problem on high temperatures on the generator bearings 1

[181273]

ok, i got two hydro generators sets,the data are:
RPM: 1000
Turbine: Francis
horizontal
type of the bearings: zoellern
generator: INDAR
weight of the rotor: 2500 kg
this generator is a francis turbine with a horizontal generator with two slide bearings,(zoellern bearings), one on the non drive end that is only a radial one, and in the drive end we´ll find a bearing with radial, and thrust bearings against the generator and against the turbine... the weight of the turbine is 200 kg, and is at a distance of 278 mm of the end of the drive end bearing... and a freewheel with dimensions: 90*1550 and a weight of 3000 kg near the non drive end side, at a distance of 70 mm....
I hope all of you will understand the way it´s mounted, the generator have 4 feets....
the bearings have external feed of oil that goes to a exchanger...to mantain the temperature of the input oil between 40 and 45 º C, we´d mesure exactly the flow of oil and it´s right...
We start up the hydro unit and on low speed, temperatures remain stables on normal values, but when we go to 1000 rpm 100 % of the speed, in ten minutes the temperatures go up very speedly, 30º C in ten minutes, but the temperature on the oil remain low, 35 º C, then we stop the machine cause we are still without load....
The force of the shaft against the turbine thrust bearing is 20 kn with no load, and 33 kn with full load but we had ask to the bearing manufacturer one thrust bearing for a load of 45 Kn, i don´t understand why this so high value of temperature.... when we have to be safe enough....
This freewheel have a excentricity on axial way of 0,6 mm when we see it...i think this could be a cause for the high values of temperature.... cause the temperatures are higher than in the factory, (in factory is only radial text cause we can´t put axial force into the generator), and the diference from factory is the presence of turbine, the freewheel and way it was mounted on the site, we didn´t supervise it.... what do you think? any ideas?? i could give you the values you need...
is it posible a problem of plumb in the erections process?? thanks in advance, i´m really worried about this, and next monday we´ll do some proofs.... and this occurs in the two hidro units....

 

[itsmoked]

Both units exhibit this same behavior?

Do others exist that are the same that this doesn't occur on?

What temperature are you talking about, since you say the oil stays cool?

Where exactly is the sensor you are referring to?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[181273]

yes, this is specially done units...not standard, and the problem is exactly on the two units... and the hottest sensor is on the thrust bearing on the side of the turbine, and the temperature is 85 ºC, with a load of 20Kn coming from the turbine, ( I can´t measure it, but the graphics says it)...and the full load is 33 Kn for this is expected to see it rise, and in other way, the temperature is not stable,it´s rising very fast
thanks

 

[electricpete]

Are the high temperatures on just one bearing or on multiple bearings?

Are the high temperatures on thrust bearings or radial bearings?

If on thrust bearings, what type of coupling do you have? Rigid or gear?

What is a freewheel?

Do you see any unusual vibration?

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[ssn596]

The first thing I would do is check your temperature indicators. How do you know they are right? I freely admit you HAVE to trust them until you have proven them wrong

Dan Bentler

 

[HCBFlash]

As Dan points out, you must verify that your temperature sensors are accurate, and that they contact either a surface or flow of lubricant-coolant that accurately reflects temperatures of the bearing rollers and races themselves.

If the thrust bearing elements are in fact attaining too high a temperature, closely inspect them visually, and be certain that the roller cages are intact, properly positioned, and not clogged with any debris.

The eccentricity you mention may be unacceptable, but a bearing mounting with a well chosen resiliency (and dampening) will tolerate it within limits. I am unclear about what you mean though when you say the eccentricity is "axial", so I am thinking that you in fact mean radial. Of course any eccentricity caused movement must be less than the combined clearances and fluid cushion produced by the oil.

Of course all these tolerances and clearances affect the ideal viscosity of your coolant-lubricant fluid. If your oil is too thin it will not produce the fluid cushion needed, although a higher viscosity may not get to the points of contact because of flow characteristics. If the temperature of a rolling thrust bearing rises noticeably when the rotational speed increases it would certainly make me suspect the lubricants flow. Is the thrust bearing submerged in oil completely? If it is not lubricated by submersion then it must be lubricated by a uniform flow of adequate volume.

Please let us all know how this works out for you! and don't forget faq731-376

 

[HCBFlash]

I meant to include this link in my posting:

http://www.fag.com/mediaDB/rel PubLanguage/114073/PubFile/-/-/-/schaeffler_internet/WL_82102_2_de_en

(if the link fails) it is intended to point to a pdf brochure from FAG on their website. It thoroughly deals with causes of bearing failures, and the introductory photo is of a worn roller-thrust bearing.

 

[ScottyUK]

Nice link HCBFlash.


----------------------------------

Sometimes I wake up Grumpy.
Other times I just let her sleep!

 

[rotman]

HCBFlash: the generators have sleeve bearings.

181273: Are the DE bearings of ZFZLA type (with round tilting thrust pads)? These bearings have separate oil connections for radial part and for both axial (thrust) parts. Is the oil circulation OK, esp. for the thrust parts?