Greenheck Product Application Guide
4
®
Fan Application No. FA/103-00
used on Greenheck’s extended pressure CUBE
exhaust fans (Model Cube-XP).
The balance of the fan and ventilator products that
exceed the limitations of the
stamped steel bearings use the
air handling ball bearing with
the set screw locking method.
This includes fans with a shaft
diameter of one inch and
larger, and a motor of 1 1⁄2
horsepower and larger. In
applications with lower speeds
the D-Lok mechanism is
available, however, the D-Lok
advantages are negligible and
not cost justified.
When the application load and speed exceed the
capacity of ball bearings, roller pillow block
bearings are typically
specified. Like ball
bearings, roller bearings
can carry a combination
of radial and thrust loads;
however, roller bearings,
in order to operate
properly, require a radial
load at least equal to the
thrust load. Insufficient
radial loading allows the rollers to skid within the
race, which could cause premature failure of the
bearing components. Tapered roller bearings that
are similar to the spherical rollers, are commonly
specified for vertical applications where high thrust
loads are encountered.
Currently, roller bearings are available with either
the standard set screw-locking method, or the
Dodge Imperial patented adapter-mounting system
(spherical roller bearings only).
Thus far all of the bearing options we have
discussed have been in a solid housing, either
stamped or pillow block. Once the application
exceeds the speed limit for the contact seal and
grease sump design of the solid housing, a split
pillow block bearing is typically specified. The split
pillow block design incorporates a friction-free
labyrinth seal and a larger grease cavity. Higher
speeds can then be attained and the rollers become
the limiting factor instead of the seal.
Split pillow block housings incorporate a tapered
adapter sleeve-mount locking
system. Because of the
geometry of the sleeve-mount
design, a larger bearing is
required for the same shaft
size as would be used in a
solid pillow block design.
Consequently, the capacity of
the rollers increases, thus
requiring a higher minimal radial load for proper
operation of the rollers.
In some applications where contaminants need to
be kept out of the bearing, special seals other than
the labyrinth-type are used in the split pillow block
housing. In these cases, the seal may be a speed-
limiting factor and must be accounted for in the
selection of the bearing.
In certain products, such as some vane axial belt
drive fans, the installation of a pillow block bearing
can be difficult simply because of physical space
constraints within the belt
tube. In such a case, a flange-
mount bearing can be used.
The bearing components are
essentially the same as the
pillow block version, but the
housing allows for face
mounting around the shaft
instead of pedestal mounting
under the shaft.
Summary
The information in this article is a guideline to help
communicate a better overall understanding of
bearings and good bearing application.
Don’t let your air handling equipment suffer a short
life span because of premature bearing failure.
Applications are often times unique, and your
selection will be based upon the bearing options
best suited to your job specifications.
Greenheck engineers have over 40 years of
experience in bearing selection and work closely
with our vendors to ensure customers receive the
highest quality products. Determine what bearing
life your application requires and let Greenheck’s
experienced engineering team specify the right
bearing for the job.
Roller bearing with set screw
Ball bearing with set
screw
Flange mount bearing
Split housing
