M2, M3, M4 Installation Instructions

Cutting the Profiles to Length
The profile length depends on the type of corner piece used:
A and D corner piece types: inner duct length minus 4 mm
S and B corner piece types: inner duct length minus 30 mm
Most circular saws are suitable to cut the profiles. Make sure to clamp the profile on both sides of the saw blade over as much surface as possible in order to restrict any movements. This will protect the sawing blade and your ears! If possible, clamp the profile section in the position as illustrated and note the direction of rotation of the sawing blade. This will ensure that the burrs remain in the inaccessible spots of the flange.

Frame Assembly
Assemble the frames vertically, and not horizontally.
a)    Insert two corner pieces in the ends of both longer profile sections.
b)    Insert the two shorter profile sections on one of the profile corners.
c)    Insert the second longer profile with its corners into the shorter profiles.
The corner pieces are designed to fit closely into the profile inner shape. A rubber mallet might therefore be necessary to insert them into the profile ends.

Frame Seating
Start at one of the upper corners and hammer along the line of the duct (not at the outer edge of the profile). To enable the profile to fit more easily hold it in a slightly inclined position. We recommend to fit the flanges with the duct in a horizontal position. Fit the flanges to both duct ends before fixing. Work on a table or any other flat surface allowing the duct to align itself. To avoid distortion, particularly on small ducts, check if the flanges are aligned on both ends before fixing. On ducts less than 1500 mm long, the flanges can be fitted in the vertical position.

Fixing the Frame
It is essential that the flange is securely fixed at the corners (i.e. spot-welding, stitching or blind rivets), where the maximum strength is required. There should be two fixing points with a maximum distance of 20 to 30 mm from each other and as close as possible to the ends of the profile sections. It is also very important that the flange is fully seated against the edge of the duct before fixing. Suitable fixing methods are spot welding, pressure jointing or blind riveting. As soon as the corners have been securely fixed, each length of profile is fixed at a spacing between 80 mm (M2 and M3 profiles) and 120 mm (M4 profiles). For profiles exceeding 600 mm a center fixing is required. Make sure that the flange is fully seated and check the duct alignment before fastening.

Sealing of the Corners
The sealing of the corners is important as they can often be a source of leakage. Due to irregularities in the length of the duct walls (i.e. offset seams), a gap can easily be formed which cannot be bridged by the duct´s sealing gasket. Injecting mastic sealant into the pockets of the corner can prevent this leakage risk. The corner pocket should be filled flush with sealant to the face of the flange and over the edge of the duct.