EN 1092 Forging Manufacturer | European Circular Flange Standard Forgings (PN Series) | Shivam Forge

PN Rating Versus Class Rating — Why EN 1092 Isn't Simply ASME B16.5 With Metric Bolt Holes

EN 1092-1 functions as the default flange standard across European piping, valve, and process equipment specification in the same way ASME B16.5 dominates North American and much of Asian and Middle Eastern practice, and for manufacturers supplying into European projects or exporting equipment to European end customers, understanding that these are two genuinely independent standards — not one standard expressed in two unit systems — is the starting point for correct flange sourcing. The confusion is understandable: both standards cover circular flanges, both organize their pressure ratings by material group and temperature, and both cover the same basic flange types (weld-neck, slip-on/plate, blind, and loose/backing flanges). But the actual numbers governing bolt circle diameter, bolt hole count and size, and facing dimensions are defined independently within each standard, and they do not convert cleanly from one to the other even at nominal pressure ratings that appear roughly comparable.

This distinction has real practical consequences in flange sourcing and manufacturing. A PN 16 flange, for instance, is sometimes loosely described as 'similar to Class 150,' and in terms of general pressure capability at certain temperatures for certain material groups, that comparison isn't unreasonable as a rough guide — but the PN 16 flange's actual bolt circle diameter, number and size of bolt holes, and raised face dimensions are defined by EN 1092-1's own tables, not derived from ASME B16.5's Class 150 table. A flange forged and machined to an approximated conversion between the two standards, rather than to EN 1092-1's genuine dimensional requirements, risks bolt holes that don't align with a mating EN-specification flange or valve, or facing dimensions that don't produce a correct gasket seating surface — problems that only become apparent during field installation, at a point where correction is expensive and schedule-impacting.

The PN rating series itself — PN 6, 10, 16, 25, 40, and upward through PN 100 — spans the same broad range of low-pressure utility piping through high-pressure process and power applications that ASME's Class series covers, and EN 1092-1's material group tables extend across carbon steel, low-alloy steel, and stainless steel grades referenced to their corresponding European material standards. Selecting the correct PN rating and material group combination for a given project's actual operating pressure and temperature envelope requires the same careful pressure-temperature table lookup that correct ASME Class selection does — the underlying engineering discipline is identical even though the specific tables, and the flange geometry that results, are not.

For European piping and valve manufacturers, and for Indian and Asian equipment exporters supplying projects specified to EN standards, Shivam Forge manufactures forged flange blanks machined to genuine EN 1092-1 dimensional tables across the PN 6 through PN 100 series in carbon, alloy, and stainless steel grades. Contact our engineering team at +91-9265772827 or sales@shivamforge.com with your PN rating, material group, and flange type specification for a manufacturability review and quotation.