steel] [minimum 1.6 mm 16 gauge carbon steel]. [Duct construction shall
include external perimeter angle sized in accordance with SMACNA HVAC Duct
Const Stds, except welded joint reinforcement shall be on maximum of 600 mm
24 inch centers; continuously welded companion angle bolted flanged joints
with flexible ceramic cloth gaskets where indicated; pitched to drain at
low points; welded pipe coupling-plug drains at low points; welded fire
protection and detergent cleaning penetration; steel framed, stud bolted,
and flexible ceramic cloth gasketed cleaning access provisions where
indicated. Angles, pipe couplings, frames, bolts, etc., shall be same
material as that specified for the duct unless indicated otherwise.]
3.1.8.2
Exposed Ductwork
Exposed ductwork shall be fabricated from minimum 1.3 mm 18 gauge, Type
304L or 316L, stainless steel with continuously welded joints and seams.
Ducts shall be pitched to drain at hoods and low points indicated. Surface
finish shall match hoods.
3.1.8.3
Concealed Ducts Conveying Moisture Laden Air
Concealed ducts conveying moisture laden air shall be fabricated from
minimum [1.3 mm 18 gauge, Type 300 series, stainless steel] [1.6 mm 16 gauge,
galvanized steel] [0.55 mm 16 ounce, tempered copper sheet]. Joints shall
be continuously welded, brazed, or soldered to be liquid tight. Duct shall
be pitched to drain at points indicated. Transitions to other metals shall
be liquid tight, companion angle bolted and gasketed.
3.1.9
Acoustical Duct Lining
Lining shall be applied in cut-to-size pieces attached to the interior of
the duct with nonflammable fire resistant adhesive conforming to ASTM C 916,
Type I, NFPA 90A, UL 723, and ASTM E 84. Top and bottom pieces shall lap
the side pieces and shall be secured with welded pins, adhered clips of
metal, nylon, or high impact plastic, and speed washers or welding cup-head
pins installed according to SMACNA HVAC Duct Const Stds. Welded pins,
cup-head pins, or adhered clips shall not distort the duct, burn through,
nor mar the finish or the surface of the duct. Pins and washers shall be
flush with the surfaces of the duct liner and all breaks and punctures of
the duct liner coating shall be sealed with the nonflammable, fire
resistant adhesive. Exposed edges of the liner at the duct ends and at
other joints where the lining will be subject to erosion shall be coated
with a heavy brush coat of the nonflammable, fire resistant adhesive, to
prevent delamination of glass fibers. Duct liner may be applied to flat
sheet metal prior to forming duct through the sheet metal brake. Lining at
the top and bottom surfaces of the duct shall be additionally secured by
welded pins or adhered clips as specified for cut-to-size pieces. Other
methods indicated in SMACNA HVAC Duct Const Stds to obtain proper
installation of duct liners in sheet metal ducts, including adhesives and
fasteners, will be acceptable.
3.1.10
Dust Control
To prevent the accumulation of dust, debris and foreign material during
construction, temporary dust control protection shall be provided. The
distribution system (supply and return) shall be protected with temporary
seal-offs at all inlets and outlets at the end of each day's work.
Temporary protection shall remain in place until system is ready for
startup.
SECTION 15895
Page 58
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