Engineering guide
This module provides the dimensions of welding-neck flanges to the classic German flange standards DIN 2627 to 2629 and DIN 2631 to 2638 as a set of dimension tables. By selecting nominal size and pressure rating, you can retrieve all principal dimensions of a welding-neck flange: flange outside diameter, flange thickness, bolt circle, number and diameter of bolt holes, and the hub dimensions for the welded connection to the pipe. Series 1, with international pipe connection sizes, covers the common pipe outside diameters.
Important: these DIN standards have been withdrawn and replaced by DIN EN 1092-1 (Flanges and their joints — Circular flanges for pipes, valves, fittings and accessories). For recalculation, spare-parts procurement, and the documentation of existing plants, however, the old table values remain highly relevant, because countless piping systems and vessels in service were built to these standards. Anyone who needs to identify an old welding-neck flange or procure a matching counterpart cannot avoid the historical dimension tables.
In practice, the module is therefore used above all for quick dimension lookup whenever flanges to the old DIN standards need to be checked, re-measured, or compared against components to DIN EN 1092-1 — for example during plant modifications, repairs, or when transferring legacy equipment into new documentation.
Scope
- Welding-neck flanges
Typical workflow
Select pressure rating and standard
First, the applicable standard from the series DIN 2631 to 2638 or DIN 2627 to 2629 is selected; each standard corresponds to one nominal pressure rating PN. The pressure rating follows from the design pressure of the piping system or vessel.
Define nominal size and connection series
Using the nominal size DN and Series 1 (international pipe connection sizes), the matching pipe outside diameter is assigned, to which the flange hub is welded.
Read off the dimensions
The module delivers the complete table dimensions of the welding-neck flange: outside diameter, flange thickness, bolt circle diameter, number and diameter of bolt holes, plus the hub and raised-face dimensions.
Match against mating flange and gasket
The dimensions are then checked against the mating flange and the intended gasket. When combining with flanges to DIN EN 1092-1, verify that bolt circle, bolt pattern, and raised face are compatible.
Frequently asked questions
May I still use flanges to DIN 2631 to 2638 for new designs?
The standards have been withdrawn; for new designs, DIN EN 1092-1 represents the state of the art and is generally also the basis for conformity assessment under the Pressure Equipment Directive. Using the old dimension series remains permissible where compatibility with existing plants is required — for spare parts, for example. Responsibility for suitability then rests with the manufacturer or operator.
Are old DIN welding-neck flanges compatible with flanges to DIN EN 1092-1?
For most nominal sizes and pressure ratings, the bolt circle, bolt pattern, and connection dimensions were carried over into DIN EN 1092-1, so the flanges can be bolted together. There are, however, deviations in details such as flange thicknesses, raised-face design, and individual DN/PN combinations. Before pairing them, the dimensions should be compared case by case.
Does the dimension table replace a strength calculation of the flange?
No. The table dimensions apply for the pressure-temperature ratings of the respective materials specified in the standard. For elevated additional loads from the piping system, unusual temperatures, or non-standard gaskets, a calculated verification is required, for example to DIN EN 1591-1 or AD 2000-Merkblatt B 7/B 8 of the German AD 2000 pressure vessel code.
Technical content source: LV-Solved-Problems-Content 628d313247e7