance of butterfly valves can be improved and meet different working conditions. In the past ten years, metal sealing butterfly valves have developed rapidly. With the application of high temperature resistance, low temperature resistance, strong corrosion resistance, strong erosion resistance, and high strength alloy materials in butterfly valves, metal sealing butterfly valves have been used in high temperature, low temperature, and strong erosion. It has been widely used under other working conditions and partially replaced the globe valve, gate valve and ball valve.