How To Calculate of Bearing Life Time?

[jonos]

Dear everybody,

Would you like to give me some information about bearing life time for a motor and how to calculate of that life time?
Thank you for your attention and cooperation.
Regards,
Jonos

 

[jbartos]

Suggestion: Visit

http://www.aidic.it/italiano/congressi/esrel2001/webpapersesrel2001/87.pdf

etc. for more info

 

[GusD]

hi jonos

The calculation for Dynamically Stressed bearings is as follows :
The rating L10 life is the nominal rating beaing life in millions of revolutions which is reached or exceeded by at least 90% of a large group of identical bearings.
L10=L=(C/P)*exp p {10 to the 6th power in revolutions)
Where
L10=L is nominal rating life (10*Exp6 revolutions)
C Dynamic load rating (KN)
P Equivalent dynamic load (KN)
p is =life exponent.

When the bearing speed is constant,the life can be expressed in operating Hours.

L10=Lh=L*10*exp6/n*60

L10=Lh nominal rating life in "Hours"
L=normal rating life (10*6exp revolutions)
n= speed (revolutions /min)
PPis based on material fatigue (This info is taken from

This info was taken from a FAG bearing manual


GusD

 

[jonos]

Dear GusD,

Thank you for your explanation, but I confuse about "in million of revolutions", would you like to explain more detail?
Thanks

Dear jbartos,

I interest with CAD-integrated Weibull Analysis, where can I get that program or more detail information, please?

Thank you very much
Rgs,
Jonos

 

[ischgl99]

Standard life calculations are expressed as X millions of revolutions, if the bearing spins fast, the life will be low, if spinning slowly the life will be long for the same number of revolutions.

Take 3000 rpm, 1 million revolutions would be 333 minutes of rated life, but 300 rpm would be 3333 minutes.
1,000,000 rev/3000 rev/min = 333 minutes

Mike Bensema

http://www.dutchmenservices.com

 

[electricpete]

I have seen available free info from SKF, FAG, NTN addressing bearing life calcs in detail.

One thing important to remember is that many of the quantitive basis for L10 life typically is fatigue calcs under certain idealized conditions. Typically in the real world there are issues of contamination, bearing misintallation, lubrication breakdown for various reasons that need to be considered carefully along with any fatigue estimate.

 

[GusD]

Hi Jonos.
I am curious to know something,is your interest in calculating "L10 bearing life" just plain curiosity on your part or;do you have an actual work related problem or problems? Myself and my colleagues,who work daily in Vibration Analyses, do not concern ourselves with the theorectical design L10 life of the bearings.
I gave you some formulas on a previous reply,however;ourselves never really bother to understand what they really mean.All the bearing manufacturers have these formulas in their manuals.SKF,FAG,NTN etc.etc
The reason why we don't really care about what the design
L10 life is,has to do with the fact that there are so many variables affecting bearing life, that makes the idealized theorectical life of a bearing meaningless in the field.
Load/Lubrication/Speed/Op Temp.Misalignments are part of the load.A bad alignment can destroy a bearing in ashort time,very short in fact.Bad Lubrication,too much or not enough grease (I'll bet on the too much)will raise havoc with your bearing life.So as you can see ,L10 design life is only as good as your treatment and care of your bearings in your plant.

GusD