Why did the screws strip out on a spiral duct coupler?

Field answer

Spiral pipe is strong as a system, but the sheet at a sleeve joint can still strip if an impact driver is run too hard. Once the hole is stripped, that screw is no longer clamping the joint.

Back off the gun, pull the bad fasteners, shift to clean metal, refasten with the approved screws, and seal the screw heads and seam. For high-velocity or pressure-tested work, reinforce the seal with the project-approved mastic/tape system.

What to check first

• Identify every stripped screw or cracked seal bead around the joint.
• Check whether the sleeve/coupler is fully inserted and seated.
• Remove loose fasteners and move to clean metal, not the same wallowed hole.
• Use the approved screw type, spacing, and sealant system for the pressure class.
• Recheck the joint during leak test or startup.

Why it matters

A stripped coupler joint can whistle, leak, separate under vibration, and fail pressure testing.

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Final direction belongs to the foreman, approved drawings/specs, manufacturer instructions, pressure/material schedule, employer policy, and AHJ/code requirements.