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 -40 degrees C to plus
55 degrees C -40 to plus 130 degrees F.
**************************************************************************
NOTE: Where motor starters for mechanical equipment
are provided in motor control centers, delete the
description of motor starters.
**************************************************************************
c.
Rotary, Dustless Unloader: 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.]
2.24.1.6
Conveyor Type Ash Handling System
**************************************************************************
NOTE: When specifying boilers with capacity greater
than 4.1 MW (14 million Btuh) per boiler, this
paragraph through paragraph Elevator Conveyor will
be deleted.
**************************************************************************
Ash pits shall be funnel shaped, constructed of 6.4 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/meter pcf at a maximum speed of 508 mm/second 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]
[across-the-line] [reduced voltage start]] type with [general-purpose]
[weather-resistant] [water-tight] [dust-tight] [explosion-proof] enclosure.]
SECTION 15555A
Page 82
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