PF 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.

Fittings: One possibility is to enlarge the duct in order to insert the flange. Depending on the fitting outer circumference, it might be possible to pass the flange around it. Since the fitting diameters vary, we recommend to  purchase one flange and to test it before placing the complete order.


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

Installed properly the air-tightness classes C and even D according to DIN EN 12237 can be reached.

Fitting the Flange

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).

Insert the flange into the duct. A rubber hammer might be necessary.

Fastening Methods

Fastening in the duct through blind-rivets and swaging (reduces the projections inside the duct).

Screws are less recommended, as they protrude inside the duct, hindering the air-flow and the cleaning operations, and could be the cause of leakages.

Spot welding only possible when the flange and duct are an exact fit (low tolerances).

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