210.100-IOM (JUL 2021)
Page 46
AcuAir Hygienic Air Units
Maintenance
Table 13: Motor bearing service conditions
Severity of service
Ambient max. temp.
Atmospheric contamination
Type of bearing
Standard
40°C
Clean, little corrosion
Deep groove ball bearing
Severe
50°C
Moderate dirt, corrosion
Ball thrust, roller
Extreme
>50°C* or
Class H insulation
Severe dirt, abrasive dust
All bearings
Low temperature
<-30°C**
Corrosion
*
Special high-temperature grease is suggested. High temperature grease may not mix with other grease types. Thoroughly
clean bearing and cavity before adding grease.
** Special low-temperature grease is suggested.
Inspecting V-belts and sheaves
Before a new set of V-belts are installed, inspect the
condition of the sheaves. Dirty or rusty sheaves impair
the drive's efficiency and abrade the belts, which result in
premature failure. See
Inspect and clean sheaves; replace worn or damaged
sheaves- Worn sheave grooves are one of the principal
causes of premature belt failure.
• Clean dirty, dusty, or rusty sheaves. Feel sheave
grooves (wear gloves or use a rag) for nicks or burrs,
and file them smooth.
• Ensure belts ride in sheave grooves so that the top of
the belt is just above the highest point of the sheave. If
the grooves are worn to the point where the belt bot-
toms out (check for shiny groove bottoms), the belts
slip and burn.
• If the groove walls are dished out, the bottom corners
of the belt quickly wears off and causes rapid failure.
Check groove wear by sight, touch, or with a groove
gauge. If grooves are dished out 1/32 in. or more - re-
place the sheaves.
Figure 53: Sheave inspection
Inspect sheave alignment
NOTICE
An incorrectly aligned sheave can substantially short-
en belt life or overload blower and motor bearings,
shortening their life expectancy. A belt tensioned too
tightly can overload the motor electrically, causing
nuisance tripping of the motor overloads and/or mo-
tor failure and/or shaft failure.
Verify sheave adjustment by placing a straight edge
across the sheave faces so that it touches all four points
of contact. Ordinarily, a misalignment of more than 1/2
of one degree (1/8 in. in 1 ft) adversely affects belt life.
Incorrect sheave alignment produces uneven wear on one
side of the belt, causes the belt to roll over in the sheave
or throws all the load on one side of the belt, stretching or
breaking the cords on that side.
After the correct operating tension has been applied to
the belts, verify the following:
• Parallel position of the sheave shafts.
• Correct alignment of sheave grooves.
Sheave alignment and parallelism of shafts is very impor-
tant. Correct alignment helps equalize the load across the
entire belt width, thereby reducing wear and extending
belt life.
shows how to align a synchronous drive
correctly using a straightedge (A) or a piece of string (B).
After aligning the sheaves, verify the rigidity of the sup-
porting framework. Ensure shafts are well supported to
prevent distortion and a resulting change in the center
distance under load. Do not use spring-loaded or weight-
ed idlers.
Alignment using a straightedge (preferred)
Place a straightedge against the outer edge of the
sheaves.
(A) shows the four points where the
straight edge must touch the sheaves. Ensure the straight
edge crosses the sheaves at the widest possible part of
the sheave.
Alignment using a string
Tie a string around either shaft and pull it around and
across the outer edge of both sheaves.
shows how the string must touch four points when the
drive is correctly aligned.
