GREASE SAMPLING METHODS: HOW TO GATHER A REPRESENTATIVE SAMPLE AND PERFORM MEANINGFUL ANALYSIS

A Webinar from Rich Wurzbach, MRG Labswww.greasethief.com

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

• Low-cost analysis solutions

• Case Studies

VALUE OF GREASE ANALYSIS

• Grease lubricated components fail

• Critical service and expensive machines are grease lubricated

• The warning signs are evident in the grease

• Leading indicator monitoring and proactive intervention

• Root-cause detection for identification of systemic issues

GREASE IS DIFFERENT

• Viscosity is the property of oil that sets the lubricating film, and dictates how oil flows

• Grease is an oil (base + additives) with a thickener

• Grease behavior is non-Newtonian; it is designed to stay put in the machine

• Dynamically, grease will flow, but only very close to the bearing/gear

• Sampling and analysis techniques for oil are inadequate for grease

ASTM D7718 STANDARD DEVELOPMENT

• Developed in 2009 and published in 2011

• Incorporation of grease sampling research (Danish Wind Industry, Electric Power Research Institute)

• Inclusion of historical methods for sampling with considerations and limitations

• Failed component sampling, care in obtaining sample or multiple samples

• Use of tubing, adequacy of suction alone, possibility of peripheral grease sampling

• Inclusion of new technologies for active and passive sampling

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GREASE THIEF SAMPLERS• Maintain purge function with little/no backpressure

for drain applications

• Allow relief of grease if sampler fills

• Use of “Handle” tools to set depth

• Designed to optimize the analysis process

GREASE THIEF – THE STANDARD

• “Effective Grease Practices” published by Electric Power Research Institute; MOV Gearbox sampling and analysis studies

• DONG Energy and Vattenfall Main Bearing research project 2011-2013; DONG and Statkraft Blade Bearing 2014-2016

• ASTM D7718: Standard for sampling greases from inservice equipment

• ASTM D7918: Standard method for inservice grease analysis by Die Extrusion, “Integrated Tester” method for 6 tests

• AWEA (American Wind Energy Association) published “Recommended Practices 812-815” for grease sampling and analysis with the Grease Thief

Pillow Block Electric Motor Grease Thief SlimTM

MOV Gearbox Robot Kit Wind Turbine

ROBOT SAMPLING

• Industrial robots are often 6-axis gearboxes, grease or oil lubricated

• Grease lubricated robots can be evaluated for wear, contaminants, and grease breakdown

• Transitioning from time-based grease purges to condition based can save $$$

DRAINS: J1, J2, J3

1. Operate and shut off power.

2. Lock Out/Tag Out3. Remove drain

plug

DRAINS: J1, J2, J3

4. Thread adapter into gearbox drain if necessary.

5. Thread Grease Thief into drain hole.

6. Pull plunger handle to fill Grease Thief with sample.

7. Cap Grease Thief.

DRAINS: J1, J2, J3

7. Some locations utilize syringe with extension tubing.

8. Robot grease is a special case where it is so fluid, a syringe and tubing can work.

9. Place Grease Thief in labeled shipping tube.

10.Mail to MRG Labs for analysis or process on-site.

11.Grease Thief requires no further handling; ready to analyze per ASTM standard.

DRAINS J4, J5, J6

1. Position robot with drains facing downward if possible and shut power off.

2. Lock Out/Tag Out

3. Remove Zerk fitting.

4. Thread provided plastic syringe into the threaded Zerk hole.

DRAINS J4, J5, J65. Place tip of syringe in Grease

Thief and fill with grease by withdrawing plunger.

6. Inject grease to fill Grease Thief.

7. Cap Grease Thief and place in shipping tube.

8. Mail to lab for analysis or process on-site.

9. Grease Thief requires no further handling; ready to analyze per ASTM recommendations.

WIND MAIN BEARING SAMPLING

• Grease flow dependent on temperature, bearing movement

• Grease Thief & T-handle used to capture flowing grease

• Revised T-handle developed for Denmark Off-shore Wind Research Project

• Project demonstrated representative grease taken without requiring disassembly or space between rollers

WIND BLADE BEARING SAMPLING (SLEWING)• Can be double-row ball or tapered roller bearings

• Grease is typically delivered through autoluber lines or manually pumped

• Expelled grease captured in bellows or containers in some cases

• Containers can be harvested for sampling

• Slim sampler may be used to obtain live zone samples through drain hole

• New method for autoluber line purging – MRG Labs Technical Bulletin 17-001

GREASE THIEF SLIM FOR SMALL OPENINGS• Blade bearing access limited

• Access opening often smaller than sampler diameter

• Blade bearing research leads to slim version, dia. drops from 0.50in (13mm) to 0.28in (7mm)

ELECTRIC MOTOR SAMPLING• Grease Thief can be threaded into drain in

place of a plug

• Quality Controlled to deliver 1-5 psi relief pressure to ensure purging

• Active methods may be required; T-handle or GT Slim

• Mixing is a common failure mechanism, causing softening and separation of grease and allowing to migrate to windings

• Periodic grease sampling can detect such issues early; hardened grease can be a source of energy losses

PILLOW BLOCK BEARINGS• Can be critical applications:

fan and AHU in bio-medical research or pharmaceutical manufacturing

• Grease mixing and contaminants can be monitored, along with wear levels and causes

• Early detection and purging can avoid failure when deficiencies are found

MOTOR OPERATED VALVE GEARBOX• Sampling with T-handle through

access plugs

• Determining optimal grease life and gear wear condition

• “Stinger probe” version of Grease Thief ensures that only grease near the gear is sampled, not peripheral grease not active in lubrication

STEM THIEFTM RELUBRICATOR• Adapter bushing is first threaded

into body

• Stem lubricator screwed down to make seal against stem nut

• Grease gun used to pump grease into threads

• Purged grease is gathered from other end using a Pillow Block kit

• Analysis can show mixing, contaminants and wear, along with grease degradation

MINING APPLICATIONS• Constant battle with contaminants, abrasives

• Lubrication as a strategy to purge contaminants

• Effectiveness can be evaluated by analyzing grease

• Slewing bearings can be accessed with Grease Thief Slim

• Suctioning grease often not effective as grease hardens

• Root-causes of wear can be determined

• Enhanced analysis methods developed

• Four types of grease analysis: wear, contaminant, consistency and oxidation

• Evaluate reliability of machine and grease to perform function

• Look for signs of incompatible mixing

• Pinpointing root causes for correction

• Perform analysis cost-effectively utilizing sampling geometry

GREASE ANALYSIS USING THE GREASE THIEF

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

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NAVIGATOR-SAMPLES IN PROCESS

NAVIGATOR-SAMPLES TO BE REVIEWED

NAVIGATOR-HISTORY AND EXPORT

LOW-COST SCREENING TEST• Key parameters can be quickly tested

while retaining majority of the sample for future testing

• Wear, Color, and FTIR for under $30, including cost of sampling tools

• Pre-paid kits supplied with Barcode labels and access to App for sampling identification and Meta-data

• Statistical analysis of sample groups and comparison to Meta-Matched data sets

CASE 1 – DETERMINING LIFE OF ROBOTICS GREASES

• Samples were selected from grease lubricated joints on industrial robots used in assembly line automation.

• Grease is fortified with zinc dialkyl dithiophosphate (ZDDP), a common antiwear and antioxidant additive.

• Samples were taken from robots assigned varying payloads and cycle times. The remaining additive concentration as compared to the supplied new lubricant reference were measured with RULER and with the Pearl 50 um pathlength FTIR.

• Results allowed for condition-based relubrication tasks, with reduction in required manpower and cost to purchase grease

• Sampling method developed from uptower efforts and on ground-level failed blade bearings at US wind farm

• Shop sampling of removed bearings using AWEA RP-814

• Use of GT Slim device for accessing smaller openings down to 8mm diameter clearance

• Results clearly correlated to as-found conditions of wear and grease condition upon disassembly

CASE 2 – MONITORING WIND TURBINE BLADE BEARING CONDITION

WIND TURBINESWEAR LEVELS IN COMPARISON

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WEAR LEVELS IN ROBOT FLEET-COMPARISON

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

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.

CAMERA SET-UP

• Thin Film extrusion sample preparation

• Lens magnification to achieve 10 micron particle resolution

• Backlit with LED lighting

PARTICLE COUNTING EXAMPLE

PARTICLE COUNTING

Sample Image Image with filter and particleshighlighted

EXAMPLE RECORDINGS

50 mg/g sample10 mg/g sample

1.0 mg/g sample0.1 mg/g sample

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%

IMPLEMENTING GREASE ANALYSIS

• Find critical applications and high-risk components for analysis

• Review sampling kit options on www.greasethief.com

• For special applications, contact MRG Labs engineering for assistance in method development

• Order pre-paid screening kits for initial sampling

• Select outliers for additional testing

VALUE FOR LUBE PROGRAMS• Grease Cleanliness Studies to determine current conditions

and calculation of benefits using Machine Life Extension Chart for lubricant cleanliness

• Testing of New Grease Supplies: Characterize for the customer the current particulate and moisture levels in the new, unopened greases that they stock (a function of manufacturing AND packaging cleanliness practices)

• Testing of Delivered Grease cleanliness: sampling some grease guns, auto-luber reservoirs to determine handling cleanliness impact prior to delivery to machine

• Spot Checking of Machine grease samples: Determine the effectiveness of seals and frequency of greasing to keep contaminants at bay inside the machine

IMPROVING CUSTOMER LUBE PROGRAMS• Provide customer with data-based recommendations for

grease supplier quality improvement initiatives

• Recommend enhanced storage methods to reduce the introduction of particulate and moisture (and cross-contamination of products) based on areas of vulnerability determined through testing (grease gun storage, auto-luber refill methods, etc.)

• Use condition-based feedback to optimize grease delivery volumes and frequencies, particularly in high-contaminant ingression environments

• Identify wrong lubricant choices, contamination introduction, and poor practices that are compromising bearing life and projecting negatively on brand

SOME GREASE THIEF USERS