26
McQuay IM 777-4
Service and Maintenance
Figure 37: Sheave Adjustment
Figure 38: Sheave Adjustment
Fan Drive Belt
General Rules of Tensioning
1
The ideal tension is the lowest tension at which the belt
does not slip under peak load conditions.
2
Check tension frequently during the first 24 to 48 hours
of operation.
3
Over tensioning shortens belt and bearing life.
4
Keep belts free from foreign material that can cause
slippage.
5
Inspect V-drive on a periodic basis. Adjust tension if the
belt is slipping. Do not apply belt dressing. This can
damage the belt and cause early failure.
Tension Measurement Procedure
1
Measure the belt span. See
Figure 39, page 27
.
2
Place belt tension checker squarely on one belt at the
center of the belt span. Apply force to the checker,
perpendicular to the belt span, until the belt deflection
equals belt span distance divided by 64. Determine the
force applied while in this position.
3
Compare this force to the values in
Belt Deflection Force
(per Browning® specifications)‚ page 27
.
Motor
Must be
parallel
Adjustable
Sheave
Center lines
must coincide
Bearing
Must be
parallel
A d j u s t a b l e
C e n t e r - F l a n g e
F i x e d
C e n t e r - F l a n g e
S t a t i o n a r y
E n d - F l a n g e
C a p s c r e w s
( D o N o t R e m o v e )
( 2 ) L o c k i n g
S e t s c r e w s " A "
F l a t h e a d S o c k e t S c r e w s
( D o N o t R e m o v e )
I n n e r L o c k i n g - R i n g
O u t e r
L o c k i n g - R i n g
S p l i t T a p e r
B u s h i n g
( 3 ) H o l e s f o r
S p a n n e r W r e n c h
o r D r i f t
