Transitions & Reducers ยท Transitions & Reducers
Rectangular-to-flat-oval transition
Space-saving change
ConnectionRectangular flange + oval joint
SupportAdjacent supports
Before you start
- Confirm the rectangular size, flat-oval profile, major-axis orientation, transition length, and both joint systems.
- Mark the oval major axis and TOP before lifting.
- Inspect the oval end for distortion and the rectangular flange for damage.
- Field-check both centerlines and available clearance.
Tools and materials
Rectangular-to-flat-oval transition, rectangular flange components, approved oval joint components, gasket, fasteners, sealant, level, laser, marker, padded lifting equipment, and adjacent supports.
Lay it out
- Establish the rectangular top and bottom planes.
- Mark the oval major and minor axes.
- Confirm the fitting orientation provides the intended clearance.
Set and support it
- Support the fitting body and both adjoining runs.
- Use padded handling to preserve the oval profile.
- Prevent the oval end from rotating.
Make the connection
- 1
Set and connect the rectangular end square.
- 2
Recheck the body and the marked oval axis.
- 3
Rotate only to the approved orientation.
- 4
Bring the flat-oval duct into alignment without flattening it.
- 5
Complete the oval connection.
- 6
Seal both joint systems.
- 7
Load supports and verify the oval end remains true.
Check the install
- The oval major axis is correct.
- The transition body is not twisted.
- The rectangular end remains square.
- The oval profile is not flattened or rolled.
- Both joints are fully seated and sealed.
Common mistakes
- Installing the oval end rotated 90 degrees.
- Using the transition to force a clearance problem.
- Flattening the oval during lifting or clamping.
- Supporting only the rectangular end.
Stop and ask
Stop if the flat-oval orientation, profile, clearance purpose, or connection method is unclear or does not match the approved drawing.