The stop valve is one of the widely used valves. It is popular because the friction between the sealing surfaces in the opening and closing process is small, durable, the opening height is small, easy to manufacture and convenient to maintain. It is not only suitable for medium and low pressure, but also suitable for high pressure. The closing principle of the stop valve is to rely on the pressure of the valve rod to make the sealing surface of the valve disc closely fit the sealing surface of the valve seat and prevent the flow of media. It 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.

The stem axis of the stop valve is perpendicular to the sealing surface of the valve seat, the opening or closing stroke of the stem is relatively short, and has a very reliable cut-off action, which makes this valve very suitable for cutting off or regulating and throttling as a medium.

Once the disc of the stop valve is open, there will be no contact between its seat and the sealing surface of the disc, and it has a very reliable cut-off action. This valve is very suitable for medium cut-off or regulation and throttling.

Once the stop valve is in the open state, there is no contact between its valve seat and the sealing surface of the valve disc, so the mechanical wear of its sealing surface is small. Because the valve seat and valve disc of most stop valves are easy to repair or replace the sealing elements, there is no need to remove the whole valve from the pipeline, which is very suitable for the occasion where the valve and pipeline are welded into one. When the medium passes through such valves, the flow direction changes, so the flow resistance of the stop valve is higher than that of other valves.

The commonly used stop valves are as follows:

1. Angle stop valve

In the angle stop valve, the fluid only needs to change the direction once, so that the pressure drop through the valve is smaller than that of the conventional stop valve.

2. DC stop valve

In the once through or Y-shaped stop valve, the flow channel of the valve body forms an oblique line with the main flow channel, so the damage degree of the flow state is smaller than that of the conventional stop valve, so the pressure loss through the valve is correspondingly smaller.

3. Plunger stop valve

This form of stop valve is a variant of the conventional stop valve. In this valve, the disc and seat are usually designed based on the plunger principle. The valve disc is polished into a column, and the plug is connected with the valve rod. The sealing is realized by two elastic sealing rings sleeved on the plunger. The two elastic sealing rings are separated by a collar, and the sealing ring around the plunger is firmly pressed by the load applied on the bonnet by the bonnet nut. The elastic sealing ring can be replaced and can be made of a variety of materials. The valve is mainly used for "on" or "off", but it is equipped with a special plunger or special collar, which can also be used to adjust the flow.