I have a situation here with our largest overhung fan with a 250hp motor...We just replaced the housing and shaft, and we use SKF split housings #628's on it...It ran for about a week before it was shut down due to a slow-up in sales which sometimes happens over the holidays. The fan sat idle for 6 weeks, all the weight sitting on those bearings. We also had some insulators come in and mix up a batch of their cement for the housing insulation.

While the fan was sitting there somehow the gritty particles of insulation built-up all over the shaft next to the backside of the bearing housing and got through the seal inside to the bearing.

The fan started vibrating one day and I was called to go up and look at it. Shook so bad it sheared off one of the base bolts which is 7/8 dia.

I was able to balance the fan down to about a .21. Took some readings and noticed a high 4AACC & 4VACC, after I balanced it...Looked like the radial clearances increased.

Do you think in that short period with that grit in the oil and all in between the bearing rollers that the bearing would have permanent damage? I did a plasti-gage test and had to add .002 shim to it, and I also tightened up on the bearing nut. That didn't help much! I;m just monitoring it now, but am afraid of a crash due to the damage done by the gritty substance...We use Mobil 626 synthetic oil in all our bearing here and it looked like a chocolate malt when I opened it up. Flushed it out best I could, but the grit is still in there...

Appreciate any of your input from anyone who has been in a similar situation...Sorry to be so long winded. Needed to give you the run down.

Thanks,

RB

What kind of gritty particles from insulation? Is it rock wool insulation?

Chocolate malt - No water in it?

Generally we try to avoid particles (insolubles) in oil, don't we?

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