Static field route #19596

What do I do when a short-radius 45-degree elbow is choking a high-velocity round duct?

Airflow/TAB Impacts From Installation⚠️ CHECK BEFORE YOU FIXField answer expansion

📖 Verified core answer

A tight pleated elbow can create system effect and turbulence on high-velocity duct. Use an approved smoother/longer-radius fitting or revised route where the system needs it.

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Field verification checklist

Confirm duct velocity/pressure class and where the fitting sits in the system.
Look for noise, vibration, or fan performance complaints.
Check whether the elbow is pleated/light-duty or smooth/heavy-duty.
Look for straight duct requirements near equipment.
Confirm revised fitting with foreman/detailer/TAB if performance is affected.

Ask foreman

This 45 on the high-velocity round run is a tight pleated fitting near [equipment/location]. It may be causing turbulence. Do you want a smoother/longer-radius fitting or a revised offset path?

Text to foreman

Route options

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

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

C Bring 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 use a cheap tight 45 elbow in a high-velocity location just because it physically clears the obstruction.

Why this matters

Bad fitting selection can create system effect, noise, pressure loss, and failed balancing.

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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