additive & bench test development - stle

Additive & Bench Test Development

Jeffrey M. Guevremont, Ph.D.Sr. R&D ScientistTechnology DevelopmentAfton Chemical

2015 STLE Tribology Frontiers:Pre-Conference WorkshopAdvances & Opportunities in Lubrication: Wind TurbinesSunday, October 25, 20158:30am – 12:30pmGrand Hyatt, Denver, Colorado

Technology Development Approach

Field

• Lubricant performance rated in highly variable environment• Changing wind speeds and directions• Starts and stops that result in high transient loads• Wide operational temperature range• Water and other contamination

Approvals / Specifications

• Tests aimed at judging ability of lubricant in field• Standardized testing• Tests of fully formulated fluids• Pass / fail criteria

Bench Tests

• Tests aimed at understanding impact of lubricant and additives• Test fully formulated fluids to singular additives• Results can be used to model rig or field test resultsOffshore wind farm using 5MW

turbines in the North Sea off the coast of Belgium

New Idea

Synthesis (Months)

Testing(Years)

Discuss Result

Time Cycle of Testing

New Idea

Synthesis (5 Days)

Testing(Days/Weeks)

Discuss Result

Rig TestingField Testing

Time Cycle of Testing

Bench testing saves time and moneyBench testing can also reduce variability of results and improve understanding of additives!

New Idea

Synthesis (5 Days)

Testing(Days/Weeks)

Discuss Result

New Idea

Synthesis (1 Day)

Testing(0.1 Day)

Discuss Result

Rig Testing Bench Testing

OEM Approvals and Industrial Specification Requirements

Industrial Specification Requirements DIN 51517 Part 3 ISO 12925-1 ISO 6743-6Gearbox Suppliers Hansen Transmissions Winergy Moventas (Metso) Bosch-Rexroth (L+S) GE Transportation Systems

(GETS) Eickhoff Nanjing

Bearing Suppliers SKF FAG / Schaeffler Timken NSK KoyoLubrication System Suppliers Hydac Parker Hannifin Internormen CC Jensen Nissens (DK)

Test Categories Included in OEM Approvals1. Viscometrics and Shear Stability Kinematic Viscosity Viscosity Index Brookfield Viscosity Dynamic Viscosity Shear stability2. Physical Properties Acid value Density Flash point Pour point Storage Stability Evaporation Loss Water content Cleanliness Heat capacity3. Surface Properties Demulsibility Air Release Foaming Air entrainment4. Corrosion Copper Iron/Steel Bearings

5. Oxidation Oxidation Stability, Temperature Oxidation Stability, Bearing Oxidation Stability, Gear6. Load Carrying and Wear Scuffing tests Wear tests EP tests Micropitting tests7. Filters and Filterability Various material and size Temperature8. Fluid Compatibility Repeat of many of tests in all categories9. Seal Compatibility Static, many materials and temperatures Dynamic, many materialsOther Compatibility Paint Sealants/Gaskets Cage material Hoses14. Product Durability High Temperature Low Temperature Sludge Formation16. Service Performance / Field Trial Field Trial Agreement

Number of individual tests is much longer…

Tests Required for a Commercial Wind Turbine Fluid

As seen earlier, these tests have common themes

Focus on two areas that bench testing can really help

Picking the Right Bench Test

There is already a wealth of knowledge on how many additives affect performance in bench tests

OR HSV

HFRR

MTM

SLIM

EHD

Surface Analysis

ANTIWEAR AGENTS

FRICTION MODIFIERS

CORROSION INHIBITORS

DETERGENTS

DISPERSANTS

OXIDATION INHIBITORS

RUST INHIBITORS

DEMULSIFIERS

FOAM INHIBITORS

PPD

VII

Used to study additive.

Sensitive to, but generally not used to study.

Low Temperature Properties

Low temperature visometrics are important for restarting of turbines in low temperature environments

Low Temperature

Viscosity

Base Oils

Solubilizers

Thickeners

Comparison of Industry Standard Low Temperature Testing

Mini-Rotary ViscometerMRV

• Rotational Viscometer

• Temperature range:• -15°C to -40°C

• Cooling rate:• Very slow (variable)

• Shear rate:• 0.4 to 15 s-1

• Results:• Yield Stress (Pa) at

final temperature• Viscosity (cP) at final

temperature



• Cooling rate:• Very slow (variable)

• Shear rate:• 0.4 to 15 s-1

• Results:• Yield Stress (Pa) at

final temperature• Viscosity (cP) at final

temperature

Cold Crank SimulatorCCS



• Cooling rate:• Very fast

• Shear rate:• 104 to 105 s-1

• Results:• Viscosity (cP) at final

temperature



• Cooling rate:• Very fast

• Shear rate:• 104 to 105 s-1


temperature

Brookfield ViscometerFixed BV



• Cooling rate:• very fast, hold

• Shear rate:• up to 100 s-1


temperature



• Cooling rate:• very fast, hold

• Shear rate:• up to 100 s-1


temperature

Brookfield ViscometerScanning BV



• Cooling rate:• 1°C per hour

• Shear rate:• 0.2s-1

• Results:• Viscosity (cP) during

cooling cycle• Gelation Index



• Cooling rate:• 1°C per hour

• Shear rate:• 0.2s-1

• Results:• Viscosity (cP) during

cooling cycle• Gelation Index

Velocity (v)

Velocity (v)

Cool

Output

Viscosity (T),Limited network

information

Velocity (v)

Velocity (v)

Cool

Output

Viscosity at EOT,No information during

cooling cycle

Viscosity (T) with network information during cooling

cycle

Rotational Rheology(i.e. Scanning Brookfield)

Rotational Rheology(i.e. MRV and Fixed BV) Oscillatory Rheology

Frequency (ω)

Frequency (ω)

Cool

Output

Relating Complex Viscosity to the Elastic and Viscous Behavior of Commercial Wind Turbine Oils

Oscillatory Rheometer results correlate to Brookfield ViscosityThere is more to learn from the OR data

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Oil A

Oil B

Oil C

Oil D

Oil E

Oil F

Oil G

Viscos

ity at

‐40°C

(cP)

Brookfield Viscosity

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Oil A

Oil B

Oil C

Oil D

Oil E

Oil F

Oil G

Viscos

ity at

‐40°C

(cP)

Brookfield ViscosityComplex Viscosity

Relating Complex Viscosity to the Elastic and Viscous Behavior of Commercial Wind Turbine Oils

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Oil A

Oil B

Oil C

Oil D

Oil E

Oil F

Oil G

Viscos

ity at

‐40°C

(cP)

Brookfield Viscosity

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Oil A

Oil B

Oil C

Oil D

Oil E

Oil F

Oil G

Viscos

ity at

‐40°C

(cP)

Brookfield ViscosityComplex Viscosity

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Oil A

Oil B

Oil C

Oil D

Oil E

Oil F

Oil G

Mod

ulus (P

a) at ‐40

°C

Elastic behavior (G’) at -40°C

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Oil A

Oil B

Oil C

Oil D

Oil E

Oil F

Oil G

Mod

ulus (P

a) at ‐40

°C

Viscous behavior (G”) at -40°C

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10

100

1000

‐40 ‐30 ‐20 ‐10 0 10 20

Complex Visc

osity

(Pa s)

Temperature (°C)

Oscillatory Rheology Gives More Than Just Viscosity

Two oils showing different viscosity curves as temperature decreases

Differences in viscosity can be attributed to changes in the elastic and viscous modulus of the oil as temperature decreases

Oil AOil B

Sample gaining structure

Summary

Oscillatory rheology (OR) used for the development of a wind turbine fluid to be used in extreme cold environments OR used to systematically optimize low temperature viscosity of

base oil, thickener, and solubilizersMeasuring the elastic and viscous behavior of an oil during the

whole cooling cycleCorrelates to BV and gives more information than BVRed flag any combinations that form any type of structure

measurable by the OR

OR allows testing of singular additives, binary mixtures as well as fully formulated fluidGreater insight into unwanted interactions in the fluid

Bearing Durability

Bearing durability is important to achieve the predicted lifetimes of equipment

Friction, Antiwearfilm formation

AntiwearAdditives

Friction Modifiers

Solubilizers

Previous Results from Research on Industry Standard Gear and Bearing Protection Testing

Rolling 4-Ball Test

• Lower thin film friction increases life to pitting

• Reduce sub-surface stress

• Lower thin film friction increases life to pitting

• Reduce sub-surface stress

FE8

• High P in tribofilmsreduces wear

• High P in tribofilmscreates a stronger film that is more resistant to wear

• High P in tribofilmsreduces wear

• High P in tribofilmscreates a stronger film that is more resistant to wear

FZG (micropitting)

• Lower boundary friction improves micropitting life

• Lower boundary friction means less stress in the aspirity-aspirity contact

• Lower boundary friction improves micropitting life

• Lower boundary friction means less stress in the aspirity-aspirity contact

Friction Measured with Mini Traction Machine (MTM)Friction coefficients from MTM have been correlated to FZG gear testsLower friction results in longer lifeChoose test conditions to mimic operating conditions of wind turbines

MTM Friction : Competitive Wind Turbine Oils

Look for best friction performance of known chemistries under benchtop “wind turbine conditions”Iterate discovery process of idea-formulate -test-discuss

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A B C D E F G H I Candidate1Reference

FrictionCoef.80 C

50%SRR35N Load

1 m/s

Friction: Lower is

better

Afton Knows how to Prevent Fatigue

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AA

AB

AC

AD

AE

AF

AG

AH

AI

AJ

AK

AL

AM

AN

AO

AP

AQ

AR

AS

AT

1

Iterative process quickly gives many candidates with low frictionTurn to another bench test to differentiate good friction candidates

Friction: Lower is

better

Reference

FrictionCoef.80C

50%SRR35N Load

1 m/s

Measuring Tribofilm Formation with MTM-SLIMResults from MTM with Spacer Layer Imaging Method (SLIM) have been correlated to bearing and gear fatigue and wearFilm formation and presence of high P in the film is better for fatigue and wear

Not Too Thick, Not Too Thin, Just Right

Thin / smooth tribofilms give the lowest thin film and boundary friction

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Castrol Optigear A Mobil SHC XMP 320 BP/ Afton

Thin Film

Frictio

n Co

efficient

nm

Fluid BFluid A Fluid C

Fluid BFluid A Fluid C

Its All About the Pressure

Motivation to study chemistry at higher pressures Industry standard

tests Field tests – High load

transient loads

Need High Amount of Phosphorus in Film at High Pressure

Need fluid that can with stand occasional high pressuresAmount of P in film increases as pressure increases

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14

B11-14072 B12-7329 B12-0361 HI24881

2 GPa 3 GPa

Nor

mal

ized

P

Tribofilm %P: Higher is

better.

Fluid BFluid A Fluid C Fluid D

SummaryMTM and MTM-SLIM used for the development of a low friction wind turbine fluid that performs under high loadsMTM used to systematically optimize desired friction and antiwear

propertiesMTM used to measure friction properties of fluidMTM SLIM used to study tribofilm formation and compositionRed flag any fluids with high friction or poor tribofilm composition

MTM allows testing of singular additives, binary mixtures as well as fully formulated fluidGreater insight into wanted or unwanted interactions in the fluid

Candidates with Good Rheology, Low Friction and Good Tribofilms have been Identified

Bench test development saves time and money

DOE testing creates understanding of additive impacts on formulations

Increase speed of development and improve chance of success in rig and field testing

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Thank You!

additive & bench test development - stle

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