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Arrangement 1
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This is perhaps the most common arrangement for industrial
and other applications. It is available in SISW and usually belt driven. Two bearings
are mounted on a pedestal and the wheel is overhung to one side. The bearing pedestals
are internal on axial fans.
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Arrangement 2
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This arrangement is similar to arrangement 1 except the
bearing pedestal is supported by the fan housing. Two separate bearings may be used
although at one time it was more common to see this arrangement with the 2 bearings
races in a common bearing housing. A/2 is usually belt driven.
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Arrangement 3
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This arrangement is available in both SISW and DIDW. A
bearing is bracket mounted on each side of the housing . . . or on axial fans, on
each side of the wheel. This results in a compact unit. Since one or both of the
bearings are in the airstream, A/3 is usually not used in application where dirt
and/or heat will run through the fan. The bearing bracket supports can make it difficult
to add ductwork to the inlet or inlets of the fan. A/3 is usually belt driven.
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Arrangement 4
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In this arrangement, the wheel is directly mounted on
the motor's shaft (& bearings). The fan itself does not have a shaft or bearings.
This arrangement is more common in axial or smaller centrifugal fans where proportions
allow the motor shaft to reach the wheel hub. However, some manufactures offer A/4
centrifugals up to 200 HP as standard. Due to the close coupling of the motor, Arrgt.
4 fans are normally restricted to a maximum temperature limit of 200°-F or less
and it is common to add some type of volume control to the fan since variable speed
motors are often not economically available.
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Arrangement 7
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An arrangement 7 fan is an arrangement 3 fan with a motor
base attached to the drive side. It is designed to be direct driven through a flexible
coupling, with the motor (or turbine) mounted on the attached base. The same cautions
that apply to arrangement 3 fans apply to arrangement 7. A very practical use is
in large mechanical draft fans which use inlet boxes. In that case, it eliminates
the need for separate independent bearing pedestals which can simplify installation.
Arrangement 7 is available in SISW and DIDW.
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Arrangement 8
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This arrangement is similar to an arrangement 1 fan. A
smaller "outrigger" motor or turbine base is customer provided, or shipped
attached to the bearing pedestal, for direct connection through a coupling. It is
most often used where V-belt drives are not appropriate, as with very high horsepower's.
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Arrangement 9
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This is an arrangement 1 belt driven fan with the motor
mounted on the fan rather than on the "floor". It allows factory assembly
of the motor and drives. On higher horsepower fans, the industry sometimes refers
to arrangement "9H". In this modification of arrangement 9 the motor is
mounted on the structural steel base that is furnished by the fan manufacture. It
also allows factory assembly of the motor and drives.
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Arrangement 10
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This SISW arrangement is similar to an arrangement 9 fan
except the motor is mounted inside of the bearing pedestal. This offers some degree
of weather protection to the motor however it restricts the motor size. It is most
important to provide adequate ventailation to the motor in A/10.
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Air Movement and Control
Association (AMCA) standards include the option of either belt drive or direct
drive for most arrangements. Rare and often impractical drive options have been
omitted.
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