be direct coupled to a driving motor, consider the height of the
motor shaft and the necessity for it to be aligned very
accurately with the blower shaft. Best arrangement is for the
blower to be bolted directly to the mounting plate while the
driver is on shims of at least 1/8 inch (3 mm) thickness. This
allows adjustment of motor position in final shaft alignment by
varying the shim thickness.
Satisfactory installation can be obtained by setting the
baseplate on a concrete slab that is rigid and free of vibration.
and leveling the top of the base carefully in two directions so
that it is free of twist. The slab must be provided with suitable
anchor bolts. The use of grouting under and inside the base,
after it has been carefully leveled by shimming. is
When blower and driver have been factory mounted on a
common baseplate. the assembly will have been properly
aligned and is to be treated as a unit for leveling purposes. It
is possible for a base mounted assembly to become twisted
during shipment thus disturbing the original alignment. For
this reason, make the following checks after the base has
been leveled and bolted down.
Disconnect the drive and rotate the blower shaft by hand.
It should turn freely at all points. Loosen the blower foot hold-
down screws and determine whether all feet are evenly in
contact with the base. If not. insert shims as required and
again check for free impeller rotation. Finally, if blower is
direct coupled to the driver, check shaft and coupling
alignment carefully and make any necessary corrections prior
In planning the installation, and before setting the blower,
consider how piping arrangements are dictated by the blower
design and assembly.
When a blower is DIRECT COUPLED to its driver.
the driver RPM must be selected or governed so as not to
exceed the maximum speed rating of the blower. Refer to
LIMITATIONS for allowable speeds for various blower sizes. A
flexible type coupling should always be used to connect the
driver and blower shafts.
For engine drives, couplings with proper stiffness must be
selected to avoid resonant torsional vibrations.
Also, safe operating speed must be limited to avoid critical
Coupling halves must be accurately aligned, and a sufficient
gap between shaft ends provided, so that side strains and end
thrust on either shaft are avoided or minimized. This will
require considerable care in the mounting of the driver. The
two shafts must be in as near perfect alignment in all
directions as possible, and the gap must be established with
the motor armature on its electrical center if end play exists.
Coupling halves must be fitted to the two shafts such that they
can be worked into place by hand. Maximum deviation in
offset alignment of the shafts should not exceed .005" (.13
mm) total indicator reading, taken on the two coupling hubs.
Maximum deviation from parallel of the inside coupling faces
should not exceed .001" (.03 mm) when checked at six points
around the coupling.
Couplings as well as sheave bushings must have a
slight slide fit with the blower shaft such that they can be
installed in place by hand. Any force used to install them
will change blower end clearances resulting in blower
damage. If an interference fit is desired for the coupling,
the coupling hub should be heated and shrunk on the
shaft. For engine drives, use "Locktite" between the
coupling hubs and the blower/engine shafts and on the
threads of the coupling set screws.
When a blower is BELT DRIVEN. a proper selection of
sheave diameters can usually be made to adapt any
standard driver speed to the required blower speed. This
flexibility can sometimes lead to operating temperature
problems caused by blower speed being too low. Make
sure the drive speed selected is within the allowable
range for the specific blower size, as specified under
Belted drive arrangements usually employ two or more V-
belts running in grooved sheaves, and a variety of positions
are available for the driver. Installation of the driver is less
critical than for direct coupling, but its shaft must be level and
parallel with the blower shaft. The driver must also be
mounted on an adjustable base to permit installing, adjusting
and removing the V-belts. To position the driver correctly,
both sheaves need to be mounted on their shafts and the
nominal shaft center distance known for the belt lengths to be
Install the blower sheave (usually the larger onel so that
its inner hub face is not more than %4 inch (7 mm) from the
bearing end cover. The shaft fit should be such that the
sheave can be worked into place by hand. A tight or driving fit
can damage a bearing, and may cause internal blower
damage by forcing the impeller out of its normal operating
position. A loose fit or wobbly sheave will cause vibration, and
may result in shaft breakage.
The driver sheave should also be mounted as close to its
bearing as possible, and again should fit the shaft correctly.
Position the driver on its adjustable base so that 2:1 of the
total movement is available in the direction away from the
blower, and mount the assembly so that the face of the sheave
is accurately in line with the blower sheave. This position
minimizes belt wear. and allows sufficient adjustment for both
installing and tightening the belts. After belts are installed,
adjust their tension in accordance with the manufacturers
instructions. However, only enough tension should be applied
to prevent slippage when the blower is operating under load.
Excessive tightening can lead to early bearing failures.
Failure to properly align the blower and drive sheaves will
result in the impeller being forced against one of the
headplates during operation causing serious damage to the
In the absence of belt manufacturers instructions for
tensioning. the following procedures may be used.
With the belts loose. pull the slack on all of them to the
bottom side of the drive.
Adjust motor position to tighten belt until they appear to be
seating in the sheave grooves.
Thump the belts with your fist. If they feel dead, tighten
them more until they vibrate and feel springy when struck.
Run-in the drive for a short period, after preparing the
blower as instructed in a following paragraph. While
running, adjust until only a very slight bow appears in the
slack side of the belts.
Stop the motor and compare the tensions of the individual
belts by pressing down firmly with one hand on the top
surface. It should be possible to deflect each