2.4
DUCTWORK SYSTEM
Provide insulated weather-tight ductwork system from the [economizer] [air
heater] [_____] outlet to the stack inlet including [reverse air ductwork,]
bypass ductwork, and manifolds complete with transitions, structural steel,
structural slide bearings, turning vanes, expansion joints, dampers, test
ports, and mechanical draft equipment. Weld by continuous fillet or
complete penetration groove welds. Design ductwork system for temperatures
of minus 12 to plus 204 degrees C 10 to 400 degrees F, internal pressures
of positive 5 kPa to negative 7.60 kPa 20 to negative 30 inches Water
Column (WC), velocities of [_____] m/s fps, and for flyash fallout of 1171
kg/m2 240 lb/sq ft. Provide penetrations for control instruments.
2.4.1
General Ductwork
Provide insulated weather-tight ductwork. For ductwork sections greater
than [_____] meters feet in length, provide hoppers, clean-out doors, and
additional structural support. Do not apply loads at interface points.
Provide 9.50 mm 3/8 inch thick turning vanes for turns greater than 45
degrees and where indicated by the model study. Brace turning vanes with
pipes and angles but do not brace with rods. Brace ductwork maintaining
bolt hold tolerances of 0.8 mm 1/32 inchbetween adjacent holes and 1 .50 mm
1/16 inch between two holes on the same side. Provide bolts, nuts, and
ethylene propylene terpolymer (EPDM) gaskets for flanged connections.
2.4.2
Manifolds
Provide insulated weather-tight inlet and outlet manifolds supported from
the baghouse structure. Include expansion joints. Locate manifolds,
minimum 6 mm 1/4 inch stiffened ASTM A 36/A 36M of welded construction,
between two rows of compartments and design to minimize pressure drop yet
avoid low velocities which may allow flyash fallout. Base structural
design on the assumption that manifolds are 30 percent full of flyash.
Taper inlet manifold and provide take-offs to each compartments at or near
the manifold bottom to assist flyash into the compartments. Provide a
replaceable, abrasion resistant baffle plate at each compartment inlet.
2.4.3
Expansion Joints
Provide nonmetallic belt expansion joints with minimum 80 by 80 by 6 mm 3
by 3 by 1/4 inch carbon steel angle flanges. Belt material shall be minimum
6 mm 1/4 inch thick, two-ply, aramid or fiberglass reinforced, solid
fluoroelastomer polymer, spliced to form an endless belt without sewn
joints. Provide nuts and bolts to attach fabric to the flanges and to
attach expansion joints to the ductwork. Flange bolt holes shall be
factory punched and located at maximum 100 mm 4 inchcenters.
2.4.4
Dampers
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NOTE: Provide items in brackets for reverse air
cleaning system baghouses only.
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Provide automatically controlled damper units, including framing,
operators, and accessories, for the induced draft fan inlet, [the reverse
air fan inlet,] the inlet manifold, the outlet manifold, the inlet of each
compartment, [the outlet of each compartment,] [the inlet reverse air
SECTION 15863N
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