odd marks on journals / bearings
odd marks on journals / bearings
(OP)
Hello Guys,
I've been sent through some photographs that show odd longitudinal marking on the journals and bearings
I suspect that they're caused by the journal roundness, but would appreciate any views (apologies for the quality of the photographs)
Thanks
Tony.


Clickable photographs back to 800x600 image
I've been sent through some photographs that show odd longitudinal marking on the journals and bearings
Thanks
Tony.


Clickable photographs back to 800x600 image





RE: odd marks on journals / bearings
RE: odd marks on journals / bearings
Thanks for replying. I wondered the same thing, although it uses a gas turbine as prime mover, there is no barring equipment attached to generator
Tony
RE: odd marks on journals / bearings
It is hard to tell, I assume that the top photo the bearing surface? What does the thrust look like?
My first thought was that it might be electrical discharge... but that would be fairly rare (although not impossible) on a gas turbine generator train. Have you had any electrical problems with the generator? If this is a generator bearing, are the bearing(s) properly insulated?
Might also be acid etching. Take a lube oil sample and get the TAN and water content checked.
How deep are the marks? can you feel them with your finger nail? Have a look with a magnifying glass. Do they look like pits with melted bottoms?
"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: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.
RE: odd marks on journals / bearings
Field service vibration analysis for several New England grinding houses often was in search of similar visual patterns. Often grinding wheel trim balancing improved the situation.
RE: odd marks on journals / bearings
http://en.wikipedia.org/wiki/Longitudinal
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RE: odd marks on journals / bearings
I see longitudinal (axial) marks on the bearing.
I see circumferential marks on both the bearing and the journal.
I suspect the original poster is talking about the circumferential marks since he said both bearing and journal.
I am under the impression that the comments about machining of the bearing are referring to the axial marks.
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RE: odd marks on journals / bearings
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RE: odd marks on journals / bearings
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RE: odd marks on journals / bearings
I guess it looks like 80 per rev on the journal, but more like it would be a 160 on the journal
RE: odd marks on journals / bearings
high vibration while the bearing is simply not turning or at rest.
RE: odd marks on journals / bearings
Do journal bearings also have rolls in them? I always thought that no. But these marks look like they were typical, although weak, EDM marks in a roller bearing.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: odd marks on journals / bearings
Just an oil filled clearance..
"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: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.
RE: odd marks on journals / bearings
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: odd marks on journals / bearings
If generator, does the generator have jacking oil?
Are the bearings insulated? Is either of them (hopefully not both) grounded? Or, should I ask are they both grounded or neither insulated?
IF it doesn't have jacking oil, is it a unit subject to lots of starts?
rmw
RE: odd marks on journals / bearings
Thanks for the all the replies
The shell and journal are the DE of a 5MW 4pole sych generator coupled to a Gearbox and then a GT - again I apologize for the poor quality photographs and especially having the shell photo upside down
We were called to check the generator bearing insulation and shell condition after 'somebody' looked into the g/box and saw bluing of the teeth which was attributed to low generator bearing IR ?, unfortunately that is all the detail I have on that discussion
but to answer some of the questions;
Hi Pete, Apologies for the confusion, I am discussing the marks that along the length (the long axis of the rotor) of the journal and shell, not the ones that are circumferential.
I haven't been to site, but the report back is that these indications cannot be felt; but please me tell more about acid etching in a bearing, this is new to me.
The unit dose not have jacking oil
but is not subject to a high number of starts, industrial generator which provides a base load to the plant.
and the bearing IR is good.
again thanks for the all the comments
Cheers
Tony.
RE: odd marks on journals / bearings
posibly the transfe of some teeth contact force on the journal. wouldn't the DE bearing be grounded?
RE: odd marks on journals / bearings
RE: odd marks on journals / bearings
"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: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.
RE: odd marks on journals / bearings
regards
John