OO-C-2868
3.7.4 Mixer. When specified (see 6.2), the concrete plant shall be
supplemented with a powered tiltable or horizontal shaft type mixer having a
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capacity rating of not less than 4-1/2 yd (3.5 m ). Mixer shall be motor
driven and compatible with the plant capacity in producing or exceeding the
specified production. A system shall be provided on the mixer for loading and
unloading the mixer. The mixer shall be equipped with a stand or other means so
as to have a discharge height of not less than 13-1/2 feet (4.11 m) above ground
level to facilitate unloading into dump trucks without spillage. The liner and
the edge of charging and mixing blades shall be fabricated of abrasion-resistant
steel. The mixer shall be furnished with a slump meter.
3.7.5 Water system. A water system, consisting of a pump of adequate
capacity to supply all demands of the plant, cycling timer, piping, hose, and
all the necessary accessories shall be provided with the plant. The required
amount of water shall be discharged to the mixer while the mixer is being
charged with aggregate. The suction and discharge connections of the pump shall
have not less than 3-inch (76 mm) National Taper Pipe Thread. The pump shall
have a constant speed motor drive, and automatic start-stop controls.
3.7.6 Air system. Air required to operate the plant shall be supplied by
compressor(s) of adequate capacity to satisfy all demands. The compressor(s)
shall be equipped with an oiler, strainer, relief valve, moisture separator,
drain, and receiver with an unloading valve.
3.7.7 Hydraulic system. Hydraulic power required to operate the plant
shall have a constant speed motor driven pump of adequate capacity with a relief
valve, and automatic start-stop controls to satisfy the operational demands.
3.7.8 Admix dispensing system. An air entraining admix dispensing system
shall be provided with the plant. The system shall include pump, meter, piping,
and all necessary components for a complete dispensing system.
3.7.9 Electrical system. All electrical equipment and wiring shall conform
to NFPA 70. Wiring shall be installed inside a conduit.
3.1.9.1 Motors. All motors for driving components of the concrete plant
shall be totally enclosed, fan cooled, conforming to NEMA MG 1, and rated for
230/460 volts (V), 3-phase, 60 Hertz (Hz), alternating current. All motors
larger than 15 horsepower shall be started from nonreversing reduced voltage
starters with under-voltage and overload protection.
3.7.9.2 Power panel. The power panel enclosure shall be NEMA type 3S in
accordance with NEMA ICS-6 with doors and shall be UL approved, certifying
conformance to UL 508A. The power panel shall contain master switch circuit
breakers, motor starters, and all items necessary for 460 V, 3-phase, hookup of
the concrete plant. The power plant shall be furnished with two 50-foot (15 m),
rubber covered, 4-conductor (one conductor for each phase, plus an equipment
ground (green) conductor) cable conforming to NEMA WC-3 or WC-7. The cable
shall have lugs for connecting to an electrical system. The cables shall have
conductive capacity to meet the electrical requirements of the concrete plant.
The cables shall be portable power cables, with extra heavy duty jacket, rated
for 600V. Cables shall be UL approved. The power panel shall have an
instruction plate permanently affixed in a conspicuous location. In addition to
instructions for connecting and operating the plant, the instruction plate shall
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