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9 comments
Anonymous Poster

Windmill Gear Box Oil

03/08/2010 6:22 AM

Hello everyone, We have just tested the gearbox oil of a wind mill. when comparing the viscosity @ 40C, we found out that the viscosity has increased from the previous year testing value. Is this normal? i think that the viscosity must decrease rite? Can you please suggest me what could be the reason for that. Please help me out. Thanks in advance

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Associate

Join Date: Mar 2010
Posts: 47
#1

Re: Gear Box Oil of a windmill

03/08/2010 6:58 AM

Modern lube oils are a sophisticated product of many years of research and development. Your gear manufacturer selected this particular oil for a reason. So why not consult the gear manufacturer on this? Also, tinkering with the recommended lubricants will surely void any warranties you might have.

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Guru
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#4
In reply to #1

Re: Gear Box Oil of a windmill

03/08/2010 8:53 AM

There seems to be an unwritten law that people who come here to ask for free help/advice/instructions/work problems never consult with the manufacturer of the equipment they are having problems with.

They also never bother to do any research prior to coming here and asking questions like, "what's a transmitter?"

Cheers.

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Anonymous Poster
#2

Re: Gear Box Oil of a Windmill

03/08/2010 8:13 AM

Increased means how much?

Some increase/ decrease are normal phenomenon.

Go for a complete oil check-up and you will knw whether the oil is still good or not.

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Anonymous Poster
#3
In reply to #2

Re: Gear Box Oil of a Windmill

03/08/2010 8:16 AM

Will this help?

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#5

Re: Windmill Gear Box Oil

03/08/2010 11:05 PM

The viscosity of your oil changes when the chemical substance changes. Viscosity measurement itself is done according a lot of different methods. I advise to have the oil analyzed. Did you notice discoloring too? Wear and tear can also increase the viscosity. Therefor it could help if you find what added to the increase out of a chemical analysis.

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Associate

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Location: Germany, City: Hannover
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#6

Re: Windmill Gear Box Oil

03/09/2010 4:16 AM

Of course, the oil analyst should be able to explain the common viscosity versus using time behaviour for the specific class of oil. However, the common situation for lubricants is that they exist from hydrocarbon molecules of different lenght(size). The oil viscosity not at least is a result how about the relationship of smaller and bigger molecules. When the oil getting warmed up a kind of evaporation takes place. The smaller fractions more easy can be evaporated than the bigger molecules. Therfore it is a common experience that oil viscosity is rising a little bit with time.

Against this general trend oil molecules might be (thermally or mechanically) cracked - depending on the stress the lubricated locations are creating to the molecules (and temperature at those places). This may lead to an increasing number of smaller molecules and consequently more fluidity (lower viscosity) of the oil.

Quite another point of influence are viscosity effecting additives (typical for engine oils > multi grade viscosity for instance). For those lubricants the condition of the additives is much important for the lubricants effective viscosity. Generally additives are subject to "wear", getting degenerated with time.

How it works (and if it is a problem) for an individual machine under the line hardly can be forecast. It should be sufficient to follow up the machine makers recommendation.

By the way: the whole matter might be different for sythetic lubricants and/or hydrocracked lubricants because for those fluids the molecule lenght can be customised within a wide degree, thus the mass of molecules are of much more uniform size than valid for mineral oil based fractions.

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Participant

Join Date: Feb 2010
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#7

Re: Windmill Gear Box Oil

03/09/2010 10:48 AM

Another question you should be asking is, "has any lubricant been added during the year", if that lubricant was of a different type, grade, or viscosity that could be affecting the viscosity you are measuring now.

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Associate

Join Date: Apr 2008
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#8

Re: Windmill Gear Box Oil

03/10/2010 7:45 PM

The viscosity of the oil increases with the oxidation represented with Total Acid Number TAN increases. TAN is an equivalent of the oxidation of the oil and it is measured in mgKOH/g. An increase of about 1 point in the TAN may represent an increase of 20% in viscosity, a range that is consider of high oxidation and therefore a limit where you should think in changing the oil. Variation in method of cinematic viscosity measurement may vary up to 3%. Look at the TAN values of last year and see if there is an increase. Ask your oil supplier what is the TAN value for fresh oil. If there is, then it might be related to the increase in viscosity. A change in viscosity inbetween 10% does not require to take any action more than watch it. Oxidation may be triggered by excessive load and temperature. Also the content of Fe particles in the oil, that are catalytic for oil oxidation. If the viscosity change is less than +/- 10%, no action needed; between 10 and 20%: ATTENTION something is developing. watch closely. Over 20%: ACTION: change the oil. If the TAN increases 0.5mg/KOH/g may be OK, between 0.5 to 1 mgKOH/g ATTENTION, oil is oxidizing, watch closely. Over 1 mgKOH/g ACTION: change the oil. hope this helps.

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Participant

Join Date: Jul 2012
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#9

Re: Windmill Gear Box Oil

08/07/2012 11:46 AM

HI

If the viscosity has changed then the oil has degraded. You must replace the oil. Ask your oil supplier what are the limits for viscosity variation allowed. If it is beyond allowable limits then the oil is not suitable. There are also other parameters that can tell you of the oil has degraded or not. Check for TAN (total Acid Number). If TAN has increased to a level that classifies your oil as degraded then you must replace the oil. Get the oil checked by a qualified lab. They will guide you.

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