Detail:
Valve also known as cut-off valve valve, belongs to compulsory seal valve, so valve is closed in the must to the valve pressure to force the sealing surface leakage. When the medium by the valve flap valve below the operating force required to overcome the resistance, is the valve stem and the friction force generated by the media pressure, the valve opening force is greater than the valve, so the valve stem diameter should be large, otherwise it will be a failure of the valve stem top. According to the connection mode is divided into three types: flange connection, threaded connections, welded connections. The emergence of self sealing valve, cut-off valve of the flow direction of the medium is replaced by the top of the valve into the valve chamber, then in the medium under pressure, force of the valve off a small, and the valve of the force is large, the stem diameter can be reduced 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 been provided, the flow of the valve, the use of top-down. Valve opening, the valve opening height, the nominal diameter of 25% ~ 30%, the flow has reached the maximum, indicating that the valve has reached the full open position. So the full open position of the valve should be determined by the valve flap.
Cutoff (stop valve, globe valve) valve opening and closing parts are plug shaped valve, sealing the upper surface is level or sea surface, the valve flap along the centerline of the valve seat for linear motion. Movement form of the valve stem, (general name: dark bar), there are also lift rotary rod can be used to control air, water, steam, a variety of corrosive media, mud, oil, liquid metal and radioactive medium and other types of fluid flow. Therefore, this type of cut-off valve is very suitable as a cut or adjust as well as throttle. Because of the valve stem to open or close the trip is relatively short, and has a very reliable cutting function, but also because of the valve seat through the mouth of the valve and the valve is proportional to the stroke, is very suitable for traffic regulation.
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