not less than [150 mm] [6 inches] [_____]. Fabricate multitube collector
outlet tubes, to convey clean gases out of collector, of material specified
in paragraph entitled "Materials," and vary length with longest row at flue
gas inlet to collector. Provide steel wear angles not less than 100 by 100
by 10 mm 4 by 4 by 3/8 inch vertically tack welded in 5 or 6 places onto
the exterior surface of the inlet row of the outlet tubes. Locate each
angle so that each leg faces the inlet flue gas and deflects the flue gas
by protecting the exterior surfaces of each outlet tube along the inlet row
from abrasive particles contained in the incoming flue gas. These vertical
wear angles shall extend between the top of the bottom header sheet and the
bottom of the top header sheet on the inlet row of the outlet tubes.
2.2.4
Hopper Heating Systems
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NOTE: Use this paragraph when units are operated
where incoming gases may be cooled below dew point.
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Provide a hopper heating system for each cyclone hopper as specified herein.
2.2.4.1
Hopper Heater System Design
The system shall be furnished by the collector manufacturer with all
material required for mounting and shall be designed to provide a 66
degrees C 150 degree F rise in temperature in the hopper, in the vicinity
of the heaters, during offline and startup conditions. The system shall be
sized to provide a hopper skin temperature of not less than 121 degrees C
250 degrees F when insulation specified herein is in place during minimum
equipment operating temperatures. Design system with a minimum heating
safety factor of 1.1 and a minimum wind heat loss factor of 1.12. Provide
system with maximum heater coverage between hopper stiffeners utilizing
modular heaters and flexible blanket or tape heaters for the hopper throat
heating. Heater modules shall cover at least 33 percent of the hopper
area, shall cover the bottom portion of the hopper to the maximum extent
possible, and shall extend at least 70 percent up the hopper height. Use
flexible electric heating blankets or tapes, capable of withstanding 427
degrees C 800 degrees F, where modular equipment will not fit. Design all
equipment to withstand natural and induced vibrations, plus shock loadings
normally experienced during operation of the dust collector and ancillary
equipment including manual rapping of the strike plates. The hopper heater
system shall be individually, thermostatically controlled with adjustable
setpoint and shall be furnished and installed complete including all power,
control, and alarm components. Locate the low temperature and control
thermocouples in the lower portion of each heater zone. Heater power
voltage shall be 480 volts AC. Heater control voltage shall be 120 volts
AC.
a.
Hopper Heater Module Design: Heater modules shall be
self-contained and each modular heater shall be furnished
complete. The modules shall have a flexible heating face to
conform to the irregularities of the hopper surface, providing
intimate contact between the heaters and the hopper, and providing
maximum heat transfer. Hopper heater modules shall be of low watt
density design (maximum of 0.0047 watts per square mm 3 watts per
square inch of resistance element) with a minimum of 6 parallel
resistance paths per heater (continuous blanket type elements
shall be deemed to meet the multipath requirement). Heating
element in the module shall be capable of being operated at and
SECTION 15861N
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