ASME, DIN, and JIS represent three major flange standardization systems used worldwide. ASME B16.5 dominates in the Americas and international oil and gas projects. DIN (now EN 1092-1) is standard across Europe and European-designed plants. JIS B2220 governs Japanese-engineered facilities across Asia. These three systems define different dimensions, bolt patterns, and pressure rating methods. Flanges from different standards cannot be bolted together.
System Comparison
Feature ASME B16.5 DIN / EN 1092-1 JIS B2220 Size system NPS (inches) DN (mm) A (mm OD) / B (inches) Pressure system Class (150-2500) PN (6-400) K (5K-63K) Dimension basis Imperial (inch) Metric (mm) Metric (mm) Bolt sizing Imperial (UNC thread) Metric (ISO thread) Metric (ISO thread) Raised face height 1.6 mm (Cl. 150/300), 6.4 mm (Cl. 400+) 2.0 mm (standard) 2.0 mm (standard) Size range NPS 1/2-24 (B16.5); NPS 26-60 (B16.47) DN 10-4000 10A-1500A Material specs ASTM EN 10222 JIS G series Geographic use Americas, Asia (oil & gas), global offshore Europe, Middle East, Africa Japan, Southeast Asia, Korea
Dimensional Comparison: 6-inch / DN 150 / 150A Weld Neck
Parameter ASME Class 150 EN/DIN PN 16 JIS 10K Flange OD 279.4 mm 285 mm 280 mm Bolt circle 241.3 mm 240 mm 240 mm Number of bolts 8 8 8 Bolt size 3/4 in UNC M20 ISO M20 ISO Bolt hole dia. 22.4 mm 22 mm 23 mm Flange thickness 22.4 mm 22 mm 22 mm RF height 1.6 mm 2.0 mm 2.0 mm
Dimensions appear close but are NOT identical. Bolt thread types (UNC vs. ISO metric) make physical bolt-up impossible without custom fasteners.
At sizes near DN 150/NPS 6, all three standards produce flanges with similar OD and bolt circle. This creates a dangerous temptation to mix standards on site. The bolt holes, bolt threading, and RF heights are different—and even 1 mm of misalignment compromises gasket seating. Never mix ASME, EN/DIN, and JIS flanges in the same joint.
Pressure Rating Cross-Reference
Service Level ASME B16.5 EN 1092-1 JIS B2220 Low-pressure utility Class 150 PN 10 / PN 16 10K Medium-pressure process Class 300 PN 40 20K / 30K High-pressure process Class 600 PN 100 63K Very high pressure Class 1500 PN 250 No JIS equivalent Extreme pressure Class 2500 PN 400 No JIS equivalent
These are approximate equivalences only. Actual P/T ratings vary by material group.
Material Cross-Reference
Type ASME (ASTM) EN JIS Carbon steel forging A105 P250GH (EN 10222-2) SFVC2A Low-temp CS A350 LF2 P285NH (EN 10222-4) SFVAF2 304 Stainless A182 F304 1.4301 (EN 10222-5) SUS 304 316 Stainless A182 F316 1.4401 (EN 10222-5) SUS 316
On international projects, the piping material specification must clearly state one standard for the entire plant. Mixing ASME and EN flanges across different units creates procurement complexity, warehouse management issues, and construction errors. If different standards must coexist (e.g., ASME process piping connecting to EN-standard equipment ), use dedicated transition spools at the boundary.
Read the full guide to flanges
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