Cut-off valve also known as The Intercept, is a mandatory sealing valve, so when the valve is closed, it is necessary to pressure the disc to force the seal surface not to leak. When the medium enters the valve under the disc, the operation force needs to overcome the resistance, is the valve stem and filler friction and the pressure of the media generated by the thrust, the force of the valve is greater than the opening valve, so the diameter of the stem is large, otherwise the valve stem top bending failure. Divided into three types by connection: flange connection, wire buckle connection, welding connection. Since the sealing valve appears, the media flow of the cut-off valve will be changed from above the disc into the valve cavity, at this time under the action of medium pressure, close the valve force is small, and open the valve force is big, the stem diameter can reduce accordingly. At the same time, in the role of the media, this form of valve is also more stringent. China's valve "three to" has stipulated that the flow of the cut-off valve, the use of Top-down. When the cut-off valve is open, the opening height of the disc is the $number of the nominal diameter. The flow has reached maximum, indicating that the valve has reached full open position. Therefore, the full open position of the globe valve should be decided by the disc stroke.
The closing valve is a plug-shaped disc, sealed above the plane or sea cone, the disc along the center of the seat line for straight motion. The movement of the stem, (common name: Dark Rod), also has the lifting and rotating rod type can be used to control air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media and other types of fluid flow. As a result, this type of shutoff valve valve is ideally suited for cutting or regulating and throttling. Because the valve stem of this kind of valve opens or closes the travel relatively short, and has the very reliable cut off function, also because the valve seat pass the mouth change and the valve petal's stroke to become the positive proportional relation, is suitable for the flow adjustment.