Rotation of the handle shut-off valve

Rotating the handle cut off valve, also known as gate valve, valve seal is mandatory, so that when the valve is closed, the pressure must be applied to the valve to force the sealing surface does not leak. When the media from below the valve into the valve, the operating force required to overcome resistance, friction is thrust by the pressure generated by the medium of stem and packing, close the valve force greater than the force to open the valve, so that the stem the larger the diameter, otherwise the stem top bend failures occur. Divided into three types according to connection: flanged, threaded connection, welded connection. From the self-sealing valve appears, turn the handle off the media flow valve on the change into the valve chamber from above the valve, then in the medium under pressure, the valve off a small force, and force open the valve, the valve stem diameter It can be reduced accordingly. Meanwhile, in the role of the media, this form of valve is also more rigorous. China's valve "three to" has been predetermined, rotation of the handle flow shut-off valve, all top-down. When rotating the handle cut-off valve open, the valve opening height, the nominal diameter of 25% to 30% of the time. The maximum flow rate has been reached, the valve has reached the fully open position. So off valve fully open position, valve stroke should be determined.