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Danny Harvey

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Reply with quote  #1 
We have a bearing on a Reliance motor that never shows defect frequencies but shows high floor energy in the spectra and random stuff in the twf's from time to time.  I have always attributed it to over lubrication because I know that is a practice in this location.

But now it is rising up in amplitudes with still no defect frequencies and my guy says it's bad from listening to it.

One thing that might shed some light on it is the bearing designation.  It is a 90BC03K30X26

I know that 90 means 90 mm nominal bore; BC means single row deep groove Conrad ball bearing; 03 means medium duty; 30 means loose clearance; and X26 means some kind of special feature.

I don't know what the K means or what the X26 special feature is.

I'm also wondering if maybe the loose clearance, the K or the X26 would make it so that we can't get fault frequencies with PeakVue or Demod. I tried all the filters in PeakVue and I expect that my guys have done it with SKF's Demod and we get nothing but noise.

I'm not afraid to make a call without data to back me up but I like to try to give them something more concrete than the voices in our heads.

Any help?
John from PA

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Reply with quote  #2 
In SKF designations, K30 would mean a 1:30 taper bore.

To my kowledge, SKF doesn't use a designation of X26 but some Japanese manufacturers do.  One in particular shows it to mean "Working temperature lower than 150 °C."

Do you know the actual manufacturer of the bearing?  It might help to tract down the specific meaning.
 
Danny Harvey

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Reply with quote  #3 
Thanks John.

I wonder if the defect frequency vibrations are so damped by over-lubrication that they are undetectable.

It's apparently an open bearing so the excess grease just goes into the motor casing.  The folks at the site say that they open the relief plug while they are greasing it and nothing ever comes out so they just make sure it's "good 'n full".  I've been covering this same motor since 1992 when my former employer sold it to them and it's always been like that but it's starting to smell funny like about 50-100 lbs of grease in the windings.

27 years isn't bad.  The Falk 2120Y2A reducer is still chugging along, too.

It's time for a change. 


John from PA

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Reply with quote  #4 
Quote:
Originally Posted by Danny Harvey

I wonder if the defect frequency vibrations are so damped by over-lubrication that they are undetectable.

It's apparently an open bearing so the excess grease just goes into the motor casing.  The folks at the site say that they open the relief plug while they are greasing it and nothing ever comes out so they just make sure it's "good 'n full".  I've been covering this same motor since 1992 when my former employer sold it to them and it's always been like that but it's starting to smell funny like about 50-100 lbs of grease in the windings.


I found a service manual for a Baldor motor (449T) that uses those same bearings.  You can find it at https://www.globalindustrial.com/site/images/universal/baldor/specs/M74304T-4.pdf.  In the early pages that make the equivalent bearing as a 6318.  Page 41 of 42 discusses lubrication while in service but doesn't directly address the 6318 bearing.  A 6318 is shown to take 4.1 in^3 of grease every 3100 Hours if 1800 RPM.  

T
here is also an SKF handbook at http://www.malloyelectric.com/wp-content/uploads/2013/07/Bearing-Handbook-for-Electric-Motors.pdf that shows much longer grease interval hours for an open type 6318 bearing.  See page 19.  By the way the bearing frequencies are also in that handbook should you need them.
ivibr8

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Reply with quote  #5 
Danny
I know this is somewhat off the subject so take it FWIW

Quote: It's apparently an open bearing so the excess grease just goes into the motor casing.  The folks at the site say that they open the relief plug while they are greasing it and nothing ever comes out so they just make sure it's "good 'n full". 

I can't imagine grease into the motor casing is ever a good thing.  
Years ago I had a number of motors that failed "electrically" <--according to the maintenance crew.

Confused, I made a trip to our motor shop and had a an interesting talk with the supervisor.
He said over greasing was one of his biggest sources of failures for motors this size.
After discussing this information with our EDiv Lead Petty Officer (Navy talk for person in charge of all things electrical), we eventually determined that the EDiv personnel were trained to open the plug to allow old grease to flow out.   So why were we having so many problems?
A few months later, a Petty Officer came to me with about 5 or 6 grease outlet tubes that were clogged with hardened grease. No one every trained them to clean these out.
We (hopefully - I've been retired for 5 years now) made changes to the continuous training and preventive maintenance cards to address this issue.

Regards
Jim P
RRS_Dave

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Reply with quote  #6 
I was going to ask if anyone had given them a small dowel rod to clean the hole out with. It's been my experience that before grease will come out of the 1/4" pipe hole there has to be pressure in the bearing housing. And if there is pressure in the bearing housing, it is pushing grease through that 0.001" clearance to the shaft backing plate, and it's going into the motor (Especially if the motor is running and the ? pumping effect takes over). Reliance has the best grease clean outs in the rectangular boxes they bring down, actual grease will come out of those. About all that will come out of one of those small holes is some oil.
Danny Harvey

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Reply with quote  #7 
Dave,

A like scenario here.  It doesn't seem that they hire well-trained young people as the old ones retire. I don't know if there is a shortage of qualified applicants or what but they tend to assign, brand new hires to lubrication without a lot of training and they get the results I would expect. Dirt gets pumped into systems through uncleaned zerks, bearings over-greased, bearings undergreased, the wrong grease used, improper relief of old grease....

Lubrication is dirty work but that doesn't mean it is for dummies.
John from PA

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Reply with quote  #8 
I agree Danny and I think there are several short comings with respect to industry practices. I have seen all too often that a company lets someone “go” perhaps even for a good reason like retirement. THEN, they hire a replacement and there isn’t any overlap to extend the knowledge. I also suggested for many years, that companies find resources through the Veterans Department or as needed a particualr service. I have known many a Navy Petty Officer Machinest Mate and virtually all exceled at their job.
tomcd3

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Reply with quote  #9 

In my 25yrs at SKF, I've rarely - if never seen - a DGBB ABMA number with a K in it. As K and J's sound the same when transcribing such a designation orally and or K and X look the same visually, I suspect your ABMA designation is actually the more common:  90BC03X30X26, where the X in the K location indicates any cage type.

ABMA special code (sc) 26 is a hard to meet - usually ignored and seldom used - heat treatment (ht) callout from when this system was first originated back in the 70's as shown in the attached from the old ABMA nomenclature guide. It is probably a carry-over from the aerospace bearing industry. I know of no bearing manufacturers that meet this stringent HT requirement.

SKF S0 ht meets ABMA sc 27
SKF S1 ht meets ABMA sc 28

SKF SN ht ensures less than .07 % of change at 120°C (248°F)

SKF DGBB's are SN ht unless marked otherwise.

The average electric motor DGBB will typically fail at 120°C (248°F) due to lubrication issues long before dimensional stability comes into play. Should an application require said brgs to run at this temperature, S1 heat treatment is usually recommended as is an applicable synthetic lubricant.
ABMA heat treatment codes.jpg  SKF Bearing catalog BU-P1 17000 EN Rolling-bearings · June 2018 captur.jpg 


Danny Harvey

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Reply with quote  #10 
Tom,

Could be. The records are old and it was very dirty when I collected them in 1996 or so.

There shouldn't be any requirement for special heat treating.  It is a kiln drive but it is outdoors so ambient is never very high. I've never looked at it with an infra-red camera but I would suspect that there is heat generated by trapped gasses from overlubrication.
Danny Harvey

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Reply with quote  #11 
John,

I do a lot of work in the Hampton Roads area and it's hard to miss the influence of the Navy around there. The ex-Navy guys I have worked with have been really sharp.

But this place is way up in the hills in a little mill town. Most of the young people want to do ANYTHING but work in the mill. And that usually means leaving the mill town.

I like the example of Pnucor's system that Rusty provided. They pay people while they train them in exactly the skills they need. Then, after they have mastered the skills, they pay them much better to do use them. 

Smart manufacturers should have already realized that nobody is going to train people to do the things they need but themselves.
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