How Butterfly Valves Work

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  • By:Latvian Trade

A butterfly valve is a kind of valve that uses disc-type opening and closing parts to turn back and forth about 90° to open, close, or adjust the flow of medium. Butterfly valves not only have a simple structure, a small size, light weight, low material consumption, a small installation size, a small driving torque, and easy and fast operation, but also have good flow regulation function and closing and sealing characteristics at the same time. One of the fastest valve varieties Butterfly valves are widely used. The variety and quantity of its uses are still expanding, and it is developing towards high temperature, high pressure, large diameter, high sealing, long life, excellent adjustment characteristics, and multi-function of a valve. Its reliability and other performance indicators have reached a high level.

With the application of chemically resistant synthetic rubber to butterfly valves, the performance of butterfly valves has improved. Since synthetic rubber has the characteristics of corrosion resistance, erosion resistance, stable size, good resilience, easy formability, and low cost, synthetic rubber with different properties can be selected according to different application requirements to meet the working conditions of butterfly valves.

Because polytetrafluoroethylene (PTFE) has strong corrosion resistance, stable performance, is not easy to age, has a low friction coefficient, is easy to shape, and has a stable size, its comprehensive performance can be improved by filling it and adding appropriate materials to obtain better strength and friction. Butterfly valve sealing materials with a lower coefficient overcome the limitations of synthetic rubber. Therefore, high-molecular-weight polymer materials represented by polytetrafluoroethylene and their filling modified materials have been widely used in butterfly valves, thus improving the performance of butterfly valves. It has been further improved, and a butterfly valve with a wider temperature and pressure range, reliable sealing performance, and a longer service life has been manufactured.

In order to meet the requirements of industrial applications such as high and low temperatures, strong erosion, and long life, metal-sealed butterfly valves have been greatly developed. 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-sealed butterfly valves have been widely used in industrial fields such as high and low temperatures, strong erosion, and long life. Butterfly valves with large diameters (9–750 mm), high pressure (42.0 MPa), and wide temperature ranges (-196–606 °C) appeared, which brought the technology of butterfly valves to a whole new level.

When the butterfly valve is fully opened, it has a small flow resistance. When the opening is between about 15° and 70°, it can also perform sensitive flow control, so in the field of large-diameter regulation, the application of butterfly valves is very common.

Since the movement of the butterfly plate is wiping, most butterfly valves can be used for media with suspended solid particles. Depending on the strength of the seal, it can also be used for powdery and granular media.

Butterfly valves are suitable for flow regulation. Since the pressure loss of the butterfly valve in the pipe is relatively large, about three times that of the gate valve, when selecting a butterfly valve, the influence of the pressure loss on the pipeline system should be fully considered, and the strength of the butterfly plate to withstand the pressure of the pipeline medium when it is closed should also be considered. In addition, the limitation of the operating temperature of the elastic seat material at high temperatures must also be considered.

The structure length and overall height of the butterfly valve are small, the opening and closing speeds are fast, and it has good fluid control characteristics. The structural principle of the butterfly valve is most suitable for making large-diameter valves. When the butterfly valve is required to be used for flow control, the most important thing is to correctly select the specification and type of the butterfly valve so that it can work properly and effectively.

Generally, butterfly valves are recommended for throttling, regulating control, and mud media where short structural length, fast opening and closing speed, and low pressure cut-off (a small pressure difference) are required. Butterfly valves can be selected for double-position adjustment, reduced-diameter channels, low noise, cavitation and vaporization, a small amount of leakage to the atmosphere, and abrasive media. Throttle adjustment under special working conditions, or working conditions that require strict sealing, severe wear, low temperature (cryogenic), and so on.

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