Babbit bearing issue

Question for any babbitt scrapers here, I was contacted about this white metal bearing in a local desalination plant. The scraping has worn down to the point where unless the use a porta-power to lift the shaft oil can't pass through. They sent me the images below but today I brought a small surface plate, V block and tenths indicator and from the original scraping to the most worn area there looks to be able 0.0013" of wear. Management apparently either can't or won't get new caps and as far as I can tell everyone else in the area they've contacted has refused to touch this job. I was planning on adhering a 1 thou shim to the bottom of the cap, pulling the dowels and matching the tops of the caps to rest of the housing before scraping the babbitt. Does that make sense or is this a horrible plan?

with Modern machine tools scraping is sometimes not needed as you can machine the bores to line up and machine the babbitt accurately so it may not have had scraping done on it initially.
Wear of 0.0013 is not much wear should be able to shim that up using plastigauge to measure the clearance.
Your bearing has a smear on the edge where the metal has contacted metal you could scrap that part lightly.
make sure the oil galleries are clean, well spotlessly clean and new lube oil is used in case there is contamination of the oil.
you can blue the shaft and see where it touches the bearing also. that smear could be caused by a bit of a foreign object / dirt / chip under the cap causing misalignment and spot loading.
make sure you know the clearance the bearing has as it needs some as the shaft heats up and expands can cause problems.

After looking at the pictures It appears we are only looking at the top 1/2 of the bearing. I always preach you have to be a detective and think about why and how come. I am not where I can print out the photo's to get a better feeling of what's going on. But by flipping back and forth looking at the pic's Here is what I see. The babbit is "smeared" and that means it got so hot it melted as it turned and wore the spot that looks scored, The scraping is worn down everywhere around the bearing accept the top meaning the sides that are visible are worn. Correctly scraped Babbitt the scrape marks are .002" deep, so the sides that you can't see the old scrape marks are a minimum of .002" per side or the top cap is worn sideways .004" and I would have to assume the other 1/2 is worn the same and smeared even worse.

I would assume the side you can't see is in far worse condition as that in under the heavy shaft and load.

The reason no one else is doing the job is they have figured that out and won't take the responisbility of doing a 1/2 assed job.

We are not seeing the side tapered thrust bearing in the pictures and it is probably hatched too (worn) You can see the bronze 1/2 seal bushing is worn too and scored. That needs to be replaced also or it will leak oil. That is probably why the bearing failed.

I do not see the logic in shimming the cap up as this will loosen the bearing and make the sides worse.

Doing that will not fix the major problem, it might get it running for a bit, but it will surely fail sooner then later. You should take heed in why the others would not do it. Because they know a 1/2 assed job will ruin there reputation and after it fails a second time they will have to pay for the porta power shaft lifting and have to eat the job.

The only way as a professional could do it right would be to pull the shaft, because the bottom bearing with the shaft weight and load is probably worse and you can see the bronze bushing that I would bet was desinged to be a running seal will no longer seal anything.

I do not want to even go into how to scrape the bearing which I could do as I have taught at Kingsbury and American Babbitt companies here in the USA and it would be a interesting project if it would be done correctly.

If I were you I would walk away unless they want to do it right. 1/2 assed work will get you into a huge headache and not make your day or year. Rich

I really appreciate the response Richard, It's the kind of encouragement I needed to turn down this job.

The bearing pictured is actually the lower bearing cap, as I understand it the oil groove feeds from the bottom to create a jacking affect.The top cap looks pretty good and still has some of the original scraping but there's some clear signs of misalignment. I called a good friend whose's a fitter based in Sydney who's probably on practical machinist at the moment and he's dealt with a similar bearing arrangement on the same size shaft in the past and the new bearing caps cost about 5k at the time. The plant management who I believe are from the oil and gas industry seemed to be under the impression that this style of babbit bearings can be re-scraped without a problem but couldnt offer anything beyond that.

Street is correct about modern bearings, but they also have pressure lube systems and not gravity sump as it appears this one has. If it was a pressure system they would not have scraped the cap.

If the bronze seal leaks then the pressure system will not work. No matter what type the leading edge of the oil groove is tapered on the side the rotation is going so a wedge of oil is between the shaft and bearing at all times. The older gravity feed would always wear a bit at start up. That's what they used to push the start and stop buttons to get a film of oil under there before the RPM got going.

Marcuschrist said:

I really appreciate the response Richard, It's the kind of encouragement I needed to turn down this job.

The bearing pictured is actually the lower bearing. as I understand it the oil groove feeds from the bottom to create a jacking affect.The top cap looks pretty good and still has some of the original scraping but there's some clear signs of misalignment. I called a good friend whose's a fitter based in Sydney who's probably on practical machinist at the moment and he's dealt with a similar bearing arrangement on the same size shaft in the past and the new bearing caps cost about 5k at the time. The plant management who I believe are from the oil and gas industry seemed to be under the impression that this style of babbit bearings can be re-scraped without a problem but couldnt offer anything beyond that.

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The cap looks like it's the top and the cap has a pin hole and the bear over the shaft has a oil hole and pin hole. The rag is laying on the bottom 1/2 of the casting. If the bottom Babbitt bearing is pinned how can you pull it out? and if the shaft wasn't lifted out how did the remove the bottom bearing?

Anyway. I would not do a 1/2 assed one sided repair. I would think you could scrape it back as long as the smear isn't layered as many smears are and as you scrape the layers off they pear layers that are smeared over and over on each other. Not being there seeing the whole thing and being able to measure the shaft, and ID of the bearings is all a BIG GUESS. Rich

Marcuschrist said:

I was planning on adhering a 1 thou shim to the bottom of the cap, pulling the dowels and matching the tops of the caps to rest of the housing before scraping the babbitt. Does that make sense or is this a horrible plan?

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I cant think why you would add additional gap between the bearing half's, its all ready worn out of spec. On the provision it doesn't need re-babbiting, and the shaft is allowed to go lower, you take meat off the joint faces, making the diameter with in the babbitt smaller, which gives you stock to whittle back into round.

Have a think about it. Its all ready worn oversize, and you want to add an additional 0.001". Then scrap it? Omit dowell pins. It's over size already, and you want to add additional clearance.You have to reduce the joint faces enough to give you scope / stock to bring it back to round. Depending on the application, round isn't good enough. Its often a tri-lobed shape with a lead in wedge.

If you want it done professionally, contact me. I'll send you Dr. Marko I'd actually warrant it.

Regards.

Much appreciated Richard, I was only dragged into this because a machinist that knew about the scraping club didn't want to deal with the job and gave my details to the maintenance department. I think he must have confused the scraping of ways with babbitt scraping. The guy in charge of maintenance was quite well mannered and understood the difference but was really quite desperate for any solution to get them out of trouble.

I don't know if you remember me but I was the young Australian Lad that attended your 2017 class in Denmark, I've since invested in all the kit for scraping and started a small club out of my machineshop. A few members have even have their own biaxs as well as decent sized granite plates save them having to drive all the way to Burliegh to use my big plate. If you ever feel like a holiday to Australia I'm sure we could house you at my family's beachhouse in Kingscliff and I'd promise not to pick your brain about scraping too much.

sorry I posted before refreshing the page and didn't see the responses, if you don't mind could you PM me your number phil for a quick chat?

This is shamefully embarrassing phil but I don't have autodesk inventor installed on this computer so I've had to use microsoft paint. this was what I was trying to convey as a method to reduce the clearances before scraping

Ahhh the young man who shared the beach house we stayed at. You did a good job in the 50 hour basic flat bearing / basic rebuilding class and I recall you were a good machinist. This project needs a pro that you could watch. Scraping Babbitt is a special skill and you need to sharpen the blades negative 15 to 20 deg's as if your scraping a round Turcite bearing. A spoon and hook scraper too. Remember I consider my students "my kids"? Well Dad says pass on this job. :-) Rich

PS: I would love to come back to Australia someday and fly down to New Zealand for some R&R and sight-seeing. Meet all the mates I have met on here. :-) I spent 2 weeks touring Australia in 1971 when I was 21...sighhhhhhhhhhhh