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    Structural characteristics of butterfly valve Working principle of butterfly valve

    Posted by Bundor valve
    A butterfly valve is a valve that uses a circular butterfly plate as an opening and closing member and rotates with the valve stem to open, close and adjust the fluid channel. There are many types of butterfly valves and they are widely used. In this article, Bundor Valve will introduce the structure diagram of the butterfly valve, the structural characteristics of the butterfly valve and the working principle of the butterfly valve.
    Structural characteristics of butterfly valve

    Butterfly valve has the characteristics of simple structure, small size, light weight, low material consumption, small installation size, rapid switch, 90° reciprocating rotation, small driving torque, etc. It is used to cut off, connect and adjust the medium flow in the pipeline. Good fluid control characteristics and shut-off sealing performance.
    The butterfly valve has a streamlined design of the disc, and the loss of fluid resistance is small.
    The stem of the butterfly valve is a through-rod structure, which has been quenched and tempered, and has good comprehensive mechanical properties, corrosion resistance and scratch resistance. When the butterfly valve is opened and closed, the valve stem only rotates and does not move up and down, the packing of the valve stem is not easy to be damaged, and the sealing is reliable.
    The connection methods of butterfly valves include flange connection, wafer connection, butt welding connection and lug wafer connection. The drive forms include manual, worm gear drive, electric, pneumatic, hydraulic, electro-hydraulic linkage and other actuators, which can realize remote control and automatic operation.
    Butterfly valve working principle
    The butterfly valve is a valve that uses a circular butterfly plate as an opening and closing part to open, close and adjust the medium flow in the pipeline. In the cylindrical channel of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, and the rotation angle is 0°~90° Between, when rotated to 90°, the butterfly valve is in a fully open state.
    The relationship between the opening of the butterfly valve and the flow is basically a linear proportional change. If it is used to control the flow, its flow characteristics are also closely related to the flow resistance of the piping. For example, the diameter and form of the valves installed in the two pipes are all the same, but the loss coefficient of the pipes is different, and the flow rate of the valve will be very different.
    If the valve is in a state of large throttling, cavitation is prone to occur on the back of the valve plate, which may damage the valve. Generally, it is used at a distance of 15°.
    When the 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 form different states. Therefore, one side of the valve body and the valve plate form a nozzle-like opening, and the other side is like a throttle hole-shaped 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, often The rubber seal may come off.
    The operating torque of the butterfly valve varies depending on the opening degree and the opening and closing direction of the valve. The horizontal butterfly valve, especially the large-diameter valve, due to the water depth, the torque generated by the difference between the upper and lower water heads of the valve shaft cannot be ignored. In addition, when an 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.
    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 very small, so it has better flow control characteristics.