2.4.2
Impeller
The impeller shall be constructed of [carbon steel] [_____] and shall be
positively fastened to the shaft with all [carbon steel] [_____] hardware.
Means shall be provided for adjustment of the impeller. If the adjustment
is on the shaft, a means shall be provided to prevent the impeller from
dropping off the shaft during adjustment. Impeller submergence shall be
determined by the equipment supplier to ensure the most efficient operation
of the aeration system.
2.4.3
Drive System
2.4.3.1
Reducer
The drive system reducer shall be constructed to maintain alignment of
bearings and gearing while absorbing the external loads of the impeller.
The unit shall be designed to withstand continuously all internal loadings
developed at the full load motor wattage horsepower, including motor
starting torques up to 250 percent of motor running torques. The unit
shall also be designed to withstand all external loadings produced by
torque, thrust, out-of-balance and vibration resulting from operating
conditions. The speed reducer shall be provided with lifting lugs. The
interior of the gear case shall be vented by an approved breather,
constructed to retard the entrance of water vapor.
2.4.3.2
Housing
Drive housing shall be weatherproof and shall be constructed of steel in
accordance with ASTM A 36/A 36M or high grade cast-iron conforming to ASTM
A 48/A 48M. A protective coating shall be applied that will not peel,
crack or discolor at continuous operating temperatures up to 121 degrees C
250 degrees F.
2.4.3.3
Rating
The gearing shall have a minimum service factor of at least [2.5] [_____]
times the rated brake horsepower of the drive motor. The gear reduction
system shall be suitable for continuous operation and moderate shock
loading in accordance with AGMA 6009 for motor reducers or gear motors
using helical and spiral bevel gears.
2.4.3.4
Bearings
Power transmission bearings shall be antifriction type and shall have a
minimum L-10 life of 100,000 hours at maximum operating speed in accordance
with ABMA 9 or ABMA 11. Bearings shall be fully sealed and protected from
water spray.
2.4.3.5
Lubrication
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NOTE: If lubricating pumps are not used delete
subparagraph b. and edit accordingly.
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a.
Lubrication shall be provided by [gears running in an oil bath]
[an oil slinger] [pumps]. Drive shall be provided with an oil
"dam" or other means of positive protection against lubricant
leakage around the output shaft. An oil level gauge or sight
SECTION 11391
Page 19
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