When the medium enters the valve from under the valve disc, the resistance that the operating force needs to overcome is the friction force between the valve stem and the packing and the thrust generated by the pressure of the medium. The force to close the valve is greater than the force to open the valve, so the valve stem. The diameter of the valve should be large, otherwise the failure of the top of the valve stem will occur.

The internal thread globe valve is a forced sealing valve, so when the valve is closed, pressure must be applied to the valve disc to force the sealing surface to not leak. After the appearance of the self-sealing valve, the medium flow direction of the internal thread and flange globe valve is changed from the top of the valve disc into the valve cavity. At this time, under the action of the medium pressure, the force to close the valve is small, while the force to open the valve is large. The diameter of the rod can be reduced accordingly. At the same time, under the action of the medium, this form of valve is also tighter. my country's valve "Three Chemicals" once stipulated that the flow direction of the globe valve should be from top to bottom. This type of valve should generally be installed horizontally in the pipeline.
When the internal thread globe valve is opened, when the opening height of the valve disc is 25% to 30% of the nominal diameter, the flow rate has reached the maximum, indicating that the valve has reached the fully open position. Therefore, the fully open position of the globe valve should be determined by the stroke of the valve disc.