Shaft Centerline
Shaft Centerline
(OP)
I want to know how I can interprete a Shaft Centerline Graphic?
I find one in a report for a Generator with 40MW at Geotermal Power Station
I find one in a report for a Generator with 40MW at Geotermal Power Station





RE: Shaft Centerline
Can you provide us with a picture of what you are trying to interpret?
RE: Shaft Centerline
RE: Shaft Centerline
Cheers
Greg Locock
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RE: Shaft Centerline
GregLocock correct me if I'm wrong but we used to call this a search for rotor's magnetic center.
RE: Shaft Centerline
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Shaft Centerline
The phrase "search for rotor's magnetic center. " applies in axial direction, but has no business being applied to the radial direction imo: magnetic force in radial direction tends to pull the rotor further off-center. (acts like a negative spring constant)
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RE: Shaft Centerline
but it looks like a calculation of the "center of shaft" taken from X/Y proximity probes. that is the center of the vibration orbit is calculated to represent the position of the rotatating shaft in its bearing. I would guess the circle shown represents the bearing clearances of 0.014"V X 0.018"H of a 9" diameter shaft.
as the unit was brought to speed and an oil wedge was developed the shaft was lifted 0.005" and pushed sligthly to the right. the expected bearing loading could be derived my knowing realitive bearing rise on the others.
I'm not a real fan of promity probe predictive anologies, nor any experance, but that rise could indicate a slightly under loaded alignment of that bearing, or an oversized bearing. my gut is a 0.003" rise would be a good loading
RE: Shaft Centerline
byrdj I agree with you.
And now I have more questions , Is it this motion common in a shaft with a journal bearing during start up?. Is possible that the shaft may have a mis alignment?
RE: Shaft Centerline
So I would want to refer back to more basic information to determine if this is a "Problem"
I'll assume this is the inboard bearing, since bearing loading there has beeen a problem with many units.
Is there an increase vibration
what are the bearing temps (metal and oil drain) for this bearing compared to the others, especially the inboard turbine (assuming 4 bearing machine)
AND was there recent maintance where a bearing elevation change made.
I interput the curve as
the little sqibble at lower 1/3 was at critical, and the knee at the upper 1/3 is when oil wedge hight increased to a point there was reduce horizonal force and the rotor came back to horizonal center line. but I do not see a sqibble at top end, so I would assume vibration was acceptable.
I would also assume since there is not a very gross sqibble at the top, the bearing loading is notlessen to a value that would cause oil whip.
Now if this was just data from a run up to speed, you might expect the loading to increase as the support pedistal grows
RE: Shaft Centerline
very interesting, thanks
RE: Shaft Centerline
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Shaft Centerline
Johnny Pellin
RE: Shaft Centerline
Johnny Pellin
RE: Shaft Centerline