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. Hoop rods shall be structurally
connected together where they pass through silo outlets on
inspection frames.
c.
Hollow Concrete Stave Silos: Construct silo of precast concrete
staves with lateral air spaces. Cast staves from a well
proportioned mix of portland cement and an expanded clay light
weight aggregate. The minimum compressive strength of the
concrete at 28 days shall be 34.50 MPa 5,000 psi. Hollow staves
shall be 92 mm thick by 250 mm wide by 762 mm long 3 5/8 inches
thick by 10 inches wide by 30 inches long with five lateral air
cores per stave, except that shorter starter staves may be used to
permit the horizontal joints to be staggered.
d.
Solid Concrete Stave Silos: Construct silo of solid lightweight
precast concrete staves. Solid staves shall be not less than 92
mm thick and 250 mm wide by 762 mm long 3 5/8 inches thick and 10
inches wide by 30 inches long, except starter staves may be
shorter. Solid staves shall be constructed from a well
proportioned mix of portland cement, washed sand and gravel which
is free from injurious organic impurities and contains less than 5
percent of deleterious substances. Grade fine aggregate from
coarse to fine. Compressive strength of solid concrete staves at
28 days shall be 34.50 MPa 5,000 psi.
2.11.6
Pulse Jet Bag Filter Vent
Provide for the silo constructed of 10 gage steel plate, fitted with rain
hood. Bag material shall be sateen cotton capable of withstanding not less
than 91 degrees C 195 degrees F, weighing 0.33 kg per square meter 9.75
ounces per square yard, having thread count of 4 by 2 per square mm96 by 60
per square inch and permeability of 76 to 102 L/s per square meter at 249 Pa
15 to 20 cfm per square foot at one inch water column. Vent shall have
not less than [_____] square meter feet effective cloth filtering area,
with each bag having a maximum effective cloth filtering area of 0.56
square meter 6 square feet.
2.11.7
Rotary Ash Conditioner (Unloader)
Provide a complete dustless horizontal, floor mounted unloading device to
discharge ashes from silo to a [truck] [railroad car]. Unloader (ash
conditioner) shall include a 762 mm 30 inch diameter revolving drum which
rotates about fixed spray nozzles, and shall be complete with conditioner
and discharge compartments, scrapers, and other accessories as required.
Unloader drum shall be constructed of steel plate not less than 10 mm 3/8
inch thick and shall be roller chain driven by a totally enclosed, fan
cooled, [_____] volt, three phase, 60 Hz electric motor not less than 3.75
kW 5 hp as specified under paragraph entitled "Motors and Drives" in this
section. Unloader shall discharge the conditioned ashes to a truck through
a 6 mm 1/4 inch thick steel plate chute. The unloader shall be designed to
eliminate most dust in unloading ash from the ash silo. An unloader that
utilizes screws as a means of mixing is unacceptable. The dustless
unloader shall add water to the ash, but not to the extent that there is
free or surplus water running or dripping from the ash after discharge.
Discharge ash shall be in a semi-fluid, loose, free flowing condition.
SECTION 15502N
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