2.6.6
Gas Distribution Devices
Provide the precipitator with inlet and outlet screens or baffles required
to obtain proper gas distribution across the face of the precipitator as
determined by model test study. Gas distribution devices shall contain
removable 915 by 610 mm 3 by 2 feet panels on each screen or baffle for
access between screens. Provide the precipitator with internal gas baffles
as required to prevent gases from bypassing the treatment zone. Gas
distribution velocities across the inlet to the precipitator shall have a
root-mean-square deviation of no more than 15 percent and no flow shall
exceed 125 percent of average flow velocity.
2.6.7
Interlocks
Provide a key type safety interlock system with sequential key arrangement
on the precipitator housing and penthouse access doors, inlet and outlet
nozzle access doors, rectifier enclosure access doors,
transformer-rectifier grounding switch, hopper level indicator sources,
hopper access doors, and control unit circuit breakers. No high voltage
equipment shall be accessible without properly locking out the power supply
and grounding the high voltage equipment. Keys shall not be able to be
removed from the locks when access doors are open.
2.7
FABRICATION
Perform shop fabrication and assembly of steel structures in conformance
with AISC Specifications, Codes and Standards. Field welding shall be
shielded metal arc or submerged arc. Shop welding shall be shielded-metal
arc, submerged arc, flux-core arc, or gas metal arc. Perform welding in
conformance with the requirements of the AWS D1.1/D1.1M and AISC
Specifications. Shop connections shall be welded, riveted, or bolted with
high-strength bolts at the Contractor's option and as allowed by the
seismic code. Unless restricted by consideration of clearance or seismic
design criteria, show field connections as bolted friction type using ASTM
A 325M ASTM A 325 or ASTM A 490M ASTM A 490 bolts and design to conform to
AISC specification for "Structural Joints Using ASTM A 325M ASTM A 325 or
ASTM A 490M ASTM A 490 Bolts." Form and weld handrails and do not exceed 6
feet from center-to-center of posts. Grind welds smooth and even with the
surface of the pipe, remove weld splatter. Carefully form transitions at
corners where change of direction of elevation occurs as required to
provide continuous handrail. Clear columns or other vertical or horizontal
projections by at least 80 mm 3 inches. Furnish plates and additional
items as required for fastening to supporting members. Extend kickplates
100 mm 4 inches above top of grating and install at the edge of uncovered
openings and at the edge of walkways and platforms. Construct kickplates
to allow water run-off. Shop fabricate as complete as possible and within
standard industry practice. Leave large pieces unassembled only to the
extent necessary for shipment.
2.8
PAINTING
Steel surfaces shall be dry and clean before painting. Remove grease,
oils, and contaminants as outlined in SSPC SP 1. Remove weld spatter and
grind burrs smooth on cut edges and rough welds. Blast-clean surfaces
after fabrication, in accordance with SSPC SP 6 and profile depth of 0.038
to 0.051 mm 1.5 to 2.5 mils. Before any rust bloom forms, apply one coat,
dry film thickness of 0.076 mm 3 mils, of any of the organic zinc-rich
primers meeting the requirements of SSPC PS 12.01, with a minimum of 82
SECTION 15862N
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