addition, all mating surfaces where water tight sealing is required shall
be machined and fitted with [nitrile] [_____] rubber O-rings.
2.7.2.3
Shafts and Seals
The mixer motor shaft shall be integral with the propeller shaft and shall
rotate on two permanently lubricated bearings. The ball bearings shall
have a minimum L-10 life of 100,000 hours as defined by ABMA 9 or ABMA 11.
Each mixer shall be provided with a tandem mechanical rotating shaft seal
system on the propeller shaft. Seals shall be of the lapped end face type
and shall run in an oil reservoir. The inner seal shall contain one
stationary and one positively driven rotating ceramic ring. The outer seal
shall contain one stationary and one positively driven rotating tungsten
carbide ring.
2.7.2.4
Mounting
The mixer shall be capable of being raised and lowered from the basin for
ease of repair and maintenance. The mixer shall be mounted on and guided
by a sliding bracket which shall be constructed to withstand all thrust
created by the mixer. A lifting cable and winch mechanism shall be
provided to permit raising and lowering of the mixer on the sliding bracket.
2.7.3
Slow Speed Mixer (With Hydraulic Motors)
Each hydraulic horizontal mixer shall consist of a hydraulic power unit and
motor, a direct drive shaft and propeller, hydraulic lines, and all
mounting and support brackets to provide for proper operation. In
addition, all components of the mixer shall be capable of continuous
operation in air, completely unsubmerged, for a minimum of [2] [_____]
hours.
2.7.3.1
Mixer Propeller
The propeller shall be constructed of [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] [_____].
2.7.3.2
Drive System
a.
Hydraulic Motor: The hydraulic motor shall be of the low speed,
high torque, fixed displacement type to drive the propeller. The
hydraulic motor shall be capable of withstanding end thrust loads
of not less than 4.45 kN 1000 pounds either into or out from the
motor. The hydraulic motor shall be rated for a B-10 life of not
less than 100,000 hours in accordance with ABMA 9 or ABMA 11. The
hydraulic motor shall be connected to the hydraulic pump with a
hose having a continuous pressure rating of not less than 20.7 MPa
3000 psi.
b.
Hydraulic Pump: The hydraulic pump shall be enclosed in the
hydraulic reservoir which shall be mounted directly to the
electric motor adapter. The hydraulic pump shall have a
continuous pressure rating of not less than 13.8 MPa 2000 psi.
The hydraulic fluid flow control mechanism shall be locking and
SECTION 11391
Page 29
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