As you are completing your occasional cooling tower checkup, you hear that noise again, something about your cooling tower doesn't sound right. What's that noise? How can you quickly diagnose the problem and find a solution? The below table will help you do just that!
Trouble |
Cause |
Remedy |
Motor will not start |
Power is not available at motor terminals |
A: Check power at starter. Correct any connections between the control apparatus and the motor.
B: Check starter contact and control circuits. Reset overloads, close contacts, reset tripped switches, or replace failed control switches. |
|
Wrong Connection |
Check motor and control connections against wiring diagrams. |
|
Low Voltage |
Check nameplate voltage against power supply. Check voltage at motor terminals. |
|
Open circuit in motor winding |
Check starter windings for open circuits. |
|
Motor or fan drive is stuck |
Disconnect motor from load and check motor and gear reducer for cause of problem. |
|
Rotor is defective |
Look for broken bars or rings |
|
Fan Stack |
Due to high winds fan stack has become oblong interfering with fan blades rotation. |
Unusual Motor Noise |
Motor running single-phase |
Stop motor and attempt to start it. Motor will not start if single-phased. Check wiring, controls, and motor. |
|
Motor leads connected incorrectly |
Check motor connections against wiring diagram on motor. |
|
Ball bearings |
Check lubrication. Replace bad bearings. |
|
Electrical imbalance |
Check voltages and currents of all three lines, correct if required. |
|
Air gap not uniform |
Check and correct bracket bearings |
|
Rotor unbalanced |
Rebalance |
|
Fan hitting guard |
Reinstall or replace fan |
Motor runs hot |
Motor overload, low voltage or unbalanced voltage |
Check voltage and current of all three lines against nameplate values. |
|
Incorrect fan blade pitch |
See Fan Service Manual |
|
Wrong motor rpm |
Check nameplate against power supply. Check rpm of motor and gear ratio. |
|
Bearings over greased |
Remove grease reliefs. Run motor up to speed to purge excess grease. |
|
Rotor rubs stator bore |
If this is not due to poor machining, replace worn bearings. |
|
Wrong lubricant in bearings |
Change to proper lubricant. See motor manufacturer’s instruction. |
|
One phase open |
Stop motor and attempt to start it. Motor will not start if single-phased. Check motor wiring controls and motors. |
|
Poor ventilation |
Clean motor and check ventilation openings. Allow ample ventilation. |
|
Winding fault |
Check with ohmmeter |
|
Bent motor shaft |
Straighten or replace shaft |
|
Insufficient grease |
Remove plugs and re-grease bearings |
|
Deterioration of grease or foreign material in grease |
Flush bearings and re-lubricate |
|
Bearings damaged |
Replace bearings |
Motor does not come up to speed |
Voltage too low at motor terminals because of line drop |
Check transformer and setting of taps. Use higher voltage on transformer terminals or reduce loads. Increase wire size or reduce inertia. |
|
Broken rotor bars |
Look for cracks near the rings. A new rotor may be required. Have motor service person check motor. |
Wrong rotation (motor) |
Wrong sequence phases |
Change any two of the three motor leads. |
Gear reducer noise |
Gear reducer bearings |
If new, see if noise disappears after one week of operation. Drain, flush, and refill gear reducer. See Gear Reducer Service manual. If still noisy, replace bearings. |
|
Gears |
Correct tooth engagement. Replace badly worn gears. Replace gears with imperfect tooth spacing or form. |
Unusual fan drive vibration |
Loose bolts and cap screws |
Tighten all bolts and cap screws on all mechanical equipment and supports. |
|
Unbalanced drive shaft or worn couplings |
Make sure motor and gear reducer shafts are in proper alignment and “match marks” properly matched. Repair or replace worn couplings. Rebalance drive shaft by adding or removing weights from balancing cap screws. See Drive Shaft manual. |
|
Fan |
Be sure blades have proper pitch and track. Make certain all blades are as far from the center of the fan as safety devices permit. All blades must be pitched the same. See Fan Service manual. Clean off deposit build-up on blades. |
|
Worn gear reducer |
Check fan and pinion shaft bearings end play. Replace bearings as necessary. |
|
Unbalanced motor |
Disconnect load and operate motor. If motor still vibrates, rebalance rotor. |
|
Bent shaft |
Check fan and pinion shafts with dial indicator. Replace if necessary. |
Fan noise |
Loose fan hub cover |
Tighten hub cover fasteners. |
|
Blade rubbing inside of fan cylinder |
Adjust cylinder to provide blade tip clearance. |
|
Loose bolts in blade clamps |
Check and tighten if necessary. |