2.6.3
Blowers
The blowers shall be in accordance with Section 11375A AIR SUPPLY AND
DIFFUSION EQUIPMENT FOR SEWAGE TREATMENT.
2.7
DIFFUSED AERATION/SLOW SPEED MIXER SYSTEM
The diffused aeration/slow speed mixer system shall be furnished and
installed as indicated. The system shall be complete and shall include air
supply, distribution and diffuser equipment designed to satisfy the oxygen
requirement, and the adequate number of submersible mixing units to create
and maintain a horizontal velocity in the basin and maintain solids
suspension. The air supply and distribution system shall include blowers,
piping, valves, diffusers, supports and all necessary appurtenances to
ensure proper operation of the equipment. The mixing units shall consist
of a propeller driven by a [submersible electric motor] [hydraulic system],
a support structure that allows the unit to be easily removed from the
basin, and all cables and appurtenances necessary to ensure proper
operation of the equipment. The combined system shall be designed for
continuous operation.
2.7.1
Diffused Aeration System
The diffused aeration and blower system shall be as specified in Section
11375A AIR SUPPLY AND DIFFUSION EQUIPMENT FOR SEWAGE TREATMENT.
2.7.2
Slow Speed Mixer (With Submersible Electric Motor)
**************************************************************************
NOTE: Designer will allow bids on either hydraulic
motors or electric motors unless job requirements
warrant eliminating one of the options.
**************************************************************************
All components of the mixer, including the motor, shall be capable of
continuous underwater operation while the mixer blade is both completely
submerged or partly submerged. In addition, all components of the mixer,
including motor, shall be capable of continuous operation in air,
completely unsubmerged, for a minimum of [2] [_____] hours.
2.7.2.1
Mixer Propeller
The propeller shall be constructed of [ASTM A 167, Type 304 stainless
steel] [cast-iron] [molded fiberglass] [_____] and shaped so that no
solids, fibrous material and other material found in normal wastewater
applications will collect on the blades. The propeller shall be
dynamically balanced to [5.3] [_____] Newtons per meter [0.03] [_____]
pounds per inch and shall [be internally keyed for engagement with the
shaft] [slide onto the shaft and be securely fastened with a screw washer
and sleeve] [_____].
2.7.2.2
Drive System
Each mixer shall be a direct-driven, close-coupled, completely submersible
unit. The mixer motor shall be a squirrel-cage induction, shell type
design, housed in an air-filled, watertight chamber. The stator winding
shall be insulated with moisture-resistant Class F insulation in accordance
with NEMA MG 1 and shall be designed for continuous duty. The cable entry
shall be an integral part of the stator casing and shall be leakproof. In
SECTION 11391
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