metric tons/hour tons/hour. Flow rate shall be automatic. A
silicon-controlled, rectifier dc drive shall automatically adjust the belt
speed to maintain the rate of material flow, as set on the controller. The
weigh feeders shall meet or exceed the requirements of NIST HB 44,
[Southern] [Eastern] [Western] Weighing and Inspection Bureau. The weigh
feeders shall have an accuracy of 1/2 of 1 percent of flow rates over their
total variable rated capacity. The feeder shall be provided with a
flexible boot for connecting the gate to the feeder inlet chute which, in
turn, shall be flared to produce a feed opening tapering from [_____] wide
to [_____] wide with the direction of flow of material. The belts for
feeders shall conform to the RMA IP-1, fire-resistant type conforming to
the standards of 30 CFR 1 Schedule 28, Part 34 of the MSHA. Top belt cover
thickness shall be 6 mm 1/4 inch with bottom cover 3 mm 1/8 inch thick.
Belt edges shall have minimum 25 mm 1 inch flanges and shall be sealed by
carrying the cover around the carcass edges during manufacture. Cover and
skim coat material shall be comparable to those meeting the requirements of
RMA IP-1, Grade 2 for impact and abrasion resistance. The weight sensor
shall be a heavy-duty, industrial, electronic force transducer
flexure-mounted to the force collection system. Each sensor shall have a
remote indicating meter and a six-digit totalizing counter located,
installed, and connected in the boiler control panel. Unit frame shall
provide rigid support for the material load, belt, and idlers. The unit
shall be shop assembled complete with drive and all appurtenances, and
shall be dust-tight in operation.
2.23.7
Track Hoppers
Track hoppers shall be standard double hopper design with a belt or
vibrating-type feeder as indicated. The hoppers shall have a capacity of
approximately [_____] metric tons tons and shall be constructed of not less
than 9.5 mm 3/8 inch thick, Type 304L stainless steel plates, with slopes
of not less than 55 degrees and shall be stiffened with angles. The
hoppers may also be of ASTM A 36/A 36M mild steel, minimum 6 mm 1/4 inch
thick with replaceable liners 6 mm 1/4 inch thick, ASTM A 167, Type 304L,
stainless steel. All rivets and field bolts inside the hopper shall have
flat heads. The hopper shall be suspended from the track girders by heavy
bolts and cast washers, or the sides shall be carried to the bottom of the
track and supported by flanges fastened to concrete ledge continuously
around the hopper with the concrete forming the top portion of hopper
sides. Track girders shall consist of wide flange beams conforming to
AREMA Manual for loading plus impact. They shall be complete with bearing
plates, WF cross struts, and rail clips. Top of hopper shall be fitted
with properly sized sections of grating made with steel bars sized [_____]
by [_____] mm [_____] by [_____] inches, and cross rods [_____] mm inches
in diameter, to form openings [_____] mm inches square.
2.23.7.1
Rack-and-Pinion Gate
A rack-and-pinion gate shall be provided at each hopper outlet and shall be
a self-cleaning type. [Hand] [Motor]-operated sliding plate shall be 9.5
mm 3/8 inch thick carbon steel, formed into the shape of a winged U. The
gate plate surface shall be completely protected by an overlapping liner of
3 mm 1/8 inch thick, ASTM A 167, Type 304L stainless steel. The gate body
material, except for the dust cover, shall be of 4.8 mm 3/16 inch thick
ASTM A 167, Type 304L stainless steel where in contact with coal flow.
2.23.7.2
Vibrating or Belt Feeders
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SECTION 15555A
Page 71
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