Twin City Engineering Supplement ES-110 5
Some smaller motors are lubricated for life. Motor
bearing lubrication, if required, must follow a rigorous
schedule. Motors less than 10 hp running about eight
hours a day in a clean environment should be lubricated
once every five years; motors 15 to 50 hp, every 3
years; and motors 50 to 150 hp, yearly. For motors in
a dusty or dirty environment or running 24 hours a day,
divide the service interval by 2. If the environment is
very dirty or high temperatures exist, divide the service
interval by 4. Lubrication requirements are normally
attached to the motor. Do not overlubricate.
Wheel and Shaft Maintenance
Periodically inspect the shaft and wheel for dirt buildup,
corrosion, and signs of excess stress or fatigue. Clean
the components and, when appropriate, apply new
coatings. (Any addition of coatings or weld can create
an imbalance.) Check the balance of the assembly.
Structural Maintenance
All structural components or devices used to support
or attach the fan to a structure should be checked at
regular intervals. Vibration isolators, bolts, foundations,
etc., are subject to failure from corrosion, erosion, and
other causes. Improper mounting can lead to poor
operation characteristics or fan fatigue and failure.
Check metallic components for corrosion, cracks, or
other signs of stress. Concrete should be checked to
ensure the structural integrity of the foundation.
Troubleshooting Guidelines
Use current safety practices when investigating fan or
system performance problems. General safe practices
and performance troubleshooting guidelines can be
found in AMCA Publications 410 and 202, respectively.
Fan application and field measurement procedures can
be found in AMCA Publications 201 and 203.
Troubleshooting Performance Problems
The lists below indicate possible areas to check when
air or sound values do not match expectations. Most fan
problems can be pinpointed to one of these common
causes.
Air Capacity Problems:
1. Resistance of system not at design rating. If
resistance is lower than expected, both airflow and
horsepower may be up. If resistance is higher than
anticipated, air volume will be down.
2. Fan speed is not at design speed.
3. Air density not at design values. Also check air
performance measurement techniques/procedures.
4. Devices for air modulation are closed or plugged.
Also check filters.
5. Wheel mounted improperly or is rotating in reverse.
6. Parts of system or fan have been damaged or need
cleaning.
Noise Problems:
1. Air performance is incorrect and fan is not at design
point of operation. Fan forced to operate in an
unstable flow region.
2. Bearing failure. Check bearings (lubrication).
3. Supply voltage high or inconsistent supply frequency.
Adjustable frequency controllers can generate motor
noise.
4. Objects which are installed in a high velocity
airstream can generate noise. This includes flow
sensors, turning vanes, etc.
5. Poor fan inlet conditions.
6. Acoustics or sound measurement procedure incorrect.
Vibration Problems:
1. Misalignment of drive components.
2. Poor foundations or mounting structure (resonances).
3. Foreign material attached to rotating components.
4. Damaged rotating components (bearings, shaft, fan,
wheel).
5. Broken, loose or missing setscrews.
6. Loose bolts.
7. Vibration transmitted by another source.
8. Water accumulating in airfoil blades.
9. Fan is operating in stall or unstable flow region.
Motor Problems:
1. Incorrect wiring.
2. Speed of fan too high.
3. Parts improperly installed - binding.
4. Bearings improperly lubricated.
5. WR2 capability of motor too low for application.
6. Protection devices may be improperly sized.
Motor Lubrication – The major cause of motor bearing
failure is contamination of grease, insufficient grease,
or incompatibility of grease. If a fan is to be stored
for any length of time at the job site and the bearings
are regreasable, the motor bearings should immediately
be filled with grease while rotating the fan and then
the bearings should be regreased and rotated monthly.
This will prevent moisture, which condenses within the
bearing, from corroding the raceways. Most greases
used on motor bearings are lithium base. Use the
greases shown in the motor information. Do not mix the
bases without completely purging out the initial grease.
All fans manufactured by Twin City Fan & Blower are
factory balanced prior to shipment. Handling and
movement of the fan during shipment may cause
the rotating assembly to shift. Balance should be
checked once the fan is installed. If a final trim
balance is required, it is the end user's responsibility
to bring the fan back to factory specifications. Final
trim balancing is not the responsibility of Twin City
Fan & Blower.
NOTICE
