encountered. Pressure parts, including watertubes, headers, and valves
shall be suitable for boiler pressure specified and shall be constructed in
accordance with ASME BPVC SEC I. Grate sections shall be properly designed
for even air distribution over the entire grate area.
2.3.4.2
Stoker Controls
Stoker controls shall be designed for connection to the combustion control
system to accurately regulate the coal feed rate and shall be arranged for
manual operation independent of the combustion control system. Variation
of coal feed rate shall be accomplished by changing the length of time of
vibrations. Vibration generator shall be belt connected or gear connected
to the electric motor. Unit shall be free of any vibration that may damage
other parts of the boiler or the building structure. Bearings requiring
lubrication shall be provided with easily accessible lubrication fittings.
Combustion air volume shall automatically vary in direct proportion with
the coal feed rate. Stoker shall be driven by [electric motor] [steam
turbine]. [Motor shall be high-starting torque [totally enclosed,
nonventilated] [totally enclosed, fan-cooled] [totally enclosed, fan-cooled
suitable for installation in a Class II, Division 1, Group F hazardous
location in accordance with the NFPA 70].] [Motor starter shall be
magnetic, reversing, [across-the-line] [reduced voltage start] type with
[general-purpose] [dust-tight] [explosion-proof] enclosure.]
2.3.4.3
Hoppers
Hoppers shall be constructed of steel plates not less than 6.4 mm 1/4 inch
thick, shall have a capacity not less than [_____] kg pounds, and shall be
provided with a suitable method of cleanout. Furnace arches of a design
suitable for the intended use and a type that will ensure proper combustion
of the fuel shall be provided. Lower furnace sidewall headers in a
waterwall boiler shall be inclined to accommodate the inclined grate
arrangement. Stoker front shall form the front of the boiler for the full
width of the boiler and shall 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 cleanout and
access 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. At the end of the grate the ash shall be
discharged into a bunker or pit as indicated. The bunker shall have a
dust-tight enclosure made of steel plates not less than 15.9 mm 5/8 inch
thick properly protected with firebrick where exposed to the furnace and
shall be fitted with cast-iron, refractory lined inspection and access
doors, and provisions for ash removal as indicated.
2.4
PULVERIZED COAL BOILERS
**************************************************************************
NOTE: Pulverized coal boilers require special
consideration since they are usually designed to
operate on one specific type of coal and usually are
utilized for large units where a steady minimum load
of 68,040 to 90,720 kg per hour (150,000 to 200,000
pounds per hour) is assured.
Small horizontal type units down to 36,290 kg per
hour (80,000 pounds per hour) of steam are
available, but horizontal units also will range up
to 113,400 kg per hour (250,000 pounds per hour) of
SECTION 15559A
Page 36
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