What is a stop valve?
The shut-off valve, also known as the gate valve, is a forced-sealed valve, so when the valve is closed, pressure must be applied to the valve flap to force the sealing surface to not leak. When the medium enters the valve from below the valve flap, the resistance to be overcome by the operating force is the friction between the stem and the packing and the thrust generated by the pressure of the medium. The force of closing the valve is greater than the force of opening the valve, so the valve stem The diameter of the stem should be large, otherwise the valve stem can be bent.
There are three types according to the connection method: flange connection, thread connection, and welding connection. After the self-sealing valve appears, the medium flow direction of the shut-off valve is changed into the valve cavity from above the valve flap. At this time, under the action of the medium pressure, the force of closing the valve is small, and the force of opening the valve is large, and the diameter of the valve stem can be correspondingly Reduced. At the same time, this type of valve is also tight under the action of the medium. China's valve "three-way to give" has stipulated that the flow of the stop valve, all from top to bottom. When the shut-off valve is opened, the opening height of the valve flap is 25% to 30% of the nominal diameter. The flow rate has reached the maximum, indicating that the valve has reached the fully open position. Therefore, the full open position of the shutoff valve should be determined by the stroke of the valve flap.
The opening and closing member of the stopvalve (GlobeValve) is a plug-shaped valve flap with a flat or sea-cone surface on the seal, and the valve flap moves linearly along the center line of the valve seat. The movement of the valve stem (common name: dark rod), also has a lifting rotary rod type that can be used to control various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. flow. Therefore, this type of shut-off globe valve is well suited for shut-off or regulation and throttling. Due to the relatively short opening or closing stroke of the valve stem of this type of valve, and the very reliable cutting function, and because the change of the valve seat opening is proportional to the stroke of the valve flap, it is very suitable for the adjustment of the flow rate.