Structural principle of globe valve（4）

Globe valve, also known as a shut-off valve, belongs to the forced sealing type valve. Therefore, 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 needs to be overcome by the operating force is the friction force between the valve stem and 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 diameter of the valve stem should be larger, otherwise the failure of the valve stem top bending will occur. There are three types of connection methods: flange connection, screw connection, and welding connection. After the appearance of self sealing valves, the medium flow direction of the shut-off valve changes from above the valve disc to enter the valve chamber. At this time, under the action of medium pressure, the force to close the valve is small, while the force to open the valve is large, and the diameter of the valve stem can be correspondingly reduced.

When the valve core moves downwards, the gap between the valve core and the valve seat gradually narrows and ultimately closes completely, thereby preventing the passage of fluid. When the valve core moves upwards, the gap between the valve core and the valve seat gradually increases, allowing fluid to pass through. By adjusting the upper and lower positions of the valve core, precise control of fluid flow can be achieved.