secondary separator shall be similar to the primary receiver in
construction, but may be smaller and of lighter material. No part
of the discharger shall extend into the main storage bin. A
housing constructed of 6.2 mm 1/4 inch steel plate with a
tight-closing access door shall be provided as an enclosure for
the discharger.
b.
The silo vent filter unit shall be mounted on top of the silo and
shall act as an air release unit to separate the air from the ash.
The ash shall drop into the silo. Back cleaning of the bag
filters shall be automatic, utilizing plant air at approximately
690 to 860 kPa 100 to 125 psig. Back cleaning unit shall be
actuated whenever the ash handling system is in use. Dust
released from the filter bags in the back cleaning operation shall
fall into the storage silo. Housing shall be provided to allow
the unit to operate exposed to the weather in ambient temperatures
ranging from minus 40 to plus 55 degrees C minus 40 to plus 130
degrees F.
c.
A rotary, dustless unloader shall be provided to eliminate all
dust in unloading ash and dust from the ash storage silo. No
water shall be added to the ashes in the conveyor or in the
storage bin. The dustless unloader shall add water to the ash in
controlled quantities so that no surplus water runs or drips from
the ash after discharge. The discharged ash shall be muddy but
loose and free flowing. Water valve shall open only when drive
motor is running. Unloader shall have a capacity of not less than
27 metric tons 30 tons of conditioned ash per hour. The rotating
unit shall be designed so that all bearings are located on the
outside and not in contact with the material handled. Platform
shall be provided for access to unit and shall have a handrail and
a safety ladder to grade. Motor shall be totally enclosed type
for outdoor operation. [Motor starter shall be [manual]
[[magnetic] [across-the-line] [reduced voltage start]] type with
[weather-resistant] [water-tight] [dust-tight] enclosure.]
2.30.1.6
Conveyor Type Ash Handling System
**************************************************************************
NOTE: When specifying boilers with capacity greater
than 4.1 Megawatts (14 million Btuh) per boiler, the
following paragraphs will be edited.
**************************************************************************
Ash pits shall be funnel shaped, constructed of 6.2 mm 1/4 inch steel
plate, minimum, and covered with a heavy grating with openings
approximately 50 mm 2 inches square. Ashes and clinkers shall be
discharged from the boiler ash hoppers into ash pits located directly below
the ash hopper doors. A combination drag chain conveyor for horizontal
conveying and an elevator conveyor for vertical conveying of ashes shall be
arranged, as indicated, to take ashes from the bottom of the ash pits for
discharge into the ash silo. Conveyors shall have a capacity of not less
than [_____] metric tons/hour tons/hour when handling ashes weighing
approximately [_____] kg/cubic meter pcf at a maximum speed of 508 mm/sec
100 fpm. Doors shall be provided for access to all parts, as required.
Motor shall be [totally enclosed, nonventilated type] [totally enclosed,
fan-cooled type] [totally enclosed, fan-cooled type suitable for
installation in a Class II, Division 1, Group F hazardous location in
accordance with NFPA 70]. [Motor starter shall be [manual] [[magnetic]
SECTION 15559A
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