JIS, ANSI/ASME and DIN/EN flange systems are not interchangeable simply because they share the same nominal pipe size. Their pressure designations, outside diameters, bolt circles, hole counts, facing details and materials are governed by different standards. A reliable joint begins by identifying the complete flange specification—not by matching only the bore.
This guide explains what JIS and DIN mean with regard to size standards, how DIN flanges, ANSI flange patterns and JIS flange dimensions differ, and which checks are essential before ordering or replacing a flange.
What do JIS, ANSI and DIN mean for flange sizes?
JIS refers to Japanese Industrial Standards. For common pipe flanges, JIS B 2220 is widely used and pressure ratings are commonly written as 5K, 10K, 16K or 20K. ANSI is often used in purchasing language for the North American flange series; current dimensions and pressure-temperature rules are generally controlled by ASME standards such as ASME B16.5 and ASME B16.47. DIN refers to German standards; in modern European projects, many flange dimensions are specified through EN 1092-1 while the older DIN terminology remains common in the market.
| System | Common reference | Typical pressure notation | Where it is frequently specified |
|---|---|---|---|
| JIS | JIS B 2220 | 5K, 10K, 16K, 20K | Japanese machinery, marine equipment and Asian process plants |
| ANSI / ASME | ASME B16.5; ASME B16.47 | Class 150, 300, 600, 900, 1500, 2500 | North America, oil & gas, power and global EPC projects |
| DIN / EN | EN 1092-1 and related DIN series | PN 6, 10, 16, 25, 40, 63, 100 | European equipment, water, chemical and industrial piping |
Why nominal pipe size alone cannot prove compatibility
DN and NPS identify a pipe-size family; they do not define a mating flange. A DN 100 DIN flange and an NPS 4 ASME flange can have a similar bore, yet the bolt circle, flange outside diameter, number of bolt holes, bolt diameter and facing geometry may be different. The same caution applies to a JIS 10K flange compared with a Class 150 or PN 16 part. Those labels should never be treated as direct conversion formulas.
Key dimensional differences: DIN flange, ANSI flange patterns and JIS flange
| Feature to compare | Why it changes between systems | What to record on the enquiry |
|---|---|---|
| Pressure designation | Class, PN and K systems use different rating methods and tables. | Full standard plus class / PN / K rating and design temperature |
| Outside diameter | Each dimensional series assigns its own flange envelope. | Measured OD and nominal size |
| Bolt pattern | Hole count, bolt-circle diameter and hole diameter vary by standard. | Number of holes, PCD, hole diameter and bolt type |
| Facing | RF, FF, RTJ and other faces have different contact geometry. | Facing type, raised-face height and finish requirement |
| Thickness / hub | Design pressure, material group and flange type affect section dimensions. | Flange type, thickness, hub dimensions and material |
Understanding ANSI flange patterns
An ANSI flange pattern is commonly used to describe the bolt-hole layout of an ASME flange. It should be specified by the governing standard, nominal size and class—for example, ASME B16.5 NPS 6 Class 300, raised face. The pattern includes more than the hole count: bolt circle, hole diameter, flange OD, thickness and facing must all correspond to the same standard table. For large diameters, ASME B16.47 Series A and Series B are separate dimensional series and must not be mixed.
How JIS flange ratings differ
JIS K ratings are a recognized Japanese pressure designation, but “10K” does not automatically mean the flange will mate with a PN 16 or Class 150 connection. At some sizes the layouts may appear close, but a visual match is not an engineering verification. Confirm the JIS standard, material, flange type and exact drawing. In marine and equipment replacement work, also check whether the counterpart is a legacy or manufacturer-specific pattern.
DIN flanges and the EN transition
Many buyers still request DIN flanges by familiar names such as DIN 2576, DIN 2633 or DIN 2635. European flange documentation today often cites EN 1092-1 instead. The correct way to source a DIN flange is to identify the current governing document, DN size, PN rating, type/form, material and facing. This avoids ordering an obsolete or superficially similar flange that does not suit the installation.
Selection workflow for replacement and new projects
- Read the line list and drawing: identify the stated flange standard, size, pressure rating, material and facing.
- Measure the existing part: verify outside diameter, bore, thickness, bolt-circle diameter, hole count and hole diameter.
- Confirm the joint design: check gasket type, bolt material, corrosion allowance and operating temperature.
- Compare official dimensional tables: use the exact standard edition and do not infer interchangeability from DN/NPS alone.
- Control documentation: request material certificates, marking, heat number and inspection requirements where required.
Common mistakes to avoid
- Equating PN 16, Class 150 and JIS 10K without checking the complete dimensions.
- Ordering only “DN 50 flange” with no standard, rating, face or material.
- Counting bolt holes but not measuring the bolt-circle diameter.
- Using a raised-face gasket on a flat-face joint or vice versa.
- Mixing ASME B16.47 Series A and Series B on large-diameter piping.
Practical enquiry checklist
For a dependable quotation, provide: standard and edition; DN or NPS; PN, Class or K rating; flange type (weld neck, slip-on, blind, threaded or lap joint); facing; material grade; pipe schedule or wall; quantity; coating; and required certificates. If the standard is unknown, include clear measurements and photos of both flange faces and the bolt pattern.
Final takeaway
JIS, ANSI/ASME and DIN/EN systems each define a complete flange connection. The safest approach is to treat DIN flanges, ANSI flange patterns and a JIS flange as distinct engineered standards until the drawings prove otherwise. Songhai can review a drawing or measured sample and help identify the matching industrial flange specification.