made while unit is in operation. Design firebars or grates to prevent
sifting of coal through spaces provided for air admission to the fuel bed.
As a minimum, construct stoker grates of alloyed cast iron.
2.4.2.5
Stoker Drive
Stoker may be hydraulically or mechanically driven through cranks and
machine cut, double reduction worms and gears, fully enclosed in an
oiltight case and running in a bath of oil. Bearings shall be antifriction
type, with hardened inner and outer races and fitted with forced
2.4.2.6
Stoker Drive Electric Motor
[_____] volt, [_____] phase, 60 Hz, [_____] rpm, totally enclosed, fan
cooled not less than [_____] kW hp as specified in paragraph entitled
"Motors and Drives."
2.4.2.7
Air Distribution Control
Divide stoker plenum chamber into high and low pressure zones. High
pressure zone shall be adjacent to retort where fuel bed is normally
heaviest. Low pressure zone shall be under end of grate furthest from
retort and shall compensate for thinner fuel bed normally carried in that
area. Make provisions to admit air under pressure through the dump grates
by manually operated blast gates.
2.4.2.8
Overfire Air System
Overfire air system shall consist of a blower, damper, manifold with
properly sized nozzles and connecting air piping to ensure full penetration
and proper turbulence. Blower volume shall not be less than 15 percent of
total volume of combustion air. Blower pressure shall be sufficient for
penetration of the full length of the furnace. Nozzles shall be located in
rear of furnace wall and nozzle spacing shall be approximately 150 to 230 mm
6 to 9 inches o.c. Utilizing air from forced draft fan for overfire air
system is not acceptable. Design shall conform to requirements of the
stoker manufacturer to suit the boiler furnished.
2.4.2.9
Ash Discharge System
Provide each stoker with power operated dump grates extending from front
wall to bridge wall on both sides adjacent to side walls and of sufficient
area to handle ash resulting from burning of coal specified at the maximum
capacity specified. Stoker dump cylinders shall be [steam] [air]
[hydraulically] operated. Perforate dump grates for admission of air to
burn out combustibles before refuse is discharged to ash pit. Provide ash
spray pipes with manually operated valves on front of stoker beneath each
dump grate.
2.4.2.10
Doors
Provide stoker front with not less than two lined furnace
access doors not
less than 460 mm wide by 400 mm high 18 inches wide by 16
inches high with
observation ports, two ash pit doors not less than 350 mm
wide by 300 mm
high 14 inches wide by 12 inches high, and two air plenum
cleanout doors.
SECTION 15501N
Page 50
Previous Page
