Grease sampling and analysis overview
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The document discusses the importance of grease sampling and analysis for improving equipment reliability and preventing failures in grease-lubricated machinery. It outlines steps for establishing an effective grease analysis program, methodologies for sampling, and the development of standards for grease sampling and analysis. Various case studies and examples illustrate how proper grease sampling can lead to early detection of issues, better maintenance practices, and enhanced machine life.
Grease sampling and analysis overview
- 1. IMPROVING EQUIPMENT RELIABILITY WITH PROPER GREASE SAMPLING AND ANALYSIS A Presentation from Rich Wurzbach, MRG Labs
- 2. WHY GREASE ANALYSIS? • Some critical machines are grease lubricated, and they can fail • Prior to failure, information in present in the grease that can lead to early detection • Root-cause determination is possible in analyzing for contaminants, the wrong or mixed greases, or wear modes such as fretting, fatigue, abrasive and adhesive wear • Not all new greases are clean: you can’t filter a grease so initial cleanliness from the grease gun or auto-luber is paramount to long machine life
- 3. HOW CAN I ESTABLISH AN EFFECTIVE GREASE ANALYSIS PROGRAM? • Step 1: Select appropriate equipment for inclusion • Step 2: Evaluate grease flow in the machine to determine “live zone” target • Step 3: Select appropriate equipment for obtaining a representative sample • Step 4: Establish a Standard Operating Procedure for grease sampling methodology and conditions • Step 5: Create an appropriate and cost-effective test slate that is right-sized for the individual component • Step 6: Generate a sampling schedule with optimized frequencies • Step 7: Review analysis results for systemic issues and implement pro-active measures to improve reliability and life
- 4. GREASE SAMPLING • Difficult challenges in gathering representative grease samples • Sampling from robots • Wind turbine samples (main, blade, generator, etc.) • Electric motors • Pillow block bearings • Motor Operated Valves (MOVs and valve stems) • Slewing bearings and other mining applications • Low-cost analysis solutions • Case Studies
- 5. GREASE IS DIFFERENT • Viscosity is the property of oil that sets the lubricating film, and dictates how oil flows • Grease is an oil (base + additives) with a thickener • Grease behavior is non-Newtonian; it is designed to stay put in the machine • Dynamically, grease will flow, but only very close to the bearing/gear • Sampling and analysis techniques for oil are inadequate for grease
- 6. ASTM D7718 STANDARD DEVELOPMENT • Developed in 2009 and published in 2011 • Incorporation of grease sampling research (Danish Wind Industry, Electric Power Research Institute) • Inclusion of historical methods for sampling with considerations and limitations • Failed component sampling, care in obtaining sample or multiple samples • Use of tubing, adequacy of suction alone, possibility of peripheral grease sampling • Inclusion of new technologies for active and passive sampling rev 0 022817
- 7. GREASE THIEF SAMPLERS • Maintain purge function with little/no backpressure for drain applications • Allow relief of grease if sampler fills • Use of “Handle” tools to set depth • Designed to optimize the analysis process
- 8. GREASE THIEF – THE STANDARD • “Effective Grease Practices” published by Electric Power Research Institute; MOV Gearbox sampling and analysis studies • DONG Energy and Vattenfall Main Bearing research project 2011-2013; DONG and Statkraft Blade Bearing 2014-2016 • ASTM D7718: Standard for sampling greases from inservice equipment • ASTM D7918: Standard method for inservice grease analysis by Die Extrusion, “Integrated Tester” method for 6 tests • AWEA (American Wind Energy Association) published “Recommended Practices 812-815” for grease sampling and analysis with the Grease Thief
- 9. Pillow Block Electric Motor Grease Thief SlimTM MOV Gearbox Robot Kit Wind Turbine
- 10. ROBOT SAMPLING • Industrial robots are often 6- axis gearboxes, grease or oil lubricated • Grease lubricated robots can be evaluated for wear, contaminants, and grease breakdown • Transitioning from time- based grease purges to condition based can save $$$
- 11. DRAINS: J1, J2, J3 1. Operate and shut off power. 2. Lock Out/Tag Out 3. Remove drain plug
- 12. DRAINS: J1, J2, J3 4. Thread adapter into gearbox drain if necessary. 5. Thread Grease Thief into drain hole. 6. Pull plunger handle to fill Grease Thief with sample. 7. Cap Grease Thief.
- 13. DRAINS: J1, J2, J3 7. Some locations utilize syringe with extension tubing. 8. Robot grease is a special case where it is so fluid, a syringe and tubing can work. 9. Place Grease Thief in labeled shipping tube. 10.Mail to MRG Labs for analysis or process on-site. 11.Grease Thief requires no further handling; ready to analyze per ASTM standard.
- 14. DRAINS J4, J5, J6 1. Position robot with drains facing downward if possible and shut power off. 2. Lock Out/Tag Out 3. Remove Zerk fitting. 4. Thread provided plastic syringe into the threaded Zerk hole.
- 15. DRAINS J4, J5, J6 5. Place tip of syringe in Grease Thief and fill with grease by withdrawing plunger. 6. Inject grease to fill Grease Thief. 7. Cap Grease Thief and place in shipping tube. 8. Mail to MRG Labs for analysis or process on-site. 9. Grease Thief requires no further handling; ready to analyze per ASTM recommendations.
- 16. WIND TURBINE 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 • Project demonstrated representative grease taken without requiring disassembly or space between rollers
- 17. BLADE BEARING SAMPLING • Can be double-row ball or tapered roller bearings • Grease is typically delivered through autoluber lines or manually pumped • Expelled grease captured in bellows or containers in some cases • Containers can be harvested for sampling • Slim sampler may be used to obtain live zone samples through drain hole • New method for autoluber line purging – MRG Labs Technical Bulletin 17-001
- 18. GREASE THIEF SLIM FOR SMALL OPENINGS • 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)
- 19. ELECTRIC MOTOR SAMPLING • Grease Thief can be threaded into drain in place of a plug • QC to deliver 1-5 psi relief pressure to ensure purging • Active methods may be required; T-handle or GT Slim • Mixing is a common failure mechanism, causing softening and separation of grease and allowing to migrate to windings • Periodic grease sampling can detect such issues early; hardened grease can be a source of energy losses
- 20. PILLOW BLOCK BEARINGS • Can be critical applications: fan and AHU in bio-medical research or pharmaceutical manufacturing • Grease mixing and contaminants can be monitored, along with wear levels and causes • Early detection and purging can avoid failure when deficiencies are found
- 21. MOTOR OPERATED VALVE GEARBOX • Sampling with T-handle through access plugs • Determining optimal grease life and gear wear condition • “Stinger probe” version of Grease Thief ensures that only grease near the gear is sampled, not peripheral grease not active in lubrication
- 22. • Enhanced analysis methods developed • Four types of grease analysis: wear, contaminant, consistency and oxidation • Evaluate reliability of machine and grease to perform function • Look for signs of incompatible mixing • Pinpointing root causes for correction • Perform analysis cost-effectively utilizing sampling geometry GREASE ANALYSIS USING THE GREASE THIEF
- 23. ANALYSIS TECHNIQUES: ASTM D7918 • ASTM D7918 approved and published in 2015. • Particle counting and moisture ppm capabilities added recently • 6 tests with 1- gram of grease Ferrous debris Die Extrusion Colorimetry Linear Sweep Voltammetry Elemental Spectroscopy FTIR Water in ppm rev 0 022817
- 25. NAVIGATOR-SAMPLES TO BE REVIEWED
- 27. SCREENING TEST • Key parameters can be quickly tested while retaining majority of the sample for future testing • Wear, Color, Moisture and FTIR can be rapidly determined with small sample size • Kits supplied with Barcode labels and access to App for sampling identification and Meta- data • Statistical analysis of sample groups and comparison to Meta-Matched data sets
- 30. CASE 1 – DETERMINING LIFE OF ROBOTICS GREASES • Samples were selected from grease lubricated joints on industrial robots used in assembly line automation. • Grease is fortified with zinc dialkyl dithiophosphate (ZDDP), a common antiwear and antioxidant additive. • Samples were taken from robots assigned varying payloads and cycle times. The remaining additive concentration as compared to the supplied new lubricant reference were measured with RULER and with the Pearl 50 um pathlength FTIR. • Results allowed for condition-based relubrication tasks, with reduction in required manpower and cost to purchase grease
- 31. • Sampling method developed from uptower efforts and on ground-level failed blade bearings at US wind farm • Shop sampling of removed bearings using AWEA RP-814 • Use of GT Slim device for accessing smaller openings down to 8mm diameter clearance • Results clearly correlated to as-found conditions of wear and grease condition upon disassembly CASE 2 – MONITORING WIND TURBINE BLADE BEARING CONDITION
- 32. WIND TURBINES WEAR LEVELS IN COMPARISON 32
- 33. WEAR LEVELS IN ROBOT FLEET-COMPARISON
- 34. NEW METHOD: PARTICLE COUNTING IN INTEGRATED TESTER D7918-17 • New method uses ASTM D7718 sampling standard capture device for presentation of 1 gram representative sample • Samples can be obtained from: • new grease in manufacturing process • packaged new greases upon opening • stored greases in opened packages • grease guns and auto-lubers • inservice samples in the machine • Method sizes and counts particles reliably down to 10 micron in major axis, and provides aspect ratio and other characterization information
- 36. PARTICLE COUNTING Sample Image Image with filter and particles highlighted
- 37. EXAMPLE RECORDINGS 50 mg/g sample10 mg/g sample 1.0 mg/g sample0.1 mg/g sample
- 39. MOISTURE ANALYSIS FOR GREASE • Method uses vial and oven at 175 deg C • Moisture is transferred using dessicated Nitrogen gas, to a humidity sensor • Humidity values are converted to water transfer rate with flow totalizer • When water transfer rate returns to background levels, the total is integrated and converted to ppm • Now included in ASTM D7918 as an approved standard. On internal lab runs at 10,000ppm moisture greases Rel Std Dev at 5.28%
- 40. PATHS OF GREASE ENTERING A BEARING
- 41. SOME GREASE THIEF USERS