AF Instructions


To make sure the flange fits

To control the inner duct-Ø please refer to the MRF measuring band instructions. In case of deviations beyond the tolerances, read the values on the scale and send us that information when placing your order.

Please advise upon ordering if the flanges are intended for fittings, as they are made smaller (diameter about 3 mm smaller / circumference about 9 mm shorter). The SR joining clip bridges 
these small diameter differences.

Fixation possibilities

Punch in the notches along the entire circumference of the duct. For more information please refer to the Notching Tools section. Distance between the notches: between 50 and 100 mm.

Alternative fastening methods: blind rivets or self-tapping screws.
Distance between the fixing points: between 50 and 100 mm.

Spot welding is not suitable.

Caution when fastening with notches

It is not possible to create notches on seams (A), and they have no use when created on a stiffening rib (B). In these areas the flange must additionally be fastened using blind rivets or self-tapping screws. Stiffening ribs also require the application of a sealant:

On larger duct diameters the seam crosses the end of the duct at a much smaller angle. The distance where a notch cannot be created might therefore be longer than the prescribed 100 mm (A). In such cases the flange must be secured with blind rivets or self-tapping screws:


When properly installed the air-tightness class C (DIN EN 12237) is reached without having to take any extra measures.

Possible additional measures for ducts with stiffening ribs or when thetightness class D must be achieved:

Before inserting the flange into the duct apply an adequate sealant into the groove of the flange along its entire circumference.

One alternatives: Before driving the flange into the duct apply an approx. 100 mm long bead of mastic into the seam's groove where it crosses the flange. 

Another possibility: After the installation of the flange apply mastic inside the duct between the flange and the duct wall (not always possible with smaller ducts). The different sealing solutions can often be combined for more security.

Self-tapping screws or blind rivets must be used on ducts fitted with stiffening ribs (additional fixing points might be required). To achieve the air-tightness class C according to DIN EN 12237, a sealant must be applied in the areas where the stiffening ribs cross the flange.

Fitting the Flange

Place the flange in front of the duct end ( grip-pliers might be helpful) and drive the flange evenly home using a rubber hammer.

The seam on longitudinal seam ducts might deform when inserting the flange.

We therefore recommend to spot weld or rivet the seam in the vicinity of the duct ends before inserting the flange.    

If the seam is too high (A) preventing the flange from being inserted all the way in, grind it down (B).

For further instructions please refer to the SR Joining Clips section.

Installation Video

Check the inner duct diameter

Punch-in the notches. Screws or blind rivets are the alternatives.

Distance between the fixing points (notches, screws, rivets): between 50 and 100 mm

The sealing lip centers, secures and . . . seals.

This parallel section is smaller than the duct Ø and enables the flange to be centered before being driven home using a hammer.

With a rubber mallet drive the flange into the duct (see also the video)