grease sampling and analysis of main and blade bearings - stle 2015 presentation
TRANSCRIPT
Grease Sampling and Analysis of Wind Blade and Main Bearings
Rich Wurzbach
MRG Labs
York, Pennsylvania, USA
Bearing Failure Impact
• Main/Blade bearings are large, slow
• Unusual and unpredictable loading patterns
• Slow speeds make vibration analysisdiagnosis difficult for early signs of bearing wear, root-causes
• Single bearing failure can cost~$200,000 for crane, downtime, replacment
Grease Sampling
• Grease sampling historically difficult
• Capturing live-zone samples presents challenge
• Typical large sample sizes required difficult to obtain
• ASTM D7718 presents new tools, methods
• Research projects at Electric Power ResearchInstitute (EPRI) and Danish Offshore Wind Research Team establish strategies and tools
Sampler Development• EPRI project established need for
active and passive sampling devices
• Capture purged samples usingmachine threads
• Insert sampling device into machine to core sample at select depth
• Test stands used to validate efficiencyof capturing live zone samples
New Challenges in Grease Sampling
• Blade bearing access limited
• Access opening often smaller than sampler diameter
• Blade bearing research leads to slim version, dia. drops from 0.50in (13mm) to 0.28in (7mm)
Main Bearing Sampling
• Grease flow dependent on temperature, bearing movement
• Grease Thief & T-handle used to capture flowing grease
• Revised T-handle developed for Denmark Off-shore Wind Research Project
Blade Bearing Sampling• Three Blade Bearings per wind turbine• Can be double-row ball or tapered roller bearings• Grease is typically delivered through autoluber lines• Expelled grease captured in bellows or containers• Containers can be harvested for sampling• Slim sampler may be used to obtain live zone sampler
through drain line
Other Sampling Locations
• Generator bearings for install of Grease Thief
• Use of T-handle to position for sample in active zone
• Sampling generator bearings has discovered inoperable auto-lubersand winding insulation damage captured in grease
Types of Grease Analysis
• Performance– Tribological, oxidation resistance, etc.
• Quality Control– Batch conformation, Penetration value
• Failure Analysis
• In-service testing– Equipment wear condition
– Contamination of grease
– Consistency changes
– Oxidation condition
10
Analysis Techniques
Sample is received. fdM+ is runDie extrusion is performed and substrate is made
Two strips are used to make
a dilution to run RDE/ICP.
One Strip is used
for FT-IR.
One Strip is Dissolved in Green
RULER solution to run RULER.
Die extrusion and sample preparation
•Extrusion of the grease at varying
rates
•Load cell response used to
measure flow and shear
characteristics of grease
•Compared to new fresh grease
13
Optical Spectroscopy
•Optical spectroscopy quantifies the appearance of grease
•Grease aging, contaminants, mixtures, chemometrics
16
17
The 100x ferrogram is seen in white reflected and green transmitted light, to show normal presentation of entry deposit particulate.
The 100x ferrogram is taken in
crossed polarized light. Resulting
illuminated particles are crystalline
debris, typically indicative or dirt or
other abrasive contaminants.
Analytical Ferrography
• Fundamental Sampling Principle–Using the Grease Thief
• Representative sampling–Thorough characterization of the heterogeneity of grease in main
bearings
Wind Turbine grease sampling & analysis
Wind Main Bearing grease sampling
• 2-year project conducted with DONG Energy and Vattenfall, two largest offshore wind operators in the world
• Dr. Kim Esbensen, internationally recognized expert in Theory of Sampling (TOS), Denmark
• Systematic evaluation of grease heterogeneity, sampling methodology, and analysis validity and repeatability for wind turbine main bearings in on-shore and off-shore applications
• Results published at OilDoc, LUBMAT, and AWEA
• Findings: Samples cored by T-handle from drain access equally representative to disassembly and extraction
• Analysis of iron (Fe) using a analytical method which only detects particles < 6 µm
• Note, this method gives iron concentration from 50 to 170 ppm
› Analysis of ALL ferrous magnetic particles irrespective of size (Hall-technique).
› Note, this method gives iron concentration from 30.000 to 40.000 ppm
Ferrous debris method comparison
Comparison of ferrous levels from different sampling procedures
“SWP” is Siemens Work Practice: standard method for grease
sampling of disassembled bearing in the shop
Trends of moisture in bearings
0
100
200
300
400
500
600
700
800
900
Mo
istu
re, p
pm
314 Front
314 Rear
319 Front
319 Rear
Grease type: SKF LGWM1
• Thickener: Li
• Base oil: Mineral oil
• Viscosity @ 40C: 200 cSt
• NLGI-class: 1
Blade Bearing Sampling Research
• Current project underway with DONG Energy and Statkraft, offshore wind operators in northern Europe
• Development of specialized sampling tools to access grease through drain holes
• Samples taken sequentially from catch drains to asses time-resolved trends in grease/wear condition
Blade Bearing Wear• Ferrous debris levels typically higher than main bearings• Different installations have higher or lower typical values• May be due to environment, load or maintenance practices
Blade Bearing Consistency• Hardening or softening a function of working, environment,
contaminants
• Criteria is enveloped around new grease values
• Most samples are satisfactory, some clear outliers
Blade Bearing Cu Levels• Cu primarily cage material, but could be a contaminant
• Levels normally very low, low trigger criteria for further test
• Analytical ferrography can determine type, size and source
Outlier Cu and Al with mixing
• Cu levels typically <10ppm, this sample >100ppm
• Very high Al values related to grease thickener
• RULER additives and FTIR confirm grease mixing, possible lowviscosity protection for cage sliding, or additive corrosion
Conclusions
• Grease sampling methods well established for wind applications
• ASTM D7718 and AWEA Recommended Practices outline tools and techniques for representative samples
• Research in main bearing and pitch bearing grease analysis support methodology
• Total cost per sample <$200, unexpected loss of single bearing across fleet cost $200,000
• Early detection of abnormal conditions can be sometimes rectified uptower (grease flushing, relubrication, etc) substantially reducing the event cost and risk of failure