Cast steel globe valve

A shut-off 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. At the same time, under the action of the medium, this type of valve is also relatively tight. The "three modernizations" of valves in China once stipulated that the flow direction of shut-off valves should be from top to bottom. When the shut-off valve is opened, the opening height of the valve disc is between 25% and 30% of the nominal diameter. When the flow rate has reached, it indicates that the valve has reached the fully open position. So the fully open position of the shut-off valve should be determined by the stroke of the valve disc.

The opening and closing part of a cast steel globe valve is a plug shaped valve disc, with a flat or conical surface on the sealing surface. The valve disc moves in a straight line along the centerline of the valve seat. The movement form of the valve stem can also be used to control the flow of various types of fluids, such as air, water, steam, various corrosive media, mud, oil products, liquid metals, and radioactive media. Therefore, this type of shut-off valve is very suitable for cutting, regulating, and throttling purposes. Due to the relatively short opening or closing stroke of the valve stem and the highly reliable cut-off function, as well as the proportional relationship between the change of the valve seat opening and the stroke of the valve disc, this type of valve is very suitable for regulating flow.