RECOMMENDED SPECIFICATIONS FOR SPIRAL DUCT AND FITTINGS IN MEDIUM AND HIGH PRESSURE SYSTEMS SEMCO PRODUCT DESIGNATIONS: SM95P AND SH95P

I. GENERAL

All round and/or flat oval spiral duct and fittings shall be manufactured by a company whose primary business is the manufacture of spiral duct and fittings and who has been in business for at least ten (10) years. All spiral duct and fittings shall be manufactured by the same firm and shall be as shown on the contract drawings.All spiral duct and fittings shall be manufactured from G-60 galvanized steel meeting ASTM-A924 and A653 requirements.

II. CONSTRUCTION

A. Branch connections shall be made with 90° conical and 45° straight taps as shown on the drawings. All branch connections shall be made as a separate fitting. Factory or field installation of taps into spiral duct shall not be allowed without written approval of the engineer. Manufacturer's published individual fitting performances shall be on file with the design engineer ten (10) days prior to bid.

B. All elbows shall be fabricated with a centerline radius of 1.5 times the diameter. 90° and 45° elbows in diameters 3" round through 12" round shall be stamped or pleated elbows. All other elbows shall be of the gored type, fabricated in accordance with the following:

Where it is necessary to use two-piece mitered elbows, they shall have a minimum number of vanes in accordance with the following:

C. Circumferential and longitudinal seams of all fittings shall be a continuous weld or spot welded and sealed with mastic. All welds shall be painted to prevent corrosion.

D. All field joints for round ducts up to and including 36" diameter and oval ducts up to and including 41" major axis shall be made with a 2" slip-fit or slip coupling. Diameters 38" round and larger shall be provided with AccuFlange, or equal, flanged connections. AccuFlange, or equal, flanged connections may also be used in lieu of slip connections on smaller sizes.Access doors shall be supplied by the duct manufacturer at all fire and/or smoke dampers.All flanges and access doors shall be factory installed. Shipments of loose flanges, access doors, or taps for field installation into spiral duct will not be allowed.

E. All flat oval duct shall be reinforced with trapeze type reinforcement, as recommended by the manufacturer, to limit wall deflection to 3/4" and reinforcement deflection to 1/4".

III. DOUBLE WALL DUCT

Where indicated on the drawings, double wall, acoustically insulated round duct shall be supplied.Double wall duct shall be constructed of an outer shell, a 1" thick layer of fiberglass insulation, and an inner metal liner. Insulation shall have a thermal conductivity "K" factor of .26 BTU/hr/sq. ft./° or less.The inner metal liner for all spiral and longitudinal seam duct shall be perforated metal. All fittings from fan discharge to a point where 35 lineal feet of spiral duct has been used shall have a perforated metal liner. All other fittings shall have a solid metal liner which may be one even gauge lighter than that shown for perforated liners.

IV. METAL GAUGES

A. Metal gauges for single wall round and flat oval duct shall be as follows:

1. Round Duct for positive pressure up to +4" w.g.:

2. Round Duct for positive pressure up to +10" w.g.:

3. Flat Oval Duct for positive pressure up to +10" w.g.:

B. Metal gauges for double wall rounded and flat oval duct shall be as follows:

1. Round Duct for positive pressure up to +4" w.g.:

2. Round Ducts for positive pressure up to +10" w.g.:

3. Flat Oval Ducts for positive pressure up to +10" w.g.:

V. MANUFACTURERS

All spiral duct and fittings shall be as manufactured by SEMCO Incorporated or approved equal.