TinnerFlow logoTinnerFlow™
Apprentice answer

Why do large TDC/TDF joints need center flange clips

1st YearDuct Assembly, Seams & JointsField Reference

Large flat flange spans can bow away from the gasket. Add the required clips per shop standard/project detail so the center span seals, not just the corners.

Ask a jobsite questionBack to Duct Assembly, Seams & Joints

Plain-English answer

You are snapping TDF center metal clips onto a completed horizontal trunk line joint on the ground, but you space them 3 feet apart to save clips, causing the metal flanges to bow out in the middle.

Large flat flange spans can bow away from the gasket. Add the required clips per shop standard/project detail so the center span seals, not just the corners. The likely recovery is to check the condition, correct prep/setup if it is within your assignment, and bring the foreman clean information before the work creates rework overhead.

Ask Foreman

Spacing those clips three feet apart is going to allow the metal flange to blow out and leak. Snap a metal clip every 8-to-10 inches along that flat span to squeeze that center gasket tight.

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.

Related questions in this category

Why do round slip joints need uniform crimps?1st YearWhy does a half-peened Pittsburgh seam leak?1st YearHow do I avoid the sliding notch lock-seamer slip?1st YearWhy does a drive cleat pop off a tight 45-degree elbow throat?2nd YearWhy do TDC flanges bind on a tight back-to-back 45-degree offset?2nd YearWhy did the flat-oval longitudinal seam open on warm air discharge?3rd Year