Bearing Selection
Bearing Selection
(OP)
Hello
We are in the cement manufacturing industry and we have a primary air 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.
We are in the cement manufacturing industry and we have a primary air 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.





RE: Bearing Selection
Replacing an SA bearing by a roller bearing may work, unless you are seeing significant misalignment or shaft bending.
bearing life calcs are fairly easy, why not get your bearing supplier to look at the design - you must be one of their best customers!
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Bearing Selection
grease in these bearings. Any evidence of this?
RE: Bearing Selection
3000 rpm*60*24*7*2= 60 million cycles
consider contamination, over heating, improper lube, fatigue
post some pictured of the failed bearings and races
RE: Bearing Selection
Russell Giuliano
RE: Bearing Selection
RE: Bearing Selection
RE: Bearing Selection
RE: Bearing Selection
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Bearing Selection
RE: Bearing Selection
I would not replace with a cylindrical bearing without checking with a bearing applications engineer. The self aligning bearing might have been installed for misalignment purposes and the cylindrical bearings are less able to tolerate this. A spherical roller bearing might be a better choice, your bearing supplier is best able to help you with this.
RE: Bearing Selection
Kari
RE: Bearing Selection
RE: Bearing Selection
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Bearing Selection
Russell Giuliano
RE: Bearing Selection
When the new large 1 or 2 groove sheaves and narrow section belts arrived I'd get the belt supplier to install the belts with me. If the belts did not squeal on start up I'd loosen them a little, unitl they just stop squealing at speed.
RE: Bearing Selection
Far as I can figure you might have, an alignment problem. The so called "self aligning bearings" are NOT designed for misalignment, but minor (minor<or= 0.005") imperfections of the whole system. (slight deflections of the bearing area) The bearing housing might be tilted, or be twisted (<90degrees) from parallel. The larger sheave might not be true. (<0.001/1"radius TIR). The sheave to sheave might be out more than 0.010". These are big numbers that I'm using, so something closer could help, but they work for a base line. I like to look to <0.001" all way round for measurment and < 0.3 ips on fans. (That should get somebody going).
All the Best.
Robert
Could be worse, could be me.
RE: Bearing Selection
Is it direct drive (coupled) running on 50 Hz or on a VFD?
RE: Bearing Selection