Straight flat-oval duct run

Before you start

• Confirm the flat-oval size, major and minor axis orientation, material, pressure class, joint type, and support detail against the approved drawing.
• Inspect the duct for sidewall dents, flattened ends, twisted axes, damaged beads, split seams, and shipping damage before lifting it.
• Check that the mating pieces use the same oval profile. A round-looking end and a truly matched flat-oval end are not the same thing.
• Stage the correct fittings, joint hardware, approved fasteners, sealant or gasket system, supports, lifting equipment, and hand tools before starting.

Lay it out

1. Establish the branch or main centerline and the correct bottom or center elevation.
2. Mark the major and minor axes on each section before lifting so one section is not rotated 90 degrees from the next.
3. Plan transverse joints and supports so a hanger does not land on the joint or pinch the narrow sides.

Set and support it

1. Install wide saddles or trapezes that carry the broad lower surface instead of squeezing the curved sides.
2. Use soft slings or padded lifting points so the oval shape is not dented during handling.
3. Support both sections close enough to the joint that one piece does not hang from the other.

Make the connection

1. 1

   Set the first section on its permanent supports and verify the major axis is in the correct orientation.

2. 2

   Bring the next section to the same elevation and align the broad faces before checking the narrow sides.

3. 3

   Match the oval profile all the way around the joint. Do not line up only the top edge.

4. 4

   Install the approved slip, gasketed, or flanged connection evenly around the perimeter.

5. 5

   Install approved fasteners in the required pattern without pulling the oval shape out of round.

6. 6

   Apply or complete the approved seal after the mechanical connection is seated.

7. 7

   Release the lift slowly and verify the support carries the load without rotating the duct.