Round Connections

Round Duct Connections Overview

In most cases your first choices would be the MU Overcollars and the AF Circular Flanges, and of course the METU-FORM duct system for your higher requirements regarding tightness and energy performance.

AF Circular Flanges
Most popular flange allowing to connect round ducts together.
Ø 200 to 3000 mm
Air-tightness class C (DIN EN 12237)
Air-tightness class ATC3 (DIN EN 16798-3)
Assembly with SR joininig clips

LF Circular Flanges
To connect ducts and fittings with tured-out edges (Vanstone) together.
Ø 200 to 3000 mm
Air-tightness class C (DIN EN 12237)
Air-tightness class ATC3 (DIN EN 16798-3)
Assembly with SR Joininig Cips

BF Circular Flanges
To connect round ducts together. These flanges enter deeper into the ducts, translating into more flexibility.
Ø 200 to 3000 mm
Air-tightness class C (DIN EN 12237)
Air-tightness class ATC3 (DIN EN 16798-3)
Assembly with SR Joininig Cips

UF Circular Flanges
To connect round ducts together. This UF flange requires more work than the others including the application of a sealant.
For duct-Ø from 200 to 3000 mm
Air-tightness class C (DIN EN 12237), ATC3 (DIN EN 16798-3)
Assembly with SR Joininig Cips

SR Joining Clips
Allow to assemble the AF, UF, LF and BF flanges together.
Must be ordered with gasket in order to achieve the air-tightness class C / ATC3

Photo of METU MU Overcollars or Quick Sleeves

MU Overcollars / Quick Sleeves
Economical connections for small round duct.
Duct-Ø from 71 to 315 mm
Air-tightness D (DIN EN 12237) or ATC2 (DIN EN 16798-3)

PF Pressed Flanges
For duct diameters from 80 to 180 mm
Air-tightness class C (DIN EN 12237) or ATC 3 (DIN EN 16798-3)
Assembly with SS joining clips

SS Joining Clips
For the assembly of ducts fitted with PF flanges.
Must be ordered with gasket in order to achieve the air-tightness class C / ATC3

METU-FORM Duct System
Laser welded ducts and welded fittings (Ø 80 to 1000 mm)
Formed-on Parallel Flanges. Airtight, oiltight, with smooth inner surfaces and an easy assembly.

Assembly Help

MRF Measuring Bands
For the precise measurement of the inner duct diameters according to DIN EN 1506

NZ and PNZ Notching Tools
For the punching of accurate notches (Distance: approx. every 80 mm) for the fastening of AF and BF circular flanges into the ducts or fittings.

Nut Runners SE
For the tightening of SR Joining Clip nuts within seconds.

Round Duct Connections

A quick and uncomplicated installation of circular ventilation ducts on site is an undeniable economic and practical advantage.

Minimum air-tightness classes C (DIN EN 12237) and ATC3 (DIN EN 16798-3).

Unless indicated otherwise, the diameters always correspond to the inner diameters of the ducts.

What differentiates the AF, LF, BF and UF flanges is the way they are fixed into the circular ducts. They can still be combined with each other (connecting an AF flange with an LF flange for example) as they have all been designed to be assembled together with SR joining clips.

In most cases your first choices would be the MU Overcollars and the AF Circular Flanges, and of course the METU-FORM duct system for your higher requirements regarding tightness and energy performance.

Usual diameters and round duct
connections according to the diameters
DIN EN 1506

Which are the advantages of flanges?

Bundle Lengths

Screws or Rivets?

Duct Tapes

Why not use laser-welded ducts instead of spiral ducts as standard?

In view of the several flange types, the different materials and the numerous diameters, circular flanges are most of the time manufactured "just-in-time".

Returns of round duct connections (i.e. flanges, joining clips and overcollars) are excluded.