Operating principle and installation instructions of butterfly valve

The relationship between the opening and flow of butterfly valve is basically linear proportional change. If it is used to control the flow, its flow characteristics are closely related to the flow resistance of the piping. For example, the caliber and form of the valve installed in the two pipelines are the same, while the flow of the valve will be greatly different if the pipeline loss coefficient is different.

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

When the butterfly valve is in the middle opening, the opening shape formed by the valve body and the front end of the butterfly plate takes the valve shaft as the center, and the two sides form different states. The front end of the butterfly plate on one side moves in the direction of flowing water, and the other side moves in the direction of flowing water. Therefore, the valve body on one side and the valve plate form a nozzle like opening, and the other side is similar to the orifice like opening, and the flow rate on the nozzle side is much faster than that on the throttle side, while the throttle side There will be negative pressure under the valve, and rubber seals will often fall off.

The operating torque of butterfly valve varies with the opening and opening direction of the valve. The torque of horizontal butterfly valve, especially large-diameter valve, due to the water depth and the difference between the upper and lower ends of the valve shaft cannot be ignored. In addition, when the elbow is installed at the inlet side of the valve, the bias current will be formed and the torque will be increased. When the valve is in the middle opening, the operating mechanism needs self-locking due to the action of hydrodynamic moment.

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