within the combustion chamber, and where moving parts are exposed to
excessive heat, such parts shall have all bearings protected by suitable
water jackets. Grease or oil lubrication shall be provided for all
bearings. Stoker shall be designed for readily adjustable feed
distribution of coal on the grates.
2.3.1.1
Spreader Stoker Grates
**************************************************************************
NOTE: Steam driven boiler auxiliaries will not be
used unless the exhaust steam can be utilized
completely. Reference to steam drives will be
deleted if inapplicable for the equipment specified.
**************************************************************************
Grates for spreader stoker firing shall be of the high air-resistant type
especially designed and arranged for powered mechanical or compressed air
actuated dumping in sections. Openings shall provide proper distribution
of air under the fuel bed. [Grates shall be in sections to match the
feeders with provisions for shutting off the forced draft to each section
so that any section of the grate can be cleaned while the others remain in
service.] Grates shall be heavy-duty, heat-resisting cast-iron.
Mechanical dumping shall be with [steam-] [air-] [water-]actuated power
cylinders connected to the grates, and grates shall be furnished complete
with cylinders, linkages, valves, and piping as required. Each section
shall dump independently of other sections. Necessary over-fire air jets
complete with fans, ducts, and air control valves shall be provided as
required for proper turbulence and combustion. Grate drives shall be
independent of feeder drives to provide independent speed variation of
feeders and grates.
2.3.1.2
Traveling Grates
Traveling grates shall be high air-resistant type especially designed for
spreader stoker firing and for continuous ash discharge. Openings shall
provide proper distribution of air under the fuel bed. Grates shall be
heavy-duty, heat-resisting cast-iron, and individual sections shall be
replaceable without taking the grate out of service. Air seals around
grate shall hold air leakage to a minimum. Moving grates shall be
furnished complete with supporting steel, shafts, sprockets, chain, gears,
skid bars, and bearings as required. The front end of the grates where the
ash is discharged shall be enclosed with a dust-tight enclosure made of
heavy cast-iron plates not less than 15.9 mm 5/8 inch thick and properly
protected with firebrick where exposed to the furnace, or shall be of
refractory-lined steel plate. The vertical fronts of the enclosure shall
be fitted with refractory-lined inspection and access doors, one for each
feeder. The roof of the enclosure shall be sealed with refractory to
protect the metal parts from the furnace temperature. The underside of the
grates shall be enclosed to form a chamber. Hopper for receiving the ashes
shall be constructed as indicated or as recommended by the manufacturer.
Over-fire air jets shall be provided as required for proper turbulence and
combustion.
2.3.1.3
Vibrating Grate
Vibrating grate of high air-resistant type shall be especially designed for
spreader stoker firing and for continuous ash discharge. Grates shall be
either air- or water-cooled with openings to provide proper distribution of
air under the fuel bed. Grates shall be heavy-duty, heat-resisting cast
SECTION 15559A
Page 30
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