How to Order EN 1092 Flanges
EN 1092-1 is the European standard for steel flanges. Unlike the ASME system (which uses NPS and Class), EN flanges are designated by DN (nominal diameter) and PN (nominal pressure). The dimensional, tolerance, and pressure-temperature rating rules are fundamentally different from ASME B16.5, and the two systems are not interchangeable.
EN 1092-1 covers forged and plate flanges in sizes from DN 10 to DN 4000 and PN ratings from PN 2.5 to PN 400.
Core Attributes
Every EN 1092-1 flange line item must include all of the following attributes.
| # | Attribute | Values / Options | Notes |
|---|---|---|---|
| 1 | Flange type | Type 01 (plate flange for welding), Type 02 (loose plate flange with weld-on ring), Type 05 (blind flange), Type 11 (weld neck flange), Type 12 (hubbed slip-on flange), Type 13 (threaded flange), Type 21 (lap joint flange) | The type number must be stated; “weld neck” alone is ambiguous without confirming Type 11 |
| 2 | Dimensional standard | EN 1092-1 | Do not reference ASME B16.5 when ordering EN flanges. The standards define different dimensions for the same nominal sizes |
| 3 | Nominal size | DN 10 through DN 4000 | Always use DN designation. Do not use NPS when ordering to EN 1092-1 |
| 4 | Pressure rating | PN 2.5, 6, 10, 16, 25, 40, 63, 100, 160, 250, 320, 400 | PN is a dimensionless number that designates the pressure-temperature rating system. The actual allowable pressure at elevated temperatures is determined from the material group and EN 1092-1 tables |
| 5 | Face form | Form A (flat face), Form B (raised face), Form C (tongue), Form D (groove), Form E (spigot), Form F (recess) | Form A: full-face gasket required. Form B: standard raised face for soft gaskets and spiral wound gaskets. Forms C/D and E/F are matched pairs for high-integrity joints |
| 6 | Material specification | See material table below | EN flanges reference EN 10222 (forgings) or EN 10025/10028 (plate). Always state the full standard and grade |
| 7 | Manufacturing form | Forged (per EN 10222) or Plate (per EN 10025/10028) | Plate flanges (cut from plate) are limited to lower PN ratings and temperatures. Forged flanges are required for higher ratings and critical services |
Material Specifications
| Service | Material Standard | Common Grades | EN Designation |
|---|---|---|---|
| Carbon steel (forged) | EN 10222-2 | P245GH, P250GH, P280GH | 1.0460, 1.0481, 1.0483 |
| Carbon steel (plate) | EN 10025-2 | S235JRG2, S275JR | 1.0038, 1.0044 |
| Alloy steel (Cr-Mo, forged) | EN 10222-2 | 16Mo3, 13CrMo4-5, 10CrMo9-10 | 1.5415, 1.7335, 1.7380 |
| Austenitic stainless steel (forged) | EN 10222-5 | X2CrNi19-11, X2CrNiMo17-12-2 | 1.4306 (304L equiv.), 1.4404 (316L equiv.) |
| Duplex stainless steel (forged) | EN 10222-5 | X2CrNiMoN22-5-3, X2CrNiMoCuWN25-7-4 | 1.4462 (2205 equiv.), 1.4410 (2507 equiv.) |
| Low-temperature CS (forged) | EN 10222-3 | P355N, P355NH | 1.0562, 1.0565 |
Optional and Special Attributes
| Attribute | When Required | Details |
|---|---|---|
| PED 2014/68/EU compliance | Equipment placed on the EU market | Specify the Pressure Equipment Directive category (I through IV) and conformity assessment module (A, A2, B+D, B+F, G, H1). The manufacturer must apply CE marking and issue a Declaration of Conformity |
| Impact testing | Low-temperature or per project spec | Specify the test temperature (e.g., -46°C) and acceptance criteria (e.g., 27J minimum per EN 10222-2). The test temperature must match the minimum design metal temperature (MDMT) |
| Dimensional tolerances | Per EN 1092-1 Table 11 | Standard tolerances are defined in the standard. Specify if tighter tolerances are required for specific applications (e.g., heat exchanger flanges) |
| NACE MR0175 / ISO 15156 | Sour service | Same hardness and heat treatment restrictions as for ASME flanges. Must be stated explicitly for EN flanges as well |
| Certificates | Almost always required | EN 10204 Type 3.1 (inspection certificate) minimum. Type 3.2 for critical services. PED category III and IV typically require 3.2 certificates |
| Surface protection | Storage and shipping | Hot-dip galvanizing per EN ISO 1461 for CS flanges in corrosive environments. Specify flange face protectors for transport |
Example Line Items
Correct
50 pcs - Weld Neck Flange Type 11, EN 1092-1, DN 150, PN 40, Form B (raised face), EN 10222-2 P250GH, PED 2014/68/EU Cat. II Module A2, MTR EN 10204 3.1
This line item is complete: flange type with EN designation, standard, nominal size, PN rating, face form, material with full EN standard and grade, PED compliance details, and certificate type.
Incorrect
50 - PN 40 flange DN 150, carbon steel
This line item is missing: the flange type (Type 11? Type 12? Type 05?), the face form (Form A or Form B?), the material specification (P250GH or P280GH? Forged or plate?), PED requirements, and the certificate type. The supplier cannot manufacture or quote without this information.
Common Pitfalls
| Pitfall | Why It Matters |
|---|---|
| Confusing PN with ASME Class | PN 16 is not equivalent to Class 150. PN 40 is not equivalent to Class 300. The pressure-temperature rating curves, bolt circles, and flange dimensions are entirely different between the two systems. A PN 40 flange cannot be bolted to a Class 300 flange |
| Omitting the face form | Form A (flat face) requires a full-face gasket and different bolting torque than Form B (raised face). Specifying the wrong form or omitting it entirely leads to gasket sealing failures |
| Mixing up Form A/B (face form) with manufacturing form | ”Form A” and “Form B” in EN 1092-1 refer to the sealing face geometry (flat vs raised). This is separate from the manufacturing method (forged vs plate). Do not confuse these two uses of the word “form” |
| Plate flanges used above their limits | EN 1092-1 restricts plate flanges to lower PN ratings and temperatures. Using a plate flange (cut from EN 10025 plate) where a forged flange (EN 10222) is required can result in a non-compliant and potentially unsafe installation |
| PED category and module not specified | For flanges placed on the EU market, the Pressure Equipment Directive requires conformity assessment. The buyer must specify (or agree with the manufacturer) the PED category and module. Omitting this may result in flanges that cannot legally be installed in the EU |
| DN/NPS size confusion | DN 150 is not identical to NPS 6” in flange dimensions. While the pipe OD may be the same, the flange bolt circle, bolt hole diameter, thickness, and OD differ between EN 1092-1 and ASME B16.5. Never mix standards on a bolted joint |
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