Rectangular Duct and Fittings Catalog

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Rectangular Single Wall Duct (Ductwork) & Fittings

Sheet Metal Connectors, Inc. (SMC) TDC, Slip/Drive and Raw Sheet Metal Connectors, Inc. rectangular duct and fittings are one part of our complete line of HVAC products. SMC manufactures coil line ductwork in 4’-5’-6’ lengths. All ductwork comes standard with stiffening beads. Ductwork is fabricated with either Snap Lock or Pittsburgh longitudinal seams. Sealant is available in the seams upon request.

Rectangular ductwork is manufactured in three different styles.
They are as follows:
• Wrap Around Duct
• L-Shape Duct All sizes shall be listed using outside dimensions.
• 4 Piece Duct
• Please refer to the following charts for specific materials, gauges, and end treatments.

TDC Ductwork and HVAC Fittings
SMACNA recommended TDC™ duct is a 4-bolt system with a difference. Instead of cutting, assembling and installing a separate flange onto the ductwork, the TDC flange is roll formed directly onto the duct. This provides a solid metal connection that reduces leakage which is why the TDC system is the best for minimum leakage application. A TDC assembly instruction manual is available upon request.

Slip and Drive Ductwork and HVAC Fittings
Slip and drive ductwork is the traditional system using s-slip and drive connectors.

Raw Ductwork and HVAC Fittings
Raw duct is fabricated for proprietary duct connection systems.

HVAC Fittings
Sheet Metal Connectors, Inc. manufactures rectangular fittings in most sizes and configurations. Fittings are manufactured on our state of the art fabrication equipment. All fittings are fabricated with stiffening beads on duct sizes 19” wide and larger which have more than 10 square feet of unbraced panel. Fittings shall be beaded unless duct will have an insulation covering or an acoustical liner. This requirement is applicable to 20 gauge or less in thickness and 3” W.G. or less. Most all fittings are fabricated with Pittsburgh seams. Fittings are available completely assembled with all accessories (reinforcement, vane & rail, etc…) installed. Fittings are also available knocked down to reduce shipping and handling costs. Sheet Metal Connectors, Inc.

Turning Vane and Rail
SMC manufactures several types of turning vane and E-Z rail. Turning vane and E-Z rail are recommended for square throat elbows and tees. When using turning vane and E-Z rail performance is greatly enhanced in the HVAC duct system. Test data is available upon request.

Maximum Unsupported Vane Length
4” single turning vane …………………36” maximum length
2” double turning vane ………………..48” maximum length
4” double turning vane ………………..72” maximum length
4” acoustical vane ………………………72” maximum length
When exceeding maximum vane length, vanes can be installed in sections or a tie rod can be tack welded to the face of the turning vane.

Transverse Joint and Intermediate Reinforcement
SMC manufactures many different types of reinforcement. SMC’s most popular types are as follows: Tie Rod Reinforcement: threaded inserts installed into each end of thin wall (emt) conduit. These are installed internally at both the joint and/or intermediate duct spacing. R-Angle Reinforcement: roll formed pre-punched angle iron reinforcement. See chart below.


Sheet Metal Connectors, Inc. duct liner shall be of the specified material, thickness, and density of the contractors request. The duct dimensions shall be increased as necessary to compensate for liner thickness. All sizes shall be listed using outside dimensions. Each layer of duct liner shall be attached with a minimum of 90% coverage of adhesive at the liner contact surface area. Pin placement as in chart below.



Specification Compliance
l-smacnaTestingSMC 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.

Rectangular Duct and Fittings