24-hour service under design load without excessive wear, damage,
or failure. The mechanism shall be capable of operating in a dry
tank without overloading the equipment. Stresses developed under
the aforementioned operating conditions and loads shall not exceed
the allowable stresses conforming to AISC 335.
b.
Drive Assembly: Drive assembly shall include motor; speed
reducer; drive sprocket on output shaft of speed reducer, drive
chain from drive sprocket to driven sprocket, shera pin, and chain
guard. Unit shall be fully enclosed and designed for mounting
outside and exposed to the weather.
(1) Motor: Motor shall be constant speed, totally enclosed,
horizontal type, suitable for outdoor service, and conforming to
NEMA MG 1. The motor shall be of adequate wattage horsepower to
drive the equipment continuously at the maximum load encountered
under any operating condition without overloading or exceeding the
nameplate rating of the motor. Motor shall be suitable for
operation on [_____] volt, [_____] phase, [_____] Hertz service.
Motor shall be protected against overload, low voltage, and
unbalanced voltage. Motor shall be directly connected to the
speed reducer through a flexible coupling.
(2) Speed reducer shall be either a helical gear reduction unit
or a worm gear reduction unit fully enclosed in a cast iron or
fabricated steel case provided with dust and oil seals with all
gears running in oil and with anti-friction bearings throughout.
Gears used in speed reducer shall conform to applicable
requirements of the following Standards. Speed reducer shall be
designed with a minimum AGMA service factor of 2.0 and shall also
have an AGMA Service Classification II.
Helical gearing: AGMA 908, AGMA 2001, AGMA 2004, AGMA 6010, AGMA
6034, ASTM A 48M ASTM A 48, ASTM A 536,
Worm gearing: AGMA 6019, AGMA 6034, ASTM A 536
(3) Bearings incorporated within the drive assembly shall be of
the antifriction type and conform to the following minimum
schedule of rated-life expectancy (L-10) based on the ABMA SBRB
Standards when operating at the normal continuous torque rating of
the mechanism:
Worm gearbox bearings:
L10-100,000 hours
Geared motor (direct drive):
L10-100,000 hours
Intermediate helical gearbox bearings:
L10- 17,000 hours
Geared motor (indirect drive):
L10- 17,000 hours
Speed reducer case shall be equipped with oil fill port, oil drain
line, and an oil level indicator pipe.
(4) Chain and Belt Drives: Drive transmission within and from
the drive assembly shall be by chain and/or belt. Chain and belt
drives incorporated in the drive assembly shall be designed with a
minimum factor of safety of 4 as applied to the ultimate breaking
of transmission strength of the chain or belt with respect to the
loads transmitted at normal continuous operating load. Chain and
SECTION 11375N
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