per cubic meter 70 pounds per cubic foot. Ash silo support shall be free
standing and of sufficient height to allow gravity discharge of ash through
the rotary ash conditioner to a [truck] [railroad car]. Provide access
stair tower with intermediate platforms at 3.66 meters 12 feet intervals
for access to ash conditioner level, silo floor level and silo roof level.
Platforms from adjacent structures with stair access may be provided in
lieu of the stair tower, but ladders with safety cages and access platforms
shall then be also provided. Provide ladder with stainless steel fall
prevention device on inside of silo from manhole in top of silo to bottom
of silo. [Provide silo roof enclosure and unloader room enclosure each
with single one by 2 meters 3 by 7 feet access door, [_____ by _____] meter
[_____ by _____] feet double door, two windows, ventilator, [heater],
insulated metal panel siding to match boiler plant walls and electrical
lighting and convenience receptacles. Unloader room enclosure shall have
reinforced concrete floor.]
2.12.7.1
Construction
Construct silo of steel with refractory lining or of concrete staves with
steel hoops and concrete roof. Roof accessories shall include manhole,
relief valve and vent filter. Bottom of silo shall be [conical, sloped a
minimum of 45 degrees] [flat with a steel plate feeding hopper in bottom of
silo to funnel the ash into the inlet of the rotary vane feeder]. Provide
hopper with expansion joints and sufficient poke holes with cover or cap.
2.12.7.2
Concrete Stave Silo
Construct of either lightweight solid or hollow precast concrete staves
with post-tensioned steel reinforcing hoops around the exterior.
Mechanically measure and mix materials in concrete staves. Vibrate and
shape staves under pressure and steam or air cure.
a.
Wall Coating: Coat interior surface with a three-step process of
a brush coat, scratch coat, and finish trowel coat of a mixture of
fine sand and portland cement in accordance with silo
manufacturer's recommendations. Apply each coat successively to
produce a smooth interior surface. Work mixture into the formed
horizontal and vertical grooves to permanently interlock the
concrete staves. Brush coat exterior surface with a double
application of waterproof mixture. Mixture shall include a
chemical agent for waterproofing and portland cement, sand, and
water. Work coating into joints and over steel reinforcing hoops
to form a weatherproof protective coating.
b.
Steel Reinforcing Hoops: Galvanized steel rods not less than 14 mm
9/16 inch in diameter with not less than 16 mm 5/8 inch rolled
threads. Join hoop ends together with nuts and heavy malleable
galvanized iron lugs or heavy duty galvanized steel lugs to a
close tolerance for a tight fit. Electrogalvanize rods, nuts, and
lugs to ensure adequate protection against corrosion. Rods shall
be high quality, metallurgically sound steel with tensile strength
not less than 488 MPa 65,000 pounds per square inch, yield point
not less than 276 MPa 40,000 pounds per square inch, and a minimum
elongation of 14 percent in 229 mm 9 inches. Reinforcing shall be
sufficient to resist the maximum lateral pressure and loads
imposed by the ash pressure within the silo. Structurally connect
together hoop rods that pass through silo outlets on inspection
frames.
SECTION 15501N
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