What is a stop valve?

On January 18, a female doctor at the Liusha Branch of Ningxiang City People's Hospital in Hunan Province was praised as the "Most Beautiful Doctor in Ningxiang" for seeing patients while receiving an IV drip. The doctor involved, Cheng Li, told The Paper (www.thepaper.cn) on January 19 that "For minor illnesses like this, as long as it doesn't affect our work, we basically insist on working." It is understood that Cheng Li is the director of the obstetrics and gynecology department at the Liusha Branch of Ningxiang City People's Hospital, where she has worked for seven years. On January 18, she felt a little unwell, but it was her turn to be on duty, so she saw patients while receiving an IV drip. According to previous reports from Hunan Economic Television, Cheng Li had an IV drip in her left hand and held [untranslated]

　　The stop valve, also known as a gate valve, is a type of positive shut-off valve. Therefore, when the valve is closed, pressure must be applied to the disc to force the sealing surface to be leak-proof. When the medium enters the valve from below the disc, the resistance that the operating force needs to overcome is the friction between the stem and the 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 stem should be large, otherwise, the stem may bend.

　　According to the connection method, it is divided into three types: flange connection, threaded connection, and welded connection. Since the advent of self-sealing valves, the medium flow direction of the stop valve has been changed to enter the valve cavity from above the disc. At this time, under the action of medium pressure, the force to close the valve is small, and the force to open the valve is large, and the diameter of the stem can be reduced accordingly. At the same time, under the action of the medium, this form of valve is also tighter. China's valve 'Three Modernizations' once stipulated that the flow direction of the stop valve should always be from top to bottom. When the stop valve is opened, the opening height of the disc 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 fully open position of the stop valve should be determined by the stroke of the disc.

　　The opening and closing part of the stop valve (stopvalve, GlobeValve) is a plug-shaped disc. The sealing surface is flat or conical. The disc moves linearly along the center line of the valve seat. The movement form of the valve stem (common name: hidden stem) also has lifting and rotating stem type, which can be used to control the flow of air, water, steam, various corrosive media, mud, oil, liquid metal, and radioactive media and other types of fluids. Therefore, this type of shut-off valve is very suitable for shut-off, regulation, and throttling purposes. Since the opening or closing stroke of this type of valve stem is relatively short and has a very reliable shut-off function, and because the change in the valve seat port is directly proportional to the stroke of the disc, it is very suitable for flow regulation.

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