automatic particle counting in greases: stle2015 presentation by rich wurzbach

1© 2015 MRG Laboratories. All rights reserved.

Automatic Particle Sizing and Counting in Greases

Rich Wurzbach

MRG Labs

York, Pennsylvania, USA


Background

• Particle counting is very important part of oil analysis programs.

• Filtration and online contamination monitoring are used to maintain lubricant cleanliness.

• No commercial-scale contamination tests for grease as exists for oil, such as laser scattering particle counting.

• Abrasive contamination can be just as destructive in grease applications.

• Monitoring can allow for intervention through improved handling and manufacturing practices, grease flushing, and changes to relubrication frequency, volume.

2


Current Methods

• Direct– Analytical Ferrography – Labor intensive, difficult

preparation– Federal Standard 791D, Method 3005.4, Dirt Content of

Grease, microscopic evaluation– DIN 51813, Solid Matter Content of Lubricating Greases

• Indirect– Elemental Spectroscopy – Elemental concentration don’t

tell the whole story– P-Q testing with Hall Effect sensor – Only Ferrous debris– Hegman Gage – Semi-quantitiative based on size– ASTM D1404 "Deleterious Particles" - effect of particles

on scratching plates

3


Current Methods

• DIN 51813, Solid Matter Content of Lubricating Greases

• Federal Standard 791D, Method 3005.4

• Hegman Gage, ASTM D1210

4Source: “Deleterious Particles in Lubricating Greases”, C. Coe, STLE Online


Current Methods

5

• Analytical Ferrography• ASTM D1404, Estimation of

Deleterious Particles in Lubricating Grease

Source: www.koehlerinstrument.com/products/K19300.html


Limitations of current methods

• Subjective interpretation of results• Selection of solvent critical to some tests,

may be more difficult when evaluating inservice lubricants to get complete dissolution

• Time consuming and some expertise may be required

• None would be considered production lab ready

6


New Method: Particle Counting

• 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

7

8© 2015 MRG Laboratories. All rights reserved.8

Grease Sampling ToolsGrease Sampling Tools


Grease Thief Analyzer for Die Extrusion


Analysis Techniques

Sample is received. fdM+ is run Die 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.

10


Grease Thief Die Extrusion and Anti-Oxidant Testing


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

12


Oil Particle Counter Principle Adapted

• Standard Test Method for Automatic Particle Counting and Particle Shape Classification of Oils Using a Direct Imaging Integrated Tester

• Use of camera and particle identification and sizing software originally used for flow-through oil particle characterization

• Modification of platform and use of alternate lighting methods


Direct Imaging Particle Counter-Oil

Source: http://www.jmcanty.com/Items.aspx?catId=111


Direct Imaging Particle Counter-Very High Viscosity Fluid

Source: http://www.jmcanty.com/Items.aspx?catId=111


Camera Set-up

• Thin Film extrusion sample preparation

• Telecentric lens

• Fixed magnification of .60x

• View is 11.79 mm x 8.88 mm

• Strobing LED Backlight

• Strobe pulses are adjusted depending on the opacity of the sample

16


Modification of Grease Thief Analyzer


Challenges

• Strobing backlight solved 2 problems

– Testing with frontlight set-ups were unsucessful due to the glare produced by the grease surface

– Samples were too dark and the film was too thick to employ a traditional backlight – the bulb would burn out at the required intensity.

• Thin film preparation

– Provides a consistent gap thickness

– Allows for volumetric calculations

18


Case Study

• Chiller Motor ODE Bearing sample

• Relatively low wear levels• Slightly elevated

concentrations of elements the could be environmental contamination

• Also showed signs of grease product mixing

• Elemental Spectroscpy doesn’t show the whole picture

19

Fe Al Si Mg Zn FdM

3.1 2.4 9.5 34 645 99


Particle Mask

20


Particle Counting

21

Sample Image Image with filter and particleshighlighted


Particle Counting - Results

22

Particle Count: 327

Mean Area: 1564.2

Mean Major Axis: 45.0

Min Major Axis: 14.6

Max Major Axis: 184.2


Particle Counting - Results

23


Future Work

1. Integration of technology to take video during extrusion

– This will allow for count averaging across a video instead of an image

1. Automation of the data collection process

2. Particle identification and characterization

– Differentiating severe wear modes from normal rubbing wear

1. Establishing target limits and evaluation criteria for different applications

24

automatic particle counting in greases: stle2015 presentation by rich wurzbach

Science

mrg laboratories

grease flushing

grease applications

new greases

new method

dirt content of grease

grease thief analyzer

die extrusion