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How is the bore diameter of a flange Type 21 - acc. EN 1092-1 determinated?

In the standard:

NOTE 5 The bore diameters of flanges type 21 are not specified in this standard, the effective bore diameters are usually given in the relevant component standard(s).

What are the relevant component standard(s)?

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  • $\begingroup$ related to the pressure rating? $\endgroup$ – Solar Mike Apr 25 '19 at 13:11
  • $\begingroup$ I would assume so, but it's not provided in the table. For ASME Long Welding Neck flanges it's provided per standard. $\endgroup$ – Mech_Engineer Apr 25 '19 at 13:14
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Type 21 flanges are "integral flanges" and in my experience these are completely manufacturer dependent. This grouping would include long weld neck (LWN), heavy barrel (HB), equal barrel (EB), or any other custom offering. I've experienced where two NPS 2" long weld neck flanges on the same pressure vessel built around 1994 had different thicknesses because they were procured from two different suppliers. I think this is less common now as manufacturers have consolidated.

I believe this is why the EN1092-1 refers to component standards, which I read to mean manufacturer's standard.

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Presumably it will be welded to pipe. Pipe is defined by outer diameter and the nozzle must match the pipe OD. The ID of the pipe depends on Schedule so it is variable. The nozzle manufacturer will probably make generic nozzles to a thick sch. like 120 ; then it can be used with Sch. 120, 80, 40, and 20. Thicker and thinner Sch. are likely to be custom orders. The ID in not specified.

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