Laboratory Grease Analysis with Grease Thief Sampling & Analysis - PowerPoint PPT Presentation

Laboratory Grease Analysis with Grease Thief Sampling & Analysis System • Grease Thief Die Extrusion • Analex fdM+ Ferrous Debris • Metal Spectroscopy Grease Anti-oxidants Consistency • RULER • FT ‐ IR Offsite Comparative Analytical Grease FTIR Ferrography Tests • Analytical Ferrography • Rheology Metals Patch Spectroscopy 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 One Strip is used One Strip is Dissolved in Green a dilution to run RDE/ICP. for FT-IR. 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 non ‐ homogenous 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 Standard Standard Relative Standard Relative Standard Method Method Average Average Deviation Deviation Deviation Deviation fdM+ fdM+ 277 ppm 277 ppm 7 7 2.53 2.53 DR- DR- 205 205 46 46 22.44 22.44 RDE RDE 57 ppm 57 ppm 16 16 28.07 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 Hardened Sample Normal Profile 1000 1000 900 900 800 800 Force (grams) Force (grams) 700 700 600 600 500 500 400 400 300 300 200 200 GTI = 89 GTI = 183 100 100 0 0 272 372 472 572 672 772 872 320 420 520 620 720 820 Sample Baseline sample baseline Softened Grease Sample with Hard Particles 1000 1400 900 1200 800 Force (grams) Force (grams) 1000 700 600 800 500 600 400 GTI = 31 300 400 GTI = 76 200 200 100 0 0 272 372 472 572 672 772 300 400 500 600 700 800 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 thin ‐ film 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 anti ‐ oxidants, 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

In ‐ Service Spectrum 0.6000 0.5000 New Fluid in ‐ service Fluid 0.4000 0.3000 Mobilith SHC 220 0.2000 0.1000 0.0000 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 0.50 0.45 0.40 New Fluid 0.35 Transmission In-Service Fluid 0.30 End of Life Fluid 0.25 0.20 0.15 0.10 0.05 0.00 400 450 500 550 600 650 700 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 in ‐ service greases • Coal dust, other known and common contaminants • Establishing contaminant level targets

Carbon Residue Experiment • Carbon residue CIE and L* Vs. % Carbon Residue used to make a 1% 70 by mass mixture. 65 • Dilutions made to y = 564.03x + 56.949 R² = 0.969 prepare 9 60 additional samples. 55 • Extruded samples y = -640.87x + 58.179 R² = 0.9534 onto substrates. 50 • Analyzed samples 45 with the i ‐ Lab using the optical 40 0.00% 0.20% 0.40% 0.60% 0.80% 1.00% spectroscopy box . 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 • Analytical Ferrography newer technique that microscopic technique utilizes a rheometer to used in oil and grease analyze the physical analysis. It is used to – properties of a grease. – Discover the origins of These properties are – the wear. – The size of the particles. – Resistance to flow – Detect signs of acid (pumpability) – Consistency corrosion. – Recoverable Compliance (tunneling)

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 on ‐ shore 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 ) On site sampling 20000 18000 Iro n (F d M P lu s) 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