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Anonymous Poster #1

Rotor Shaft Defective

12/03/2011 11:43 PM

Hi,

Need assistance for temporary repair on COMBIMAC motor 60kW rotor shaft defective.

The shaft at the drive end bending. Someone advice me to apply metal spray which built up the at bent surface instead of fabricate new rotor shaft.. But is it ok and suit with the high speed rotating motor @ 3600rpm when it rotates.
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SolarEagle
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#1

Re: Rotor Shaft Defective

12/04/2011 11:57 PM

I hope you mean the shaft has been damaged, not bent...If it is damaged due to bearing or seal failure, you might be able to build up the shaft by stick welding, then turning to specs..If it is just worn a few thousandths then fusible metal spray will be ideal. Powder which will give required hardness needs to be selected. There are 3 popular ranges -one giving 10-15 RC ( Fully machinable), 40RC ( Machinable with Tungsten Carbide tip tool on automatic lathes) and 55- 60RC ( can only be ground finished).

For this application the powder with high hardness will be suitable.A spray torch, oxy-acytelene gas welding set with a good set of pressure gauges will be required.Mechanically or Chemically clean the area to be sprayed.Mount shaft on a vertical drilling m/c.Set 5000 RPM to rotate the shaft.Preheat the shaft worn out area with the spray torch to light Blue color.Spray the powder on required area for 30 seconds. Fuse the powder.Take away the spray torch from the job and allow the shaft to rotate till it cools to room temperature.You will have a distortion free job.Grind finish the shaft to required dimension..

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Jimh77
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#2

Re: Rotor Shaft Defective

12/05/2011 12:00 AM

Pull the motor apart and insert the rotor in a lathe and turn down the bent shaft till true. Before you reinstall the motor, determine how the shaft was bent and rectify the problem before you fire it up again.

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Wal
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#3

Re: Rotor Shaft Defective

12/05/2011 2:29 AM

That would depend on how bent it is, what caused the permanent bend in the first place and how well the metal spray repair procedures are followed.

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zhar84
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#4

Re: Rotor Shaft Defective

12/05/2011 5:11 AM

Thanks all... I already install the defective rotor shaft with repair using metal spray method completed with installed pump. I cannot do individual test for motor itself where installation for rotor shaft and motor completely done onboard (limited space). Pump and motor successful running, but after 20 minute, found the unwanted smoke comes from bearing Drive end side.suspected bearing seize.

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Wal
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#5
In reply to #4

Re: Rotor Shaft Defective

12/05/2011 8:20 AM

Right. Do you think you cooked the bearing during your "repair"? How did you attempt to true the shaft after build up? Was the tight bearing the cause of the bend in the first place?

The longest distance between two points is a shortcut.

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SolarEagle
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#6
In reply to #4

Re: Rotor Shaft Defective

12/05/2011 10:46 AM

Need forensic analysis of bearing failure...

http://www.machinerylubrication.com/Read/638/failure-analysis-bearings

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zhar84
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#7

Re: Rotor Shaft Defective

01/04/2012 10:42 PM

Did anyone have ideas and theory what makes the shaft temperature running until 98 degree celcius? is this a normal running temperature for 3600rpm motor with direct connection between rotor shaft and pump impeller. Need advice....

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