Why did the inner liner buckle when installing double-wall spiral duct?

Pull it apart before it gets buried. The inner liner and outer shell need to slide together cleanly, not pack insulation into the airstream.

['Double-wall spiral has more going on than single-wall pipe. If the perforated liner catches the collar, it can buckle backward and shove insulation into the airflow path.', 'Separate the joint, straighten or replace the damaged liner, clean up the collar, and use a guide sleeve/alignment method so the inner and outer walls seat together. If the liner is torn or the insulation is packed, replace the damaged section.']

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