Laboratory Grease Analysis with Grease Thief Sampling & Analysis System Grease Thief Die Extrusion Analex fdm+ Ferrous Debris Metal Spectroscopy Grease Consistency Anti-oxidants RULER FT IR Analytical Ferrography Comparative FTIR Offsite Grease Tests Analytical Ferrography Rheology Metals Spectroscopy Patch Microscopy Grease Rheology
Prep for Analysis When grease is tested for consistency, it can be extruded onto sample substrates: IR Card for FTIR Substrate for weighing and dissolution in RULER vial Substrate for weighing and dissolution for spectroscopy; same dissolved grease can be used for Ferrography/MicroPatch
Sample Handling and Preservation Sampling Procedures: ASTM Standard Practice D7718 Use proper PPE Instrumentation Wipe down between runs Do not reuse Extrusion Dies or Grease Thieves (GT)
Analysis Techniques Sample is received. fdm+ is run Grease Thief Analyzer 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.
Wear Monitoring with the ANALEX fdm+ Hall effect type sensor to determine the amount of ferrous debris present in the sample. Instrument has calibration standards for Grease Thief. The instrument measures the entire sample which is important due to the nonhomogenous nature of grease.
Wear Monitoring Method Comparison Sample was taken in grease sampler Extruded sample was weighed and dissolved for direct reading ferrography Results were normalized to 0.1 gram grease Full sampler analyzed by ferrous density instrument (Hall effect sensor) for ppm Fe result Quantity of grease in sampler weighed and tared, and result in ppm normalized to 1.0 gram grease Method Average Standard Relative Standard Deviation Deviation fdm+ 277 ppm 7 2.53 DR- 205 46 22.44 RDE 57 ppm 16 28.07
Grease Thief Die Extrusion Test This instrument detects changes in the consistency of a grease. It is sensitive to the presence of hard particles, seen as spikes in the data, and hardened chunks of grease, seen as broad peaks in the graph. This test only requires one gram of grease. Grease Thief Index (GTI) calculates the deviation in percent of the force of the sample compared to that of the baseline. A GTI of 100 shows a perfect match to the baseline.
Die extrusion and sample preparation Grease extruded through die to create ribbon on substrate Load profile at varying speeds developed for consistency evaluation Sample prepared for subsequent analyses
Predicted Response Graph Average stable load value after speed change related to NLGI grade, or penetration values Rapid speed changes used to leverage non Newtonian response Critical areas expected immediately after speed change; possible data rich regions to characterize rheology, oil shear, dryness, etc.
Grease Thief Analysis Profiles 1000 Normal Profile 1000 Hardened Sample 900 900 800 800 Force (grams) 700 600 500 400 300 Force (grams) 700 600 500 400 300 200 100 GTI = 89 200 100 GTI = 183 0 272 372 472 572 672 772 872 Sample Baseline 0 320 420 520 620 720 820 sample baseline Softened Grease Sample with Hard Particles 1000 1400 900 800 1200 Force (grams) 700 600 500 400 300 200 100 GTI = 31 Force (grams) 1000 800 600 400 200 GTI = 76 0 272 372 472 572 672 772 0 300 400 500 600 700 800 Sample Baseline Sample Baseline
Actual Load Response Graphs
Consistency Testing
Standard Laboratory Tests FT IR Takes a fingerprint of the grease. Helps determine if mixing is present. It is also used to determine the presence and origin of unknown contaminants and oxidation. RULER Measures the amount of anti oxidant remaining in the grease. Metal Spectroscopy RDE/ICP/XRF determines the wear metals, additive metals and thickener metals used in the grease formulation. This test also aids in the detecting mixing of greases. Optical Spectroscopy Uses visual color absorbance to evaluate degradation and potential mixing.
FTIR Analysis
Prep for Analysis
Linear Sweep Voltammetry (RULER) analysis for grease Preparation of thinfilm substrate streamlines and standardizes analysis Additive levels normalized to mass of grease
Linear Sweep Voltammetry Samples from similar coal crushers, same time in service Both have an adequate remaining anti oxidant level to protect grease from oxidation Lower sample shows more rapid degradation of antioxidants, due to higher temperatures, contaminants, or other oxidation stressors. Differences in time of service or relubrication quantities or effectiveness could also affect anti oxidant amount
Optical Spectroscopy Cell
0.6000 0.5000 0.4000 0.3000 0.2000 0.1000 0.0000 In Service Spectrum New Fluid in service Fluid Mobilith SHC 220 400 413 426 439 452 465 478 491 504 517 530 543 556 569 582 595 608 621 634 647 660 673 686 699
50:50 Mixture
New Lubricant to End of Life Transmission 0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 New Fluid In-Service Fluid End of Life Fluid 400 450 500 550 600 650 700 Wavelength (nm) New: Mobil XHP 222 S, In-service: Used Mobil XHP 222, EOT: Used Unirex N2 (both were the same at end of life).
Chemometric Techniques Evaluate particulate contamination of new and inservice greases Coal dust, other known and common contaminants Establishing contaminant level targets
Carbon Residue Experiment Carbon residue used to make a 1% by mass mixture. Dilutions made to prepare 9 additional samples. Extruded samples onto substrates. Analyzed samples with the i Lab using the optical spectroscopy box. 70 65 60 55 50 45 CIE and L* Vs. % Carbon Residue y = 564.03x + 56.949 R² = 0.969 y = -640.87x + 58.179 R² = 0.9534 40 0.00% 0.20% 0.40% 0.60% 0.80% 1.00% Carbon Residue (percent mass) CIE E L*
Carbon Residue Experiment Carbon Residue Experiment 2 Visual Spectra Comparison 0.7 0.6 0.5 Transmittance 0.4 0.3 0.2 0.1 0 400 450 500 550 600 650 700 wavelength (nm) 1.00% 0.90% 0.80% 0.70% 0.60% 0.50% 0.40% 0.30% 0.20% 0.10% 0.00%
Advanced Laboratory Testing Rheometric Analysis is a newer technique that utilizes a rheometer to analyze the physical properties of a grease. These properties are Resistance to flow (pumpability) Consistency Recoverable Compliance (tunneling) Analytical Ferrography microscopic technique used in oil and grease analysis. It is used to Discover the origins of the wear. The size of the particles. Detect signs of acid corrosion.
Rheometer testing Work by Nolan and Sivik to evaluate grease properties with rheometer Bryan Johnson published method for correlating penetration to rheometer German DIN draft method Yield stress point and equilibrium recoverable compliance Measuring flow point and elastic recoil
Rheometer Consistency Testing
Elasticity or Recoverable Compliance
Consistency Testing
New fresh grease G = 18,260Pa
Suspected Mixture G =10,510Pa G is 57% of new
Ferrographic and Micro Patch inspections
Ferrographic and Micro Patch inspections Analytical ferrography more difficult than oil; may require special fixer mixtures Patch can be clouded by residual grease particles, but can be more effective at finding non ferrous
Wind Turbine grease sampling and analysis 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 Rich Wurzbach, MRG Labs, inventor of Grease Thief Systematic evaluation of grease heterogeneity, sampling methodology, and analysis validity and repeatability for wind turbine main bearings in onshore and off shore applications Results published at OilDoc, LUBMAT, and AWEA
Fundamental Sampling Principle Using the Grease Thief Representative sampling Thorough characterization of the heterogeneity of grease in main bearings
Test parameters of Grease For the heterogeneity characterization of grease in main bearings of wind turbines the following parameters were used: Consistency and flow characteristics Ferromagnetic iron (Hall effect sensor) Wear metals Particle characterization (size & distribution) Residual oil in grease Antioxidants
Heterogeneity characterization Ferromagnetic iron Sampling of grease while draining the main bearing through the drain plug 27 increments collected (each sample approximately 20 grams) 20000 On site sampling 18000 Iron (FdM Plus) 16000 14000 12000 10000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Sample no