The stop valve, also known as the stop valve, is a forced sealing valve. Therefore, when the valve is closed, pressure needs to be applied to the valve disc to force the sealing surface not to leak.

When the medium enters the valve from below the valve disc, the resistance to be overcome by the operating force is the friction between the valve stem and packing and the thrust generated by the pressure of the medium. The force to close the valve is greater than the force to open the valve, so the diameter of the valve stem should be larger, otherwise the failure of valve stem jacking will occur.

There are three connection modes: flange connection, screw connection and welding connection. After the emergence of the self sealing valve, the medium flow direction of the stop valve changes from above the valve disc to enter the valve chamber. At this time, under the action of medium pressure, the force to close the valve is small, while the force to open the valve is large, and the diameter of the valve stem can be reduced accordingly. At the same time, under the action of medium, this form of valve is also more tight. The "three modernizations" of valves in China once stipulated that the flow direction of stop valves should be from top to bottom.

When the stop valve is opened, when the opening height of the valve disc is 25% ~ 30% of the nominal diameter, the flow has reached greater, indicating that the valve has reached the fully open position. Therefore, the full open position of the stop valve shall be determined by the stroke of the valve disc.

The opening and closing part of the stop valve is a plug-shaped disc. The sealing surface is a plane or sea cone, and the disc moves in a straight line along the center line of the valve seat. The movement form of valve stem (general name: concealed rod) is also of lifting rotary rod type, which can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil products, liquid metal and radioactive media. Therefore, this type of shut-off valve is very suitable for cut-off or regulation and throttling. Because the opening or closing stroke of the valve stem of this kind of valve is relatively short, and has a very reliable cut-off function, and because the change of the valve seat opening is directly proportional to the stroke of the valve disc, it is very suitable for the regulation of flow.