When you say the bearing had wear (Pictures are often difficult to see things.), did you measure any wear; were the clearances off? Was there any babbit distress, cracks, missing, bonding issues? Babbit does not fail at 200 degrees if normally loaded, and the oil viscosity could contribute to the higher than desired temperatures.

Many applications today have precision bearings, and scraping is not allowed. Bearing geometry is often more complicated than being round. Many bearings are elliptical with horizontal clearance (greater) different from the horizontal clearance, there can be more than two pads (or less), bearing halves can be offset, pressure dams may be present (They have to have the right height and position.), pads may have grooves or other relief areas, etc. . Fit in the housing is important.

Thanks Pete. I'm not always the best at reading as close as I should all the time... too much hurry nowadays.

I don't think any of us are far apart and practice may be very close - but, isn't anyone using a standard? Blue the standard, transfer to the bearing and scrape some more off? I've done the scraping in the past or years ago but not in a position to actually do that type of hands-on stuff anymore due to labor restrictions, union grievences, not being of sound mind, cte.......

Morning Bill,

You're on!!! I'm simple on what I'm assuming to be a discussion on 'simple'.

There are so many you just don't mess with. Our Elliott comperssors have tilting pads and operate ~51,300 RPM so I by-pass the electrical and run the aux oil pump just to turn the rotor for alignment. I think few do it and I really don't see the OEM tech reps doing it but it's a practice with me.

I agree Sam. As far as I know, there are not any written standards that cover performance of blue checks. It's good to look at what different people do and why.

Your approach for the Elliot compressor sounds reasonable to me. We start the thrust bearing oil lift pump whenever we do manual rotations of our vertical reactor coolant pump motors. In that case, the whole purpose of the lift pump is to help provide an oil film when shaft is rotating slowly during manual rotation, startup, and possibly shutdown. I have never worked with anything like an Elliot compressor.

Jason, what is the material of the journal bearing?

First of all I would like to thank everyone for their comments and suggestion. Here's my story for asking so many questions.

We recently had increased temperature levels on this pump. We had some other issues with the plant at the same time and so we took one of our turbines off line to perform some work. Supposed to be 7 days. This bearing temperature issue was one of the tasks to be repaired. Our maintenance department does not have a lot of experience with sleeve bearings to start the explanation. I'm the reliability engineer for the site doing vibration, thermography, oil analysis, and alignment support (w/Maintenance). My recommendations were to perform a hot alignment check, verify adequate oil flow and check bearing contact pattern. Previous to working for this company I worked for one of the premiere apparatus repair facilities in the Midwest. For close to ten years I had the opportunity to perform thousands of alignments on equipment from 10 hp motors and pumps to large steam turbine generators. Along the way several motor installations and repairs including a majority of sleeve bearing application.
Our procedures for sleeve bearing installation were as follows:
1: Clean everything, shaft, bearings, seal surface and make sure everything was smooth, no nicks or burrs.
2: pour a small amount of oil on the top of the shaft, set the lower bearing half on and roll into place (off coarse the shaft would be lifted for enough clearance).
3: Bolt the upper bearing half together and then install the top bearing cap, end bell, or whatever to complete the bearing installation. 4: Rotate the shaft by hand to gain enough inertia to allow the rotor to rotate on its own a few turns.
5: Disassemble the bearing and inspect for the contact pattern on the lower shaft. Use the "scraping" method to gain contact pattern.
6: Reassemble and repeat this process until 80% contact was achieved.

Ok this all sound good and all but with out all your feedback and suggestion I cant convince our Maintenance Manager to perform the scraping (due the vendor telling him it wasn't "necessary because nobody scrapes bearings anymore") if for nothing at all but to rule it out as a possible source of the heating. After talking to the vendor rep, actually two of them neither one of them understood what scraping actually was.
Oh and by the way we install a new bearing, aligned, verifies oil flow and never did the contact pattern per vendor recommendation. Needless to say we started up and still have the hign bearing temperatures but it did change -2.5 degrees.

This message has been edited. Last edited by: NuclearJason,

So, did you have a bearing problem to start with, and how did you determine this?

Bill,

We have a bearing temperature problem. We have four identical pumps. Two of them run abour 20-25 degrees lower and one 10 deg. lower. I believe it is a contact issue (not equal contact or enough contact). The temp increases to 186 within 10 minutes and takes almost an hour or more to add another 3-4 deg. My experience tells me the quick temp increase is due to contact surface and the rest is system ralated changes. You will always have the sudden increase at start up due to friction but should peek out lower if contact is even (more surface area means more even oil film).

The bearing should not have much thermal lag to reach temperature. Alignment can gradually increase temperature (or decrease). Bearing load (factors such as alignment affect this) can cause a temperature increase. Are the oil supply temperatures the same?

Did the old bearing have any damage? This bearing didn't do much if anything - What tells you the old bearing was bad? You are talking bearing metal temperature and not oil temperature? Does the oil cooler keep the oil supply the same as the other machines? Are all oil viscosities the same? Are the bearings the same type (meaning geometry of the bearing)?

The bearing does have to be aligned with the journal. Are assembly clearances the same?

quote:

I cant convince our Maintenance Manager to perform the scraping (due the vendor telling him it wasn't "necessary because nobody scrapes bearings anymore") if for nothing at all but to rule it out as a possible source of the heating.

It is really difficult to un-scrape if the temperatures go up after scraping.

Bill,

The oil supply temps are with-in one or two deg. for each pump. The old bearing had no damage but a noticeable uneven ware pattern (about 40% contact). Nothing about the old bearing was bad. Yes bearing temps and not oil temps both are continuously monitored. Oil temps are controlled near 100 deg. with same oil with all four systems. All bearing are the same. I am aware that scraping can not be reversed but if a good contact pattern is achieved I have never saw temps increase with this procedure only decrease.

Jason

Have you checked that the pocket in the bottom pad is in the same angular location relative to the bottom and rotation as it is on the other machines?

100 degree oil seems cold for most applications. Is there a heat source to transfer heat into the bearing?

Bill,

The bearing inserts can only be installed one way so yes the pocket is the same on all of the bearings. The only other heat source is from the water in the pump and there is seal cooling water between there and the bearings. This temperature is also the same on all four pumps.

The inserts may only be able to be inserted in one way, but are the inserts the same? Position and width of the pocket affects the temperature. Oriface size makes a difference, too.

Bill,

Yes both halves are identical, size, shape, and oil pocket location. In fact there are no special identifications to indicate a designation of top or bottom.

Are inboard and outboard bearings the same?

Having a pocket on the bottom decreases load carrying capacity and increases temperature. When this is done, there should be a reason. Also, other bearing designs may work and reduce temperatures.

Do the other pumps' bearings look exactly the same as this pump?

Also, it is difficult to say there is a problem here. Bearing metal temps are acceptable, and there was no bearing damage.

Yes the in and outboard bearings are the same. There may not be a problem with the bearing other than temperature. The manufacture says to not operate over 200 deg. if we continue with temps at 190 in February when cooling water is 40 deg, it is inevitable that we will bypass 200 degrees in August when cooling water is 70 deg. There lies the problem.

200 degrees should not not a problem, nor would 220 likely cause a failure. The bearing is probably good for somewhat higher temperatures,as well. We like to have our bearing design below 190 or even lower providing a margin, but design is not always what you get.

So, if you flip that bearing around to the other side, does the pocket change sides with regard to rotation and the bottom? We would ask for the bearing design to not allow installation of a top in a bottom or inboard in an outboard, unless the same design is used.

Are the bearings in the other pumps just like this one? Are the pumps similar?

Bill,

I would like to discuss this with you further. Email me so we don't have to drag this forum out any longer. jason.haugen at nmcco.com

We had mentioned there don't seem to be a lot of standards (other than OEM info – sometimes hard to come by). For sleeve bearings in electric motors, I did find some fairly specific guidance in IEEE 1068-1996 ("IEEE Recommended Practice for the Repair and Rewinding of Motors for the Petroleum and Chemical Industry"):

quote:

IEEE 1068-1996:
"Reassembly of bearings. Split sleeve bearings that are either new replacements or have been rebuilt should be fitted to journals by bluing and scraping as in the following:
1) Using a bearing scraping tool (typically a triangular Þle with the teeth ground off), scrape any side reliefs and lands to the clearances and contours recommended by the motor manufacturer. Apply a small amount of nondrying bluing compound to the shaft journal, spreading it out to form a uniform coating 1 - 2 in wide over the full length of the bottom of the journal. Lift the shaft slightly, roll the lower bearing half into place, then lower the shaft onto it, ensuring that the normal rotor weight is applied to the bearing. Turn shaft 1/2 to 1 revolution. Lift the shaft again, and roll the lower bearing half out. A pattern of very light blue and dark blue areas will be seen on the bearing surface. These correspond to high and low portions of the bearing surface, respectively. Scrape the high spots to make the light/dark pattern uniform; the fitting process should be repeated with bluing as required until at least 80% contact has been achieved. When this is complete, leave the lower bearing half in place with the rotor weight resting on it."

2) Lay two or three pieces of lead wire or other calibrated deformable gage material on the journal, perpendicular to the shaft centerline; their ends within 1/2 in of the horizontal split line. Make sure the upper and lower bearing halves are clean. If shims are used between the halves, make sure they are clean also. Place the upper bearing half over the journal on the wires or gage. Install the upper bearing cap or housing and tighten its bolts to speciÞcation. Then unbolt and remove the upper bearing housing and upper bearing half carefully. Measure the thickness of the lead wire or the clearance of the deformed material as instructed on the package. If the clearance is within limits, remove the wires or gage and proceed with reassembly. If it is not within limits, both bearing halves must be rebabbitted if too loose, or top half of bearing must be scraped if too tight."

Journal Bearings, Scrapping, heck I thought that went out with tasting the oil for babbitt. Mic out the shaft, I use a ball end micrometer for diameter all over and surface plate and indicator on a set of matched V blocks for flat. Anything over two tenths or more on the larger journal out of spec I send it out to be ground. If you send it out to be ground specify that that it must be polished. If you have the opportunity, have the bearing TIN coated or other on the shaft. The messy blue stuff, save that to check the fit under the bearing. Plastigage the final fit for conformation. That should be the only steps taken. Some other tricks are cross drilling and rounding the oil holes but that is another story. Modern journals extremely precise so if you do have a problem it is likely the shaft or the journal seat, do not scrape the bearing. Do not mess with the surface of the babbitt with scotchbrite, sand paper or any other abrasives. Bad contact under the bearing equals bad transfer of heat and thus high temperature. Did you check the relief valve?