Round Double Wall Duct

Monroe Metal’s acoustically lined, double wall, duct and fittings consist of an outer shell, a layer of fire resistant fiberglass insulation and an inner shell next to the air flow. Pipe is constructed of the solid outer shell and a perforated inner shell. This perforation serves as noise reduction. The inner shell can also, upon request, be manufactured with a solid liner for use where noise is not a factor. The fittings are constructed with a solid outer shell, a solid inner shell and a solid liner for use where noise is not a factor.

Advantages of Double Wall:
• Fan noise reduction
• Positive vapor barrier integrity
• Assured thermal conductivity
• Lower friction loss for noise reduction
• Speedier completion of installation, eliminating additional time and labor cost in the field for duct that otherwise would be field insulated
• Easy as installing single wall duct

Monroe Standard Spiral:
• High pressure application
• 4-ply lockseam provides strength
• Machine made precision guarantees uniformity and reliable performance
• Available in 20’ maximum lengths

Monroe “V-Rib” Spiral:
• Low pressure application
• Lighter gauge material with five reinforcing ribs on outer shell and ribbed inner shell provide extra savings in field cost due to less weight
• Available in 20’ maximum lengths

The fiberglass installation meets the requirements set forth in NFPA pamphlet #90A (catalog MFPA #255) as to flame spread and smoke developed ratings. The K-Value of the insulation at 75º M.T. = 260 BTU.

Products & Accessories

Accessory Fittings

To complete your job, we also offer a complete line of accessory fittings. These can be factory installed or shipped loose for field installation.

• Access Doors
• Angle Rings
• Insulation Stops
• Grille/Register Taps to fit double wall duct
• Rectangular to Oval
• Saddle Taps

Saddle taps can be lined or unlined and fabricated to fit major or minor axls.

No other manufacturer can offer such a complete line of accessories!

Duct Construction Standards

Double Wall Flat Round Spiral Duct - High Pressure, 1985 SMACNA
Pipe:       Outer Shell Gauge Inner Perf. ShellGauge
 5" - 14"26 3" - 18"26
 15" - 26"24 19" -  36"24
 27" - 36"22 38" - 60"22
 38" - 50"20 62" - 84"20 
52" - 84"18 
Fittings: Outer Shell Gauge Inner Solid. ShellGauge
 5" - 14"24 3" - 36"24
 15" - 26"22 38" -  84"22
 27" - 50"20 
 52" - 60"18 
62" - 84"16 

• Fittings will be continuously welded with seams painted to prevent corrosion
• Spiral pipe in 1” increments to 30”; 2” increments to 84”

Double Wall Flat Round Spiral Duct- Low Pressure, 1985 SMACNA
Pipe:       Outer Shell Gauge Inner Perf. ShellGauge
 3" - 26"26 3" - 36"24
 27" - 36"24 38" - up2
 38" - 50"22 38" - 60"22
 52" - 60"20 62" - 84"20 
62" - 84"18 
Fittings: Outer Shell Gauge Inner Solid. ShellGauge
 3" - 14"26 3" - 36"24
 15" - 26"24 38" -  up22
 27" - 36"22 
 38" - 50"20 
 52" - 60"18   
62" - 84"16 
• Fittings will be spot welded and sealed
• Spiral pipe in 1” increments to 30”; 2” increments to 84”
 

 

** Spiral pipe is made in 20’ maximum lengths or cut to length
** Constructed of galvanized metal meeting ASTM A-527 with a 4-ply spiral lockseam
** Other materials and gauges available upon request

Fiberglass insulation meets the requirements set forth in NFPA pamphlet #90A as to flame spread and smoke developed rating. The K-value is 75º MT = .260 BTU