Utility and Centrifugal Fans
17
®
Belt Drive Maintenance
V-belt drives must be checked on a regular basis
for wear, tension, alignment and dirt accumulation.
Premature or frequent belt failures can be caused by
improper belt tension (either too loose or too tight)
or misaligned sheaves. Abnormally high belt tension
or drive misalignment will cause excessive bearing
loads and may result in failure of the fan and/or motor
bearings. Conversely, loose belts will cause squealing
on start-up, excessive belt flutter, slippage and
overheated sheaves. Either excessively loose or tight
belts may cause fan vibration.
When replacing V-belts on multiple groove drives
all belts should be changed to provide uniform
drive loading. Use a set of matched belts whenever
possible. Do not pry belts on or off the sheave.
Loosen belt tension until belts can be removed by
simply lifting the belts off the sheaves. After replacing
belts, ensure that slack in each belt is on the same
side of the drive. Belt dressing should never be used.
Do not install new belts on worn sheaves. If the
sheaves have grooves worn in them, they must be
replaced before new belts are installed.
The proper tension for operating a V-belt drive is
the lowest tension at which the belts will not slip at
peak load conditions. Belts are adjusted by raising or
lowering the motor
pivot plate. For
initial tensioning,
the proper
belt deflection
halfway between
sheave centers is
1/64-inch for each
inch of belt span.
For more information about measuring belt tension,
refer to Product Application Guide, FA/127-11,
Measuring Belt Tension, found online at www.
greenheck.com in the library section.
Check belt tension two times during the
first 24 hours of operation and periodically
thereafter.
Belt Span
Deflection =
Belt Span
64
Recommended Bearing Lubrication Schedule
Relubrication Schedule in Months
Standard Grease
Fan
RPM
Bearing Bore (inches)
1/2 -1
1
1
⁄
8
- 1
1
⁄
2
1
5
⁄
8
- 1
7
⁄
8
1
15
⁄
16
- 2
3
⁄
16
2
7
⁄
16
- 3
To 250
12
12
12
12
12
500
12
12
11
10
8
750
12
9
8
7
6
1000
12
7
6
5
4
1250
12
6
5
4
3
1500
12
5
4
3
2
2000
12
3
3
2
1
2500
12
2
2
1
0.5
3000
12
2
1
0.5
0.25
3500
12
1
0.5
0.25
x
4000
12
0.5
0.25
x
x
5000
12
0.25
x
x
x
Number
of Shots
4
8
8
10
16
Bearing Lubrication Schedule
Shaft bearings are the most critical moving part of a
fan. Therefore, special attention should be given to
keeping the bearings clean and well lubricated. Proper
lubrication provides for reduction in friction and
wear, transmission and dissipation of heat, extended
bearing life, and prevention of rust.
In order for a lubricant to fulfill these tasks, the proper
grease applied at regular intervals is required. See the
recommended bearing lubrication schedule below.
If unusual conditions exist (temperatures below 32°F
or above 200°F), moisture or contaminants - more
frequent lubrication is required.
• Lubrication interval is based on 12 hour per day operation
and maximum 160°F housing temperature. For 24 hour
per day operation, the interval should be cut in half.
• Lubricant should be added with the shaft rotating and
until clean grease is seen purging from the bearing.
The lubrication interval may be modified based on the
condition of the purged grease. If bearing is not visible to
observe purged grease, lubricate with number of shots
indicated in chart for bore size.
• For conditions including high temperatures, moisture, dirt
or excessive vibration, consult the factory for a specific
lubrication interval for your application.
• Lubricant should be a high quality lithium complex grease
conforming to NLGI Grade 2. Factory recommends
Mobilux EP-2.
• The use of synthetic lubricants will increase lubrication
intervals by approximately 3 times.
In addition to lubricating the bearings at specified
intervals, set screws in the bearing collars should be
checked for tightness. A bearing collar which has
loosened will cause premature failure of the fan shaft.
Fasteners attaching the bearings to the drive frame
should also be checked.
Wheel and Fastener Maintenance
Wheels require very little attention when exhausting
clean air, however, air heavily laden with grease or
dirt will tend to accumulate on the wheel causing
unbalance. Wheels exhausting dirty or grease-laden
air require frequent cleaning to assure smooth and
safe operation.
All fasteners, including set screws in the bearing
collars, should be checked for tightness each time
maintenance checks are performed.
A proper maintenance program will help preserve the
performance and reliability designed into the fan.
