2.3.2.2
Grate Surface
Grate surface shall include the underfeed retort area, air admitting
tuyeres, side combustion grates, and the side dumping plates. Retorts
shall be sectional construction of large capacity and proper shape to
distribute coal uniformly over the entire grate surface with a minimum of
moving parts within the furnace. Stokers having total grate width of more
than 2.1 m 7 feet shall have movable grates providing positive lateral
feeding of the coal from the retort toward the dump plates. Retort and
grate sections shall be constructed of heavy-duty, heat-resisting
cast-iron, shall be cored for proper air distribution, and shall be
designed for easy replacement of individual sections. Ash dump plates
shall be provided with necessary levers and linkage for hand operation from
the front of the boiler.
2.3.2.3
Ram Feed
Ram feed shall be mechanical, pneumatic, or hydraulic driven by an electric
motor connected through an efficient gear reduction unit, crank shaft, and
connecting rod. Motors shall be [totally enclosed fan-cooled type]
[totally enclosed fan-cooled type for installation in a Class II, Division
1, Group F hazardous location in accordance with NFPA 70]. [Motor starter
shall be magnetic [across-the-line] [reduced voltage start] type with
[general-purpose] [dust-tight] [explosion-proof] enclosure.] Stoker
controls shall be for connection to the combustion control system to
accurately regulate the coal feed rate. Manual setting of the coal feed
rate shall be possible without disconnecting linkage, with variation of
stoker feed as required to maintain any desired capacity between 25 and 110
percent of boiler capacity in 10 or more equal increments. Regulation of
the coal feed rate shall be by varying the time increments between strokes
of the ram. A throw-out release shall protect the coal feeding mechanism
from injury in case foreign materials obstruct normal operation.
2.3.2.4
Hoppers
Hoppers shall be constructed of steel plates not less than 6.4 mm 1/4 inch
thick and shall have a capacity of not less than [_____] kg pounds.
Hoppers shall be provided with cleanout doors. Stoker front plate shall
form the front of the boiler for the full width of the boiler and extend
from the firing floor to some point above the stoker where it shall connect
to the boiler structural framing. Front shall be cast-iron or steel plate,
refractory lined with [auxiliary firing doors and] cleanout doors of
refractory-lined cast-iron. Structural framing as required shall support
the stoker and its components from the boiler foundation or boiler room
floor. Water spray pipes and nozzles shall be provided for quenching the
ashes in the ash pit.
2.3.3
Conveyor Stokers
Conveyor stokers shall be the grate level feed, forced draft [chain grate]
[traveling grate] type and shall be provided complete with hoppers, feed
gate, drive shaft, sprocket wheels, grate, drive, and all necessary
auxiliary equipment. Stokers shall be capable of handling the coal
specified. Coal shall be fed automatically at a constant rate from the
hopper onto the moving grate and shall be evenly distributed across the
full width of the grate. The stoker frame shall be provided with not less
than four air-tight zones for supply of forced draft and shall have
suitable zone control dampers with external indicating, operating, and
SECTION 15555A
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