TinnerFlow
Flat Oval Duct · Straight Runs & Assembly

Flat-oval transition to round

Shape transition

ConnectionOval joint to round slip/gasket
SupportAdjacent saddles/bands

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.

Tools and materials

Flat-oval-to-round transition, adjoining round duct, approved joint systems for both ends, fasteners, sealant or gasket, supports, level, marker, soft slings, and hand tools.

Lay it out

  1. Confirm the flat-oval axis orientation, round centerline, airflow direction, and transition length.
  2. Verify the round diameter and flat-oval profile match the drawing.
  3. Check whether the transition is concentric or offset and mark the intended flat or offset side.

Set and support it

  1. Support the transition body and both adjoining runs independently.
  2. Keep the flat-oval end from rotating while the round end is aligned.
  3. Use padded handling to preserve the shaped body.

Make the connection

  1. 1

    Mark the flat-oval major axis and the round centerline before lifting.

  2. 2

    Set and connect the flat-oval end first when that end controls the elevation and orientation.

  3. 3

    Align the round end without rolling the transition.

  4. 4

    Complete the round slip, gasketed, or flanged connection.

  5. 5

    Install approved fasteners and seal both joints.

  6. 6

    Set both runs into their supports.

  7. 7

    Inspect the internal shape change for a smooth path.

Check the install

  • The flat-oval axis and round centerline are correctly aligned.
  • The transition is not rolled or twisted.
  • The round end remains round and the oval end remains true.
  • Both connections are fully seated and sealed.
  • The fitting carries no unsupported load from either run.

Common mistakes

  • Treating the transition as concentric when it has an intentional offset.
  • Rolling the fitting to make the round branch reach.
  • Flattening the round end during clamping.
  • Using one joint to support the transition.

Stop and ask

Stop if the round diameter, oval profile, transition offset, or orientation is unclear or does not match the approved drawing.