Better ways of sealing spiral ducts shown at the AHR Expo.
Several new products have been unveiled recently that will make your duct fabrication projects go together in less time, with fewer air leaks.

For example, Lindab Inc., Stamford, Conn., introduced at the AHR Expo in Atlanta this year a new double wall spiral connector that is intended to save installation time and produce a better seal.

The new connector fills several needs. The standard means of connecting double wall duct using an inner and outer slip fit connection was cumbersome and time-consuming, and didn't always yield the best of results. Adding to the difficulty were the serrated or scalloped edges on the ends of the perforated inner liner on duct and fittings which made the duct hard to handle cleanly without snagging on insulation or other materials. As a result, some installers routinely request factory installed flanged connections to eliminate the problems associated with the double wall slip fit connections. But they find that the flanging itself adds considerable costs and is also time consuming to align and bolt into place.

Sheet metal contractor Carolina Sheet Metal offered to help Lindab with a cost-comparison using the new double wall spiral connector and the old standard type of connectors, on two similar furniture store installations. Results showed the costs savings to be appreciable using the new Lindab connectors.

Mike Kinnet at Carolina Sheet Metal said, "We installed the new double wall product in half the time as the traditional product."

"Our goal," said Dave Shaeffer, director of sales for Lindab, "was to make double wall as easy to install as single wall." The result was a new inner liner that mounts flush with the duct to be connected, along with a closed cell, foamed, EPDM material that is used to blank-off the fiberglass insulation between the inner and outer liners much like a gasket. In this position the foamed EPDM acts to keep fiberglass material from eroding into the airstream. When combined with a non-woven fiber retaining fabric, it effectively isolates the fiberglass insulation, preventing it from eroding into the air stream.

"The foamed EPDM gasket isn't intended to seal the connection but acts as a thermal barrier at the connections," Shaeffer said.

The inherent advantages of using double wall spiral - better sound attenuation, for instance, as well as improved energy efficiency - can now be used to full advantage.

Both the insulation blank-off material (closed cell, foamed, EPDM) and the non-woven, fiber retaining fabric used in the Lindab Doublewall product have been tested by Underwriters Laboratories in accordance with UL 723 (ASTM e84-91A) for conformance with Flame Spread 25/ Smoke Developed 50 ratings which are commonly required in building materials.

Tests conducted by UL show the new gasket materials not only met industry standards for flame spread and smoke developed ratings, but actually received ratings of FS=0 and SD=5.

New way to join oval

Another product developed recently is called SPIROflange and is meant to create an improved addition to three common methods of joining oval ductwork.

Oval duct is still popular in some instances where it is specified as a logical compromise between rectangular and spiral duct, offering some of the installation and air movement advantages of spiral while fitting in some tight spaces where spiral won't.

However, joining oval pipe can be difficult to install, in some circumstances. Standard "Ovalmate" 4-bolt connectors, AccuFlange and oval iron rings all work, but require room to make field connections. The common practice of using oval in tight spaces means that the installer sometimes has a difficult time in reaching the ceiling-side of the connectors, particularly in tight-access situations. The new SPIROflange is meant to lend an easier, quicker alternative.

The flange eliminates leakage through its single piece construction which encircles the duct completely. A connection is made by affixing a self-adhesive neoprene gasket to the face of the flange prior to butting the faces of the two flanges together. As the two flanges are pressed together they are held in place by use of a "drive" cleat, similar to those used for years by installers of rectangular duct. They are simply hammered into place across the flat sides of the oval. The short sides of the oval connection are held together by sheet metal screws. The new flange offers less leakage and an easier connection with better grip than a 4-bolt connector. It also offers considerable reinforcement value, according to Shaeffer. It's seen as such a welcome improvement that it will become Lindab's standard oval connector as of June 1.

"We already know the advantages of using spiral duct in so many situations," Shaeffer said. "Now we're working at ways to make the connections go even easier and faster for the installers in the field. This will allow installations to be completed more quickly and allow contractors to reduce their project costs, passing the savings along to their customers."

Lindab manufactures its products in Portsmouth, Va.; St. Petersburg, Fla.; Skokie, Ill.; Memphis, Tenn.; and Dallas; and distributes products throughout the eastern and southwest through a network of 51 local stocking manufacturers' representatives.

For more information or for the name of the Lindab distributor nearest you call 800-79-SPIRO or visit www.Lindab