Back-to-back 45-degree TDC flanges bind and the bolts will not seat

Close back-to-back flanged fittings can run out of corner clearance. Align the faces, protect the gasket, and get approval before trimming or using alternate hardware.

Stop if

• The back-to-back 45s are so tight that the TDC corners are binding before the gasket faces seat. I can clamp and align it, but the corner lip may need approved cleanup. How do you want it handled?

Watch out

• Do not force TDC/Ductmate corners together with a drift pin so hard that the flanges twist or the gasket gaps.

Check

• Check whether the gasket faces are square or being pulled sideways.
• Identify the exact corner lip or bracket that is binding.
• Loosen nearby hangers if the run is locked under stress.
• Use clamps to align faces before bolting.
• Verify any trimming or alternate bolt detail with the foreman/shop standard.

Steps

• Check whether the gasket faces are square or being pulled sideways.
• Identify the exact corner lip or bracket that is binding.
• Loosen nearby hangers if the run is locked under stress.
• Use clamps to align faces before bolting.
• Verify any trimming or alternate bolt detail with the foreman/shop standard.

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