will not affect the alignment of the antifriction bearings or cause
misalignment of the gearing during the mixing/aeration operation. The
shaft supporting the impeller shall be removable from the drive assembly,
without disassembly of the gear box. Rolling, antifriction type bearings
on the impeller shaft shall have a minimum L-10 life of 100,000 hours in
accordance with ABMA 9 or ABMA 11. The entire weight of the shaft and
turbine will be supported by a thrust bearing integral with the gear
reducer. A rigid coupling shall be used to connect the shaft and turbine
assembly to the output shaft of the reducer. Bearings on the shaft shall
be either grease or oil lubricated and shall be positively sealed against
penetration of moisture or leakage of lubricant down the shaft. Provisions
shall be included for checking the adequacy of lubrication.
2.5.2
Impeller
The impeller shall be constructed of [carbon steel] [_____] and shall be
positively fastened to the shaft with all [carbon steel] [_____] hardware.
The impeller shall be removable from the shaft. 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.
2.5.3
Drive System
2.5.3.1
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.
2.5.3.2
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.
2.5.3.3
Rating
The gearing shall have a minimum service factor of at least [2.0] [_____]
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.
2.5.3.4
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.
SECTION 11391
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