Flanges to EN 1092-1: types, sealing faces and pressure ratings
The flange is the most common detachable connection in pipework. EN 1092-1 governs designs, dimensions, facings and pressure ratings – and ensures that components from different manufacturers fit together. Here is what matters when selecting.
The designs to EN 1092-1
The standard assigns a type number to each design. Quoting it in your enquiry saves queries – “EN 1092-1 type 11” is unambiguous, “welding flange” is not.
| Type | Design | Rating | Typical use |
|---|---|---|---|
| Type 11 | Weld-neck flange | PN 6–400 | High pressures and temperatures, steam, power plant |
| Type 05 | Blind flange | PN 6–400 | Closing ends, nozzles, inspection openings |
| Type 01 | Slip-on flange | PN 6–40 | Water, low pressure, economical standard lines |
| Type 02 | Loose flange with collar | PN 6–40 | Where bolt holes must be aligned, stainless |
| Type 13 | Threaded flange | PN 6–40 | Retrofitting without welding, threaded pipe |
A full comparison of all types is under flange types, the actual dimensions in the flange dimension tables.
Facings – the most common source of error
Two flanges only mate if pressure rating, nominal size and facing match. The facing is the detail most easily overlooked when ordering.
| Form | Designation | Counterpart | Application |
|---|---|---|---|
| Form A | flat face | Form A | Low pressure, plastic and cast valves |
| Form B1 | raised face | Form B1 | Standard for all PN – the most common case |
| Form B2 | raised face, finer | Form B2 | Only by agreement – finer finish (Ra 0.8–3.2 µm) |
| Form C / D | tongue / groove | C to D | Gases, critical media, high tightness |
| Form E / F | spigot / recess | E to F | Where the gasket needs to be located |
Practical rule: tongue always mates with groove, spigot with recess. Two tongue flanges against each other will not seal. With Form B1 the facing is identical on both sides – which is why it is so widespread.
Pressure ratings PN
EN 1092-1 covers PN 2.5 to PN 400. Bolt circle, number of bolts, outside diameter and flange thickness are defined for each rating and nominal size – only this makes flanges from different manufacturers compatible.
| Rating | Typical use |
|---|---|
| PN 6 / PN 10 | Water, ventilation, unpressurised and low-pressure lines |
| PN 16 | The all-rounder: water, cooling circuits, general service lines |
| PN 25 / PN 40 | Process and steam lines, compressed air, chemicals |
| PN 63 – PN 160 | High-pressure steam, boiler feedwater, power plant |
| PN 250 – PN 400 | Special applications, high-pressure technology |
Note: the rating applies at reference temperature. As temperature rises, permissible working pressure falls – see DN, PN and Schedule.
Materials
The flange material must match the pipe material – otherwise different expansion behaviour at the weld leads to stresses in service.
- Carbon steel: P250GH (C22.8), P235GH, S235JR – water, compressed air, general lines
- Creep-resistant: 16Mo3, 13CrMo4-5, 10CrMo9-10 – steam, boilers, power plant
- Stainless: 1.4301, 1.4404, 1.4571 – chemicals, food, ultrapure media
- Duplex and special alloys: 1.4462, 1.4410, CuNi 90/10 – seawater, chloride-bearing media
What else a flange joint needs
A flange alone does not seal. A complete joint requires gasket, bolts, nuts and washers in matching grades. The gasket is selected by medium, temperature and rating, the bolt grade by temperature and load.
Further reading: choosing the right gasket and bolts and studs for flanges. The matching bolt set for a given DN and PN is also determined by the piping calculator.
ASME instead of EN
In international plant engineering you will meet flanges to ASME B16.5 in Class 150 to 2500. The systems are not compatible: bolt circle, number of bolts and flange thickness differ. Where both worlds meet, transition flanges or adapter spools are required – plan for this early, not on site.
Frequently Asked Questions
Which flange types does EN 1092-1 define?
The most common are type 11 weld-neck, type 05 blind, type 01 slip-on, type 02 loose flange with collar and type 13 threaded flange. Quoting the type number in an enquiry avoids queries.
Which facing mates with which?
Identical forms belong together: form B1 to form B1, form A to form A. For tongue and groove it is form C to form D, for spigot and recess form E to form F. Two tongue flanges against each other will not seal.
Which pressure rating do I need?
PN 6 and PN 10 for water and low pressure, PN 16 as the all-rounder, PN 25 and PN 40 for process and steam lines, above that PN 63 to PN 160 in power plant applications. The rating applies at reference temperature and falls as temperature rises.
Are EN 1092-1 and ASME B16.5 flanges compatible?
No. Bolt circle, number of bolts and flange thickness differ. Where both systems meet, transition flanges or adapter spools are required.
What else does a flange joint need?
Gasket, bolts, nuts and washers in matching grades. The gasket is selected by medium, temperature and rating, the bolt grade by temperature and load.
Do you need exactly these parts?
Grade, size, pressure rating and quantity are enough – you usually receive your quote the same day, with an inspection certificate 3.1 on request.
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