weighted wire design precipitators are not acceptable. The discharge
electrodes in each passageway shall run in a vertical direction and shall
be supported by a welded pipe, tube, or channel frame. Provide the frame
with vertical pipe, tube, or channel supports spaced at a maximum interval
of 1.22 meters four feet. Also provide the frame with horizontal pipe,
tube, or channel supports spaced at a maximum interval of 1.22 meters four
feet. The electrodes shall have a cross-sectional area of not less than 16
square mm 0.025 square inches and not more than 64.52 square mm 0.10 square
inches. Fabricate collecting surface from rolled seamless sheet of not
less than 16 gage thickness. Collecting surface plate spacing shall be not
less than 280 mm 11 inches or greater than 330 mm 13 inches. Support
discharge electrodes and collecting surfaces as required to maintain proper
alignment during operation. Support each main discharge electrode bus
section support frame by four alumina support insulators. Design
collecting surfaces so that deflection from a plane surface will not exceed
plus or minus 6 mm 1/4 inch about any axis. Design and construct discharge
electrodes and collecting surfaces to be readily located and aligned within
plus or minus 6 mm 1/4 inch of the normal design position. Assemble the
collecting surfaces at the factory. Factory assembled modules which can be
shipped to the field for erection may be provided. Provide high voltage
frames with sway braces or other devices as required to prevent swaying.
Incorporate gas baffles into the collecting plates to provide a gas flow
quiescent zone and to provide stiffening.
2.3.10
Rappers
Provide falling hammer collecting surface and discharge electrode rappers
with individual hammers for each plate and frame. Design plate rappers for
sequential rapping to prevent simultaneous rapping of plates and provide a
minimum of 27 N.m 20 foot pounds of rapping force per plate. Design
discharge electrode rappers for sequential rapping to prevent simultaneous
rapping of frames and provide a minimum of 12.24 N.m 9 foot pounds of
rapping force per frame. Provide solid steel rapper drive shafts with a
minimum diameter of 50 mm 2 inches. Provide magnetic impulse gravity
return gas distribution plate rappers with individual rappers for each
plate or screen.
2.3.10.1
Rapper Controls
Rapper controls shall have adjustments for independent field repeat
intervals and for independent field rest time.
2.3.10.2
Rapper Control System
Provide a rapper control system conforming to NEMA ICS 1 and NEMA ICS 2
consisting of necessary devices for the complete control of each rapper
system. Factory install and wire the system for [indoor] [outdoor]
installation in a NEMA [12] [3R] cabinet as described in NEMA ICS 6 and
locate in [control house] [control room] [roof]. Provide outdoor mounted
units finish painted for outdoor service, wind braced for [_____] km miles
per hour wind and completely weatherproofed.
2.3.10.3
Rapper Disconnects
Provide disconnecting switches for individual rapper groups to deenergize
for servicing.
SECTION 15862N
Page 31
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