How to change wind turbine gearbox oil based on oil properties and not on time intervall. Also about cupper corrosion with aging oil. Published at VGB Powertech, O&M conference in Hamburg march 2017

1. WHEN TO CHANGE
GBX OIL
VGB, Hamburg, 22nd of Mars 2017, Thomas Stalin

2. Confidentiality - Medium (C2)
Oil Exchange
• Oil should be changed based on Oil Quality Properties
- Instead of exchanging an oil based on yearly intervals
- Dialog with turbine manufacturers, gearbox suppliers and oil
companies
• After five years the oil sample should be sent in for full analyze
- If Quality is acceptable good, the oil should be used for another
1year/6 months.
- When Oil reaches end of life it should be tested every 6 months.

3. Cost Savings
• SRL and SOH
- 40 + 9 Vestas V90 2/1.8 MW with each 300 liters
- Oil bath temperature +55 degrees Celsius
- HSS bearing temperature 62 to 68 degrees Celsius
- >10 degrees lower operating temperature than 80 degrees =>2X life
- Cost of exchanging oil 5 000 Euro/turbine + production loss
- Cost of extra oil sampling 35 Euro + workmanship
- Total positive cash flow 245 000 Euro, during 20 years of operation
one oil exchange saved
• Offshore even larger savings
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4. Test of new and used oil
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Figure 5.2: Overall assessment normalized to one by dividing through the sum of the weighing coefficients.
All test data is included and multiplied with the weighing coefficient obtained above
Two of our most used synthetic oils; brown and green, showed stable tribological values
after 5 years. Mineral oil red showed decreased values after 3 years.Note: Lower is better.

5. Viscosity and aging
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C
C
H
H
H
H
C
C
Polyalphaolefin
Monomer
Dimer
Trimer
Polyalkylene glycol
Lifetime
Viscosity
Brown
Yellow
Red
Green
Viscosity nearly never shows bad values for synthetic oils after 5 years.

6. Test Results Used Oil Analysis, FUCHS Spain
Dark blue fresh oil:
No. 12-2494
RENOLIN UNISYN CLP 320
Green used Oil:
No. 12-2365
RENOLIN UNISYN CLP 320
Machine A 3.3
Weight loss very low: GFKT high !!
Excellent wear protection after 5 - 6 years !!
Micro Pitting short test: DGMK FZG (after 5 - 6 years)
GFKT – C 8,3/ 90 (16 h / load stage)
January 2017 - FS, Product Management Industrial Oils, W. Bock, R. Ambrosi; Research & Development Industrial Oils, Dr. J. Braun, T. Schuermann

7. Weight loss: 14 mg, 10 mg !!
Excellent wear protection after 8 years !!
January 2017 - FS, Product Management Industrial Oils, W. Bock, R. Ambrosi; Research & Development Industrial Oils, Dr. J. Braun, T. Schuermann
Test Results Used Oil Analysis, FUCHS Spain

8. Life Time
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Mineral oils, CLP-M: 2 years or 10.000 h
Synth. Ester („Bio“), CLP-E: 2 years or 10.000 h
Polyglycol, CLP-PG: 4 years or 20.000 h
Polyalphaolefins, CLP-PAO: 4 years or 20.000 h
Lifetime at an average oil sump temperature of 80 °C
(according to Flender)
Contaminations
(e.g. water, dirt, abrasion / wear products, acid gases, etc.) have a negative influence on the lifetime.
Lifetime depends on operating conditions

9. Oil Temperatures
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• Oil bath temperature +55 degrees
• High speed shaft bearing temperature 62 degrees
• Temperatures well below 70 degrees and 2X lifetime to be assumed
• Differs 5 degrees between turbines.

10. 2X lifetime = 10 degrees lower temperature
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11. Arrenius Rate Rule
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The Arrhenius equation, named for 19th-century Swedish
chemist Svante Arrhenius. In 1903, Arrhenius won a
Nobel Prize when he figured out the relationship between
temperature and most chemical reaction rates. Often
called the Arrhenius Rate Rule, it relates to the fact that
lubricants, once they've exceeded their base activation
temperature, will degrade (oxidize) twice as fast for every
10 degrees C (18 degrees F) increase in temperature

12. FTIR Analyses and TAN
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Infra red analyses can show if antioxidants are depleted.
If curve remarkably lower oil is aged.
Total Acid Number <2.0 mgKOH/g

13. Prediction of remaining lifetime, Additives
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Trend the decrease of additives.
Limit values is needed. Many times stable values.

14. Test Results Used Oil Analysis, FUCHS Spain
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325330,3330326,5331 330329328,4322,7317 312,7316,3
270
320
370
jul-10
ene-11
jul-11
ene-12
jul-12
ene-13
jul-13
ene-14
jul-14
ene-15
jul-15
ene-16
V40
35,035,035,035,234,735,335 36
33,734,3 34,234,4
24,0
34,0
44,0
jul-10
ene-11
jul-11
ene-12
jul-12
ene-13
jul-13
ene-14
jul-14
ene-15
jul-15
ene-16
V100
153151151 153
149 152151
156
147
153 154153
130
150
170
jul-10
ene-11
jul-11
ene-12
jul-12
ene-13
jul-13
ene-14
jul-14
ene-15
jul-15
ene-16
VI
0,750,70,720,770,77 0,80,83 0,76
0,9
0,75 0,780,7
0,4
0,9
1,4
1,9
jul-10
ene-11
jul-11
ene-12
jul-12
ene-13
jul-13
ene-14
jul-14
ene-15
jul-15
ene-16
Acidity number
8 7 8 10 5 12 5
201516 1822
0
50
100
jul-10
ene-11
jul-11
ene-12
jul-12
ene-13
jul-13
ene-14
jul-14
ene-15
jul-15
ene-16
Iron
7 - 8 years lifetime with good experience !!

15. Interpretation of results, Limit values
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Demand to get limit values at time of purchase
Note: It is not this oil that is used in the samples presented

16. Tar in offline filter
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17. Sludge formation
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18. Tar deposits, ICP Analyses
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High contents of metal Fe, Cu
and Additives P and Zn

19. Tar on brass surfaces
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20. Tar and clogged filters
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21. Brass corrosion
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Fast increasing Cu values

22. Cracking oil on heaters, low oil level
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Check oil level to avoid cracking. Look at sight glasses.
Low oil level destroys the oil and clogs filters.

23. General observatíon
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A) High cupper values 20 to 80 ppm rapidly increasing over
one year.
B) Tar products as precipitated sludge found in offline filter
and on gearbox walls
C) Black large tar particles found in the inline filter and at
other places in the gearbox
D) Black tar on brass casings in the bearings
E) Corrosion of the brass cages
F) Black oil
Found on aged oil +5 years and <5% of samples
No failed gearboxes observed

24. Recommendation
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• Take sample every 6 months when oil older than 5 years
• Look on tar inside gearbox, filters, sight glasses
• Be observant
• If Cu level >5 ppm take new sample within 3 months
• If Cu level >10 ppm prepare for oil exchange
• Use flush oil
• Unsolved questions
• Are tar on brass disappearing? After new fill.
• Is brass corrosion on brass cages lowered by early exchange of oil
• Endoscopy investigations needed
• Is this a general problem with more oil formulas?

25. More information
• Can be found in the report :
- Tar and brass corrosion problems
If you have any problems or notice this phenomena
Please contact Operational Support, Thomas Stalin.
Thomas.stalin@vattenfall.com
Thanks for your Cooperation! This work was possible with combined
information from several sites.
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