Double Wall Pipe and Fittings with E-Z Flange and Barrel Clamp or Standard Slip Connection
Sheet Metal Connectors, Inc. double wall round spiral duct and fittings are one part of our complete line of HVAC products. Double wall round spiral duct has two different types of applications:

• Acoustical double wall for noise control
• Thermal double wall duct for temperature control

SMC double wall round spiral pipe and fittings are manufactured with an E-Z Flange with Barrel Clamp, E-Z Flange Jr. with Barrel Clamp or standard slip construction. All sizes shall be listed using inside dimensions.

Acoustical Double Wall
Standard acoustical double wall is for noise control. Constructed of a perforated inner shell surrounded by a layer of insulation and covered by a solid outer shell. The perforated inner shell has 3/32" diameter holes staggered at 3/16" on center for a clear open area of 23%

Thermal Double Wall
Standard thermal double wall is for temperature control. Constructed of a solid shell surrounded by a layer of insulation and covered by a solid outer shell.

Double Wall Fittings
Sheet Metal Connectors, Inc. double wall duct has a complete line of compatible
fittings. Fittings can be fabricated with standing seam, elbow lock or welded seam
construction. Double wall fittings can be fabricated to desired length and many
different configurations. All sizes shall be listed using inside dimensions.
All fittings can be manufactured with:

• E-Z Flange Jr. with Barrel Clamp - 6" to 24" Diameter
• E-Z Flange with Barrel Clamp - 26" to 96" Diameter
• Double Wall Couplings

Insulation
SMC double wall round spiral duct is a dependable, erosion resistant alternative to lined round spiral duct, providing improved protection for insulation exposed to the airstream. In double wall round spiral duct a metal inner liner insures that high airflow velocities cannot separate insulation by pulling away from the duct’s outer wall and creating erosion or airflow problems.

SMC constructs each piece with an inner shell (perforated or solid) surrounded by a layer of insulation and covered by a solid outer shell. The insulation is used in both acoustical and thermal duct systems.

SMC solves air quality problems caused by bacteria and other contaminants that can embed in fibrous materials, which can be a health hazard in environments such as schools, hospitals, laboratories, and food or pharmaceutical plants. In cases where additional erosion or contamination protection is desired for such an environment, we can provide a customer specified barrier material (mylar) between the insulation and the perforated liner.

Standard insulation is 1" thick with 1 1/2 lb. per cubic foot density. See chart below for specifications. Many other thickness’ and densities are available, consult factory.

Specification Compliance
SMC standard insulation meets the requirements of the following codes and specifications:
    NFPA 90A and NFPA 90B
    NAIMA Standard AHC-101
    ASTM C 1071 Type 1 Replaces HH-I-545B Type 1

Note: SMACNA Testing and Research Institute verified that Sheet Metal Connectors, Inc.
shop standards comply with the 1995-2nd edition of the SMACNA HVAC Duct Construction Standards.