This document discusses lessons learned from condition monitoring of wind turbine gearboxes regarding effective contamination control. It shows that clean oil is crucial for reducing wear and extending gearbox life. Condition monitoring has validated that offline and inline filtration systems best maintain low dirt levels. It also demonstrates that removing offline filters allows oil to get dirtier and that inline filters release particles during cold starts. The document concludes clean oil must be maintained throughout a gearbox's lifecycle and that submicron particle control via nanofiltration is important.

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BRIGHT IDEAS
The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 1
2011 Wind Turbine Condition Monitoring Workshop
The Road Map to Effective Contamination Control
in Wind Turbines:
Lessons From Condition Monitoring
Justin Stover
C.C. Jensen

2. CLEANOIL
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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 2
Wind Turbine Manufacturer
Collaborating Partners
(Design Offices)
Gearbox Manufacturers /
Lubrication Systems
Our Experience… >70,000 Wind Turbines

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 3
0
2
4
6
8
10
12
14
0 10 20 30 40
10
6
rotations
MacPherson Graph 1
Level of Filtration in Microns
The graph is based on a test
with 10 bearings. The lubricant
was contaminated by wear
from gearboxes.
The Importance of Clean Oil
Life Extension!

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 4
The Importance of Clean Oil
Concluding Remarks from Bo O. Jacobson in his book
Rheology and Elastohydrodynamic Lubrication 2

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 5
Gearbox Flushing and Condition Monitoring
Filter System with Built In
Particle Counter
Filter system
validates that oil is
clean during run-in
and factory tests3

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring
2/3 load
TIME (Minutes)
Static Dynamic 1/3 load 100% load
TIME (Minutes)
Page 6
ISOCODE
(OilCleanliness)
Target :
ISO Code ≤
17 / 15 / 11

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 7
What Happens Before a Breakdown?

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 8
What Initiated the Breakdown?
December 25th - 26th
Wear particles increase from
1,000 to more than 18,000
particles/ml (21 µm) at Start Up
(Full Load & Low Temperature)

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 9
Wear Particles Found
During Service Stop
Micropitting and
Macropitting Observed
On Gears

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 10
Many wear particles found on the
filter’s surface
Magnification shows metal wear
particles (70% of filter’s surface
covered)

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 11
Offline Filter w/ Particle Counter Retrofit
2.0 MW Turbine

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 12
What Happens If The Offline Filter Insert Is Removed?
1.5 MW Turbine with Offline Filter
and Particle Counter Installed 2006
Offline Filter Insert Removed 2009
Turbine Originally Equipped with a
10 Micron Inline Filter and 3 Micron Bypass Filter

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Overview: Offline Filter Insert Removed

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 14
Offline Filter Insert Removed
4 Micron Particles

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Test Bench: 10 Micron Fiberglass Inline Filter

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page ‹#›

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What Happens to the Particles
Released by the Inline Filter?
Red Particles Released
By Inline Filter Captured
by Offline Filter

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What Happens to Inline Filter Performance when the
Oil is Suddenly Cooled?

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Nano-Filtration
Is It Important To Remove Submicron Particles?
Particle Size Distribution
12, 10, 5, 3, 2, 1, 0.8, 0.6, 0.4, 0.2 Micron
Top Row: Red Iron Oxide Test Dust
Bottom Row: Actual Particles From Used Gear Oil

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page ‹#›

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Removal of Submicron Particles
2.0 MW Turbines Retrofitted with Offline Filter

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Removal of Submicron Particles
1.5 MW Turbines Retrofitted with Offline Filter
May (Retrofit)
MPC 39
July (3 Months)
29 MPC

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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring Page 23
1. The importance of clean oil in gearboxes and bearings has been well
documented for decades
2. Clean oil must be a focus throughout the lifecycle of a gearbox – from the
cradle to the grave
3. Condition Monitoring validates that a filtration scheme that includes Inline and
Offline Filters keeps the dirt content as low as possible and this ‘always pays’
off in less wear and tear, greater reliability and longer lifetime
4. Condition Monitoring proves that when an offline filter is removed the oil gets
dirtier
5. Condition Monitoring confirms that Inline Filters release particles during cold
starts and their inability to maintain cleanliness as the temperature decreases
6. Submicron particles must also be controlled with nano-filtration and monitored
with analyses such as SEM-EDS and MPC .
CONCLUSIONS

24. CLEANOIL
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The Road Map to Effective Contamination Control in Wind Turbines: Lessons From Condition Monitoring
1. Sayles, R. and Macpherson, P. (1982). Influence of Wear Debris on
Rolling Contact Fatigue. Rolling Contact Fatigue of Bearing Steels.
ASTM STP 771. pp. 255-274.
2. Jacobson, Bo O. (1991). Rheology and Elastohydrodynamic
Lubrication. Published by Elsevier Science Ltd p. 351
3. Errichello, R. and Muller, J. (2002). Oil Cleanliness in Wind Turbine
Gearboxes. Machinery Lubrication, July/August, 2002, pp. 34-40.
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REFERENCES