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ivibr8

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Reply with quote  #16 
Rusty
You've probably been thru this yourself..... a client has problems with a machine and the solution is to balance; right?  that must be the cure.

The problem was 3 bearing failures of the same fan within a month. They just assumed it was out of balance cause it "made horrific noise". This fan was critical as it was used to ventilate a clean room for manufacture of opiods.  They told me they were losing $80K a day each time the bearing failed. I just couldn't get it out of my head why bearings supporting an axial vent fan (very flexible mount support) would fail due to imbalance. 

Once I got to the utility building to see the recently failed bearing (a Dodge pillow block bearing), it seemed fine to me. When I looked at the shaft, I could see several 360 deg gouges around the shaft and interestingly and STRANGELY, even axially?? <-- Once we figured out the root cause, this started to make sense.
We went over the installation instructions which they followed, including filing a flat spot for the setscrew. So at this point, I'm still puzzled.

That's where my prior post kinda begins. Once we figured out they were using the laser alignment tool incorrectly it explained the unusual scoring on the shaft. When the fan was up and operating, the large misalignment of the pulleys resulted in high axial loads that eventually overcame the setscrew's ability to hold the bearing in place. I guess the "high noise" was simply the metal on metal rubbing (and not unbalance [tongue]).

Of course, I wasn't 100% positive since I wasn't involved in the prior 2 repairs, but it made sense; and a year later they said it is still quiet.  
Yes, the never used the reflector during the prior repairs....they never thought they had to and nope, the fan did not need balancing (all I needed was a good set of eyes).

Sorry for the long post guys.....but it was an interesting problem that had a simple answer. For me, it also reinforced the need to not always look to the analyzer for answers, sometimes you just gotta look at the machine itself.

The mechanics were sharp but no one took the time to teach them how to use the pulley laser system. I suspect most of you on this forum has been through something similar. This seemed to be as much a procedural and training issue as it was a technical one.

Jim

 

 
Danny Harvey

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Reply with quote  #17 

Jim,

One of my clients several hours away asked us to balance a big fan. They had some balancing equipment and said they would give it a  try but asked us to come up and check them out.

When I got there, they had the top half of the cover off and had done like the instructions said and attached the accelerometer to the fan. 

Their interpretation of the instruction to "attach the Accel to the fan" was that they were to mount the accel on the fan wheel, then run the fan and take the reference readings. They were there with the magnet on the fan wheel and a really confused look on their faces, but fortunately hadn't worked up the courage to hit start.

The point is that, like your case, just having the instrument doesn't make you an expert.  

MarkL

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Reply with quote  #18 
Quote:
Originally Posted by Danny Harvey

Jim,

One of my clients several hours away asked us to balance a big fan. They had some balancing equipment and said they would give it a  try but asked us to come up and check them out.

When I got there, they had the top half of the cover off and had done like the instructions said and attached the accelerometer to the fan. 

Their interpretation of the instruction to "attach the Accel to the fan" was that they were to mount the accel on the fan wheel, then run the fan and take the reference readings. They were there with the magnet on the fan wheel and a really confused look on their faces, but fortunately hadn't worked up the courage to hit start.

The point is that, like your case, just having the instrument doesn't make you an expert.  

Danny I just spat my tea on my computer screen reading this then near choked on my biscuit....seriously?
Danny Harvey

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Posts: 1,403
Reply with quote  #19 
True story.
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