quote:[Nailen (2nd page of pdf):]In assembling the bearing, then, the essential step is what’s sometimes called “blueing and scraping.” The make sure the babbit contacts the journal as uniformly as possible throughout the contact angle of Figure 2 calls for a fitting procedure like that given in the accompanying box [Figure 15].
quote:[Figure 15b caption, 2nd page of pdf]Final fitting accounts for the difference in radius between the two curved surfaces, leading to the more uniformly distributed contact at (b).”
quote:EPRI18.104.22.168 Journal Bearings. Minor jounral bearing repair, too can be accomplished in the field using hand tools. ... Full, circular jounral bearings can be repaired in the field using a wide blade hand scraper, 0.0012 inch (30 micron) Mylar film, and Bear Cloth or Scotchbrite. Care must be used not to remove too much material thus changing the dynamics of the bearing. The contact pattern of the bearing to the shaft can be obtained by applying Prussion blue to the shaft, restin gthe bearing on the shaft, and visually inspecting the contact areas. Scrape the areas that show contact with the shaft until an even contact pattern is achieved....Elliptical, three-lobe or lemon bore jounral bearings are more difficult to refinish using this procedure. Extreme care must be taken not to change the special configurations o fthe bearing bore. Normally these repairs are best done by the original manufacturer.Pivoted-shoe journal bearings are the most difficult to repair in the field. Normally the radial thickness of the shoe is held to a 0.0005 inch (13 micron) tolerance. For this reason, only a minimal amount of material can be removed. Minor scratches should be treated with nothing more abrasive than Bear Cloth or Scotchbrite. Field patching of pivoted shoe jounral shoes is not recommended, as it is difficult to blend the patched areas back to the original contour without a proper mandrel.
quote:EASA:Fitting. Fitting a new sleeve bearing is an important part of the assembly process. Install the bottom half of each bearing and then spin the rotor with the bearing journal dry (or with a small amount of oil wiped onto the journal) to establish a wear pattern quickly. Thrust the shaft axially several times while it rotates. Scraping is generally done using a babbitt knife or bearing scraper, followed by polishing with a Scotchbrite pad.The bearing should be thoroughly cleaned after each fitting before being rolled back in for further fitting. The objective is a minimum of 60% contact centered in the bottom half, with no contact at the corners or top.
quote:EPRI:9.4.2 Sleeve and Tilting Pad Bearings22.214.171.124 Minor babbitt scratches shall be repaired by polishing the damaged surfaces witha polishing pad such as Scotch-brite cloth.
quote:Today, these items are taken care of by the design and manufacturing of the bearing, not by trial and error scrapping.
quote:EPRI supports the US power industry which probably has more industrial sleeve bearing machines than any industry other in the US. EASA sets the standard for motor repair practices (for customers from all industries) across the US.
quote:Design locates the bearing on concentric center-lines with other machine components on concentric center-lines.
quote:The motor in question; is it of a poor design? Can it be improved? Can engineering correct the problem?
quote:It leads me to a question: Of those who perform blue test during bearing replacement, what fraction do you find fails the check?
quote:Bill wrote:Say one scrapes a bearing wth measurable (significant) material removal and this results in the best vibration ever seen or not seen, 0. Did you measure the geometry of the bearing so that this could be repeated, on purpose that is? No 3-d measurements? The boss tells you to do it again with motor B.
quote:J. Heber wrote:Scraping is one of the final checks in equipment assembly along with tilt and twist
quote:J. Heber wroteself aligning bearings (some type of spherical seating) scraping is rarely needed. ....As for comparing a motor bearing to a generator bearing, kinda apples and oranges...worked on a lot of 100Mw to 550Mw machines and all had spherical seating can't remember ever working on a motor with spherical seats, probably did and don't remember it
quote:Dan wrote:The folks at navsea apparently never had to concern themselves with this..
quote:I wonder how much a fat motor rotor bows it's shaft, and could create edge loading in beautifully colinear/concentrically machined bearings. I think including features to make inserts self aligning are smart, not a cover up for "poor" machining.