The control unit shall contain a pushbutton to manually reset the controls
after a thermal overload. The controls shall be housed in a NEMA 250, Type
4 enclosure.
2.4.5
By-Pass Bar Screen
A by-pass bar screen shall be provided for stand-by service during shredder
clogging or maintenance. Screen shall have no greater than 10 mm 3/8-inch
spacing between bars and shall be sized for treatment plant peak flow. The
by-pass bar screen shall be located such that flow passes through it only
when the shredder is clogged.
2.5
BLOWERS
Two electric motor driven positive displacement blowers with all necessary
accessories and appurtenances shall be provided.
2.5.1
Performance and Design Requirements
Each blower shall meet the following performance and design requirements:
2.5.1.1
Capacity
Each blower shall have sufficient capacity to supply the entire plant
demand, including air for the specified air diffusion equipment and air
lift pumps. Air pressure shall be as required for proper operation of the
treatment plant. Blowers shall be designed for continuous operation.
Certified blower capacity shall equal [_____] standard cubic meters per
second SCFM at [_____] kPa psig.
2.5.1.2
Impellers
Impellers shall be accurately machined from cast iron. Impeller shaft
shall be either a common casting with the impeller or permanently fastened
to the impeller. The blower casing shall be heavily ribbed cast iron.
Headplates shall be cast iron. Timing gears shall be machined from alloy
steel. Bearings shall be anti-friction. Drive end bearings shall be
grease lubricated. Timing gears and gear end bearings shall be splash oil
lubricated. Positive oil seals shall be provided to prevent lubricant from
entering the air stream. Suction and discharge connections for sizes under
150 mm 6-inch nominal diameter shall be threaded and for sizes 150 mm 6-inch
nominal diameter and larger shall be ASME B16.1 Class 125 flanged.
2.5.1.3
Discharge
Each blower shall be provided with a filter-silencer on the suction side
and a check valve, gate valve, pressure relief valve, and pressure gauge on
the discharge side.
2.5.2
Drive
The blower drive shall consist of an electric motor, V-belts, and sheaves.
V-belts shall be sized for the horsepower required to drive the blowers.
Sheaves shall be provided for full capacity operation. Extra sheaves and
V-belts shall be provided to permit operation of blowers at 2/3 rated
capacity. Blower speed shall not exceed [_____] revolutions per minute.
Blower motor shall operate on [_____] volts ac [_____] phase, 60 Hz.
Blower motor shall produce [_____] kW hp. Blower motor shall be
weatherproof conforming to NEMA MG 1.
SECTION 11390
Page 17
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