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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 Greenheck's 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.
Variable Frequency Drive Operation
For operation with variable frequency drive (VFD),
always check motor amps when adjusting the
operating frequency. Motor may be sized for the
original selected operating speed under 60 Hz.
Bypassing the VFD or increasing the speed from this
original selection, even if less than 60 Hz, may cause
motor to overload or failure. Consult factory with fan
serial number, before increasing the upper limiting
frequency.
Always check the fan rpm when adjusting the
operating frequency. Do not exceed maximum class
fan rpm of the wheel.
®
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.
To 250
Belt Span
Deflection =
64
Number
of Shots
• Lubrication interval is based on 12 hour per day operation
Belt Span
• Lubricant should be added with the shaft rotating and
• For conditions including high temperatures, moisture, dirt
• Lubricant should be a high quality lithium complex grease
• The use of synthetic lubricants will increase lubrication
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.
Recommended Bearing Lubrication Schedule
Relubrication Schedule in Months
Standard Grease
Bearing Bore (inches)
Fan
RPM
1/2 -1
1
1
⁄
- 1
1
⁄
8
2
12
12
500
12
12
750
12
9
1000
12
7
1250
12
6
1500
12
5
2000
12
3
2500
12
2
3000
12
2
3500
12
1
4000
12
0.5
5000
12
0.25
4
8
and maximum 160°F housing temperature. For 24 hour
per day operation, the interval should be cut in half.
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.
or excessive vibration, consult the factory for a specific
lubrication interval for your application.
conforming to NLGI Grade 2. Factory recommends
Mobilux EP-2.
intervals by approximately 3 times.
Utility and Centrifugal Fans
1
5
⁄
- 1
7
⁄
1
15
⁄
- 2
3
⁄
2
7
⁄
- 3
8
8
16
16
16
12
12
12
11
10
8
8
7
6
6
5
4
5
4
3
4
3
2
3
2
1
2
1
0.5
1
0.5
0.25
0.5
0.25
x
0.25
x
x
x
x
x
8
10
16
13
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