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“We replaced the bearings three times and it still makes noise”…Sound Familiar?
If you are responsible for the reliability of HVAC air handling equipment, you probably have units that rumble and make more noise than they should.
Most often this is due to the shaft to bearing fit up. Improper bearing installation can cause the bearing’s inner ring to wear a groove into the shaft.
Once the shaft is grooved it’s only a matter of time before you realize that repeated bearing changes is not the solution. You also know that shaft replacement is difficult and very expensive.
HI-TEK specializes in shaft repair of all rotating machinery.
Our innovative approach to equipment repair can save you thousands. We have numerous repair methods that allow for restoration of bearing fits without removing the shaft.
See our examples below.
Supply Fan #2 at Retail building in Harvard Square
Here is the arrangement before repair. This is a very typical Sealmaster Low Height pillow block, belt drive. The Bearing rests on a shelf with a shim under to adjust ride height.
Problem:
Fan unit has high vibration and elevated noise, Dial indicator reading reveals .010 run-out on shaft suggesting shaft wear. Red substance in the area is iron powder emitting from the shaft to bearing fit degradation.- Repeated bearing replacement has not solved the problem.
- A new Shaft is not available as the unit is almost 60 years old. Replacing the shaft is very difficult as the blower wheels are fragile and frozen onto the shaft. Downtime could be days where summertime temperatures are almost 100 degrees.
Solution:
- Sleeve the shaft in place.
- Repairing the shaft involves taking careful measurements and making a precision shaft sleeve to cover over the worn area.
- A new bearing arrangement is needed to accommodate a larger bearing as the sleeve needs to be at least ½ inch in diameter larger than the original shaft.
See photos below.
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- The sheave is removed to reveal the arrangement. Typical low height air handler pillow block bearing.
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- Stripping off the bearing reveals the shaft wear. The red rust area is the worn area. A close look reveals the bearing was not seated properly on the shaft due to excessive clearance between the inner race of the bearing and the shaft. The locking screws on the bearing causes the inner race to run crooked on the shaft causing elevated axial vibration, noise and repeated bearing failures.
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- The custom sleeve is installed. The sleeve is honed to fit the shaft tight. Proper manufacturing tolerances are critical to the longevity of the repair. High strength Loctite retaining compound is applied to the shaft fit and locking screws are tightened.
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- A completely new bearing arrangement is used. The original bearing shelf is has been cut out and a custom plate has been made to hold the oversize bearing, and then bolted and welded in place.
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- Here is the finished product. Downtime only 5 hours!
Supply Fan #3 at Retail building in Harvard Square
This is the arrangement as it was when we were called in. This is the belt drive side with the drive pulley removed. The bearing support structure was previously modified by another company. The original bearing was a four bolt flange style that bolted to the fan cabinet.
Problem:
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The original bearing location was abandoned as the bearing had loosened and wore a deep grove in the shaft. Another company modified the structure to allow for the retrofit of the pillow block style bearing. This allowed the bearing to seat on a undamaged part of the shaft. - As you will see below the shaft has been previously worn in all available locations. Continued replacement of the bearing does not solve the problem.
Solution:
- Sleeve the shaft in place.
- Repairing the shaft involves taking careful measurements and making a precision shaft sleeve to cover over the worn area.
- A new bearing arrangement is needed to accommodate a larger bearing as the sleeve needs to be at least ½ inch in diameter larger than the original shaft.
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- With the bearing removed you can see the damage. The shaft has worn every available place to run a bearing. This is usually a hopeless situation. The standard solution would be to replace the shaft.
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- This is a photo from inside the fan cabinet you can see the shaft is buried deep inside. The shaft is heavily corroded. The entire cabinet would have to be disassembled. The shaft has been in service for almost 60 years. You can’t see the two blower wheels but they are beautiful complex aluminum cast fan wheels. Removing the shaft would be a huge task. The customer considered replacing the entire unit. The replacement cost was $80,000 with labor. We fixed it for $3500 including parts with new belts and sheaves.
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- The shaft was carefully cleaned and all burrs were removed. The sleeve is hone fitted on site to slide on tightly.
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- High Strength Loctite is applied inside and out.
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- A larger bearing is installed and the support was moved lower to accommodate the oversize bearing. Sometimes we can find a bearing that does not require structure modification. Each situation is different. The pulleys and belts were installed and the unit was ready for another 60 years. Total Downtime, 6 hours.
Tags: Air Handling Equipment, Bearing Repair, HVAC, Noise Reduction
