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A butterfly valve can be used for the on/off control of media in low-pressure pipelines. It is a type of valve in which the closing element is a disc that rotates around the valve shaft to achieve opening and closing. Butterfly valves not only feature a simple structure, small size, light weight, reduced material consumption, compact installation dimensions, low driving torque, and easy and rapid operation, but they also possess excellent flow control capabilities and good sealing properties when closed. They are one of the valve types that have seen the fastest development over the past decade or so. Structural features of butterfly valves: The standard structure of a butterfly valve consists mainly of a valve body, a valve disc, driving components, and an actuator; the disc-shaped valve disc rotates back and forth by about 90° to open, close, or regulate the flow of fluid. Its prominent features are small size, light weight, and compact installation dimensions. When the butterfly valve is fully open, the flow resistance is low; when it is opened at an angle of around 15° to 70°, precise flow control is possible, resulting in a nearly logarithmic flow characteristic. Conventional butterfly valves have high leakage rates, and improvements to these valves are primarily aimed at reducing their leakage. The leakage rate of a butterfly valve when it is closed: Traditional butterfly valves are not tight-sealing, with leakage rates exceeding 2%. Through the study of sealing principles, the structural design was improved, and the sealing methods as well as the sealing materials were enhanced; as a result, the leakage rate during closure was **reduced, and hard-sealed butterfly valves can achieve ANSI VI levels of leakage control. The most suitable application for butterfly valves: Butterfly valves are best suited for applications with large diameters and high flow rates, where fast opening and closing speeds are required, as well as in situations where good fluid control properties are necessary, especially when dealing with dirty media. Why will butterfly valves become the dominant valve type for large-diameter applications? The main reasons are as follows: 1. It can be turned on or off with just a 90° rotation, resulting in fast operation; within the range of 15–70°, it exhibits an approximately logarithmic flow characteristic, offering good control performance. 2. The valve body has a function similar to that of a valve seat; it can use the scouring effect of throttling to clean the inner wall of the valve body, thus possessing a \"self-cleaning\" effect, and it can be used with dirty media. 3. It requires little installation space and is easy to maintain. 4. The valve can be opened and closed many times, resulting in a long service life. 5. Through years of effort, Toho Valves has improved the sealing performance of butterfly valves, enhancing their sealing characteristics; butterfly valves with soft seals can achieve zero leakage. What are the limitations of butterfly valves? Due to limitations in structure and sealing materials, butterfly valves are not suitable for use under particularly high pressure or pressure difference conditions. Compared to ball valves and gate valves, butterfly valves have a higher pressure loss, making them unsuitable for applications where extremely low valve resistance is required. The valve disc cannot avoid the erosion caused by the high-speed medium at the center of the channel, and the \"crescent\"-shaped throttling area resulting from low-opening throttling affects the valve’s resistance to clogging, thereby impacting its usability. Actuators for butterfly valves In practical applications, butterfly valves can be equipped with electric actuators or pneumatic actuators. For use in switching and shutting off functions, electric actuators are used to create electric switch-type butterfly valves, while pneumatic piston actuators are used to create pneumatic switch-type butterfly valves. Alternatively, an electrically controlled actuator can be used to form an electrically controlled butterfly valve; a valve positioner is installed on the pneumatic actuator, which sends control signals in the 4-20mA format, thereby enabling regulation of the valve and resulting in a pneumatically controlled butterfly valve.