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PUBLICATION NO: LMCW03A2
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3) Sheaves & Belts
Fans with v-belt drives need periodic belt main-
tenance. Belts should be inspected for wear,
frayed edges and proper tension. Sheaves must
be inspected for wear, alignment and other me-
chanical damage. Sheaves that are worn need
to be replaced.
Whenever replacing belts and/or sheaves always
use new parts. Use new set screws, bushings etc.
On multiple belt applications always replace the
entire set of belts with a matched set.
To replace belts the following procedure should
be followed. First lock out and tag fan motor to
prevent accidental start. Remove belt guard by
loosening the six retaining bolts. Loosen but
do not remove motor mount bolts. Adjust mo-
tor to loosen belts using motor base adjustment
bolt. On large motors a properly blocked bottle
jack can assist in moving the motor as the ad-
justment bolt is turned. Care should be taken to
prevent damage to the motor and/or injury. Belts
should be loosened so that they can be taken off
by sliding over the sheave rather than shifting
the belts from groove to groove.
If sheaves are to be removed loosen the setscrew
in bushing. Loosen and remove the three bush-
ing retaining bolts. Use all three retaining bolts
to extract the bushing by screwing them into the
threaded holes on the bushing. The bolts should
be tightened evenly to prevent damage to sheave,
shaft or bushing.
Clean and inspect all parts for wear and/or dam-
age. When installing sheave and bushing make
sure all mating surfaces including threads are
clean, dry and oil free. Place the motor sheave
as far onto the shaft as clearance allows. This
will minimize the overhung load on the shaft
and increase bearing life. Locate the driven
sheave using a straight edge as shown in fig.3.
Incementally tighten the three bushing bolts tak-
ing care not to warp the sheave. On large diam-
eter sheaves it is highly recommended that a dial
indicator be used to prevent excessive runout
due to a misaligned bushing. Belt and bearing life
will be shortened if sheaves are not properly aligned.
Torque all setscrews and bolts to manufacturer's
specified values. If torque specifications are not
available from component manufature consult fig-
ure 6.
Place all belts onto sheaves and tighten making sure
that sheaves remain in the same plane. Rotate
sheaves manually to help seat the belts while tight-
ening. Check belt tension by using a tension tester
or "fish" scale. Press on center of each belt and
check deflection for the specified force. See fig. 3.
For correct deflection contact the drive provider if
not LMC or LMC.
After belts are properly installed replace guard and
tighten bolts. New belts will require retightening
after about 1 week of operation. Check all bolt and
set screws at the same time.
4) Wheel and Shaft
Inspect fan wheel for wear and build up of dirt or
debris. Build up on fan wheels will cause an imbal-
ance that can lead to catastrophic failure. Check set
screws and retighten if necessary. Check for signs
of fatigue and/or corrosion. Special skills and equip-
ment are required to balance fan wheels therefore
this procedure should be left to a skilled profes-
sional.
Inspect fan shaft for trueness and signs of fatigue.
If the shaft is suspect it should be replaced with a
new LMC approved shaft.
5) Fan Housing & Base
The safety, reliability and performance of the fan
relies on the structural integrity of the fan housing
and base. Periodically inspect welds, bolt connec-
tions and anchors for fatigue and/or corrosion.
