2.6.2.1
Fan Size
Size fans to handle combustion gases at maximum firing rate. Maximum fan
speed shall not exceed 1200 rpm at test block rating. Design allowances
and corrections for furnace, economizer, [scrubber,] [baghouse,] dust
collector, breeching pressure drop when operating at [10] [20] [40] percent
excess air, flue gas temperature, plant elevation, and other design factors
shall be made. Add the following allowances for momentary overloads and
normal deterioration of fans, firing equipment and boilers after sizing
fans in accordance with the above, to obtain the required test block rating:
Coal-Fired
Excess Volume
Excess Pressure
Induced Draft
20 percent
32 percent
Oil Fired
Induced Draft
10 percent
20 percent
2.6.2.2
Fan Construction
Fan shall be arrangement [_____] in accordance with AMCA 801. Fan wheel
shall be radial tip design (forward curved-backward inclined) or straight
radial blade with shrouds for high efficiency design. Blading shall be 8
gage minimum thickness steel [with the addition of 6 mm 1/4 inch thick
steel partial blade wear strips, 125 mm 5 inch minimum width each side of
centerplate]. A minimum number of blades is preferred; a maximum of
twenty-four is acceptable. Balance fan wheels both statically and
dynamically at factory. Minimum static efficiency at maximum rating
including allowances shall be 67 percent.
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NOTE: At the text below, heat slingers may not be
necessary on low temperature flue gas applications.
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a.
Bearings and Pedestals: Provide fan with water-cooled
self-aligning sleeve type bearings mounted in suitable pillow
blocks. Bearings shall be independent high temperature, oil
lubricated, pedestal type with dust seals. [Provide fan shaft
heat slingers.] Cast iron or fabricated steel pedestals mounted
on fabricated steel soleplates shall be provided. Provide a
self-contained temperature control valve, with water piping to
control temperature of bearings.
b.
Housing: Fan shall have 5 mm 3/16 inch thick welded steel housing
and inlet boxes which shall be split with flanged and gasketed
joints. Construction shall permit one piece removal of rotor from
rear of fan without disturbing duct connections.
Provide hinged,
quick opening access door in scroll and inlet boxes and 50 mm 2
inch plugged openings in low points of scroll and inlet boxes.
c.
Dampers: Provide inlet dampers with multi-parallel-stream flow
blades with anti-friction bearings with 80 mm 3 inch minimum
spacers and stuffing boxes to keep bearings cool. Dampers shall
be mounted in 200 mm 8 inch channel frames and interconnected with
one extended, ball bearing mounted control level for connection to
control actuator.
d.
Welding:
Welding of fan components shall be in accordance with
SECTION 15502N
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