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Apprentice answer

Why did the spiral 45-degree elbow slide off its collar during testing

2nd YearRound, Spiral & Flat Oval DuctCheck first

Angled round fittings can see thrust and vibration. Re-seat the joint, confirm overlap, fasten mechanically per approved standard, and seal after the connection is solid.

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Plain-English answer

A 45° elbow changes airflow direction, so a weak slip joint can walk apart under velocity, fan pulsing, or vibration. Sealant cannot hold a joint that does not have enough mechanical engagement.

Pull it back, check collar depth, seat the pipe fully, add proper mechanical fasteners per the pressure class/shop standard, and seal the seam only after the joint is locked. If collar engagement is too short, replace the fitting or use an approved coupling.

Ask Foreman

The high-velocity 45 elbow at [location] is walking off the collar. I checked overlap and fasteners. Do you want it refastened per shop standard or swapped for a deeper-collar fitting?

Verify before acting

Use this as training guidance. Foreman direction, approved drawings, project specs, manufacturer instructions, employer safety policy, and AHJ/code requirements always control the final answer.

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