Single-Wall, Round and Flat Oval Duct and Fittings

McGill AirFlow's single-wall, round duct is fabricated to exacting tolerances that make it easy to assemble and essentially leak free. Round duct costs less to install than rectangular duct and because of its efficiency, a round duct system offers lower operating costs. Three standard types of single-wall, round duct are available: spiral lockseam, spiral lockseam with a standing rib, and longitudinal seam.

View chart of McGill AirFlow's Duct and Fitting Construction Methods

UNI-SEAL™ Duct
Spiral lockseam duct is constructed with an interlocking helical seam that runs the length of the duct. The lockseam is formed on the outside of the duct, providing a smooth interior that results in minimal friction loss. This seam increases the duct's structural strength and rigidity so that it can be used in lighter gauges than rectangular or longitudinal seam duct, making it less expensive, easier to handle, and easier to install. Another factor which makes spiral lockseam duct economical is that it can be fabricated in lengths of 20 feet or greater. These longer sections of duct mean fewer joints and faster installation.

UNI-RIB® Duct
Spiral lockseam duct is available with a standing rib. This external stiffening rib gives the duct strength and rigidity equal to that of heavier gauges of standard spiral lockseam duct.

Longitudinal Seam Duct (fully welded or pipelock)
Longitudinal seam duct is available for applications that require very heavy gauges or large diameters. The longitudinal seam of the duct is solid welded. Construction meets or exceeds HVAC Construction Standards, 1995 Sheet Metal and Air Conditioning Contractors National Association (SMACNA).

A pipelock construction is used for some lighter gauge duct (residential and light commercial) and some PVC-coated metal duct.

Single-Wall, Round Duct
Available Sizes, Materials, and Thicknesses

(1) McGill AirFlow’s single-wall, round duct is available with the following diameters: 3-inch through 15-inch diameters in 1/2-inch-diameter increments, 16-inch through 38-inch diameters in 1-inch-diameter increments, and 40-inch through 90-inch diameters in 2-inch-diameter increments.

(2) Standard lengths of round UNI-SEAL and UNI-RIB duct are 10, 12, and 20 feet; longer lengths are available. Standard lengths of round longitudinal seam duct are 5 and 6 feet.

(3) Single-wall, round duct is also available in nongalvanized carbon steel and paintable galvanized steel. Stainless steel is generally type 304 or 316. Aluminum is generally type 3003-H14. UNI-COAT single-wall, round duct (polyvinyl-chloride-coated galvanized steel) is available on special order.

(4) Aluminum single-wall, round duct is available in diameters greater than 60 inches on special order.

(5) Single-wall, round longitudinal seam duct is available in diameters smaller than 8 inches on special order.

(6) SilverGuard™ single-wall, round duct (pre-coated with an antimicrobial) is available on special order.

© 2002-2008 McGill AirFlow LLC
An enterprise of United McGill Corporation—Family owned and operated since 1951

Unless otherwise noted, all (™) trademarks and (®) registered trademarks are property of United McGill Corporation.