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Easy Solutions to Common Tower Troubles

April
22
2015

 

Easy Solutions to Common Tower Troubles


 

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.

 



If you have an issue that cannot be fixed using these tips, Contact Cooling Tower Depot for professional guidance and assistance.



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