The reasons for the difference in thermal expansion include the difference in the thermal expansion coefficient of materials, the difference in the thermal load of parts and the difference in the constraint conditions of parts. For bare valves, if the working gap between valve parts is not designed accurately under the condition of cold flow, The possibility of abrasion and seizure during work is greater than that of mild and good words. Because in the process of thermal alternation, for the same valve, there are more times of hot state closing and lifting state opening when it is exposed than when it is well insulated. The cause of scratches and seizure is that when the hot fluid enters the cold valve, the valve disc is surrounded by the hot fluid. Since the heat dissipation of the valve disc is only carried out by the valve stem with smaller section connected to it, the whole valve disc can quickly reach the temperature of the pipeline fluid. The seat ring is almost heated at the same time as the valve disc. The heat dissipation condition of the seat drawing is better than that of the valve disc. However, the linear expansion of the valve body is often less than that of the seat ring, so the valve body limits the radial expansion of the seat ring. In this way, scratches may occur between the flap and the seat ring. For the valve body with good temperature, the overall average temperature of the valve body will be higher than the average temperature of the valve body without thermal insulation. Although the linear expansion of the valve body is correspondingly larger, the restriction on the linear expansion of the seat ring will be smaller, and the possibility of scratches between the valve disc and the valve seat will be smaller.

High speed mechanical performance can increase the difference between them. The trend of multinational companies coming to China to buy pneumatic butterfly valves is still unfolding, and the opening of new international shopping malls is also promising. Therefore, although the overall development speed of the pneumatic butterfly valve profession in China has slowed down, and the competition is fierce, the prospects are still optimistic.