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Dual Wall Insulated

Foremost has a complete line of dual wall pipe and fittings. Each piece is fabricated with an inner metal liner surrounded by insulation and covered by a solid metal outer shell. All Dual Wall ductwork is available with 1, 2, or 3-inch insulation in galvanized steel, stainless steel, aluminum or Foremost PCD material. Concentricity of liner to outer shell is maintained by mechanical means on all fittings and pipe with more than 1" of insulation.

The inner liner is available in either perforated or solid metal. Perforations are 3/32 inch diameter with an overall open area of 23%. Inner liners are 24 gauge for 3" through 36" round and 22 gauge for 38" through 58" round. The sheet metal liner protects the insulation from airflow velocities while it checks fiberglass erosion.

The insulation in our dual wall pipe and fittings has both acoustical and thermal benefits. It can reduce radiated noise by 25 dB or more, compared to fiberglass duct board. Our standard 1-inch insulation has a thermal conductance of 0.27 Btu/hr x sq. ft. x degree Fahrenheit. Dual wall pipe and fittings are available with insulation thicknesses of 2-inches (0.13 Btu/hr x sq. ft. x degree Fahrenheit) and 3-inches (0.09 Btu/hr x sq. ft. x degree F). Where fiber erosion is of special concern, we would wrap the sheet metal liner with a barrier material prior to the insulation being attached to the liner.

The outer shell will be fabricated per 1995 SMACNA duct construction standards for 4" W.G. This outer shell is available in galvanized, stainless steel, aluminum and Foremost PCD material for medium pressure systems. The outer shell can be sealed O.D. upon request.

Dual wall pipe and fittings are joined by slip connectors and fitting collars. The inner liner connectors are extended to mate the inner liners before the outer shells are mated. The outer shell may be joined by slip fit, flanges, Ductmate Spiralmate™ rings or AccuFlange™.

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