start] type with [general-purpose] [dust-tight] [explosion-proof]
enclosure.] Hoppers shall be constructed of 6.4 mm 1/4 inch steel sheet,
minimum, shall be reinforced, and shall have a capacity of not less than
[_____] kg pounds. Hoppers shall be provided with suitable cleanout. Feed
screw shall be removable and conveyor compartment shall have cleanout.
Stoker shall rest on boiler room floor.
2.3.3
Conveyor Stokers
**************************************************************************
NOTE: Any paragraphs describing stoker equipment
not necessary for the system specified will be
deleted.
**************************************************************************
Conveyor stokers shall be of the grate level feed, forced-draft [chain
grate] [traveling grate] type with hoppers, feed gate, drive shaft,
sprocket wheels, grate, [electric motor] [steam] drive, and all necessary
auxiliary equipment. 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 locking devices.
2.3.3.1
Grates
Grates shall have individual sections constructed of heavy-duty,
heat-resisting cast-iron, shall be fitted or cored for proper air
distribution, and shall be designed for easy replacement of individual
sections. [Chain grates shall have staggered links connected by pins to
form a continuous flat chain the full width of the furnace.] [Traveling
grates shall have grate blocks mounted on carrier bars which, in turn,
shall be fastened to two or more drive chains to form a continuous flat
grate surface the full width of the furnace.] Continuous grates shall be
supported at the ends by suitable sprockets and at intermediate points on
suitable tracks or skids.
2.3.3.2
Grate Operation
**************************************************************************
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.
**************************************************************************
Conveyor grate shall be driven by [electric motor connected through a
suitable speed reduction unit] [steam] [hydraulically operated variable
speed drive]. Gears and chains required for the drive shall be enclosed in
a dustproof and oil-tight housing. Main shafts for the grates shall have a
forced system of lubrication with fittings located outside the casing or
have self lubricating bearings. If the forced lubrication system is
supplied, bearings shall be fitted with dust seals and easily accessible
forced lubrication fittings. Stoker controls shall be suitable for
connection to the combustion control system to accurately regulate the coal
feed rate. Manual setting of the coal feed rate by varying stoker feed, as
required to maintain any desired capacity between 25 to 125 percent of
boiler capacity, shall be possible without disconnecting linkage. Feed
SECTION 15559A
Page 34
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