Double-Wall Duct

  • Duct shown or specified as double-wall to be constructed with outer pressure shell, 1", 2" or 3" thick (as specified) 1-lb insulation layer over a solid or perforated inner liner. Construct shell and liner of galvanized steel complying with latest ASTM standards of spiral lockseam and gauged as specified for pressure class.
  • Fittings and coupling: Construct of minimum gauges as specified for pressure class.
  • Perforated inner liner: 24-ga galvanized steel, perforate with 3/32" holes on 3/16" staggered centers for a 22% free area.
  • Insulation stops: Provide at all locations where insulation ends.


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