Gents, I would appreciate your experiences of the benifits of a lubrication schedule.
Soon after I took on the off-line vibration analysis, I asked also to maintain a greasing schedule for the electric motors and some of the rotating machinery which was greased.
There had been no greasing schedule, therefore when I was getting HFB on the vib rounds, there was no way of knowing when the equipment had last been lubricated. I thought that it was better for myself to be in control of the greasing. As time progressed, I should have seen the results of a pattern and amount of greasing on the machinery. That worked for about two years then I was stopped from doing the greasing and no-one else was given the job.(This was bout five years ago).
Now! the strange thing. The lack of greasing has had no significant effect on the pattern of machine failures. I had expected a gradually increasing stream of bearing failures to back up my request for a return to a greasing schedule.
The truth is that some machines which had been greased regularly had failed, and a good number of non greased machines are still running after 20 years. There were some machines which were 'sealed for life' and some machines which couldn't be greased because of guards, inaccessable grease nipples etc. I havn't been able to detect a pattern of failure.
Although it goes against what I believe is sensible, the evidence locally is that the greasing schedule had a fairly random effect on reliability. Although, I believe by the greasing schedule being stopped, valuable info was lost. e.g. The frequency, the amount or the type of grease would all have had an effect on the MTBF.
The feeling in my water is that the correct amount at the correct interval of the correct grease should keep a GP machine running ad infinitum.
I would appreciate your opinions.
regards,
Joe Mc Cormack

Having been in your shoes I can certainly feel your pain.
When I worked at Amoco Chemical we were tasked with putting together a greasing progragm for preventive maintenance. First thing we did was gather up all the grease guns we could find and tested them all to see how much grease each produced with one pump.
We then gathered mnufacturing info for each bearing type in each motor,pump, etc.
After years of what we felt was the most effective lubrication program we found the following.
That no matter what we wrote on the PM sheet for the Mechanic to follow, he was going to do what he was going to do. We found failed machines that were severely over greased which should have never happened had the PM sheet been followed. We found failed bearings with little or no lubrication, which should have never happeened had the PM sheet been followed.
We found bearings failed because of contaminated grease. This had to have been caused by improper greasing techniques,i.e. not cleaning the fitting before greasing or allowing the tip of gun to be contaminated.
We also found situations where the bearings would not take the grease.
There were many more success stories than failures so I think that overall our progragm was a good one.
I guess I am just saying that the best programs are only as good as the people doing it.

I would love to have that kind of equipment, but it looks to good to be true.

Things that come to my mind

1) Are you sure there is not an old grandpa operater that have been taken care of the equipment while you are not around? The type that knows every thing of the equipment.

2) Does operations has a nibbit store where grandpa every two months takes a grease gun, to grease the electro motors you are watching? Grandpa probably don't wrote his lubrication schedule, but he has enough experience to know when something is wrong. I read somewhere that for contiuous operating motors the recommended interval is two months.

3) What is the load on the equipment? If the load is about 30% the forces geneated by the rotating parts are much smaller then a 95% load. (overdimensioned equipment)

4) You are focussing on the electromotor, what is on the other side? A pump? who does the aligning?

There was a very interesting topic on shielded bearings, and one of the facts I learned, that motor fabricants put grease nipples on the frame, and double shielded bearings inside, of course greasing will have no effect.

We have a 80 HP electromotor coupled to possitive displacement pump. Operations told us that noise was coming out of the motor, when they greased it the noise stopped. I have my suspicions, maybe some shifts have a grease gun, but I never have seen an operator near a motor with that type of equipment. I also runned operations shifts for years.
Maintenance goes in, the new VB 3000 (experimental) gives high peaks, the old SPM gives condition red on the display.
Motor gets overhauled (first time), everything smooth running now. I asked for the bearings and receive two double shielded bearings.
Didn't found any grease nipple on the frame..., probably they where removed in the shop, or ...

Maybe you should be more in the field, to find out what is going on.

Great post Joe. What you report amounts to a large scale experiment. I have never had the oppotunity to see it because we have always greased our bearings.

It's another good datapoint in the continuing controversy over best methods for lub of greased bearings. Many would suggest we should use double-sealed or shielded and never lube. Your experience suggests these bearings would have a long life even without lub.

One question: Are most of your machines continous run? Or most standby service? Also roughly what horsepower range.

The reason I ask is that I think safe period without lub is some multiple of the oem-recommended relube frequency. For example SKF states shielded or sealed bearings can operate without lube reliably for twice the lubrication interval of a comparable lubricateable bearing in same application. High speed, high run-time, large bearings all drive us toward more frequent lube interval. If you have small machines, mostly standby service, perhaps 1800 rpm or lower, reasonable lube interval might be a few years and not surprising to make it to 5 years.

I've looked at some bearings from 2 identical machines recently. One of the motors had a double shielded bearing and a sealed bearing installed. The other motor had open bearings installed. Both had been greased once a year for the past 25 years, because we didn't know the one had non-greasable bearings installed. The one with the double shielded and sealed bearings was starting to show signs of lubrication issues, noise in the vibration data after 25 years of service. The grease inside the double shielded bearing was very dry and "flakey" so this bearing was getting close to failure, the open bearing in the other machine looked great... Under the right circumstances, you can get excellent life out of a non-greasable bearing, but the lube will eventually fail... on the other hand, the greasable bearings looked great, and would probably go another 25 years!

This message has been edited. Last edited by: Ed Hudson,

Doc2.doc (127 Kb, 36 downloads) bearing pics

Ed, good to see that your keeping busy. I've been tasked by the powers to be review all of our grease evolutions and revise frequencies as required. The new EPRI Guide has hit the street but their recommendations don't take into account old grease in old bearings so I'm forced to plug along on my own. Has anyone done a similar evaluation ? Any other studies out there I can use as reference material ?
rgf

quote:

Originally posted by rgf:
The new EPRI Guide has hit the street but....

Can you clarify Which EPRI guide is that? I don't think I've seen any new ones lately regarding lube but if I'm missing one I'd like to know.

Another consideration to add to the confusion might be the arrangement of the machines. Where 2 machines are installed side by side, with one operating and the other in standby, the operating schedule comes into play. When the units are swapped, the newly stopped unit will cool down and suck possibly moisture-laden air into the bearing. There are many considerations in how often to swap machines over. The stopped machine will suffer brinnelling of the bearings if not rotated for a long period, but swapping too often may cause bearing problems too.

Jon
Spintelligent Labs

The EPRI (Electric Power Research Institute) Electric Motor Predictive and Preventative Maintenance Guide EPRI NP-7502s has a Regreasing Interval Table B-1 that groups motors by HP, RPM and Operation and gives a recommended lubrication interval. I contacted the authors and inquired about age factors for both the machines and the grease and whether the table factors in these parameters. Apparently it was not a consideration but a new revision will address these conditions. My point being that if you have a 20 year old bearing that has been greased at some known (or unknown) interval and you have no idea of the condition of either its hard to make an accurate call on grease intervals. Another report of interest is EPRI's Acoustic Monitoring of Bearing Lubrication Proof of Concept Study report 12/2004 No 1009585.
rgf

rgf
Is there a web site that we can get a look at the report you are refering too from the EPRI.
I've just become alarmed onsite that our strategists have changed lubrication schedules for greasing motors to every 91 days, they have no quantity of grease and they are to be greased while shut down.
So much for not the easy life of Condition Monitoring.

David

EPRI documents are available to EPRI members from www.epriweb.com

If you are not a member you will probably find it too expensive.

We have before talked about double-shielded bearings and how EPRI's recommendation is fragmented. Since we mentioned EPRI NP7502, I looked up page 2-28 which reads:

"Double Shielded Bearings. These type of bearings are used when... Lubrication of this type of bearing arrangement is more difficult because grease cannot be easily pushed out of the bearing. Because of this relubrication intervals are usually longer and quantities less than a similar open bearing. In a non-hostile environment with a proper greasing program, a double-shielded bearing should have approximately the same useful life as an open bearing".

Came acros some info about greasing ball bearings in AC motors

AC motor regreasing schedule

Easy: motor operating infrequently ( 1 hr per day)
1.5 - 7.5 hp = 10 years
10 - 40 hp = 7 years
50 - 200 hp = 5 years

Standard: machine tools, fans, pumps, textile machinery
1.5 - 7.5 hp = 7 years
10 - 40 hp = 5 years
50 - 200 hp = 3 years

Severe: motors for continuous operation in key or critical locations
1.5 - 7.5 hp = 4 years
10 - 40 hp = 2 years
50 - 200 hp = 1 years

Very severe: Dirty and vibrating applications were end of shaft is hot from high ambient temperature
1.5 - 7.5 hp = 9 months
10 - 40 hp = 4 months
50 - 200 hp = 4 months

This is applicable to ball bearings if no better information exists

The information can be found in the Mechanical Trades Pocket Manual from AUDEL