How do I determine the size of a flange?
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When notifying the maintenance staff to remove the flange, they often ask what size the flange is – there are 25-inch and 40-inch ones. How is it determined?
What is mentioned refers to the inner diameter of the pipe~ Pay attention to the pressure rating
The last edit to this post was made by lzhrain on 2016-12-27 at 07:55. “There are those with a diameter of 25 and those with a diameter of 40” refers to DN25 and DN40; these are nominal diameters (not the outer or inner diameter). Refer to HG/T 20592~20635-2009 for information on steel pipe flanges, gaskets, and fasteners, as well as the corresponding outer diameter of the pipes
The flange itself should have markings. . . .
Check the size, or look at the markings on the flange; they are usually covered by paint and therefore not visible.
The sides of the flange usually have markings indicating the pipe diameter and pressure rating. Furthermore, the diameter of the pipes in the workshop should be visible at a glance.
Yes, looking at the side of the flange, if you are familiar with pipelines, you can also check the size of the pipes at the butt-welded ends
This is all based on the diameter. Flanges usually have markings such as WN 300LB 1\" RF A105 ASME B16.5, etc. It’s not difficult to determine a flange’s diameter (as long as it’s not a custom-made one). But once the diameter is known, what about the pressure? With practice, one can figure out what the pressure and specifications are; however, those who are not familiar with this need to know the standards for flanges. Because even if the diameter is the same, different pressures result in different outer diameters, thicknesses, bolt hole sizes, etc. (There are also cases where these remain the same, usually for smaller diameters like DN15-DN50, where pressures from PN10 to PN40 are identical)
There are markings on the flange; if you don’t check the valve
Generally, flanges are denoted as DN**, CL150 or CL300, CL600, SCH20 or SCH40, followed by the face type RF or RJ, M, FM. Flanges also come in American standards and Chinese standards, with different nominal diameters and different pressure ratings; the Chinese standard uses the PN** series.
Check the markings; if it doesn’t work, measure to meet the standard