vertical and bottom surfaces at a maximum spacing of 1.22 meters 4 feet on
centers. Provide subgirts on roof surfaces at a maximum spacing of 610 mm
two feet on centers. Provide a roof surface system that will transmit an
external 114 kg 250 pound walking load from the casing to the structural
steel grid system without compression of the insulation material.
3.8.2
Access Openings
Closely fit insulation to fittings around access doors and other
penetrations through the insulation. Neatly frame and flash to make
weathertight and to create a pleasing appearance. Provide insulated hinged
or lift-off doors designed for convenient opening or removal at nameplates,
code stampings, nonprojecting connections, and access openings. Pitch
access openings for water runoff and have flashing at door head as shown in
SMACNA Arch. Manual.
3.8.3
Weatherproofing
Install casing with proper overlap to make the installation weathertight.
Fabricate and fit the casing to ensure a neat appearance. Provide
closures, flashings, and seals required. Provide the open ends of fluted
sections with tightfitting closure pieces. Suitably form and install
flashing so that water cannot enter and wet the insulation. Design and
install flashing to readily drain any water that might enter. Weatherproof
joints or openings in casing which cannot be effectively sealed from entry
of moisture by application of an aluminum-pigmented sealer manufactured for
this type of service.
3.8.4
Convection Stops
Provide steel channel or Z-girt convection stops on all vertical surfaces
over 3.66 meters 12 feet tall. The maximum interval between convection
stops shall be 3.66 meters 12 feet.
3.8.5
Casing Attachment
**************************************************************************
NOTE: If a separate insulation section is part of
this specification, add a note to that section to
indicate that insulation of the precipitator is
covered by this section.
**************************************************************************
Attach aluminum casing to the steel structural members by means of Number
14 stainless steel Series 300 self-tapping screws on 305 mm 12 inchcenters.
Fasten vertical laps and flashing by means of 20 mm 3/4 inch Number 14
stainless steel Series 300 sheet metal screws on 305 mm 12 inch centers.
Provide exposed screws with aluminum of stainless steel backed neoprene
washers preassembled to screws. Do not compress insulation below nominal
thickness when installing screws.
3.9
HEATER INSTALLATION
Thoroughly clean hopper surfaces prior to heater module, tape, or blanket
installation. Install the heater module so the module surface contacts the
hopper wall to the maximum extent possible. Provide heaters with necessary
mounting hardware, channels, and brackets. Install throat heaters so the
heater conforms to the surface of the throat and contacts the throat to the
maximum extent possible. Do not overlap throat heaters. Hold throat
SECTION 15862N
Page 45
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