trouble shooting

Trouble shooting Guide Problem Probable causes Remedy 1. VIBRATION 1.The most common cause

of vibration problems is anout of balance fan Impeller or the rotor.

1.Check the impeller for any dirt or foreign material, especially hard-to-see places like the backside of the impeller and the underside of the blades.

2.Airfoil blades are usually hollow. When exposed to rain or excessivemoisture they can get water inside of them. Drilling one small drain hole inthe upper surface of each blade near the trailing edge should cure theproblem. Rebalancing is necessary.

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Trouble shooting contd.

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Problem Probable causes Remedy

3. Inspect the Impeller for erosion or corrosion. Usually impeller erosion will occurat the leading edge of the blade. An airfoil impeller exposed to sand or abrasive dust canactually develop pin holes in the leading edge of the blades. Do all you caneliminate these damaging conditions and then rebalance the impeller . If theImpeller is seriously damaged it will have to be replaced.

VIBRATION contd 2.Improper or loose mounting

1.Foundation bolts and bearing mounting bolts can loosen themselves. Makesure they are tight.

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VIBRATION contd Loose set screws that holdthe impeller -to the shaft

Bent fan shaft

Misaligned V-belt drive.

Air pulsation.

Again tighten the screws, but first be certain the impeller hasn't shifted on theshaft or is rubbing on the inlet cone or drive side of the housing.

First, check the shaft with a dial indicator. If bent, it should be replaced assoon as possible to avoid replacing the entire fan.

Realign assembly so fan and motor shaft are parallel and faces of pulleys are flush to a straight edge. We've found that a taut string will work fine

Fan may be operating in the stall area of its performance curve. That meansit is oversized for your particular system or the system resistance is higherthan intended. You can lower the system resistance by cleaning the filters oropening the dampers.

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NOISE Foreign material in the fanHousing

Squealing V-belts.

Worn ball or roller bearings

This could be anything from a loosened bolt to somebody's lunch bag.Inspect the wheel and inside of fan housing and clean thoroughly.

The belts are either loose or misaligned. If belts show wear, you are betteroff to replace them now and avoid a future .breakdown,

Change the bearings immediately before they cause additional damage.Failing bearings tend to wear the shaft, so you want to be absolutely certainthe shaft is full size before installing those new bearings. Measure the shaftwith a micrometer both under the bearing and next to it and compare thetwo beadings. If they don't match replace the shaft. New bearings installedon a worn shaft will not last long.

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NOISE

OVERHEATEDBEARINGS

Bearing seal misaligned

If the fan housing has ametal shaft seal it could bemisaligned andrubbing on the shaft.

Bearings may be worn andFailing.

Improper grease.

Realign the face of the bearing so that it is perpendicular to the shaft.

Loosen seal plate bolts, re-center the seal on the fan shaft and tighten thebolts. If the seal is fiberglass, cork or rubber, be sure the metal backingplate does not touch the shaft.

Replace the bearings, Remember to also check the shaft (refer back to theNOISE section).

Use a lithium base, high speed, channeling type grease. Do not use hightemperature or general-purpose grease.

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OVERHEATEDBEARINGS

Over greasing.

Bearing exposed to "heatsoak" from an oven or dryerafter shut down

Loose V-belts may causebelt slippage and frictionheating resulting in hotbearings, shafts

If you allow the bearing to run for a few hours it will normally purge itself of theextra grease. You can simply remove excess grease from split roller bearings bylifting the top half of the block for access.

"Heat soak" occurs when a fan is idle and it's shaft cooling wheel can no longercool the inboard bearing. Heat from inside the fan can then actually cook thegrease. A 15-minute fan run after the oven heat is turned off will cool the fanshaft and protect the bearing.

Tighten belt to the proper tension.

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OVERHEATEDBEARINGS

POOR AIRPERFORMANCE

Excessive V-belt tension.

Fan rotation incorrect

Abrupt turn in the duct closeto the fan discharge or airpre-spin caused by ductworkelbows at the inlet.

If fan has an Inlet VolumeControl is it improperlyinstalled?

Belts may be too tight. Adjust to the correct tension.

Refer to the Vibration section. An easy way to change rotation on most 3-phasemotors is to reverse any two motor leads

Install turning vanes or elbow splitters in the duct. if air performance is stillinadequate, the discharge position may have to be, changed.

Be sure the Damper /IGV is installed in correct direction of rotation of impeller.

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POOR AIRPERFORMANCE

Fan horsepowerunexpectedly low.

Fan horsepowerunexpectedly high.

Correct one or more of the following conditions.* Air pre-spin into the fan inlet.* Resistance to airflow, such as caused by a closed damper, much higher thanCalculated.

Be sure fan speed is not too high. Fan may be operating without ductwork at lowresistance so that too much air is flowing.The fan may be handling ambient air when it was originally intended for hot, lessdense air.Fan may be running backwards.

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NOTE: Ball or roller bearings tend to heat up when they have been over greased and will cool down to their normal running level when the excess grease oozes out. Thenormal operating temperature of a bearing may be well above the 140- which is "hot" to touch, Temperatures over this have to be read with instruments and anything over180* should be questioned. If you put a drop of water on the bearing and it sizzles, the bearing is in distress and should be changed before it seizes and ruins the shaft.

Bearing Failure Causes

• 36%- Inadequate lubrication• 34%-Normal fatigue• 14%-Contamination• 16% Other causes such as faulty mounting,

Static vibration, electric currents, Incorrect fits.

Noise Problems 1. Fan Unbalance 2. Resonance of fans or attached components3. Rotating equipments rubbing on stationary parts4. Failing , misaligned or contaminated bearings 5. Air leakage 6. Belts slipping7. Coupling misalignment8. Motor noise especially with improper power supply9. Air turbulence10.Operation surge11.Loose components12.High velocity air blowing over fixed components which

are not part of fan