Flanges UF

UF Circular Flanges

Same profile shape as the AF circular flange, but without the sealing lip.
Contrary to the AF, BF and LF flanges, a sealant must be applied.
Fastening with self-tapping screws or blind rivets.
Assembly using SR Joining Clips.
For duct-Ø 200 up to 3000 mm.

  1. Duct wall
  2. No sealing lip
  3. Fastening with screws or rivets
  4. Sealant (must be ordered separately)
  5. SR joining clip

Suitable Ducts

For inner-duct diameters from 200 up to 3000mm. In-between diameters are also available. IMPORTANT: Please indicate if flanges are intended for fittings, in which case their Ø is made 3 mm smaller.

Suitable duct types: spirally wound ducts, longitudinal seam ducts, fittings, ducts with stiffening ribs.

Not suitable for ducts and fittings with turned-out edges.

Fixation Methods

Fastening in the duct through blind-rivets.

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 should not be used.

Spot welding not suitable



Universal flange 
often used when the others are not suitable
(i.e. by important Ø deviations).


The flanges stiffen the ducts and help maintaining their round shape. They also improve the resistance of the ducts under negative pressures. Ducts should nevertheless be strong enough by themselves and resist the required pressures (+ or -) without taking the flanges into account.

Any gap, created when the flange is fixed into the duct, is bridged by an integrated connecting part. The stability of the flange is that way maintained.

Available in galvanized steel. Stainless steel V2A (1.4301 ASTM 304) and V4A (1.4404 ASTM 316) upon request. There are a few technical differences between the flanges in galvanized steel and the ones in stainless steel. Please refer to information on metals (ZI-101) and the page about the UF flange dimensions.



The installation of this flange is more time consuming than the AF, LF and BF flanges, since sealant must be applied.
The UF flanges also have longer delivery times.


Which are the advantages of flanges?

Installation Instructions

UF in Stainless Steel
(see AF in stainless steel)

Screws or Rivets?



STP Documents


Equipotential Bonding of the AF, BF, LF and UF Circular Flanges and the SR Joining Clips 

Made by METU in Germany