2.9.13.7
Scale Weigh Hopper
Construct scale weigh hopper and discharge gate of not less than 14 gage
stainless steel plate, continuously welded and stiffened with angle irons.
Weigh hopper shall be of such design and construction to ensure clean
discharge.
2.9.13.8
Controls
Provide controls, except those required for weigh hopper discharge,
prewired and located in a [NEMA 12] [NEMA 3] dusttight enclosure. Provide
circuit breaker interlocked with the electrical panel door. Control
circuits shall be two wire nominal 120 volt systems obtained by using an
isolation transformer with one side grounded and shall be wired to a single
terminal block which shall be included in the electrical panel. Segregate
circuits of different voltage levels. Controls shall include large,
oiltight, industrial type pushbuttons for use as "start-stop," "test," and
"dump" switches mounted on the scale body adjacent to the electrical panel.
2.9.13.9
Counters
Mount a mechanical type coal counter on the scale body. Counter shall be
rugged, reliable, with heavy duty register and designed so that double
counting is impossible. [A remote motor operated counter shall be
furnished located on the coal handling control panel in the control room.
Counter shall be designed so that double counting is impossible.] [Provide
a contact closure for sending a pulse signal of each weigh hopper discharge
to the operator control console, specified under VAMS Section 15901N
CONTROLS AND INSTRUMENTATION BOILER PLANT.]
2.9.13.10
Scale Inlet
Scale inlet shall contain coal gate with opening not less than 457 by 457
mm or 406 by 508 mm 18 by 18 inches or 16 by 20 inches along with a
dusttight metal slip joint constructed of not less than 4.76 mm 3/16 inch
thick steel plate. Slip joint shall be of split construction to allow for
installation after coal scale is in place. Design slip joint to allow the
necessary flexibility to take care of deflection of the [bunker] [silo]
outlet due to varying load and temperature variations without imposing load
on the scale. Rope packing or other resilient gasket material shall be
provided to make the slip joint completely dusttight.
2.9.13.11
Scale Outlet Hopper
Not less than 6 mm 1/4 inch thick 410 stainless steel plate of capacity not
less than 227 kg 500 pounds and 13 mm 1/2 inch thick steel plate flanges.
2.9.14
Stoker Hopper Extension
Stoker hopper extensions shall be dusttight and bolted to hopper furnished
with stokers. Construct hopper extensions approximately as indicated of 6
mm 1/4 inch thick 410 stainless steel plate with structural stiffeners.
Hopper extension shall hold not less than [_____] Mg tons of coal at a
density of 800 kg per cubic meter 50 pounds per cubic foot. Hopper
extensions shall have bolted emergency firing doors of not less than 610 by
610 mm 24 by 24 inches which shall contain a 152 by 152 mm 6 by 6 inch
glass observation window.
Connections shall be dusttight.
SECTION 15502N
Page 112
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