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Apprentice Q&A · #100

What is "oil-canning," and how do I cross-brake duct to prevent it?

2nd YearField ModsYELLOW · Check First

Oil-Canning: The loud popping, flexing, or rattling sound made when large, flat sheets of duct metal expand and buckle under structural system air pressure changes. * The Fix: Cross-braking. Before assembly, score or crease the flat sheet metal sections diagonally from corner to corner in a large 'X' shape. This adds physical structural rigidity to the flat face, preventing the metal from flexing back and forth.

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Plain-English answer

Oil-Canning: The loud popping, flexing, or rattling sound made when large, flat sheets of duct metal expand and buckle under structural system air pressure changes. * The Fix: Cross-braking. Before assembly, score or crease the flat sheet metal sections diagonally from corner to corner in a large 'X' shape. This adds physical structural rigidity to the flat face, preventing the metal from flexing back and forth.

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Field checklist

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Hey boss, I’m checking field mods: What is "oil-canning," and how do I cross-brake duct to prevent it? I found the likely issue and want to verify the next step before I lock it in. Do you want me to adjust it now or check the drawing/detail first?

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Verify before acting

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

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