Pic - 100HP Motor Failure

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We had a customer with a 250 hp that did virtually the same thing within a few weeks of installation. That motor was gone and the new one mounted when we were called in to check the installation of the replacement. With all the noise of the equipment around this fan you don't hear anything specific. Using a Fluke 43 B we could watch the current change as the belts slipped then caught again. We had the belts tightened until the current stabilized. Better than two men with a four foot cheater and a wrench, which seems to be a typical method of belt tensioning.

One of the first things we do with belt driven equipment is to check the amp draw and belt tension. There is a noticable difference, at least on smaller equipment.
 
TwinCitySparky said:
Or sounds or the decreased/stopped production output. That thing had to be making some really wild noises to get to that point.

The paint is cooked off around the shaft. They must only have heat detectors for fire detection.
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The motor is located in a remote corner of a basement in a papermill where noise levels range from 85 to 100 decibels. Operators walk the area a few times a shift but it's very difficult to hear anything unusual until it is too late.

zog said:
Not necessarily the installer, more likely the operator that replaced the proper OCPD with a larger one when the motor tripped off line, seen it many times.

Good point, but proper sizing of OCPD's/settings should be selected with the motor damage curves in mind. Again, maybe I am too used to larger equipment where some actual engineering is done.
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Fuses are time delay 175A, overloads are AB W78 for 105 Amps, both correct. Engineering is always done on our installations, this particular installation has been in service for over twenty years. We needed to move it and we installed a spare motor and pump when we did it to save time on the changeover. Unfortunately it appears that the team assigned to perform the pre-startup inspections missed the lubrication check on the motor, a valuable but expensive lesson learned.

I am not convinced that the belts were too tight but I will really never know. Once the shaft temperature was high enough for the shaft to become malleable even correct belt tension would be enough to start bending the shaft. At that point rotational forces would take over and continue bending the shaft until the failure.
 
Sounds like it was lack of Lube. where is the lube and tune guy when hou need them.
 
mivey said:
Can you get some pictures of the innards?
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Here is a close up of the bearing and shaft damage.
DSCF0007.jpg


CIECO said:
Is that running a large blower or fan
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It drives (drove) a high pressure water pump.
 
eric9822:

Your orignal post mentions lack of lube as the cause. Not that it's not there but your pictures don't show any grease fittings.
 
wptski said:
eric9822:

Your orignal post mentions lack of lube as the cause. Not that it's not there but your pictures don't show any grease fittings.
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The fitting was at about the 10 O'clock position which cannot be seen in the the picture. We removed it to confirm the lack of lubrication. Nice observation!
 
eric9822 said:
The fitting was at about the 10 O'clock position which cannot be seen in the the picture. We removed it to confirm the lack of lubrication. Nice observation!
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In that close-up above, it looks like what's left of a Speedi Sleeve used to repair a worn oil seal diameter, although I've seen that on brand new equipment too! What happened to the machine nut on the shaft?

Depending on how the seals are installed, too much grease using a grease gun can actually pop a seal right out and therefore cause the lose of grease!
 
another possible cause...

another possible cause...

I've read this entire thread and I have a couple of thoughts on what might have happened.

First, it is mentioned that a spare motor was used. If the motor sat in a store room for a long period of time without the shaft being rotated occasionally, the bearings can pit and/or flat spot just from the weight. This is especially true of large motors. It is important to make sure you rotate those shafts periodically...

Second, you mentioned the pump was being relocated. My guess is that there was welding involved and many a motor gets wiped out by an improperly placed ground clamp when arc welding...

Mike Tribout
 
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