2-Pole induction large motor.Babbit bearings.
Journal area looks slightly bad.To assess the need for repair of journal please tell me the allowable variation of journal diameter(ovality or out of roundness) and allowablejournal taper.Original diameter of journal =110mm.Journal length=130mm.

I don't have an out-of-round spec handy.

I do know that EASA AR-100 (1996) section 9.6 specifies diametrical clearance for sleeve bearings by shaft diameter. For your shaft 110mm (between 4 and 4"), the diamaterical clearance range is 0.007" - 0.009" (0.175mm to 0.225mm).

I can't recall ever seeing a spec on taper or ovality on a shaft, but I wouldn't expect to see any noticeable taper or out of round. One would think the shaft diameter should vary by more than a small fraction of the clearance (perhaps 0.001"?).

One thing for sure, if you can't get a good blue check or dry-rub check showing 80% contact, then the shaft needs work. Also you might check for shaft bow? Do you know the origin of the out of round? Severe wear?

When doing prox probe work, the allowable runout radially from the API spec is .45 mils on the surface the probe is reading. That would be a sum of the journal runout and the probe surface runout both electrically and mechanically. Not the question you asked, but should give you a ball park to work in. I would guess this number also applies to the taper as well, since it is a change in the diameter.

I have never seen a taper tolerance chart for a sleeve bearing journal. Most of our machinists said no taper after polishing. Which I convert to a couple or three ten thousandths. There are out of round tables in one of the SKF books for rolling bearing journals. Hope this will help.

Sean

I believe API670 Spec for vibration calls for prox probe surface with combined electrical plus mechanical runout to not exceed 25% of allowed peak to peak vibration amplitude or 0.25 mils, whichever is greater.

Thanks for the correction Dave. The motor I worked on was .45 mils. I didn't realize it was a percentage of anything. Thanks again.

Sean