Structural principle of globe valve（3）

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.

The working principle of a globe valve is to rely on electric thrust to rotate the valve stem, causing the sealing surface of the valve disc to closely fit the sealing surface of the valve seat, preventing medium flow. The sealing of the globe valve is reliable, with a simple structure and convenient maintenance. The sealing surface and spherical surface are often in a closed state and are not easily eroded by the medium. As an extremely important globe valve, the sealing of the globe valve is achieved by applying torque to the valve stem and pressure to the axial direction of the valve disc, making the sealing surface of the valve disc and the sealing surface of the valve seat tightly adhere to prevent medium leakage along the sealing surface gap.