Pipe bends to DIN 2605: types, radii and materials
Pipe bends redirect a line without disturbing the flow more than necessary. DIN 2605 has largely been absorbed into EN 10253 – but the selection criteria remain the same: angle, radius, wall thickness, manufacturing method and material.
Angle and radius
The most common bends are 90° and 45°. The bend radius is given as a multiple of the nominal diameter: note the designation: to EN 10253-2 (type 3 to DIN 2605) a “3D” bend has R ≈ 1.5 × D and a “5D” bend R ≈ 2.5 × D; a radius of 3 × D is a special radius that ASME calls a “3D bend”. The larger the radius, the lower the pressure loss and the gentler the change of direction.
| Radius | Space required | Pressure loss | Typical use |
|---|---|---|---|
| 1 D | very compact | high | Tight installations, secondary lines |
| 1.5 D | compact | medium | The standard in plant engineering |
| 2.5 D / 3 D | medium | low | Steam, higher velocities |
| 5 D | large | very low | Abrasive media, solids conveying, metering runs |
Straight settling lengths must be maintained upstream and downstream of measuring devices – a tight bend directly before a flow meter falsifies the reading.
Seamless or welded
Seamless bends are first choice at high pressures and temperatures – there is no weld to be tested, documented and monitored in service. In boiler and power plant construction they are generally mandatory.
Welded bends are more economical and entirely adequate for many standard applications – water, compressed air, ventilation, low pressure. The longitudinal weld is tested by ultrasound or radiography as required.
Note: bending thins the wall on the outside of the bend and thickens it on the inside. On pressure-bearing lines the remaining wall thickness at the extrados must still satisfy the design – which is why bends are available in standard and heavy wall.
Connection types
| Design | Connection | Use |
|---|---|---|
| Butt-weld bend | butt welded, ends bevelled | The normal case in pipework |
| Threaded fitting | internal or external thread | Small sizes, retrofitting, threaded pipe |
| Press fitting | pressed, with sealing ring | Building services, fast installation |
| Grooved joint | roll groove with coupling | Fire protection, demountable lines |
Materials
The bend must match the pipe – in material as well as wall thickness. Joining a 16Mo3 pipe to an unalloyed bend produces unequal behaviour at the weld under temperature.
- Carbon steel: P235GH, P265GH, formerly St 35.8 – water, compressed air, general lines
- Creep-resistant: 16Mo3, 13CrMo4-5, 10CrMo9-10, P91 – steam and boilers
- Stainless: 1.4301, 1.4404, 1.4571 – chemicals, food
- Duplex: 1.4462 – chloride-bearing and aggressive media
When a standard bend will not do
Not every change of direction can be solved with a catalogue bend. In confined installations, at unusual angles or with very large radii, the pipe is bent rather than fitted. We supply special radii to drawing – this saves welds, further reduces pressure loss and shortens installation time on site.
For very large sizes or one-offs, mitred bends are also an option: bends welded from pipe segments, economical where drawn bends would be disproportionately expensive or simply unavailable. On pressure-bearing lines, weld testing must be planned for.
Both are part of our special parts to drawing – from a single piece, on request with inspection certificate 3.1 or 3.2.
What else belongs to the fitting
Alongside bends we supply reducers (concentric and eccentric), tees and caps from a single source – to EN 10253-1 to 4 as well as ASME B16.9 and B16.11. Ordering everything together avoids the classic problem of a fitting arriving on site in the wrong wall thickness.
More on dimensions and designations in DN, PN and Schedule, on documentation in inspection certificate 3.1 or 2.2. The full range is under flanges, fittings and connections.
Frequently Asked Questions
What does a 3D bend mean?
To EN 10253-2 a radius of about 1.5 × outside diameter (type 3 to DIN 2605); 2D means R ≈ 1 × D, 5D means R ≈ 2.5 × D. In ASME usage “3D bend” means R = 3 × D – when in doubt, state the radius in mm.
Seamless or welded – which is better?
Seamless bends are first choice at high pressures and temperatures because there is no weld to be tested and monitored. Welded bends are more economical and adequate for water, compressed air and low pressure.
Why are bends available in standard and heavy wall?
Bending thins the wall on the outside of the bend. On pressure-bearing lines the remaining wall thickness must still satisfy the design, so heavy wall is used where loading is higher.
Which material for which application?
P235GH and P265GH for water and general lines, 16Mo3 through 10CrMo9-10 and P91 for steam and boilers, 1.4301 to 1.4571 for chemicals and food, duplex 1.4462 for chloride-bearing media.
Are bends available with special radii?
Yes. Where a standard bend does not fit, we supply bends to special radii to drawing. For large sizes or one-offs, mitred bends are also an option.
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.
Request a quote