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+
• Metal Spectroscopy
• RULER
• FT‐IR
• Analytical Ferrography
• Rheology

Offsite Grease Tests

Ferrous Debris Anti-oxidants Analytical Ferrography Patch Microscopy Grease Rheology Metals Spectroscopy Comparative FTIR Grease Consistency

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 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

Method Average Standard Deviation Relative Standard Deviation fdM+ 277 ppm 7 2.53 DR- 205 46 22.44 RDE 57 ppm 16 28.07 Method Average Standard Deviation Relative Standard 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

Normal Profile

Force (grams)

Sample Baseline

GTI = 89 Hardened Sample

Force (grams) sample baseline GTI = 183 Sample with Hard Particles

Force (grams) Sample Baseline GTI = 76 Softened Grease

Force (grams) Sample Baseline GTI = 31

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‐

• xidants, due to higher

temperatures, contaminants,

• r other oxidation stressors.
• Differences in time of service
• r relubrication quantities or

effectiveness could also affect anti‐oxidant amount

Optical Spectroscopy Cell

In‐Service Spectrum

0.0000 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 400 413 426 439 452 465 478 491 504 517 530 543 556 569 582 595 608 621 634 647 660 673 686 699 New Fluid in‐service Fluid

Mobilith SHC 220

50:50 Mixture

New Lubricant to End of Life

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 400 450 500 550 600 650 700 Wavelength (nm) Transmission

New Fluid In-Service Fluid End of Life Fluid

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

used to make a 1% by mass mixture.

• Dilutions made to

prepare 9 additional samples.

• Extruded samples
• nto substrates.
• Analyzed samples

with the i‐Lab using the optical spectroscopy box.

y = 564.03x + 56.949 R² = 0.969 y = -640.87x + 58.179 R² = 0.9534 40 45 50 55 60 65 70 0.00% 0.20% 0.40% 0.60% 0.80% 1.00%

Carbon Residue (percent mass)

CIE and L* Vs. % Carbon Residue

CIE ∆E L*

Carbon Residue Experiment

Carbon Residue Experiment 2 Visual Spectra Comparison

0.1 0.2 0.3 0.4 0.5 0.6 0.7 400 450 500 550 600 650 700

wavelength (nm) Transmittance

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 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

10000 12000 14000 16000 18000 20000 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 Iro n (F d M P lu s)