Bearing Selection
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Posted by: lewy07 ® 03/12/2007, 10:52:53 Author Profile eMail author Edit

Hello We have a fan that operates at 2970rpm and over the years we were using self-aligning ball bearing 2316 C3 as specified and provided by the equipment manufacturer. Until recently we have been changing the bearings at a frequency of once every two weeks. On mounting we check the fan for balancing and it is within specifications. On initial start up and after a week of running both the fan and motor bearing vibrations are within specifications but the bearing condition of the fan is out of spec. Thus after the fan runs for two weeks the fan starts vibrating and the bearings eventually seize. The lubrication that we use is grease (Shell Alvania R3) as specified by the equipment manufacturer. My question is what could be the cause of this? Is it also possible to substitute the bearing on the impeller side with a cylindrical roller bearing of the NU or N type, whilst keeping the self aligning ball bearing on the motor side of the fan because I think we are easily exceeding the load limit of the self aligning ball bearings. The bearings are mounted in SNR316 plummer block housing.

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Re: Bearing Selection
Re: Bearing Selection -- lewy07	Post Reply	Top of thread	Forum

Posted by: nadkarni ® 03/14/2007, 02:25:19 Author Profile eMail author Edit

Hi... Please tell us the application where fan is used...incase it it for dedusting system or the fan is meant for dusty air then in due course of time..may be 15 days for your appication the impeller of fan develops a layer of dust thus leading to imbalance resulting inpremature failure of bearing...i would suggest you to provide a filter at suction if possible or clean the impeller after every 5 days and replace the bearings with spherical roller bearing...hope this solves your query... thanks, sujeet

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Re: Re: Bearing Selection
Re: Re: Bearing Selection -- nadkarni	Post Reply	Top of thread	Forum

Posted by: lewy07 ® 03/15/2007, 03:32:22 Author Profile eMail author Edit

We are in the cement manufacturing industry and the fan is used to provide primary air for the kiln for combustion purposes. I have looked at ways to substitute the bearings with spherical roller ones but the RPM is low for the same size bearings. The fan has a filter at the suction and we are just coming out of our annual shutdown were we cleaned both the impeller and the filter.

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Re: Re: Re: Bearing Selection
Re: Re: Re: Bearing Selection -- lewy07	Post Reply	Top of thread	Forum

Posted by: nadkarni ® 03/15/2007, 06:03:55 Author Profile eMail author Edit

Actualy right the spherical roller bearing is not meant for this rpm...even we had encountered similar problem...the only way out may be to increase the width of self alligning ball bearings...secondly see that the bearing at impeller side is floating type...this is most important...but definately the cause of your problem is dust coupled with undersize bearing...pls tell me the details of fan...ie. power, mass flow rate, water gauge pressure etc...I will try out for you.

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Re: Bearing Selection
Re: Bearing Selection -- lewy07	Post Reply	Top of thread	Forum

Posted by: randykimball ® 03/13/2007, 17:50:58 Author Profile eMail author Edit

OK, understand that this is not a qualified answer.. but.. I tend to believe that the bearings used in most self alignment setups (off-the-shelf) are not the most precision bearings. I'd be tempted to figure out a way to install a high end bearing. Bearings come in all kinds of different quality. At that RPM you shuold be looking for a good one.. My next call would be to a bearing representive, and if the first one doesn't seem to care or know enough, I'd go over his/her head. I 'got'ta think, you could afford a top of the line bearing with a fraction of the money you are spending on labor and down time. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

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Re: Re: Bearing Selection
Re: Re: Bearing Selection -- randykimball	Post Reply	Top of thread	Forum

Posted by: lewy07 ® 03/15/2007, 03:36:34 Author Profile eMail author Edit

Thanks, we will consider your suggestion.

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