This document discusses establishing an effective grease analysis program to monitor critical equipment lubricated with grease. It recommends the following steps: 1) select equipment for inclusion, 2) evaluate grease flow to determine sampling locations, 3) select appropriate sampling equipment, 4) establish standard sampling procedures, 5) create appropriate test methods, 6) generate a sampling schedule, and 7) review results for issues and implement proactive measures. The document also describes various grease sampling and analysis techniques like particle counting, moisture analysis, and color measurement that can identify contamination, wear, or grease degradation issues.

1. A Proactive Grease Analysis Strategy for
Critical Equipment
Ensuring a clean and dry grease supply through inspection,
testing and corrective actions

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. 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
• Monitoring new grease supplies

4. Paths of grease entering a bearing

5. 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
Systemic Issues include dirty and mixed greases that can
compromise lubrication and damage equipment

6. Grease Thief Samplers
• Obtain 1 gram grease sample
• Multiple locations from the same container
• Use of “Handle” tools to set depth
• Sampler designed to optimize the analysis process

7. Pillow Block Electric Motor Grease Thief SlimTM
MOV Gearbox Robot Kit Wind Turbine

8. 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

9. Protecting New Grease Supplies
• Key parameters to spot check and periodically evaluate:
• Cleanliness
• Particulate
• Moisture
• Mixing
• Color
• Batch variation
• Color
• Mis-labeling
• Color
• Color – Particulate – Moisture

10. 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

11. Camera Set-up
• Thin Film extrusion sample
preparation
• Lens magnification to achieve 10
micron particle resolution
• Backlit with LED lighting

12. Particle Counting Example

13. Particle Counting
Sample Image Image with filter and particles
highlighted

14. Example Recordings
50 mg/g sample10 mg/g sample
1.0 mg/g sample0.1 mg/g sample

16. 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%

17. Measuring Grease Color
• The appearance of grease is variable based on ambient conditions
• When ambient conditions are controlled, changes in grease color
can indicate differences of varying significance
• Mixing of greases with different color greases
• Accumulation of debris (wear, contaminants) in grease
• Oxidation or aging of grease
• Color change itself does not dictate an unacceptable change in
performance, but may be a warning parameter for further
investigation
• Comparision to new grease can help determine need for further
testing in service
• Checking new grease batches to confirm consistent product

18. 18
L*
40
50
60
70
80
90
a*
40
50
60
70
80
90
b*
40
50
60
70
80
90
CIE color space chromaticity diagram
ASTM E308 Defines CIE Color
a* is the change in color in the red spectrum.
a* is positive in the red direction and negative in the
green direction.
b* is the change in color of the yellow spectrum.
b* is positive in the yellow direction and negative in the
blue direction.
L* is the change in shade from white to black.

19. Grease Color Examples
• Three different
greases
• Follows the patterns
identified by the
chromaticity diagram
Colors Sample 1 2 3
Light…dark
L* 48.6 63.5 61.3
Red…green
a* 42.5 13.6 25.8
Yellow…Blue
b* -14.0 -52.1 3.8

20. Grease Thief Colorimeter
• Controls optical pathlength to
0.035, 0.010, and 0.005”
• D50 and D65 light sources
• RGB, CIE and other color
measurements

21. Grease under varying conditions
New grease (Vigo)
Significantly dark (3418)
Moderately dark (384)
Slightly dark (389)
Significantly dark (391)

22. #3481: 0.035” path, 0.010” path, & 0.005” path

23. #391: 0.035” path, 0.010” path, & 0.005” path

24. #389: 0.035” path, 0.010” path, & 0.005” path

25. #384: 0.035” path & 0.010” path

26. Some Grease Thief Users

27. Thank you.