Access and inspection doors shall be provided as indicated and required.
Ducts shall be constructed with long radius elbows having a centerline
radius 1.5 times the duct width, or where the space does not permit the use
of long radius elbows, short radius or square elbows with
factory-fabricated turning vanes may be used. Duct joints shall be
substantially air-tight and shall have adequate strength for the service,
with 38 x 38 x 3.2 mm 1-1/2 x 1-1/2 x 1/8 inch structural steel angles used
where required for strength or rigidity. Duct walls thickness shall be as
follows:
Duct, Maximum Dimension
Galvanized Steel Sheet, Minimum Thickness
Up through 1525 mm
1.613 mm
Up through 60 inches
16 gauge
1526 m and larger
2.753 mm
61 inches and larger
12 gauge
2.11
BREECHING
Breeching shall be constructed of not less than 3.416 mm (10 gauge) 10 gauge
steel sheets conforming to ASTM A 36/A 36M. Breeching shall be adequately
reinforced and braced with structural steel angles not smaller than 50 x 50
x 6.4 mm 2 x 2 x 1/4 inches, and all joints and seams in the sheets and
angles shall be welded. Expansion joints shall be installed as indicated
and as required to suit the installation and shall be flexible type
requiring no packing. Breeching shall have angle flanges and gaskets for
connection to boilers, fans, equipment, or stacks. Breeching connections
shall be gas-tight and caulked-tight all around and sealed with cement to
form an air-tight joint. Clean-out openings of suitable size and at
approved locations shall be provided for access to all sections of the
breeching and shall have tight-fitting, hinged, cast-iron doors with
cast-iron frames. Plastic materials polyetherimide (PEI) and
polyethersulfone (PES) are forbidden to be used for vent piping for
combustion gases.
2.12
STACKS
Stacks for individual boilers shall be self-supporting double-wall
insulated type. Unless otherwise indicated, each stack shall be complete
with structural steel base, base plates, anchor bolts and nuts, cleanout
door, [induced-draft fan] [boiler] connection and a thermometer well. Stub
stacks for packaged boiler units may be supported directly on the boiler
providing the boiler structure is designed to accommodate such an
arrangement. Insulation shall be suitable for sustained flue gas
temperature of 485 degrees C 900 degrees F with intermittent temperatures
up to 650 degrees C 1200 degrees F and the wall section shall provide a "U"
factor of approximately 0.26. Stacks shall be fabricated of high-strength,
low alloy, structural steel resistant to atmospheric corrosion and
conforming to ASTM A 242/A 242M for both inner and outer shell. Inner
shells of each section shall be provided with an air-sealed and concealed
expansion and contraction device to allow for differential expansion of
inner and outer shells. Stacks shall be extended above the roof to the
height indicated. Plastic materials polyetherimide (PEI) and
polyethersulfone (PES) are forbidden to be used for vent piping for
combustion gases.
2.13
ELECTRIC MOTOR-DRIVEN PUMPS
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SECTION 15555A
Page 52
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