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DocuSign Envelope ID: 9826C043- 4C32- 49CD- A4CC- DC28ABAB7CE7
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<br />SECTION 239000 - METAL DUCTS
<br />haust system shall be constructed to the listed classification for smoke exhaust ductwork. Care should
<br />be taken in this determination to avoid field replacement of duct sections.
<br />MATERIALS
<br />Galvanized Steel Sheet: Use ASTM A 653 galvanized steel sheet of lock forming quality.
<br />Galvanized coating to be 1.25 ounces per square foot, both sides of sheet, G90 in accordance with
<br />ASTM A90.
<br />Uncoated Black Steel Sheet: First quality, soft steel sheet capable of welding or double seaming
<br />without fracture.
<br />Aluminum Sheet: Use ANSI /ASTM B209 aluminum sheet, alloy 3003H -14, capable of double
<br />seaming without fracture.
<br />Stainless Steel Sheet: Use ASTM A167, Type 304 or 316 stainless steel sheet as specified, 316L if
<br />welded ductwork, with No. 2B finish for concealed work and No. 3 finish for exposed work.
<br />Polyvinylchloride Coated Steel Sheet: Use hot - dipped galvanized steel sheet with prime coat and a
<br />polyvinyl chloride film on both sides. Thickness of coating to be a minimum of 4 mils on each side.
<br />United Sheet Metal Uni -Coat, made by United McGill Co., may be used at contractor's option.
<br />1. Where any duct surface is scratched, marred, or otherwise damaged, paint with PVC aerosol
<br />spray.
<br />2. All couplings shall be slip -joint construction with a minimum 2 inches insertion length. Seal all
<br />couplings with sealants as specified.
<br />PREFABRICATED GREASE DUCTS: Dual wall construction with stainless steel inner liner,
<br />insulation and stainless steel (for exposed locations) or aluminized steel (for concealed locations)
<br />shell. Furnish all items which form a part of the assembly, including, tee sections, straight sections,
<br />elbows, end caps, cleanouts, expansion joints, fan /hood transitions, supports, flashing, counter
<br />flashing, and insulated roof thimble where required. Each section shall bear the factory applied
<br />Underwriters Laboratories Label.
<br />HIGH PRESSURE DUCTWORK (Pressure class 3 inch and over)
<br />Manufacturers: Ajax, Semco, United Sheet Metal, or approved equal.
<br />Machine formed round and /or flat oval spiral lock seam duct constructed of galvanized steel.
<br />Rectangular high pressure duct using a transverse joint system as manufactured by Ductmate,
<br />Nexus, TDC, TDF, or approved equal, may be used at contractor's option. Duct to be flanged,
<br />gasketed and sealed.
<br />Contractor fabricated ductwork meeting specified construction standards is acceptable with prior
<br />approval of Arch itect/Engineer. Submit construction details, a description of materials to be used,
<br />type of service, reinforcing methods, and sealing procedures.
<br />Use a perforated inner liner on double wall high - pressure duct. Annular space between inner liner
<br />and outer duct to be filled with 1 inch glass fiber insulation.
<br />Use cemented slip joints with 2 inch minimum overlap, flanged connections, or welded /brazed
<br />connections, unless noted otherwise for special applications. Prime coat welded joints.
<br />Provide standard 90 degree conical tee takeoffs except for exhaust at velocities over 2000 feet per
<br />minute, use 45° lateral connections; straight taps or bullhead tees are not acceptable.
<br />Internal bracing will not be accepted on ductwork below 48 inches.
<br />Use turning vanes as specified in Section 23 33 12.
<br />Provide bellmouth fittings or expanded fittings at each duct connection to air plenums.
<br />Provide pressure relief fittings as indicated on the plans and /or details.
<br />Transform duct sizes gradually, not exceeding 15 degrees divergence and 30 degrees convergence.
<br />LOW PRESSURE DUCTWORK (Maximum 2 inch pressure class)
<br />Fabricate and install ductwork in sizes indicated on the drawings and in accordance with SMACNA
<br />recommendations, except as modified below.
<br />Construct so that all interior surfaces are smooth. Use slip and drive or flanged and bolted
<br />construction when fabricating rectangular ductwork. Use spiral lock seam construction when
<br />fabricating round spiral ductwork. Sheet metal screws may be used on duct hangers, transverse
<br />joints and other SMACNA approved locations if the screw does not extend more than 1/2 inch into
<br />the duct.
<br />Use elbows and tees with a center line radius to width or diameter ratio of 1.5 wherever space
<br />permits. When a shorter radius must be used due to limited space, install single wall sheet metal
<br />splitter vanes in accordance with SMACNA publications, Type RE 3. Where space will not allow and
<br />the C value of the radius elbow, as given in SMACNA publications, exceeds 0.31, use rectangular
<br />elbows with turning vanes as specified in Section 23 33 00. Square throat - radius heel elbows will not
<br />be acceptable. Straight taps or bullhead tees are not acceptable.
<br />Where rectangular elbows are used, provide turning vanes in accordance with Section 23 33 00.
<br />Provide expanded take -offs or 45 degree entry fittings for branch duct connections with branch
<br />ductwork airflow velocities greater than 700 fpm. Square edge 90- degree take -off fittings or straight
<br />taps will not be accepted.
<br />Button punch snaplock construction will not be accepted on aluminum ductwork.
<br />Reece, Noland & McElrath, Inc.
<br />239000-2
<br />Orange County Board of Elections
<br />Orange Co., NC 05/04/18
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