The PN1.6MPa flange cast steel globe valve belongs to the forced sealing type 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 6 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. In recent years, since the emergence of self sealing valves, the medium flow direction of PN1.6MPa flange cast steel globe valves has shifted from above the valve disc to 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 PN1.6MPa flange cast steel globe valve is opened, the opening height of the valve disc reaches 25% to 30% of the nominal diameter, and 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. This type of valve should generally be installed horizontally in pipelines.
Operating principle and structural description of PN1.6MPa flange cast steel globe valve
1. When the handwheel is turned clockwise, the valve stem moves downward and the valve disc descends to seal the sealing surface, cutting off the passage. When reversed, it opens and the valve stem is lifted to the highest point for sealing to take effect.
2. This valve has added an upper seal. When the valve is open, it has two layers of sealing effect together with the packing, and has a certain protective effect on the packing
3. This valve uses nylon products as the sealing surface, and the filler is soft formed filler. The upper seal is also made of soft material, with good sealing performance.
