Re-metaling or re-babbiting of journal bearings 1

[rmw]

I'd like to hear anyone's experience with re-babbiting bearings in the 240MM and larger range, good, bad, or ugly. I have a client that has to make a decision due to the fact of his having to turn down a generator shaft (possibly 40-50 mils) and have undersized bearings but can't wait for new mfg bearings.

He also has to deal with the issue of maintaining the insulation on the bearings (or replacing depending on the re-metallizing process and temperatures.)

Do you recommend for, against, what are the pitfalls, who are the good guys, the fly by nighters, etc.

I have some that I know but I'll wait to see if their names appear anywhere in here if I get any answers.

rmw

 

[sms]

Plain journal or tilt pad??

It is not unusual, and if done right should be ok. Turbocare in Houston has a pretty new facility to do this sort of work.

http://www.turbocare.com/journal_bearing.html

I have often used TCE for this sort of thing. They really specialize in bearings and know their stuff...

http://www.tce1.com/

And then there KMC who also does a fine job at this sort of thing...

http://www.kmcbearings.com/index.htm

I would probably start with TCE or KMC...

"Why don't you knock it off with them negative waves? Why don't you dig how beautiful it is out here? Why don't you say something righteous and hopeful for a change?" Oddball, "Kelly's Heros" 1970

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[rmw]

Plain journal.

Turbocare is one that I am familiar with (all the way back to when they were Pro Mac) and have visited their facilities. The other two are new to me. Thanks for the links.

My goal is to get the pros and cons as well as the names of the major players. My client has a case of the nerves about puddling on metal in order to make the bearings undersized once the shaft is machined.

rmw

 

[GTstartup]

These guys are OEM approved.

http://www.pioneer1.com/

We use them all the time, no complaints

 

[byrdj]

While I don't see plain journal bearings listed on their web page, I would recomend RPM

http://www.mdaturbines.com/rp/mda_renewal_parts.htm

 

[rmw]

I'd like to try to revisit the OP and emphasize less the specific suppliers (some of the ones that have been mentioned are the ones I referred to in the OP and others are new to me and I appreciate that) and emphasize the "in's and out's" of re-babbiting. When to do it and when not to; when it worked and when it didn't.

The bearing supplier to the OEM of the generator, while not being one of the major players in the field of rebabbiting on the scale of a Turbocare or Pioneer does perform some babbit repairs on their bearings. However, in this case they have made the choice of resizing this bearing by either re-babbiting altogether or puddling on more babbit to seem like a real slippery slope and my client is very nervous about considering this option. I have to be suspicious that their motive might be the sale of a replacement set of bearings instead of a resizing.

For my part, not that I am an expert-hence seeking the advice of those who are-is that I don't see it as a big problem, but then again, it is the Generator OEM who's name is out on the limb with respect to the warranty and their reputation if they acquiesce to the need to re-babbit due to time constraints. They too have a say in it and are at the mercy of the recommendation of their bearing OEM. The generator shaft was damaged at commissioning by the site contractor who let contaminated oil get to the bearings. I'd tell you more details, but I'd have to kill you.

I'm looking for pitfalls, dire warnings, or the 'are you nuts, everyone does this successfully' type answers.

rmw

 

[sms]

The main pitfall may be that 40-50 mils...

It is a plain journal, about 10 in diameter, and you are doing a turndown on the journal of about 50 mils right? What actually cause the journal damage? What are the chances of that happening again?

What is the machine speed? How well balanced is it? How thick was the original babbit, and what clearance are you looking for on the bearing (about 15 mil I guess)? Is it truly a plain journal, or does it have pressure dams or lemon bores?

Thick babbitt bearings, (on the order of up to 100 mils) are not necessarily unusual, just more common on older machines. If it is slow (1800 or less) and well balanced that may not be an issue. If it is a 3000 or 3600 rpm machine, it may be a bit more of an issue. The problem is dynamic stress/loading of the babbitt surface. If it is well balanced it will help. The other thing to pay attention is the PSI loading on the bearing. If that was marginal to begin with, then adding babbit may be a problem. If you had really low psi to begin with, then it should be ok.

Post rebuild a thorough UT of the babbit is required to make sure you had a good bond, and that there are no inclusions. The simpler the geometry the better, to prevent stress risers in the babbit (ie no pockets, pressure dams, etc).

The good news is that if the job is well done, and both the static and dynamic psi is low, then if loose lube oil, or have a problem scuffing the bearings on startup due to lube oil, then having more babbitt is a blessing, and may save some journal damage...

"Why don't you knock it off with them negative waves? Why don't you dig how beautiful it is out here? Why don't you say something righteous and hopeful for a change?" Oddball, "Kelly's Heros" 1970

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[byrdj]

How about rethinking

you are custom manufacturing new bearings using the original steel backing ring.

The Shops listed could just as easy make a new complete bearing. (and might even have the specs for that unit) Using the original steel just saves time.

Here is one thing I found, but proably won't apply to yours

the journals were ground about 3/4" beyond where the bearing while the unit was cold. When the unit went to full load, the rotor growth was a little more than 3/4" so the original diameter tried to go into the smaller ID bearing.

 

[byrdj]

Still trying to see what the concern is.

Is the journal going to be ground in place (rotating or stationary) or is it going to be performed in a lathe.

I have seen all three. the confidence and the quality of the machinest performing is paramount. a two pole machine is like rotating a 1X8 long board, and this can cause the newly machined journal to be oval. there can be similar problems with 4 poles.

Now how deep can they go and still provide the shaft stregnth. I ran into that limit on FPTs. the factory always provide a do not exceed cut.

If you don't clean up the journals, what are the options. a new rotor? OR if the damage is just radial grooves, knock of the edges and run as is. If it is just couple or few grooves, it can be acceptable.

The big thing would be maintaning the bearing geometry and clearances

 

[sms]

So rmw, did you get what you needed?

"Why don't you knock it off with them negative waves? Why don't you dig how beautiful it is out here? Why don't you say something righteous and hopeful for a change?" Oddball, "Kelly's Heros" 1970

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[rmw]

sms,

Yes I did and thanks to all who contributed. No one threw rocks at the concept which was one thing I was probing for.

The generator rotor was taken to a reputable shop which ground the journals. Althought the initial description make it appear that the shaft was severly scored, the actual scoring didn't appear to be more than 0.005-0.010" deep. The shop also had a bearing rebabbiting operation and it was a first class operation.

The generator OEM had a service technician who accompanied the rotor to the shop and who made a good report and recommendation to the generator OEM and I did the same. Between the two of us the OEM got the warm and fuzzies that they needed to procede and do the repair and continue with the warranty on the unit.

When I asked the question in the OP, initial field reports had made it seem like the gouges in the shaft were going to be measured in hundreds of thousandths. They were even asking how much the journal could be cut down before a torsional analysis would have to be performed.

rmw

 

[unclesyd]

Glade to hear that you resolved your dilemma.

I have been trying dig up a little information on some fairly large babbitted bearing that I recovered a number of years ago. Over time we reclaimed 3 bearings.
The bearings in question were 8" dia. and were in a split cast steel shell. The damage to the shell was deep enough to require machining to clear. Once the damage was cleared I had the shell Iron Plated to bring the diameter up to allow a normal rebabbitt. The buildup was around 1/8".

The old "Van der Horst" company did the iron plating and machining.