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Oxygen shut-off valves are often used in physical and chemical experiments with gases such as oxygen, nitrogen, hydrogen, argon, etc. These gases are usually stored in dedicated high-pressure gases. When in use, the gas pressure is reduced to the required range for the experiment through a pressure reducing valve, and then finely adjusted through other control valves to input the gas into the system.
The oxygen shut-off 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 not to leak. When the medium enters valve six from below the valve disc, the resistance that the operating force needs to overcome is the frictional force between the valve stem and the packing, as well as the thrust generated by the pressure of the medium. The force required to close the valve is greater than the force required to open it, so the diameter of the valve stem should be larger, otherwise the valve stem will bend due to failure. After the appearance of self sealing valves, the flow of medium in flange globe valves is changed to enter the valve chamber from above the valve disc. At this time, under the pressure of the medium, 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. Meanwhile, under the influence of the medium, this type of valve is also relatively tight. The "Three Modernizations" of valves in our country have stipulated that the flow direction of globe valves must be from top to bottom.
When the oxygen shut-off valve is opened and the opening height of the valve disc is 25% to 30% of the nominal diameter, the flow rate has reached its maximum, indicating 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.