Introduction: 
The stop valve, also known as the cut-off valve, is one of the most widely used types of valves. It is so popular because during the opening and closing process, the friction between the sealing surfaces is small, it is durable, the opening height is not large, the manufacturing is easy, and maintenance is convenient. It is not only suitable for medium and low pressure but also for high pressure. The closing principle of the stop valve is that it relies on the pressure of the valve lever to make the sealing surface of the valve disc closely adhere to the sealing surface of the valve seat, thereby blocking the flow of the medium. In China's "Three Modernizations" regulations for valves, the flow direction of the stop valve is uniformly required to be from top to bottom, so there is a directionality in installation. The structure length of the stop valve is longer than that of the gate valve, and at the same time, the resistance of the fluid is large. When it is in long-term operation, the sealing reliability is not strong. 
The stop valve, as one of the most important types of shut-off valves, plays a significant role in the aerospace field. As an important component of aerospace equipment, the stop valve realizes functions such as medium transportation, cutoff, and regulation. Its sealing performance directly affects the safe and reliable operation of aerospace equipment. Studying the influencing factors and patterns of the sealing characteristics of typical stop valves has guiding significance for the structural design of valve sealing pairs, thereby improving the sealing performance and reliability of the valves. 

Working principle: 
Valves play a crucial role in cutting off and regulating the medium within the pipeline. The stop valve, as an extremely important type of cutting-off valve, achieves sealing by applying torque to the valve stem. The valve stem exerts pressure on the valve disc in the axial direction, causing the sealing surface of the valve disc to closely adhere to the sealing surface of the valve seat, thereby preventing the medium from leaking through the gaps between the sealing surfaces. 
The sealing pair of the stop valve consists of the valve disc sealing surface and the valve seat sealing surface. The valve stem drives the valve disc to move vertically along the center line of the valve seat. During the opening and closing process of the stop valve, the opening height is relatively small, which is conducive to the regulation of flow rate, and it is easy to manufacture and maintain, with a wide range of pressure application. 
Compared with the other commonly used type of stop valve in industrial production - the gate valve, in terms of structure, the stop valve is simpler and easier to manufacture and maintain. In terms of service life, the sealing surface of the stop valve is less prone to wear and scratching, and there is no relative sliding between the valve disc and the seat sealing surface during the valve opening and closing process. Therefore, the wear and scratching of the sealing surface are smaller, thus increasing the service life of the sealing pair. During the full closing process of the stop valve, the stroke of the valve disc is small, and its height is relatively smaller than that of the gate valve. The disadvantage of the stop valve is that the opening and closing torque is large and it is difficult to achieve rapid opening and closing. Due to the relatively complex flow path inside the valve body, the flow resistance of the fluid is large, resulting in significant loss of fluid energy in the pipeline.