Sheet Metal Connectors Inc. – Spiral duct is manufactured from a variety of metals, including galvanized, stainless steel, aluminum, polyvinyl coated and paint grip. Spiral duct machines wind a continuous sheet of strip metal, about six inches wide, locking the edges together and forming it into a continuous spiral tube. The four-ply spiral lockseam serves as a continuous reinforcing rib, boosting the pipe’s crushing resistance to more than twice that of longitudinal lockseam or welded pipe. The stronger, more rigid construction also allows long lengths of spiral duct to be made in a wide range of diameters, from three to 96 inches and manufactured in lengths from one to 20 feet.

Common methods of sealing spiral ductwork include standard slip-fit connections which require the application of caulk or some other joint sealant. In addition, top ductwork manufacturers now offer factory-applied gaskets that effectively seal spiral duct connections without the use of sealants.