All double wall fittings that are 20 gauge or less in thickness with 3” W.G. or less are fabricated with stiffening beads on duct sizes 19” wide and larger with more than 10 square feet of unbraced panel. These radius offset duct fittings are typically fabricated with Pittsburgh seams and are always completely assembled with all accessories installed.
The Rectangular Doublewall Radius Offset is constructed with TDC end treatments. There are two different types of applications:
• Acoustical double wall duct for noise control
• Thermal double wall duct for temperature control