The fluorine-lined globe valve is a forced seal valve, so when the valve is closed, pressure must be applied to the valve disc to force the sealing surface not to leak. When the medium enters the valve from below the valve disc, the resistance that the operating force needs to overcome is the friction force of the valve stem and the packing force and the thrust generated by the pressure of the medium. The force of closing the valve is larger than the force of opening the valve, so the diameter of the valve stem should be large, otherwise the failure of the top bending of the valve stem will occur. After the self-sealing valve appears, the medium flow of the stop valve changes from the top of the valve disc into the valve chamber, then under the action of the medium pressure, 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 reduced accordingly. At the same time, under the action of the medium, this form of valve is also more tight. China’s valve “three to” has stipulated that the flow of the globe valve, all top-down.
When the fluorine lined stop valve is opened, the opening height of the valve disc is 25% to 30% of the nominal diameter, and the flow rate has reached the maximum, indicating that the valve has reached the fully open position. Therefore, the full open position of the globe valve should be determined by the stroke of the valve disc.