3.3.1.1
Bearing
The bearings for positive displacement type blowers shall have a minimum
rated life expectancy (L-10) of 50,000 hours, and for centrifugal type
blowers, 30,000 hours, based on the ABMA SBRB Standards. Internal bearings
shall be splash lubricated from the gear housing oil reservoir. Drive-end
bearings shall be grease lubricated through grease fittings in each bearing
housing located so that they are easily accessible. Grease vents shall be
provided in the bearing housing to prevent rupture of grease seals due to
overgreasing. Air vents shall be provided between the seals and the
impeller chamber to relieve excessive pressure on the seals.
3.3.1.2
Couplings for Centrifugal Blowers
The couplings shall be self-aligning forged steel gear type having two
identical hubs; two identical sleeves, a flanged gasket, a set of flange
bolts, nuts, and lockwashers, and four lubrication plugs with copper
gaskets. Torque shall be transmitted through the mating gear teeth of the
hubs and sleeves.
3.3.2
Blower Driver
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NOTE: Insert electrical power characteristics.
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Positive displacement type blower shall be driven by an electric motor
through a V-belt drive. Centrifugal type blower shall be driven by a
direct-connected motor through a flexible coupling. Maximum speed of
centrifugal type blowers shall be 3600 rpm. Motor shall be constant speed,
totally enclosed, fan-cooled 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. If
induction type, motor shall have NEMA Class B insulation, normal starting
torque, low starting torque, low starting current. If synchronous, it
shall operate on unity power factor or 0.8 power factor. Excitation shall
be by direct-connected exciter. The electric motor shall have an operating
sound pressure level not to exceed 90 decibels over a frequency range of
37.5 to 9,600 cycles per second measured at 1.5 m 5 feet from the unit.
The manufacturer shall provide any silencing of the motor needed to meet
this requirement.
3.3.3
V-belt Drive for Positive Displacement Type Blower
V-belt drive shall be designed to produce a blower speed not greater than
the following:
Blower Size
Maximum Speed
(mm)
(Rpm)
50
3,500
75
2,750
100
2,400
125
1,900
150
1,600
SECTION 11375N
Page 103
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