The prominent feature of the midline butterfly valve is that the valve stem axis, butterfly plate center, and body center are in the same position. This structural design is relatively simple, with low manufacturing process difficulty and relatively economical cost. Common centerline butterfly valves often use soft sealing forms, such as rubber lined butterfly valves and fluorine lined butterfly valves. The sealing principle is to use elastic sealing materials such as rubber or polytetrafluoroethylene. When the valve is closed, the butterfly plate squeezes the sealing material, causing it to undergo elastic deformation and filling the gap between the butterfly plate and the valve body, thereby achieving a good sealing effect.

The advantages of the midline butterfly valve are very prominent. It has a simple structure, is easy to manufacture and maintain, and has reliable sealing performance. It performs well in general low-pressure, room temperature, and non corrosive medium transportation scenarios, making it a cost-effective valve choice. However, it also has some limitations. Due to the constant compression and scratching of the butterfly plate and valve seat during the opening and closing process, there is significant resistance and rapid wear of the sealing surface, which affects the service life of the valve. Moreover, due to the sensitivity of the elastic sealing material used to temperature, the performance of the sealing material will decrease in high temperature environments, and even deformation, aging and other problems may occur. Therefore, the centerline butterfly valve is usually not suitable for working conditions with high temperature, high pressure and strong abrasion media.