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The information below is only an excerpt of the original document as a reference for those looking to purchase Gripnail® products. The full text can be found at www.smacna.org
7.5.1 - Liner Fastener Commentary
INSTALLATION STANDARDS FOR RECTANGULAR DUCTS USING FLEXIBLE LINER
Ducts with interior widths of 8" (203mm) or less do not require mechanical fasteners in addition to adhesive.
Except as noted in S2.6, mechanical fasteners shall be located with respect to interior dimensions and regardless of airflow direction as in the accompanying table and in Figure 7-11.
|Velocity||Transversely Around Perimeter||Longitudinally|
2500 fpm (12.7mps) and less
|At 4" (102mm) from longitudinal liner edges, at 6" (152mm) from folder corner and at intervals not exceeding 12" (305mm)||At 3" (76mm) from transverse joints and at intervals not exceeding 18" (457mm)|
|2501 fpm (12.7mps) to 6000 fpm (30.5mps)||At 4" (102mm) from longitudinal liner edges, at 6" (152mm) from folder corners and at intervals not exceeding 6" (152mm)||At 3" (76mm) from transverse joints and at intervals not exceeding 16" (406mm)|
Liners shall also be installed with mechanical fastening devices that:
These standards assume that the designer of a duct system has:
Typically, duct liner is of flexible fibrous glass material of 1" (25mm) thickness and 1.5lbs per cubic feet (24kg/m3) density. It is primarily used for its sound absorption characteristics, although it may have some thermal resistance value. Molded round liner is available. Metal wall inner lining is available for all conventional duct shapes; typically it is of 22 gauge (0.85mm) galvanized steel with 3/32" (2.4mm) diameter holes on 3/16" (4.8mm) or 1/4" (6.4mm) centers. The double-wall style of lined duct is used where increased resistance to damage is desired or where erosion of the liner surface might occur.
Standard felxible liner is normally shop-installed. Minor damage to the liner surface may occur in transportation and handling.