The cut-off valve, also known as the cut-off valve, is a forced-to-close valve, so when the valve is closed, pressure must be applied to the valve to force the sealing surface not to 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 the closing valve is greater than the force of the opening valve, so the valve stem The diameter should be large, otherwise there will be stem bending failure. According to the connection is divided into three types: flange connection, screw connection, welding connection. From the appearance of the self-sealing valve, the media flow direction of the stop valve is changed into the valve cavity from above the valve flap. At this time, under the pressure of the medium, 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 corresponding. Reduce. At the same time, this type of valve is also tighter under the influence of the medium. China's valve "three to give" has stipulated that the flow direction of the globe valve shall be adopted 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 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 valve of the stop valve (Globe Valve) is a plug-shaped valve flap. The sealing surface is a plane or a sea cone, and the valve flap moves linearly along the centerline of the valve seat. The valve stem movement mode (common name: dark rod), and lifting and rotating rod type can be used to control various types of fluids such as air, water, steam, various corrosive media, mud, oil products, liquid metal, and radioactive media. flow. Therefore, this type of shut-off shut-off valve is very suitable for cutting or regulating and throttling. Because the valve stem of this type of valve has a relatively short opening and closing stroke and a very reliable cutting function, because the change of the valve seat port is proportional to the stroke of the valve disc, it is very suitable for regulating the flow rate.