Static field route #19340

What do I do when flat-oval spiral duct starts changing shape under pressure?

Spiral, Round & Oval Duct Install⚠️ CHECK BEFORE YOU FIXField answer expansion

📖 Verified core answer

Flat-oval duct needs shape control across the flat spans. Hold the run and add approved reinforcement or replace with properly rated duct.

Open in Field Rescue Open category

Field verification checklist

Look for top/bottom bowing, hanger rods pulled out of plumb, or joints opening.
Confirm pressure class and flat-oval reinforcement detail.
Check whether supports are squeezing or failing to cradle the duct.
Hold pressure/startup if deformation is growing.
Get foreman/detailer approval before adding internal supports.

Ask foreman

The flat-oval line at [location] is changing shape under pressure and pulling rods out of plumb. I checked supports and pressure class. Do you want reinforcement added or the section replaced per detail?

Text to foreman

Route options

ACorrect it only if the fix is within your assignment and approved method.

BHold and document if it affects pressure class, listed assembly, material spec, support load path, fire barrier, equipment, TAB, or another trade.

CBring the foreman/detailer the location, what you checked, and what decision you need before sealing, testing, cover, or startup.

Do not do this

Do not keep pressurizing flat-oval duct that is visibly deforming.

Why this matters

Shape loss can create leaks, hanger stress, airflow problems, and permanent duct damage.

Final verification

Use this as field training guidance. Final direction still comes from the foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, pressure/material schedule, and AHJ/code requirements.

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