Overview of EU Flange Standards | EN 13445 | EN 1759 | etc.
The EU’s flange standards extend beyond EN 13445 and EN 1759 to include EN 1092,which is essentially equivalent to ASME B16.5.Currently,major EU corporations widely endorse the EN 13445 standard.Particularly when equipment is exported to Europe or the owner is a large EU enterprise,design compliance with EN 13445 is typically required.
Regarding flange standards,EN 1092 is sometimes adopted,while ASME B16.5 is directly specified in other instances.However,both ASME BPVC and EN 13445 standards carry certain regional limitations,potentially restricting their acceptance.

Furthermore,even if alternative standards are agreed upon,approval from AI/NOBO is required.For standard steel or nickel-based pipe flanges,it is impractical to perform non-standard calculations for each one,and even if attempted,such calculations may not be approved.Currently,standards like EN 13445-3/6/8/10 only directly reference EN 1092-1.
EN 13445 Gasket Strength
However,it is noteworthy that the flange and gasket matching table in EN 13445-3 explicitly lists CLASS grades,indicating that European steel flanges also fall under the CLASS classification (though the main text of EN 13445 does not explicitly state this).Furthermore,the application examples in CEN/TR 13445-101 explicitly reference EN 1759-1.
| PN designated series | Classe designated series | Gasket type | Minimum bolt strength category required |
|---|---|---|---|
| 2,5 to 16 | – | Non-metallic flat gasket with or without jacket | Low strength |
| 25 | 150 | Non-metallic flat gasket with or without jacket | Low strength |
| Spiral-wound metal with filler Corrugated metal jacketed with filler Corrugated metal with or without filler | Medium strength | ||
| 40 | – | Non-metallic flat gasket with or without jacket | Low strength |
| Spiral-wound metal with filler Corrugated metal jacketed with filler Corrugated metal with or without filler | Medium strength | ||
| Flat metal jacketed with filler Grooved or solid flat metal | Alta resistência | ||
| 63 | 300 | Non-metallic flat gasket with or without jacket | Low strength |
| Spiral-wound metal with filler Corrugated metal jacketed with filler Corrugated metal with or without filler | Medium strength | ||
| Flat metal jacketed with filler Grooved or solid flat metal Metal ring joint | Alta resistência | ||
| 100 | 600 | Non-metallic flat gasket with or without jacket Spiral-wound metal with filler Corrugated metal jacketed with filler Corrugated metal with or without filler | Medium strength |
| Flat metal jacketed with filler Grooved or solid flat metal Metal ring joint | Alta resistência |
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Table in Chapter 11 of EN 13445-3
In Chapter 11 of EN 13445-3,we find a crucial table.This table details the matching relationships between flanges and gaskets,particularly the explicit correspondence of CLASS grades.This content further confirms that steel flanges in the European flange system indeed fall within the CLASS grade framework,even though the main text of EN 13445 does not explicitly state this. Furthermore,the application examples within CEN/TR 13445-101 explicitly reference EN 1759-1,underscoring the latter standard’s critical importance in the European flange industry.
| Material | 1.4362 | Design Temp. | 165℃ (329℉) | Rp0.2 at T | 294Mpa |
| Rp0.2 at RT | 400 Mpa | ||||
| Rm at RT | 600 Mpa | ||||
| Allowable stress f: min (Rm/3, Rp0.2/1.5) | at 165℃ | 196 Mpa | |||
| Selected stress: min (0.7Rp0.2 at RT/T,1.25f) | at 165℃ | 205.8 Mpa | |||
| Class 300 Allowable Pressure: min(300×10×Ss/8750, Table B1) | at 165℃ | 49.79 bar 4.979 Mpa | |||
| Class 150 Allowable Pressure: min(115×10×Ss/8750, Table B1, Pt) | at 165℃ | 49.79 bar 4.979 Mpa | |||
| Pt=C2-C3T | at 165℃ | 15.27 bar | |||
| Symbol | Classe | Cal. Press | Allowable Press | U% |
|---|---|---|---|---|
| M6 | 300 | 0.7031 | 4.979 | 14.12 |
| M8 | 300 | 0.9002 | 4.979 | – |
| M10 | 300 | 1.0101 | 4.979 | 20.29 |
Application of EN 13445
Currently,standards such as EN 13445-3/6/8/10 only directly reference the EN 1092-1 standard.However,it is noteworthy that the flange and gasket matching table in EN 13445-3 explicitly lists CLASS grades,indicating that steel flanges in Europe also fall under the CLASS classification system.This content enhances the standard’s influence in Europe.Despite its regional limitations,it is widely accepted and exerts significant impact across the continent.
Comparison and Application of EN 1759
If the flange standard specified in the conditions is ASME B16.5,it is recommended to switch to the EN 1759-1 standard to ensure design consistency.Using this standard simplifies the calculation of pipe flanges and is generally accepted by both AI and NOBO in most cases.However,EN 1759-1 also has limitations.The standard has not been updated since 2004,resulting in some newer material standards not being covered.Nevertheless,Appendix D of this standard provides a method for calculating the Maximum Allowable Working Pressure (MAWP) for European standard materials at specific design temperatures,partially addressing this deficiency.For MAWP issues involving new materials at design temperatures,this can be resolved by creating custom Excel spreadsheets.
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