Engineering guide
This module provides the dimension and characteristic-value tables for pipe bends to DIN 2605-1: butt-welding fittings with a reduced performance ratio (utilization factor). If you need to calculate a pipe bend to DIN 2605 or use one in a piping calculation, the module returns, for each series, type and nominal size, the associated values for outside diameter, wall thickness, bend radius, bend height and — for 45° bends — the auxiliary dimension, together with the utilization factor.
The utilization factor is the key quantity for pressure design: it states to what extent the bend may be utilized under pressure compared with a straight pipe of the same wall thickness. In practice, the tabulated value is taken directly into the internal-pressure calculation of the piping (e.g. to DIN 2413 or DIN EN 13480-3) to verify the required wall thickness of the bend.
DIN 2605-1 has been withdrawn. New designs today follow the fittings standards of the DIN EN 10253 series (in particular DIN EN 10253-2 for ferritic steels with types A and B). For existing plants, spare-part procurement and re-rating calculations of older piping, however, the DIN 2605 tables remain relevant — and that is exactly what this module is intended for.
Scope
- Bends
Typical workflow
Select series and type
First, the series and type of the bend are chosen. The types in DIN 2605 differ in the ratio of bend radius to outside diameter; this fixes the sharpness of the curvature and, indirectly, the load-bearing capability of the bend.
Specify the nominal size
The nominal size (DN) addresses the specific table entry. The standard assigns to each nominal size the standardized outside diameter and the associated wall thickness.
Read off the geometry data
The module returns the bend radius, the bend height and, for 45° bends, additionally the auxiliary dimension needed to establish the installation length. These dimensions are required for isometrics, take-off and prefabrication of the piping.
Adopt the utilization factor
As the strength-relevant characteristic value, the reduced utilization factor per Part 1 is output. It enters the internal-pressure wall thickness calculation of the bend as a reduction factor and ensures that the increased stress at the intrados of the bend is covered.
Frequently asked questions
What does "reduced performance ratio" mean in DIN 2605-1 as opposed to Part 2?
DIN 2605-1 covers pipe bends whose wall thickness is not designed for the full pressure utilization of the connecting pipe; the allowable pressure of the bend is therefore lower than that of a straight pipe of the same dimensions. DIN 2605-2, by contrast, contains bends with full utilization (utilization factor 1), which may be loaded under pressure like the straight pipe. For design purposes it is essential to know to which part the bend was ordered or manufactured.
May I still use DIN 2605 for new designs?
The standard has been withdrawn and replaced by the DIN EN 10253 series. For new piping, fittings should be specified to DIN EN 10253. For re-rating calculations, repairs and spare parts in existing plants built to DIN 2605, falling back on the old tabulated values remains common and sensible, because only they reflect the dimensions and utilization factors actually installed.
Why does a pipe bend need its own strength verification at all?
In a curved pipe the circumferential stress is unevenly distributed: at the inside of the bend (intrados) it exceeds that of the straight pipe, at the outside it is lower. In addition, the wall thickness may decrease at the extrados as a result of manufacturing. The utilization factor, or bend-specific design formulas, capture these effects; the straight pipe alone is not the governing case.
What is the auxiliary dimension of the 45° bend used for?
For a 45° bend, bend radius and bend height are not sufficient to define the installation length unambiguously in the isometric. The auxiliary dimension describes the additional characteristic measure of the obliquely ending bend and is needed for dimension chains and the fit-up accuracy of the weld preparation.
Technical content source: LV-Solved-Problems-Content 628d313247e7