entire surface of mineral fiber block and board insulation in place using
wire threaded lugs. Thread lugs with wire both ways, pull tight, twist
ends together with pliers, bend over, and carefully press into the surface
of the insulation.
3.3.1.2
Mineral Fiber Blanket Insulation
Secure mineral fiber blanket insulation with speed washers and impaling
pins spaced not greater than 305 mm 12 inches on centers. When applying
speed washers, do not compress the insulation below the design insulation
thickness. Reinforce mineral fiber blanket insulation with expanded metal
on the outer surface and wire mesh or expanded metal on the inner surface.
Tightly butt blanket sections together and tie at joints to prevent the
blanket edges from peeling or bulging, and to provide maximum sealing.
3.3.1.3
Calcium Silicate Insulation
Provide calcium silicate insulation over 12 Gage steel pins studwelded on
610 mm 2 feet centers. Do not place calcium silicate insulation directly
in contact with the aluminum casing. Closely fit insulation around
penetrations. Hold insulation in place by 65 mm 2 1/2 inchsquare speed
washers. Protect calcium silicate on horizontal surfaces by 16 Gage sheet
steel coated with a non-slip paint. On other areas, apply 13 mm 1/2 inch
thick insulating concrete or cover using 16 Gage sheet steel. Provide
access panels with removable insulation panels.
3.3.2
Casing
3.3.2.1
Structural Steel Grid System
Design the structural steel grid system to provide a smooth finished
surface of insulation over the stiffeners, access doors, flanges, ribs, and
uneven surfaces. Weld the grid system onto the equipment and structural
support surfaces. Install aluminum casing onto grid system. Design the
roof to transmit an external 114 kg 250 pound walking load from the casing
to the structural grid system without compression of the insulation
material.
3.3.2.2
Access Openings
Closely fit insulation to manholes, inspection doors, access doors, and
flanged openings. Frame and flash to make weather-tight. Provide hinged
or lift-off doors with nameplates, code stamping symbols, and
non-projecting connections.
3.3.2.3
Weatherproofing
Fabricate and overlap casing to make weather-tight. Provide closures,
flashings, and seals. Provide the open ends of fluted sections with
tight-fitting closure pieces. Form and install flashing so that water
cannot enter and wet the installation. Design and install flashing to
readily drain any water that might enter. Weatherproof joints or casing
openings which cannot be sealed by flashings or laps with an aluminum
pigmented sealer.
3.3.2.4
Convection Stops
Provide convection stop on vertical surfaces over 3.67 meters 12 feet tall.
The maximum interval between convection stops shall be 3.67 meters 12 feet.
SECTION 15863N
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