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Orange County Health Department Improvements Smith Sinnett /2024008 <br />Hillsborough,NC Orange County Asset Management Services <br />HVAC DUCTS AND CASINGS 23 31 00 - 2 <br />a.Seal:Class A,apply sealing of transverse joints,longitudinal seams,and duct wall penetrations. <br />b.Leakage: <br />1)Rectangular:Class 4 <br />2)Round:Class 2 <br />C Duct Fabrication Requirements: <br />1.Duct and Fitting Fabrication and Support: SMACNA (DCS)including specifics for continuously <br />welded round and oval duct fittings. <br />2.Use reinforced and sealed sheet-metal materials at recommended gauges for indicated operating <br />pressures or pressure class. <br />3.Construct tees,bends,and elbows with radius of not less than 1-1/2 times width of duct on centerline. <br />Where not possible and where rectangular elbows must be used,provide airfoil turning vanes of <br />perforated metal with glass fiber insulation. <br />4.Provide turning vanes of perforated metal with glass fiber insulation when acoustical lining is <br />indicated. <br />5.Increase duct sizes gradually,not exceeding 15 degrees divergence wherever possible;maximum 30 <br />degrees divergence upstream of equipment and 45 degrees convergence downstream. <br />6.Provide turning vanes of perforated metal with glass fiber insulation when an acoustical lining is <br />required. <br />7.Where ducts are connected to exterior wall louvers and duct outlet is smaller than louver frame, <br />provide blank-out panels sealing louver area around duct.Use same material as duct,painted black on <br />exterior side;seal to louver frame and duct. <br />D Duct transverse joints and reinforcement materials,including angle ring flanges and stiffeners,shall be of the <br />same material as the duct. <br />E Low Pressure Supply: 2 inch w.g.pressure class,galvanized steel. <br />F Medium and High Pressure Supply: 6 inch w.g.pressure class,galvanized steel. <br />G Return and Relief: -2 inch w.g.pressure class,galvanized steel. <br />H General Exhaust: -2 inch w.g.pressure class,galvanized steel. <br />I Transfer Air and Sound Boots: ​​1 inch w.g.​​pressure class​​​​. <br />2.02 MATERIALS <br />A Galvanized Steel for Ducts: Hot-dipped galvanized steel sheet,ASTM A653/A653M FS Type B,with <br />​​G90/Z275​​coating. <br />B "Paint Grip"Finish or Mill Phosphatized Steel (Exposed Ductwork): <br />1.Galvanized G90 steel shall be put through a phosphate bath and have a layer of Chromate applied and <br />dried leaving it ready to accept paint.This shall be done at the mill.The process produces a dull gray <br />colored finish. <br />C Joint Sealers and Sealants: Non-hardening,water resistant,mildew and mold resistant. <br />1.Manufacturers: <br />a.Childers <br />b.Ductmate <br />c.Durodyne <br />d.Foster <br />e.Hardcast <br />f.McGill Airseal <br />g.Sheet Metal Connectors,Inc. <br />h.Or Approved Equal <br />2.Flexible,water-based,adhesive sealant designed for use in all pressure duct systems. After curing,it <br />shall be resistant to ultraviolet light and shall prevent the entry of water,air,and moisture into the duct <br />system. Sealer shall be UL 723 and UL 181B-M listed and meet NFPA requirements for Class 1 <br />ductwork.VOC shall be <75 g/l. <br />Docusign Envelope ID: 2D852F9B-A7CF-462A-9536-444A53AA848A