What does Lmhr refer to? 1

[PhilBW]

I recently got a quote for a gearbox. It listed the L10 life for the bearings and also the Lhmr life. I assume the Lhmr life is an adjustment to L10 life based on operating conditions, but I had never seen that term before. Searches on the internet haven't turned anything up. Can anyone provide more information or direct me to a source?

 

[ischgl99]

I could not find a reference for that either, the h most likely indicates hours instead of revolutions. The mr is most likely the same as na in Lhna in the FAG catalogs which is an adjustment according to ISO 281 for the level of contamination of the lubricant, condition of the lubricant film thickness and stress index on the bearing.

I would reguest from your gearbox manufacturer the formula they use for the Lhmr calculation so that you can compare it to other standards to make sure you are comparing apples to apples.

 

[PhilBW]

mbensema - I appreciate your response. Since Lhmr doesn't seem to be a standard abbreviation, I think it would be an excellent idea to ask them how it is calculated. Thanks for the suggestion.

Phil

 

[ietech]

I Googled -- Define Lhmr -- I found that this has something to do with harmonic functions, not sure if this helps

http://www.springerlink.com/index/g32628t02158t477.pdf

Several of the other results may be of interest to you.

The web site does not explain much but might get you in the ballpark. Harmonics can have a definite effect on mechanical components.

Hope it helps ---

 

[ischgl99]

I should have checked with our applications engineers first, Lhmr is a new modified rating life calculation based on ISO 281:2007 that takes into account the stresses on the bearing components as well as lubricant conditions. This supercedes Lhna which was based on ISO 281:1990. The main difference between the two is the new rating is a more accurate estimation of the actual operating conditions then the older standard. You should be seeing this designation more often in the future.

Something you may not be aware of, the Lhmr or Lhna rating can be higher then the L10 life. The L10 life only takes into account the load on the bearing and the new life calculations can have a correction factor greater then 1 if the lubrication is very clean and there is a sufficient film thickness between the rolling elements and races. As an example, if the bearings are lubricated by a filtered oil system, the oil quality will be higher then for a sump and lead to longer life due to the level of contamination buildup in the sump system.