Engineering guide
Module EF02 provides the dimensions of Type 02 loose (lap-joint) flanges to DIN EN 1092-1, edition 2002-05, as a lookup table. The loose flange is not fixed to the pipe; it sits freely rotatable behind a collar or lapped stub end (weld-neck collar or lapped pipe end) and presses it against the mating gasket face when the bolts are tightened. The big practical advantage: the bolt holes can be aligned freely during assembly, and the flange itself never comes into contact with the medium – for corrosive media, only the collar needs to be made of high-grade material.
Via nominal pressure (PN) and nominal size (DN), the module delivers the bore diameter, outside diameter and thickness, bolt circle diameter with chamfer, bolt hole diameter with number of bolts and the associated thread. Note that the underlying edition DIN EN 1092-1:2002-05 has been withdrawn and replaced by newer editions (currently the 2018 edition with amendments). For existing plant, spare parts and re-assessments the 2002 tables remain relevant; for new designs the valid edition governs.
For the strength and tightness verification of a lap-joint flange connection, the module serves as the geometry source for the calculation to DIN EN 13445-3 Clause 11, which models the load path through loose flange and collar.
Scope
- Loose circular flanges type 02
Typical workflow
Select nominal pressure and nominal size
The PN rating and the nominal size DN uniquely identify the EN 1092-1 table entry for the Type 02 loose flange.
Read off the flange dimensions
The module delivers the bore diameter, outside diameter and thickness of the loose flange as well as the bolt circle diameter and chamfer, which define the seat on the collar or lapped end.
Define the bolting
Each PN/DN combination comes with its bolt hole diameter, number of bolts and thread. Since the loose flange rotates freely, there is no need to align bolt hole patterns when joining the piping.
Select the matching collar and perform the verification
The loose flange always acts together with a collar or lapped end (e.g. Type 32/33 or 35-38 per EN 1092-1) through which the gasket force is transmitted. For the numerical verification, the combination of loose flange and collar is calculated to DIN EN 13445-3 Clause 11.
Frequently asked questions
When are loose flanges used instead of fixed weld-neck flanges?
Loose flanges pay off when bolt hole patterns have to be aligned during assembly (long pipe runs, prefabrication), or when the medium is corrosive: then only the wetted collar is made of stainless steel or a special alloy, while the loose flange itself is made of inexpensive carbon steel. Their limits lie at high pressures, high temperatures and strongly fluctuating loads, where fixed hubbed flanges have greater load-bearing capacity.
How does the load transfer differ from a fixed flange?
In a lap-joint connection, the load path runs from the bolts through the loose flange onto the bearing face of the collar, and only from there into the gasket and pipe. The loose flange is thereby loaded in bending like a ring, while the collar additionally sees bearing pressure. In the flange calculation to DIN EN 13445-3 Clause 11, both components are therefore verified with their own lever arms – a point often underestimated in rough estimates.
Is the withdrawn 2002-05 edition still usable?
For new designs, the current edition of EN 1092-1 applies. The mating and principal dimensions of the loose flanges have remained largely unchanged across the editions, so the tables can still be used for identifying and recalculating existing parts and for procuring spares. For gasket face types and material/pressure-temperature assignments, however, a check against the valid edition is advisable.
Technical content source: LV-Solved-Problems-Content 628d313247e7