128347108-EPRI-Lubrication-Guide-1003085

Lubrication Guide

Revision 3 (Formerly NP-4916-R2)

Technical Report

LI

CE

NS E D

M A T E

RI

AL

Equipment

Reliability

Plant

Maintenance

SupportReduced

Cost

WARNING:Please read the License Agreementon the back cover before removingthe Wrapping Material.

EPRI Project ManagerM. Pugh

EPRI • 3412 Hillview Avenue, Palo Alto, California 94304 • PO Box 10412, Palo Alto, California 94303 • USA800.313.3774 • 650.855.2121 • [email protected] • www.epri.com

Lubrication GuideRevision 3 (Formerly NP-4916-R2)

1003085

Final Report, October 2001

DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES

THIS DOCUMENT WAS PREPARED BY THE ORGANIZATION(S) NAMED BELOW AS ANACCOUNT OF WORK SPONSORED OR COSPONSORED BY THE ELECTRIC POWER RESEARCHINSTITUTE, INC. (EPRI). NEITHER EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR, THEORGANIZATION(S) BELOW, NOR ANY PERSON ACTING ON BEHALF OF ANY OF THEM:

(A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED, (I)WITH RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, ORSIMILAR ITEM DISCLOSED IN THIS DOCUMENT, INCLUDING MERCHANTABILITY AND FITNESSFOR A PARTICULAR PURPOSE, OR (II) THAT SUCH USE DOES NOT INFRINGE ON ORINTERFERE WITH PRIVATELY OWNED RIGHTS, INCLUDING ANY PARTY'S INTELLECTUALPROPERTY, OR (III) THAT THIS DOCUMENT IS SUITABLE TO ANY PARTICULAR USER'SCIRCUMSTANCE; OR

(B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER(INCLUDING ANY CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY EPRI REPRESENTATIVEHAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOURSELECTION OR USE OF THIS DOCUMENT OR ANY INFORMATION, APPARATUS, METHOD,PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT.

ORGANIZATION(S) THAT PREPARED THIS DOCUMENT

Bolt & Associates

ORDERING INFORMATION

Requests for copies of this report should be directed to EPRI Customer Fulfillment, 1355 Willow Way,Suite 278, Concord, CA 94520, (800) 313-3774, press 2.

Electric Power Research Institute and EPRI are registered service marks of the Electric PowerResearch Institute, Inc. EPRI. ELECTRIFY THE WORLD is a service mark of the Electric PowerResearch Institute, Inc.

Copyright © 2001 Electric Power Research Institute, Inc. All rights reserved.

iii

CITATIONS

This report was prepared by

Nuclear Maintenance Applications Center (NMAC)EPRI1300 W.T. Harris BoulevardCharlotte, NC 28262

This report describes research sponsored by EPRI.

The report is a corporate document that should be cited in the literature in the following manner:

Lubrication Guide: Revision 3 (Formerly NP-4916-R2), EPRI, Palo Alto, CA: 2001. 1003085.

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REPORT SUMMARY

A large number of lubricants are used in power plants for various purposes. Maintenancepersonnel need concise guidelines for selecting the correct lubricant for a specific application.Also, specific knowledge is required regarding a lubricant’s characteristics to determine itsapplicability.

BackgroundThis lubrication guide has traditionally provided useful information to power plant personnelinvolved in this area of plant operation and maintenance. This revision of the Lubrication Guideincorporates changes within the lubrication industry including consolidation and discontinuationof product lines and features. As in Revision 2, it also includes topics that were covered underEPRI report, Radiation Effects on Lubricants, NP-4735.

Objectives• To provide general guidance to plant personnel involved with lubricants

• To provide information on current oils and greases and their operating limitations fordifferent plant applications

ResultsThis guide addresses lubricants, lubrication, testing, and friction and wear. It includes sectionson basic lubrication, application problems, tests and analysis. Tables are provided that profileeach use category, listed lubricants for specific applications, and temperature and radiationtolerances of these lubricants. A glossary of technical terms is also included. Guidance onselecting the correct lubricant for a specific application is also provided. Information ondetermining the remaining life of a lubricant is addressed, which can help reduce unnecessaryand costly lubricant change-outs.

EPRI PerspectiveKnowledge of lubrication is important to maintenance personnel in their day-to-day work. Thisguide provides, in a concise form, a substantial amount of information on properties ofcommonly used lubricants. Selection of correct and compatible lubricants can help preventunscheduled maintenance or shutdown. Information contained in this guide can be useful to atraining instructor and to persons being initiated in the technology of lubrication. This revisionto the NMAC Lubrication Guide attempts to incorporate recent changes within the lubricationindustry including consolidation and discontinuation of product lines and features.

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KeywordsPlant engineeringPlant maintenancePlant operationsLubricantsLubrication

EPRI Licensed Material

vii

ACKNOWLEDGMENTS

This publication was developed by the Nuclear Maintenance Application Center (NMAC). Thefirst versions of the Guide were prepared by Dr. Bob Bolt and the late Jim Carroll. This thirdversion, built on the prior work, was prepared largely by Dr. Bolt with the major assistance ofDr. Howard Adams. Additionally, Dr. Bolt would like to acknowledge the valuablecontributions from the following:

Chesley Brown TXU

Jim Fitch Noria

Doug Godfrey Wear Analysis; Bolt & Associates

Bill Herguth Herguth Laboratories

Steve Mitchell AEP


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ABSTRACT

This Guide gives information on lubricants from many manufacturers, suitable for variousnuclear power plant applications. Lubricant operating limits with respect to temperature andradiation dose are listed. The Guide also addresses the basics of how lubricants work, howradiation affects them, and how this relates to their composition. Friction and wear is anotherbasic topic presented, along with lubricant stress effects, shelf life, compatibility, troubleshootingand testing, all important in maintenance. The testing section has received particular attentionwith the addition of several new test methods. A summary of the lubricants study in theEPRI/Utilities Motor-Operated Valve Performance Prediction Program is also included, as it wasin Revision 2. The Guide is intended for use by power plant maintenance and engineeringpersonnel.


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CONTENTS

1 LUBRICANTS: WHAT THEY ARE AND HOW THEY WORK ............................................. 1-1

1.1 Base Oils................................................................................................................... 1-1

1.2 Key Measurements ................................................................................................... 1-2

1.3 Additives ................................................................................................................... 1-3

1.3.1 Vl Improvers ......................................................................................................... 1-4

1.3.2 Detergent/Dispersants.......................................................................................... 1-4

1.3.3 Basic Metal Compounds....................................................................................... 1-4

1.3.4 Antiwear and Antiscuff (EP) Additives................................................................... 1-4

1.3.5 Antioxidants.......................................................................................................... 1-5

1.3.6 Rust Inhibitors and Antifoamants .......................................................................... 1-6

1.3.7 Gelling Agents ...................................................................................................... 1-6

1.4 Synthetic Lubricants.................................................................................................. 1-6

2 RADIATION EFFECTS ON LUBRICANTS.......................................................................... 2-1

2.1 Effect on Elastomers ................................................................................................. 2-8

3 LUBRICATION, FRICTION, AND WEAR ............................................................................ 3-1

3.1 Hydrodynamic Lubrication (HDL)............................................................................... 3-1

3.2 Elastohydrodynamic Lubrication (EHL) ..................................................................... 3-2

3.3 Boundary Lubrication (BL)......................................................................................... 3-3

3.3.1 Physically Adsorbed Film...................................................................................... 3-3

3.3.2 Chemisorbed Film ................................................................................................ 3-4

3.3.3 Chemical Reaction Film........................................................................................ 3-5

3.4 Solid Lubricants......................................................................................................... 3-5

3.5 Nature of Machined Surfaces.................................................................................... 3-6

3.6 Wear ......................................................................................................................... 3-6


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4 APPLICATION PROBLEMS................................................................................................ 4-1

4.1 Compatibility of Mixed Products ................................................................................ 4-1

4.1.1 Oils ....................................................................................................................... 4-1

4.1.2 Greases................................................................................................................ 4-1

4.2 Shelf Life ................................................................................................................... 4-4

4.3 Time/Temperature/Radiation Considerations ............................................................ 4-5

4.4 Continuous Versus Intermittent Use and Lube Performance..................................... 4-7

5 TESTS AND ANALYSES .................................................................................................... 5-1

5.1 Sampling ................................................................................................................... 5-1

5.2 Troubleshooting ........................................................................................................ 5-1

5.3 Lubricant Testing....................................................................................................... 5-2

5.3.1 Sensory Tests ...................................................................................................... 5-2

5.3.2 Other Simple Tests............................................................................................... 5-4

5.3.3 Diagnostic Laboratory Tests ................................................................................. 5-5

5.3.4 Standard Laboratory Tests ................................................................................. 5-12

5.3.5 Analytical Test Methods...................................................................................... 5-14

5.4 Using Test Results .................................................................................................. 5-19

5.5 Trending.................................................................................................................. 5-19

5.6 Warning Limits ........................................................................................................ 5-20

5.7 Cleanup Considerations .......................................................................................... 5-22

6 LUBRICATING MOTORIZED VALVE ACTUATORS .......................................................... 6-1

6.1 Stem Nut Friction and Wear – Off-the-Shelf Products ............................................... 6-2

6.2 Stem Nut Friction & Wear – Solid Lubricants and Improved Nut CuttingProcedure........................................................................................................................... 6-4

6.3 Search for Improved Actuator Lubricants .................................................................. 6-6

6.4 Long-Term Thermal Effects On Greases................................................................... 6-9

6.5 Conclusions ............................................................................................................ 6-11

A APPENDIX A.......................................................................................................................A-1

A.1 Lubricant Property Tables .........................................................................................A-1

A.2 Footnotes. ...............................................................................................................A-14

B APPENDIX B ......................................................................................................................B-1

B.1 Glossary....................................................................................................................B-1


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LIST OF FIGURES

Figure 1-1 Effect of Antiwear and Antiscuff Additives .............................................................. 1-5

Figure 1-2 Hydrocarbon Oxidation Process............................................................................. 1-6

Figure 2-1 Dose Levels for Radiation Effects .......................................................................... 2-1

Figure 2-2 Interaction of a Gamma Photon with Organic Matter.............................................. 2-2

Figure 2-3 Upper Limits of Radiation Doses Resulting in Failure of Various Base Fluids ........ 2-3

Figure 2-4 Radiolysis Effects on a Lithium Complex-Gelled, Mineral Oil-Based Grease.......... 2-4

Figure 2-5 Relative Oxidation Stability of Irradiated Mineral Oil-Based Steam TurbineOils in Turbine Oil Stability Tests (TOST) (ASTM D 943) ................................................. 2-5

Figure 2-6 Effect of Temperature and Irradiation on Bearing Life of a Sodium Salt-Thickened, Mineral Oil-Based Grease ............................................................................. 2-6

Figure 2-7 Relative Sensitivity of Common Lubricants and Elastomers to Irradiation .............. 2-8

Figure 2-8 Resistance of Elastomers to Irradiation.................................................................. 2-9

Figure 3-1 Hydrodynamic Lubrication...................................................................................... 3-2

Figure 3-2 Elastohydrodynamic Lubrication ............................................................................ 3-2

Figure 3-3 Boundary Lubrication (Fragmented Roughness) .................................................... 3-3

Figure 3-4 Representation of Physically Adsorbed Film—Non-Polar Molecules ...................... 3-4

Figure 3-5 Physically Adsorbed Film—Polar Molecules .......................................................... 3-4

Figure 3-6 Chemisorbed Film .................................................................................................. 3-4

Figure 3-7 Effects of Various Parameters on Friction Coefficient............................................. 3-5

Figure 3-8 Machined Surface .................................................................................................. 3-6

Figure 4-1 Compatibility of Mixtures of Greases With Different Gelling Agents........................ 4-3

Figure 4-2 Time/Temperature/Irradiation Interplay Continuous Operation in Air of HighQuality Lubricant Under Stress........................................................................................ 4-6

Figure 5-1 Observing the Appearance..................................................................................... 5-3

Figure 5-2 Detecting the Odor................................................................................................. 5-3

Figure 5-3 Viscosity Gage for Measuring the Viscosity of Oils................................................. 5-4

Figure 5-4 Sample Blotter Spot Test ....................................................................................... 5-5

Figure 5-5 Wear Particle Size/Concentration and Machine Condition ..................................... 5-8

Figure 5-6 Detection of Wear and Other Particles ................................................................... 5-9

Figure 5-7 Schematic of TGA Setup...................................................................................... 5-15

Figure 5-8 Schematic of DSC Apparatus............................................................................... 5-15

Figure 5-9 Ruler™ (Remaining Useful Life Evaluation Routine) Instrument .......................... 5-16


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Figure 5-10 Example of Three Additives and Voltammeter Response................................... 5-17

Figure 5-11 Chromatographs of Fresh and Used Gear Oils .................................................. 5-18

Figure 5-12 Sample Plot of Lubricant Properties................................................................... 5-20

Figure 6-1 Composite of Friction Coefficient (@10,000 lbs) Versus Number of Strokes.......... 6-4

Figure 6-2 Cross-Section of Macrograph of New SMB-O Stem Nut Thread – StandardMachining........................................................................................................................ 6-5

Figure 6-3 Pin-On-Disk Machine Schematic (Tribometer) ....................................................... 6-7


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LIST OF TABLES

Table 1-1 Oil and Grease Requirements ................................................................................. 1-1

Table 1-2 Common Additives in Various Lubricants ................................................................ 1-3

Table 1-3 Synthetic Base Oils and Their Application ............................................................... 1-7

Table 1-4 Comparative Properties of PAO Synthetic Base Oil and Various Mineral BaseOils.................................................................................................................................. 1-8

Table 2-1 Effects of Irradiation on Common Oils ..................................................................... 2-7

Table 2-2 Effects of Irradiation on Common Greases.............................................................. 2-7

Table 2-3 Resistance of Elastomers to Effects of Common Oils and Greases......................... 2-8

Table 4-1 Compatibility of Greases ......................................................................................... 4-2

Table 4-2 Grease Compatibility Tests ..................................................................................... 4-4

Table 5-1 Sequence of Lubricant Testing................................................................................ 5-2

Table 5-2 IR Peak Regions of Interest..................................................................................... 5-6

Table 5-3 Sources of Metals in Lubricants .............................................................................. 5-8

Table 5-4 Wear and Its Causes............................................................................................... 5-9

Table 5-5 Range Number Determination............................................................................... 5-11

Table 5-6 Key Tests for Lubricants........................................................................................ 5-13

Table 5-7 Typical Warning Limits for Certain Lubricant Services........................................... 5-21

Table 6-1 Friction and Wear Performance Summary (500 Stroke Stem/Stem NutLubricant Tests with SMB-0)............................................................................................ 6-3

Table 6-2 Bleeding Tests on Grade 1 Greases (including effects of gelling agents) ................ 6-6

Table 6-3 Pin-on-Disk Tribometer Data for Some Grease Types............................................. 6-8

Table 6-4 Grease Consistency Changes in Long-Term Thermal Tests ................................. 6-10

Table A-1 Turbine Oils ISO Viscosity Grades 32, 46, 68 ........................................................A-1

Table A-2 Engine Oils for Large Diesels.................................................................................A-2

Table A-3 Low-Pressure Hydraulic Oil ISO Viscosity Grades 32, 46, 68, 100.........................A-3

Table A-4 High-Pressure Hydraulic Oil ISO Viscosity Grades 32, 46, 68, 100........................A-4

Table A-5 Compressor Oils ....................................................................................................A-5

Table A-6 High Load Extreme Pressure (EP) Gear Lubricants...............................................A-6

Table A-7 Open Gear Lubricants............................................................................................A-7

Table A-8 Antiseizure Compounds.........................................................................................A-8

Table A-9 Limitorque Valve Actuator Lubricants.....................................................................A-9

Table A-10 Fire Resistant Hydraulic Fluids ..........................................................................A-10


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Table A-11 General Purpose Greases—Grades 00, 0, 1, 2, 3..............................................A-11

Table A-12 Coupling Greases ..............................................................................................A-12

Table A-13 Grease Types and Performance ........................................................................A-13

Table B-1 Viscosity Equivalents .............................................................................................B-4


1-1

1 LUBRICANTS: WHAT THEY ARE AND HOW THEYWORK

Oils and greases have to meet the several requirements shown in Table 1-1.

Table 1-1Oil and Grease Requirements

Properties Oils Greases

Prevent metal/metal contact x x

Act as a hydraulic medium x

Act as a coolant x

Carry away contaminants x

Protect against wear x x

Protect against corrosion x x

Protect against deposits x x

Resist foaming x

Remain in place x

Note that the only function exclusive to greases is the ability to stay in place. This results fromthe semi-solid nature of greases. On the other hand, there are several functions exclusive to oilsthat are derived from their fluid nature.

1.1 Base Oils

To perform the indicated tasks, commercial lubricating oils consist of about 85 to 99+ % baseoil. The remainder consists of additives. Additives are used to enhance the properties of the baseoil or to create a necessary property in it. Base oils are classified as:

• Mineral oils

• Synthetic oils


Lubricants: What They Are and How They Work

1-2

The principal advantage of synthetic oils is their relatively low viscosity at low temperatures.They also can have somewhat better high temperature performance. However, the cost ofsynthetic-based lubricants is 3-8 times the cost of mineral oil-based products. (For additionaldiscussion on synthetic lubricants, see Section 1.4.)

The term “mineral oil,” as opposed to “synthetic oil,” implies that little processing is involved inthe manufacture of mineral base oils. This is not true. The fraction distilled from selectedpetroleum crude oils for subsequent base oil manufacture contains many organic molecularspecies. Several of these must be removed to yield a high quality final base oil. Aromatic andwax compounds are two classes that are removed. Aromatics (alternating carbon-to-carbondouble bonds in six membered rings) show a particularly high rate of viscosity change withtemperature. This is not a good property in a lubricant. Waxes are solids at room temperature andare, therefore, unsuitable in base oils. Removing these requires considerable processing. Physicaltreatment, for example solvent refining, is still used as a method of removal, but catalytichydrogenation under pressure and temperature is now the preferred method of removal.

The product of solvent refining of a base oil feed is called a Group I base oil. Relatively mildcatalytic hydrogenation yields a Group II base oil, while more rigorous hydrogenation produces aGroup III base material. Some properties of these and of a common synthetic hydrocarbon baseoil (Group IV) are listed in Table 1-4.

1.2 Key Measurements

Viscosity is a measure of a fluid's resistance to flow, in other words, its fluidity. It is measured incentistokes (cSt.). The viscosity at 40°C is used in industrial oil grading. For example, a 32 gradehas a viscosity at 40°C of around 32 cSt. Other grading methods exist but they are used primarilyfor engine oils. Some of these, including their interrelationships, are shown in the Glossary(Appendix B).

Viscosity Index (VI) is a measure of viscosity change with temperature. VI has its origins inpetroleum antiquity. An oil derived from a Gulf Coast crude oil showed a high rate of change ofviscosity with temperature and was arbitrarily given a VI value of 0. A Pennsylvania crude-derived oil, with a low rate of change of viscosity with temperature, was given a VI of 100. Alloils since then have been compared on this scale. The best of the normal mineral base oils(Group I and some Group IIs) have VIs in the 90's. Synthetic oils and some very highly refinedmineral oils (Group III, some Group IIs) can have VIs in the 105 to 160 range, reflecting theirsuperior viscosity/temperature properties.

Temperature Viscosity Coefficient (λλλλ)))) is a more fundamental indication of change of viscositywith temperature, which may soon become more widely used. It is (see Table 1-4 for somevalues):

λ = viscosity in cSt at 40°C – viscosity in cSt at 100°C viscosity in cSt at 40°C

Grease consistency is measured by “penetration” values. These are determined from thedistance (in 0.1 mm units) that a standard American Society for Testing and Materials (ASTM)



1-3

cone sinks into a standard cup of grease at 77°F (25°C). Because consistency can change withshear or “working,” greases are often worked in a standard worker before penetrations aremeasured. The worked penetrations corresponding to the various grease grades are shown in theGlossary (Appendix B). P60 refers to the penetration after 60 double strokes in the worker; P 10,000

refers to 10,000 double strokes, and so on. Grease grades are determined by P 60 values (seeAppendix B for grade determinations).

Dropping Point is another ASTM grease measurement. It is the temperature at which a greasejust begins to melt or separate. The use temperature of a product is related to its dropping point.

1.3 Additives

Up to about 15% of a finished lubricant consists of materials added to the starting base oil tocreate properties or enhance those that already exist. Table 1-2 shows finished lubricants and theadditives they might contain.

Table 1-2Common Additives in Various Lubricants

Common Lubricants Engine Oils TurbineOils

Hydr.Oils

GearOils

Compr.Oils

Greases

Gasoline Diesel

Additives

VI Improvers x x x x

Detergent/Dispersants x x x

Basic MetalCompounds

x x x

Antiwear Agents x x x x x x

Antiscuff (EP) Agents x x*

Antioxidants x x x x x x x

Rust Inhibitors x x x x x x x

Antifoamants x x x x x x

Gelling Agents x

* Premium greases for ball and roller bearing lubrication generally do not contain antiscuff agents.



1-4

1.3.1 Vl Improvers

Viscosity Index (VI) improvers are listed first because they are used in the largest amounts toperform their function. They thicken lower viscosity base oils and, in the process, flatten themixture's viscosity/temperature slope. This improves VI. These additives are widely used tomake mineral oil-based multigrade engine oils. VI improvers are not required to makemultigrade products from synthetic base oils or some Group III mineral base oils. This is becauseof the superior viscosity/temperature properties of such base oils (see Table 1-4).

1.3.2 Detergent/Dispersants

Detergent/dispersants keep any deposit precursors in suspension instead of agglomerating to plugpiston rings, key oil passages, etc. or collecting as sludge. Detergent/dispersants were among thefirst additives used and continue to be of high importance in engine oils where deposits can comefrom combustion products. They are sometimes used in compressor oils, as well.

1.3.3 Basic Metal Compounds

Basic metal compounds have some detergency and good rust preventing properties but theirmain function is to neutralize acids in diesel engine oils. The acids come from the combustion ofsulfur in fuel and the fixation of nitrogen in combustion air. Reaction with water converts thesulfur and nitrogen oxides to corresponding acids. If not neutralized, they cause corrosive wearof engine parts. The need for basic metal compounds (base reserve, high base number) in partdepends on the sulfur content of the fuel – the lower the sulfur the less need for base. Thenational trend toward low sulfur diesel fuel to control emissions will eventually reduce the use ofbasic metal compounds.

1.3.4 Antiwear and Antiscuff (EP1) Additives

Antiwear additives are very widely used in engine and industrial lubricants, but not universallyso. Antioxidants, on the other hand, are universally used. Antiscuff additives are less widelyused, as indicated in Table 1-2. Antiscuff materials can be viewed as more surface-invasive and,therefore, stronger in action than antiwear additives. Both antiwear and antiscuff additivesfunction by interposing a relatively shear-resistant chemical film between load bearing metalsurfaces. The general mechanism by which these additives work is shown in Figure l-l 2.

At the top, two moving metal surfaces under little or no load are held apart by an oil film. Withthe application of a load, metal-to-metal contact occurs. At the bottom, when the load is applied,the contact is prevented by a tough chemical film. Sulfur/phosphorus compounds are the mostcommon antiwear agents and they form films of iron, sulfur, and phosphorus compounds toprotect the surfaces. Active, organic sulfur compounds are the principal materials used as

1 Antiscuff is a modern replacement for the term, EP. Scuffing is defined as metal transfer due to adhesionin metal-to-metal contact.2 Footnote refers to q, Appendix A, Section A.2.



1-5

antiscuff agents. All of these additives act similarly in both oils and greases and they can betemperature-sensitive. Mild antiwear can also be provided in greases from the gelling agents.

Figure 1-13

Effect of Antiwear and Antiscuff Additives

1.3.5 Antioxidants

The principal enemy of any lubricant is oxidation. The onset of oxidation cannot be preventedbut only delayed. The delay is called the induction period. Antioxidants extend the inductionperiod very effectively. Once this period is exceeded, however, oxidation can occurexponentially, as shown in Figure 1-2. This results in physical and chemical property changes,for example, fluidity change and acid formation. In common with all chemical reactions,oxidation increases with temperature – the rate doubles with each increase of about 18°F (10°C).However, doubling a very low rate still yields a low rate and the rate is low during the inductionperiod.

3 Footnote refers to q, Appendix A, Section A.2.



1-6

Figure 1-2Hydrocarbon Oxidation Process

1.3.6 Rust Inhibitors and Antifoamants

Rust or corrosion inhibitors are also widely used. They perform by forming a weakly adsorbedfilm on the surfaces to be protected. An antifoamant is also used in most oils. They are polymersand silicone fluids in low concentration, which affect surface tension to reduce the foamingtendency. They also help provide good deaeration properties. Recently, there is a move awayfrom silicone antifoam materials for oils, for example, turbine oils. This is because there can betight silicon content specifications to control dirt contamination.

1.3.7 Gelling Agents

A gelling agent is used to convert an oil into a grease, thus providing the lubricant with itsunique stay-in-place function. The oil that is gelled also contains the other additives requiredto provide the necessary properties shown in Table 1-2. In addition, the gelling agentidentity defines many of the grease's other performance characteristics. These are detailedin Appendix A, Table A-13.

1.4 Synthetic Lubricants

Synthetic lubricants are man-made lubricants whose base oils are chemical productsmanufactured or “synthesized” to provide properties not available in Group I and some Group IImineral-oil-based products. Although the synthetics represent less than one percent of the totallubricant inventory, they are available for and are used in many applications. Table 1-3 showsthe various classes of synthetic base oils and the finished products in which they are used.



1-7

Table 1-3Synthetic Base Oils1 and Their Application

Engine Oils IndustrialOils

Greases FireResistant

Oils

RelativeCost2

Jet Other

Synthetic Oils

Poly(alpha-olefins)(PAOs)

x x3 x3 4-8

Diesters x x4 5-7

Polyolesters x 10-14

Phosphate Esters x5 10

Polyethers(Polyglycols)

x 6-8

Silicones(Siloxanes)7

x6 x6 30-100

Perfluoropolyethers x x 80-800

Polyphenylethers x x 100+

Chlorofluorocarbons x 100+

1 In the field of metalworking/cutting fluids, water-based fluids are sometimes called “synthetic.”2 Approximate cost multiplier relative to most common mineral oil.3 Mobil SHC series, Mobilgrease 28.4 Beacon 325 (Exxon).5 Fyrquel (Akzonobel), etc.6 Dow Corning; GE.7 Including halogenated species.

The poly(alpha-olefins) (PAOs - Group IV) are the most widely used synthetic base oils inindustrial and automotive lubricants. However, the differences between them and the new highlyrefined (hydrocracked4) mineral oil base stocks (Group III) are becoming blurred as shown inTable 1-4. Because of this, the marketplace is likely to see fewer PAO-based products in thefuture. The hydrocracked base oils cost half as much as the PAOs and their properties are oftensimilar.

4 This process involves hydrogenation of normal mineral oil feed material with special catalysts. These catalystsdirect the process to rearrange the undesirable molecular constituents of the feed into species that resemble those inthe polymerization of the alpha-olefins (PAOs). The severity of the process dictates the properties of the finalproduct as in Table 1-4.



1-8

Table 1-4Comparative Properties of PAO Synthetic Base Oil and Various Mineral Base Oils

Mineral OilsGroup I*

Mineral OilsGroup II*

Mineral OilsGroup III*

PAOAPI Group IV*

Viscosity, 40°C, cSt 32 44 39 32

Viscosity, 100°C, cSt 5.3 6.6 7.0 6.0

Viscosity Index 95 102 135 136

Pour Point, °C -15 -15 -20 -66

Flash Point, °C 210 230 240 246

Fire Point, °C 240 — — 272

Evaporation Loss,Wt%(6.5 Hr. at 204°C)

16 — — 4

Aniline Point, °C(ASTM D 611)

108 115 127 127

* American Petroleum Institute (API) base stock classification

The good low temperature properties of the PAOs are reflected in the viscosities, viscosity index,and pour point. They are matched, except for the last, by the Group III mineral base oil. Thelower volatility for a given viscosity shows up in higher fire point and lower evaporation loss.The aniline point is a measure of solvency – the lower the number, the higher the solvency. Herethe PAO and Group II and III oils are inferior to the normal, or Group I, mineral oil. That is, ifsludge is formed, it will precipitate out later with a Group I-based product. However, the sludge,which is oxidized material, might not form so readily with the synthetic oil- or Group II- or III-based product. This is because the Group II, III, and IV oils generally give a higher degree ofoxidation resistance with a given amount of antioxidant.

Improved performance with synthetic oil-based lubricants comes with an increased price tag.This is shown in Table 1-3. Such costs make it hard to justify the use of synthetic-based productsunless the application demands their superior properties. For example, if equipment needinglubrication is used in subzero weather, it is worth the added cost reliably to start or operate thefrigid apparatus with a PAO-based oil. The cost, of course, is only half as much if a Group III-based product can be used. In another example, if fire-resistant oil is needed, then the additionalcost is justified. But if these properties are not required, there is no need to use expensivesynthetic products. The vast majority of the nuclear power plant lubrication requirements can bemet with high quality mineral oil-based products.


2-1

2 RADIATION EFFECTS ON LUBRICANTS5

In normal operation, lubricants must withstand the stresses of temperature, shear, pressure (load),and exposure to oxygen in the air. In nuclear power plants, exposure to nuclear radiation is anadded stress. Overall effects of thermal and radiation exposures are similar. For example, bothshow thresholds below which changes in bulk properties of exposed materials are not significant.Both also accelerate oxidation, the main foe of lubricants in service.

With radiolysis, as well as pyrolysis, color change occurs first, signaling beginning oxidation andother structural changes. Gas evolution also takes place early, followed by changes in fluidity assecondary reactions take over. The final product of very high thermal or radiation exposure is anintractable solid, no longer a lubricant.

Radiation effects are directly related to the radiation energy input. This input is expressed interms of the rad (100 ergs/gram of absorber = 4.3 X 10-6 Btu/lb). The radiation sensitivity oflubricants versus other things is shown in Figure 2-1. The more complex the irradiated object theless tolerant it is of irradiation. Note the effect on the ultimate in complexity – homo sapiens!

Figure 2-1Dose Levels for Radiation Effects

5 Bolt, Carroll, “Radiation Effects on Organic Materials,” chapter 9, Academic Press (1963); Bolt chapter in Boozer,“Handbook of Lubrication,” Volume 1, CRC Press (1983).


Radiation Effects on Lubricants

2-2

Mechanistically, incident gamma radiation affects organic matter through initial collisions withelectrons of individual atoms of molecules. This is shown in Figure 2-2. About half an incomingray's energy is given up to a scattered electron and the weakened gamma ray goes on to repeatthe process. The charged electron, knocked from its position by the incoming gamma ray, goeson to lose its added energy by creating increasingly intense ionizations and excitations inneighboring molecules.

Figure 2-2Interaction of a Gamma Photon with Organic Matter

Incident high energy neutrons interact initially with atomic nuclei of irradiated material insteadof with the electrons in gamma ray interactions. This knocks out protons and these chargedparticles go on to act in the same fashion as described for incident gamma rays.

Primary interactions in radiolysis take place in some 10-14 seconds. Secondary reactions thatresult in new molecular products occur in the next 10-2 seconds. To minimize change, excitationwithout decomposition needs to be fostered. Use of additives, for example selected compoundscontaining sulphur that neutralize excitation without C-C bond fissure, is a means of doing this.Another means is to employ base oil molecules that dissipate the input energy largely throughthe generation of heat (resonance), that is, aromatic compounds. Thus, the effect on lubricantsdepends on the chemical makeup of both the base oil and additives. Figure 2-3 shows this forbase oils.



2-3

Figure 2-3Upper Limits of Radiation Doses Resulting in Failure of Various Base Fluids

Note the effect of aromatic content – the polyphenyls, poly(phenyl ethers), and alkylaromaticshead the list in radiation resistance. Phenyl groups are basic units of aromaticity. Aromatics,because of their poor viscosity/temperature properties, are deliberately removed from mineralbase oils. However, aromatic compounds can be designed through synthesis to have goodproperties. Such materials (alkylaromatics) are employed in making lubricants designed formaximum radiation resistance. The introduction of phenyl groups even into poor performingmolecules will improve their radiation resistance. For example, phenyl silicones are a notchbetter than methyl silicones in radiation resistance.

The physical effect of radiolysis on greases is that they mostly soften with initial exposure,reflecting degradation of their sensitive gel structure. Eventually, this is followed by hardeningas the effect on the oil component takes over. Figure 2-4 shows the typical softening effect.Although this grease exhibits stability in the 106-108 rad region, other greases can either harden orsoften in this region. This is before the major softening indicated in Figure 2-4 and before effectson the oil component set in.



2-4

Figure 2-4Radiolysis Effects on a Lithium Complex-Gelled, Mineral Oil-Based Grease

The effect of radiation exposure on oxidation stability, a key property of turbine oils, is shown inFigure 2-5. Other effects on oils include gas evolution, evidenced by a decrease in flash pointand increase in vapor pressure. The gas is hydrogen and low molecular weight hydrocarbons thatcome from C-H and C-C bond fissure. The C-C bond breakage can also yield compounds thateventually “double” or similarly polymerize to cause viscosity increase.



2-5

Figure 2-5Relative Oxidation Stability of Irradiated Mineral Oil-Based Steam Turbine Oils in TurbineOil Stability Tests (TOST) (ASTM D 943)

The effect of radiation dose rate is also highlighted in Figure 2-5. The doses shown weredelivered to the test samples at widely different rates – differing by a factor of about onethousand. Yet the variation in the test results falls within the reproducibility limits of the ASTMD 9436 test. Thus, there appears to be no appreciable dose rate effect. All the exposures weremade in air for the indicated doses and then the oils were tested. Note that the dose below whichno significant oxidation takes place is about 5 X 106 rads.

This dose rate concern comes up primarily in applying radiation effects studies to plantsituations. Most radiation effects studies are accelerated, that is, at higher dose rates than those inthe plant, to allow results in a reasonable time. The answer is complicated by oxidation effects –more oxidation would be expected over the longer term, simply due to heating in air underirradiation. Oxidation is mitigated by oxidation inhibitors. All high quality lubricants have suchantioxidants. Without them oxidation could be interpreted as a dose rate effect.

Even with good inhibitors, the acceleration of oxidation in the presence of radiation is animportant consideration from a maintenance point of view. Lubricant life will be reduced if thereis excessive exposure to oxygen in the air, for example, where there are unrepaired air leaks onthe inlet side of a pump in a radioactive area. In the example, a rich supply of oxygen andirradiation at high temperature can take its toll on the lubricant.

6 ASTM D 943-81 (91), “Test Method for Oxidation Characteristics of Inhibited Mineral Oils” [Turbine OilStability Test (TOST)].



2-6

Generally, radiolysis of lubricants is not a problem in nuclear power plants. It takes radiationdoses above those prevailing in normal nuclear plant operations to make appreciable changes inbulk properties of lubricants. An accident scenario (a DBA) may produce high enough radiationexposure to cause significant property changes. In such a case, the equipment being lubricateddoesn't have to operate very long or be maintained. The equipment itself is very tolerant offluidity changes in lubricants. For example, antifriction bearings in motors can go just fine, atleast in the short run, with grease worked penetrations from about 200 to over 400. This isequivalent to a change in consistency from a 4- to a 00-grade – a wide variation.

This tolerance exists even under stress. Figure 2-6 shows test data for a grease in a 10,000 rpmbearing at various temperatures. An Arrhenius plot (log bearing life versus inverse of absolutetemperature) is shown. Note the change in life of irradiated grease versus that of unirradiatedproduct. It took over 108 rads to make much of a difference in the grease's performance.

Note: Irradiations were conducted in air (allowing some oxidation) to the doses shown.Tests as per ASTM D 33367 were then run on the greases.

Figure 2-6Effect of Temperature and Irradiation on Bearing Life of a Sodium Salt-Thickened, MineralOil-Based Grease

7 ASTM D 3336, “Test Method for Life of Lubricating Greases in Ball Bearings at Elevated Temperatures.”



2-7

The effects of irradiation on oils and greases are summarized in Tables 2-1 and 2-2.

Table 2-1Effects of Irradiation on Common Oils

Radiation Dose Effect

< 106 Rads No unusual problems.

106 - 107 Rads Things begin to happen; someturbine oils borderline.

107 - 108 Rads Most oils usable; somemarginal.

108 - 109 Rads The best oils usable; mostbecome unusable.

109 - 1010 Only special products willwork.

> 1010 No oil usable.

Table 2-2Effects of Irradiation on Common Greases

Radiation Dose Effect

< 106 Rads No unusual problems.

106 - 107 Rads Things begin to happen; some greases borderline.

107 - 108 Rads Most high quality products usable; others not.

108 - 109 Rads Most greases unusable.

109 - 5 x 109 Rads Special products required.

> 5 x 109 Rads No grease usable.

Values for temperature and radiation operating ranges are given for individual products inAppendix A, Tables A1-A12. In these tables, the first number listed in each category is the valuebelow which little, if any, property change will occur and long use life can be expected. Thesecond number is the point where appreciable change is expected and surveillance of theequipment is required. The need for lubricant changeout should be anticipated at this point.



2-8

2.1 Effect on Elastomers

Elastomers are used frequently as seal materials in nuclear power plants. If one is concerned withradiation-resistance, elastomers are the weak link. Figure 2-7 shows the resistance to irradiationof elastomers versus lubricants. The elastomers are about ten times more sensitive to radiationthan lubricants.

Figure 2-7Relative Sensitivity of Common Lubricants and Elastomers to Irradiation

Table 2-3 shows the effect of common lubricants on various elastomers. Neoprene and Nitrilerubber and the epichlorohydrins are the principal oil and grease resistant products.

Table 2-3Resistance of Elastomers to Effects of Common Oils and Greases

Elastomer Resistance

Natural Rubber Very Poor

Neoprene Good - Excellent

Ethylene/propylene Very Poor

Isoprene Very Poor

Nitrile (high) Excellent

Epichlorohydrin Excellent

Urethane Fair - Excellent

Silicone Fair - Poor



2-9

The picture changes somewhat as the elastomers are exposed to radiation. Figure 2-8 illustratesthis performance. The natural rubbers and urethanes are most resistant to radiation, with thenitriles ranked a close second.

Figure 2-8Resistance of Elastomers to Irradiation


3-1

3 LUBRICATION, FRICTION, AND WEAR

Three lubrication mechanisms have been established in tribology – the study of surfaces inrelative motion. These are:

• Hydrodynamic lubrication (HDL)

• Elastohydrodynamic lubrication (EHL)

• Boundary lubrication (BL)

A single mechanism might not prevail in any one application but a combination might existdepending on geometry and/or operating conditions. For example, the balls in ball bearingsinvolve EHL in their relationship to the bearing races and BL in their relationship to the cages orretainers. It is important to understand the three types of lubrication in order to be clear aboutlubricants and how they function.

Friction is the resistance to the relative motion of surfaces and is an indicator of the efficiency ofthis motion. It is important because poor efficiency relates to high energy consumption. Wear, orthe undesirable removal of material from contacting surfaces due to relative motion, shortensequipment life and decreases its reliability.

3.1 Hydrodynamic Lubrication (HDL)

HDL conditions exist when a fluid film completely separates moving surfaces and there is nosurface-to-surface contact. This is the most desirable regime of lubrication because friction andwear are low under these conditions. HDL is the most common mode of lubrication forcomponents of industrial machines. Examples include simple journal bearings and bushings, andturbine shaft bearings. Factors affecting HDL are the viscosity of the lubricating fluid, itsadhesion to the surfaces, the sliding or rolling velocity of the components, the shape of thesurfaces, and pressure (load) between them.

Film thicknesses for effective HDL range from 0.0001 to 0.005 inches (40-200 microns). Thecreation of such films is fostered when the shape of the surfaces allows a wedge of lubricant toform between them (see Figure 3-1). The failure of HDL usually results from too thin a film, dueto high temperatures, that reduces the viscosity of fluids, low speed that discourages wedgeformation, and shock loads. Another very common cause of film failure is damage bycontaminants, such as dirt, in the oil.


Lubrication, Friction, and Wear

3-2

Figure 3-1Hydrodynamic Lubrication

3.2 Elastohydrodynamic Lubrication (EHL)

The name, elastohydrodynamic, implies that a full oil film exists between moving surfaces thatare elastically deformed. EHL occurs only in situations where loads are concentrated over smallareas, for example between balls/rollers and races in rolling element bearings and between gearteeth. In EHL the load is sufficient to deform the surfaces elastically at the point or line of nearcontact (Figure 3-2). The oil is trapped between the deformed surfaces and the resulting highpressure increases the oil's viscosity by several orders of magnitude. The surface deformationalso increases the load bearing area. The combination of extremely high oil viscosity andincreased area over which the load is applied keeps the surfaces from touching.

Figure 3-2Elastohydrodynamic Lubrication

Lubricant film thickness in EHL is smaller than in HDL and the thinner the film for a given oilviscosity the higher the friction. As with HDL, conditions that make for thinner films shortencomponent life in EHL. High temperatures and loads, low speed or oscillatory operation, andespecially lubricant contamination, shorten life. If bearings oscillate, HDL and EHL fail to occur.Wear is low under ideal EHL conditions. Failure of components in EHL is by contact fatigue.



3-3

Because of the cyclic elastic deformation, fatigue cracks and pits are formed. This contact fatiguedetermines the catalog life of a rolling element bearing.

3.3 Boundary Lubrication (BL)

BL conditions prevail when HDL and EHL fail and surface-to-surface contact occurs (see Figure3-3). The word, boundary, suggests surface involvement. BL occurs with high loads andtemperatures, low sliding velocities, and rough surfaces. Examples of BL are bearings duringstart up and shut down, oscillating bearings, piston rings at top-dead-center, worm gears, andmetal cutting operations. Friction and wear in BL are dependent upon the shape and compositionof the surfaces and the properties of the lubricant. Friction results from the shear of theinterfacial material, which includes adhesion between the surfaces and the shear of other solidsor liquids in the contact. For example, if the additives in an oil form a soap film of low shearstrength on the surface, friction will be low. If the film formed is a shear resistant inorganic salt,for example iron sulfide, friction will be higher. Three types of films might form in BL,physically adsorbed, chemisorbed, and chemical reaction films.

Figure 3-3Boundary Lubrication (Fragmented Roughness)

3.3.1 Physically Adsorbed Film

Physically adsorbed film involves the adsorption of the non-polar molecules of the base oil atrandom on the surfaces (see Figure 3-4). The adsorption is reversible so, as temperatureincreases, the film desorbs and fails to keep the asperities in the surfaces apart (for asperities, seeSection 3.5). Mineral oils or PAO synthetic base oils are in this category. If the oil molecules arepolar, for example a polyester synthetic, their adsorption is stronger because of their closepacked nature (see Figure 3-5). Higher temperatures are required to desorb them.



3-4

Figure 3-4Representation of Physically Adsorbed Film—Non-Polar Molecules

Figure 3-5Physically Adsorbed Film—Polar Molecules

3.3.2 Chemisorbed Film

Chemisorbed films (see Figure 3-6) are chemical reaction products between long chain polarcompounds in the oil (or compounds that are added to it) and compounds in the metal surfaces.An example is the reaction between a fatty acid in the oil and a metal oxide film from the surfaceto form a soap. The reaction is irreversible so an increase in temperature increases its rate. Themelting point of the soap film is the temperature limitation. The additives in an oil thatchemisorb are termed lubricity additives because they reduce friction as compared to that of thebase oil alone.

Figure 3-6Chemisorbed Film (Xs indicate chemical bond)



3-5

3.3.3 Chemical Reaction Film

Chemical reaction films are also formed through irreversible reactions but the products areinorganic salts. Additives such as sulfur compounds react with surfaces containing iron to formiron sulfide. Such high melting point compounds inhibit scuffing by preventing bare metal-to-metal contact. They are called antiscuff (formerly known as EP) additives. Oxygen, which is inoils from the air, can also act as an antiscuff agent by reacting with metals to form thicker oxidefilms and prevent metal-to-metal contact.

The relationship between HDL and boundary lubrication (BL) for various operating conditions isshown in Figure 3-7. Note the effects of the various parameters on the friction coefficient. With agiven speed and load, a low viscosity oil will allow boundary lubrication and a very highviscosity oil will increase fluid friction.

Figure 3-7Effects of Various Parameters on Friction Coefficient

3.4 Solid Lubricants

The presence of a film or a coating of other solids between surfaces reduces surface-to-surfacecontact. It might also reduce friction and wear. Solid lubricants are classified as follows:

• The metal oxides that form in air, for example iron oxide, Fe3O4, on steel (which reducesfriction), or aluminum oxide (which increases friction).

• Preformed coatings such as soft lead or Babbitt on aluminum in a journal bearing, thelaminar graphite or molybdenum disulfide on steel, or poly(tetrafluoroethylene) (Teflon) onsteel.

• Boundary lubricant films such as soap from a fatty acid in the oil, or iron phosphate fromtricresyl phosphate additive, iron borate from boron additive compound, or iron sulfide froma sulfur additive compound in the oil.

• Inorganic conversion coatings such as iron/manganese phosphate on steel.



3-6

3.5 Nature of Machined Surfaces8

Machined metallic surfaces are rough on a microscopic scale (see Figure 3-8) and covered with athin film of oxide. The microscopic bumps contained on these surfaces are called asperities.When two machined surfaces are placed together, the area of real contact (where a few asperitiestouch) is much less than the apparent area of contact. This real contact area increases with loadbecause more asperities are crushed, thus increasing the contact surface.

Figure 3-8Machined Surface

3.6 Wear

Wear is the undesirable removal of solids from a sliding or rolling component. There are manykinds of wear. In analyzing a wear problem in a machine, it is necessary to determine the kind ofwear that occurred. Analysis requires microscopic examination of the worn area and a close lookat the used lubricant. Wear is generally proportional to the applied load and the amount ofsliding. The major kinds of wear are:

• Adhesive Wear — the removal of material due to adhesion between surfaces.

– Mild adhesion — is the removal of surface films, such as oxides, at a low rate. This is theminimum wear expected under BL conditions.

– Severe adhesion — the removal of metal due to tearing, breaking, and melting of metallicjunctions. This leads to scuffing or galling of the surfaces and even seizure.

• Abrasive Wear — the cutting of furrows on a surface by hard particles, (for example, sandparticles between contact surfaces, or hard asperities on an opposing surface). Hard coatingscan reduce abrasive wear.

• Erosive Wear — the cutting of furrows on a surface by hard particles contained in a fluidtraveling at high velocity. Wear caused by sand blasting is an example of erosive wear.

• Polishing Wear — the continuous removal of surface films, laid down via a chemicalreaction from an additive in oil or by very fine hard particles in the lubricant, and so on.

8 Godfrey, Douglas, “Recognition and Solution of Some Common Wear Problems Related to Lubricants andHydraulic Fluids,” Lubrication Engineering, 43, 2 (1987).



3-7

• Contact Fatigue — the cracking, pitting, and spalling of a surface in sequence due to cyclicstresses in a contact. Contact fatigue is most common in rolling element bearings, gear teeth,and cams.

• Corrosive Wear — the removal of corrosion products from a surface by motion, such as therubbing off of rust.

• Fretting Corrosion — the removal of metal oxides from a surface due to a reciprocatingsliding motion of extremely low amplitude generated by vibration.

• Electro-Corrosive Wear — the removal of metal by dissolution in a corrosive liquid with theaid of electric currents. One source of currents is streaming potential from high velocityfluids. The oil serves as the electrolyte.

• Fretting Wear — localized wear of lubricated surfaces due to reciprocating sliding ofextremely low amplitude because of vibration.

• Electrical Discharge Wear — the removal of molten metal from surfaces due to electricalsparks between them. High static voltages are sometimes generated by large rotatingmachinery and these are relieved by sparking to regions of lower potential.

• Cavitation Damage — the removal of material due to cracking and pitting caused by high-energy implosions of vacuous cavities in a cavitating liquid. Liquids cavitate when suddenlysubjected to low pressures.

• False Brinelling — localized wear in lubricated rolling element bearings due to slight rockingmotion of rollers against raceways. Wear depressions match the position of the rollingelement.


4-1

4 APPLICATION PROBLEMS

4.1 Compatibility of Mixed Products

Lubricants can be incompatible with one another on mixing and can potentially causedegradation of properties and performance. Solid formation with oil mixtures can take placebecause of additive interaction or solubility difficulties. With greases, the usual result ofincompatibility is breakdown of the grease gel structure to produce softness. Both of theseeffects can be undesirable in lubricant applications.

Incompatibility can be avoided by not mixing products. Procedures should be set up to eliminateunwanted mixing. When a change to a new product is dictated, careful cleanup should beemployed to keep less than about 5% of the old material in the new. Remember, don't mix! Ifyou inadvertently do, you face incompatibility risks.

4.1.1 Oils

Lube oils are mostly compatible and miscible with one another in all proportions. A notableexception is mixing a product that contains a chemically acidic additive, for example a turbineoil, with a product that contains a basic additive, for example an engine oil. One will neutralizethe other in the presence of moisture and frequently cause a precipitate to form. Precipitates canplug filters and/or other oil passages and cause oil starvation and equipment failure. If you don'tknow the chemical makeup of the particular products you have, your lubricant supplier can giveguidance on this point so you can avoid the acid/base concern. (Anyhow, mixing of lubricantsshould be avoided.)

4.1.2 Greases

These products present a different case. With inadvertent mixing, possible additive interactions(other than those involving gelling agents) pose only some loss of those functions provided bythe reactants. Precipitates are generally no problem (grease is already semi-solid). Gelling agentinteraction is a concern, depending on the application. Table 4-1 gives compatibility information(Meyers, E. W., NLGI Spokesman 47, (1), 24,1983; Meade, F.S., “Compatibility of Greases,”Rock Island Arsenal Report 61-2132, 1961). Examples of data on which the table is based are inFigure 4-1. (See also Note No. 5, NMAC Lube Notes, July 1993.)

A consistency change of 30 points or less in worked penetration in more than one mixture in agiven set denotes compatibility (“C”) in the table. This change is measured by deviation from thestraight line between the two 100% points. Softening is the most likely result of incompatibility,


Application Problems

4-2

although hardening can take place (< 10% of the cases). Softening is of little concern in acontained system, such as a Limitorque gearbox (unless leakage is rampant). It is only the stay-in-place function that is affected – the lubrication function is largely handled by the oilcomponent and its soluble additives. A problem does occur if the grease flows away from thepart being lubricated. Rolling element bearings are vulnerable here although they have quite atolerance for changes in grease consistency. This tolerance runs from about 200 to about 400 inworked penetration. However, the departure from around the 280 norm might cause someincrease in required maintenance.

Table 4-1Compatibility of Greases

Alu

min

um

Co

mp

lex

Bar

ium

So

ap

Cal

ciu

m S

oap

Cal

ciu

m 1

2-H

ydro

xyst

eara

te

Cal

ciu

m C

om

ple

x

Ino

rgan

ic (

Cla

y)

Lit

hiu

m S

oap

Lit

hiu

m 1

2-H

ydro

xyst

eara

te

Lit

hiu

m C

om

ple

x

Po

lyu

rea

So

diu

m S

oap

Cal

ciu

m S

ulf

on

ate

Co

mp

lex

(Cal

ciu

mC

arb

on

ate/

Su

lfo

nat

e –

CC

S)

Aluminum Complex I I C I I I I C I NA I

Barium Soap I I C I I I I I I NA B

Calcium Soap I I C I C C B C I C NA

Calcium 12-Hydroxystearate

C C C B C C C C I NA NA

Calcium Complex I I I B I I I C C NA C

Inorganic (Clay) I I C C I I I I I B I

Lithium Soap I I C C I I C C I C C

Lithium 12-Hydroxystearate

I I B C I I C C I NA C

Lithium Complex C I C C C I C C I NA C

Polyurea I I I I C I I I I C I

Sodium Soap NA NA C NA NA B C NA NA C I

Calcium SulfonateComplex (CalciumCarbonate/Sulfonate– CCS)

I B NA NA C I C C C I I

*Incompatiblity is defined as a change exceeding 30 points (1 point = 0.1mm) in ASTM worked penetration in more than one of25/50/75% blends. B = Borderline Compatibility, C = Compatible , I = Incompatible, NA = Not Available.



4-3

As with oils, different greases should not be mixed. The data cited in the table should beconsidered generic in nature. A “C” in Table 4-1 is not an endorsement to allow mixing becausedifferent grease formulations might give different data. With inadvertent mixing, compatibilityrisks are generally less if products with at least the same gelling agent are involved. However,reversals do occur. To be sure of compatibility or incompatibility, tests on specific greases mustbe run.

Figure 4-1Compatibility of Mixtures of Greases With Different Gelling Agents

Compatibility test results will sometimes vary with the method used. Table 4-2 lists some ofthese methods. High temperatures in the storage (aging) phase are employed to provide testacceleration and assure that any incompatibility will be picked up. A consideration here is not toexceed the heat stability of the individual mixture components. The more severe mix proceduresare undertaken to assure thorough mixing.

The method we prefer involves 25/75, 50/50, and 75/25 mixtures (10/90 and 9/10 are sometimesalso used) of two components stirred with a hand-held electric mixer before aging at 250°F(121°C) for 72 hours. The starting materials get the same treatment. Then, after cooling to roomtemperature, the 60-stroke worked penetrations are run on all samples. Compatibility/incompatibility is determined as in Figure 4-1. Dropping points can also be run on the treatedsamples. ASTM has now developed the compatibility test listed in Table 4-2. It is more complexand, therefore, three times as expensive to run as the method just cited. Its interpretation is alsomuch more restrictive.



4-4

Table 4-2Grease Compatibility Tests

Group Mix Storage(Aging) Time

Temp Difference in P60 1 to Fail

Rock IslandArsenal

Hand Mix +P10,000 1

0 70°F (21°C) ±10

Meyers Hand Mix 72 hr. 250°F (121°C) ±30 for > one mixture

Mobil RIV Tester 2 hr. 200°F (93°C) 0 - 30 (Compatible)31- 60 (Borderline)61+ (Incompatible)

Bolt &Associates

Motor Stirrer 72 hr. 250°F (121°C) ±30 for > one mixture

ASTMD 6185

P100,000 1 248°F (120°C)

167°F (75°C)

70 hr.

1400 hr. 2

> about 11 above thevalue for the thickestcomponent or 11 belowthat of the thinnestcomponent

1 ASTM 60-stroke or 10,000- or 100,000- stroke worked penetration2 Applies to low dropping point greases.

4.2 Shelf Life

In general, lubricants are very stable when exposed to the mild conditions encountered in storageor “on the shelf.” Storage life of many years should result. This assumes, of course, no exposureto rain, sunlight, or sources of heat such as adjacent steam lines. Why then do suppliers oftenlimit recommended shelf life to some two to three years? For several reasons:

• Formulations change from time to time for supply and performance reasons – base oilchanges, additive changes, and so on. Incompatibility between old and new versionssometimes is a problem. Storage life restrictions limit the supplier's responsibility for oldformulations.

• Conditions of storage can vary widely and some deterioration can take place under situationsover which the supplier has no control. For example:

– If an oil were frozen, that is, cooled below its pour point, the solubilities of its additivescould change. In an extreme case, a part of the additive package could drop out ofsolution and perhaps not re-dissolve upon return to normal ambient temperature. Such anevent would be rare.

• With greases, some cosmetic (but mostly nonfunctional) changes can take place. These relateto the problems described in Section 4.4, “Continuous Versus Intermittent Use.” Forexample:

– Age hardening, that is, hardening during the first few months of life. This occurs mostlywith soft greases – consistency generally recovers on working.



4-5

– Surface color change.

– Surface cracking from shrinking on cooling after manufacture or on heating and coolingin storage.

– Bleeding, or oil separation. The separated oil can be decanted or stirred back in; it is onlya small portion of the total. This occurs mostly with soft greases made with low viscosityoils. A small amount of bleeding is acceptable. (See ASTM D 1742 for perspective.)

Suppliers' reluctance to sanction extended shelf life is understandable. Although lubricantchanges in storage are mostly cosmetic, they can be sources of many complaints. However,attention to storage conditions (including those for drums), for example, avoidance oftemperature and other environmental extremes, will eliminate virtually all the potentialproblems. A few simple tests, for example, sensory tests and infrared (see Section 5.3,“Lubricant Testing”) on the questionable lubricants versus an authentic sample will giveconfidence that stored material is still acceptable. Storage of the drums should be indoors ifpossible. If outdoors, drums should be out of the sun and stored with a plastic lid or on their side(bung on the upside) to avoid standing water and its leakage into the drum contents.

4.3 Time/Temperature/Radiation Considerations

Figure 4-2 shows how time, temperature, and irradiation relate to lubricant life (point at whichchange-out is necessary). The vertical scale is logarithmic and gives lubricant life in hours. Thehorizontal scale is the inverse of absolute temperature.

The slope of the band represents an approximate doubling of life for every 10°C (18°F)temperature decrease. One expects this for chemical reactions. The band is used to illustrate thatthe change might be more or less, depending on the chemical make-up of the lubricant. Also, thebest performing lubricants will be on the right side of the band and the poorest performinglubricants on the left. Note that the whole band moves to the right in a parallel fashion as lessstress is involved. The band moves to the left if there is more stress.



4-6

Figure 4-2Time/Temperature/Irradiation InterplayContinuous Operation in Air of High Quality Lubricant Under Stress

As an illustration, suppose a piece of equipment must be relubricated every 36 months in anapplication at 93°C (200°F) (A). Then at 104°C (220°F), the relubrication interval woulddecrease to 18 months (B). At 121°C (250°F), the required interval would be 9 months (C). Itwould be somewhat more than this (C') or less (C"), as the temperature effect is smaller orgreater within the band, depending on the lubricant. Note that at 66°C (150°F) lubricant lifewould be extended and off the chart at 300 months! Of course, lubricant life cannot be extendedindefinitely – contamination from dirt, wear debris, etc., might dictate a shorter interval.

Another way to use the figure is to follow a temperature line across the band. For example, at93°C (200°F) the best lubricant under stress would last about 45,000 hours (D), the poorestlubricant, about one-tenth as long (E). More stress would move the band to the left and shortenlubricant life. Irradiation is one of these stresses but it takes a lot of radiation – more than 107

rads – to shift the band appreciably.

The approximate 107 rad level is an irradiation threshold. Below it, most lubricants can tolerateirradiation. Appreciably above it, the life of most lubricants is increasingly at risk (see Section2). Similar temperature thresholds also exist for many lubricants. Up to a certain level, thermal



4-7

effects are relatively minor but, above that threshold, the thermal component of total stress canbecome increasingly large. This is tied in, of course, to the approximate doubling of chemicalreaction rate by each increase of 10°C (18°F) in temperature. If the rate is very low, a doublingdoesn't do much. When the reaction rate is appreciable, doubling has a discernible effect. Thethreshold is where this rate becomes apparent. Note that temperature and radiation dosethresholds are shown for various lubricants in Appendix A.

Oxidation is not addressed specifically in the figure except as an increased stress that would shiftthe band to the left. However, the lubricant life shown is for products exposed in the presence ofair. This is a normal condition and only abnormal exposure conditions, for example bubbling airthrough the lubricant, would be considered an increase in stress.

4.4 Continuous Versus Intermittent Use and Lube Performance

In any plant, much lubricated equipment operates continuously under relatively stableconditions, as when a grease lubricates a motor bearing. The life of that grease, or of the greasedbearing, can be estimated from prior experience or, more generally, from a knowledge oflubrication practice. Often such bearings can run continuously for years. Sometimes, thelubricant must be replenished at prescribed intervals. Now and then, the bearing must be replacedwhen it becomes noisy or shows other distress.

In other situations, a piece of equipment might be on stand-by status until a specified eventoccurs. Then, on signal, the equipment must quickly come up to speed and perform its function.This intermittent duty is not always benign. Start-stop operation of bearings (especially underload) can create wear debris from unusual slippage, even with proper lubrication. A spinningbearing also tends to deflect dirt, dust, and debris more readily than does a stationary unit.

Further, as a heated bearing cools after running, it tends to attract rust-producing moisture. Also,a grease in a stationary bearing can slowly separate oil from the gel, causing the lubricant to dryout. Then, too, stationary bearings are vulnerable to vibrations that can shorten bearing life dueto fretting or false brinelling (see Section 3.6). Thus, extended periods of inactivity are not goodfor long-term performance. Care must be taken to “exercise” the lubricated equipmentoccasionally.

When radiation is involved during lubrication, one would expect frequent operation to be moredamaging to the lubricant than intermittent operation. This is because more exposure to oxygenin the air is involved during agitation and oxidation is accelerated by irradiation. However, thisdoes not hold for greases. Their key gel structure generally benefits from shearing action(agitation) and this offsets the effect of increased oxidation.

In any event, good maintenance practices dictate that the lubricated equipment should undergo:

• Periodic inspections for signs of leakage of oil, accumulation of dirt, oil thickening, greasedrying, or wear fragments in the lubricant.

• Periodic “exercise” to assure that it functions properly without distress. This also maintainsadequate distribution of grease to lubricated parts.



4-8

• Periodic lubricant changes based on experience. Lacking experience, change should be basedon intervals established in similar applications. In some instances, lubricant changeoutperiods are specified by the equipment supplier.


5-1

5 TESTS AND ANALYSES

Lubricant testing is recommended for a host of reasons. These include:

• To check an incoming lubricant to verify its authenticity.

• To determine if a lubricant in storage is still of acceptable quality.

• To study the condition (wear, etc.) of the machine being lubricated. If there is a problem withthe lubricant, there is a strong possibility that the machine will need maintenance.

• To determine if preventive maintenance is being performed properly and effectively.

• To know when it is time to relubricate the machine.

Lubricant testing is both an art and a science. The art is in determining how much science to usein addressing a concern. The full complement of lubricant tests is very broad in its scope andcomplexity but seldom is this full set of tests required. Part of the process is:

• Selecting adequate and appropriate tests.

• Not overkilling with the unnecessary – do the minimum that will resolve the concern.

5.1 Sampling

The first and most crucial step in lubricant testing is to get a representative sample. Samplesshould be taken as follows and handled carefully:

• When the system is stabilized, neither just before nor just after makeup lubricant has beenadded.

• Ahead of filters or centrifuges so as not to miss the contaminants that they remove.

• In suitable, clean, well-labeled containers. Be consistent in sampling method. Take thesample from the same location and under the same operating conditions. In addition, beaware that sampling from the bottom of sumps, where dense materials (for example, waterand metals) settle, can give valuable information on the history of the lubrication.

5.2 Troubleshooting

Operating equipment has a great tolerance for lubricant property changes. Greases or oils canchange by a consistency grade or two and the machinery being lubricated will continue tooperate smoothly. However, an off-grade or contaminated product can hasten equipment distress,which might be manifested by:


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• Temperature increase (at the lubricated part)

• Output decrease

• Noise

• Change in vibration pattern

• Visual indicators, for example leakage

• Wear and corrosion

Often the equipment distress can be anticipated by trending the data from lubricant analyses.(More details are provided on trending in Section 5.5.) Whenever any of these symptoms occur,corrective action must be taken. The action required might sometimes be evident from theinformation derived from the lubricant analysis program itself.

5.3 Lubricant Testing

The first line of surveillance in lubricant testing, or the first step in isolating a problem, is simpleon-site sensory examination. A lot can be learned from looking at, feeling, and smelling the usedlubricant. These sensory tests can signal the need for more complex laboratory tests. A hierarchy,or sequence of tests from the simple to the complex is shown in Table 5-1. Remember, do thesimple ones first!

Table 5-1Sequence of Lubricant Testing

Test Type Description

Sensory Tests Simple tests on-site; compare to known product.

Other Simple Tests Easily done on-site; again back-to-back with known product.

Diagnostic Tests Laboratory; relative test - compare to known product. Skill of technician isvital.

Standard Tests Laboratory; well developed, ASTM methods formulated from round-robintesting. Can be compared on the basis of determined repeatability andreproducibility.

Analytical Tests Laboratory; Not always standard - compare to known product. Skill oftechnician is vital. Often a judgment call is involved.

Each of these test types is discussed in detail in the following sections.

5.3.1 Sensory Tests

These tests can be performed at the plant by personnel with only limited experience. The bestsample containers for the sensory observations are 4-ounce stoppered glass bottles for oils and 2-ounce capped bottles for the greases. The stoppers/caps confine and concentrate odors fordetection. All the tests should be done at the same time that similar observations are being madeon a known, fresh, “good” product. Sensory tests include the following:


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• Appearance: Look at the sample, as shown in Figure 5-1. Is the oil clear and bright? Or is ithazy and cloudy, indicating the presence of water? Is it foamy? Or does it show suspendedmatter? When examining grease, smear a small amount on a piece of white paper with aknife or spatula. Examine the sample for lumps and other particles, and don't forget thecomparison with the fresh, unused sample.

• Color: Compare with that of the original product. This observation is sometimes useful withlight-colored materials. Darkening can indicate oxidation and/or exposure to hightemperatures. Remember that color can change by just adding the new lubricant to the systembeing lubricated!

Figure 5-1Observing the Appearance

• Odor: (Figure 5-2) Again, compare with that of the original product. Oxidized oils andgreases eventually acquire an acidic, pungent, or “burned” smell. This occurs also at aradiation dose of about 100 megarads. The strong odor of some additives might for a timemask the developing pungent smell.

• Feel: Oils should feel slippery; greases should feel buttery, not stringy or lumpy. Neithershould feel gritty, as from wear debris.

Figure 5-2Detecting the Odor


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5.3.2 Other Simple Tests

• Viscosity: This is a measure of the resistance to flow of an oil and is its single mostimportant property in hydrodynamic lubrication (see Section 3.1). The various gradingsystems for oils are given in Appendix B. Oil viscosity is generally specified by theequipment builder for operating machinery. If the viscosity is too high (thick), performancecan be sluggish because of increased drag. This also can cause increased temperature, whichhas an adverse effect on lubricants and sometimes machine life. If viscosity is too low, the oilfilm might not be able to keep the moving parts separated. In the absence of an antiwear orantiscuff additive, this can result in metal-to-metal contact, contamination with wear debris,and shorter life for both the lubricant and the machine. It is important to remember thatrotating machinery has a tolerance for everything but major changes in viscosity in service.

The simplest means of determining viscosity is to compare an unknown to a known materialthrough sensory-like tests – sight and feel. If this is not accurate enough for the requiredpurpose, a viscosity gage, shown in Figure 5-3, can be used. This works on the principle thatthe rate a ball falls in a column of oil depends on the viscosity of the oil.

Figure 5-3Viscosity Gage for Measuring the Viscosity of Oils(courtesy of Visgage by Louis C. Eitzen Co.)

With this device, the unknown is drawn into a tube containing a ball. A parallel tubecontaining a known oil and a like sphere is used for the comparison. After the two oils areallowed to reach equal temperatures and each ball the same starting point, the instrument isinclined at a slight angle. This starts the spheres rolling. The inclination is stopped wheneither oil's sphere reaches a calibration point. Then the position of the lagging ball in eithertube shows directly the viscosity of the unknown. Both high and low viscosity oils can beused in this equipment. Accuracy of 95% or so is achievable with little effort.

• Consistency: This, as applied to a grease, is much like the viscosity of an oil – a measure ofits thickness. It can be estimated in a sensory-like examination, too. Just collect a series ofgreases of known thicknesses (National Lubricating Grease Institute (NLGI) penetrations)and compare with the unknown. Use a knife or spatula to work the greases around – it is easyto spot the known that matches the unknown.

• Water “Crackle” Test: This test might be appropriate when considerable amounts of waterare suspected in the oil. A metal plate is heated to at least 120°C (250°F) and a few drops ofoil are added (be careful, sometimes it spatters). If the oil crackles and pops, it suggests waterin excess of 0.1-0.2%. If it simply spreads and smokes, then water concentration is low.


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• Blotter Spot Test: This is most useful when a series is conducted over a period of time. Todo this test, a drop or two of a representative oil sample is put on a piece of blotter paper. It isimportant that the paper be placed so that the wetted area does not rest on a supportingsurface. After it reaches equilibrium, examine the oil spot, which might look like one of thosein Figure 5-4.

Figure 5-4Sample Blotter Spot Test

The spot is interpreted in this way:

– No Sludge: Oil spot fades out with indefinite boundaries.

– Sludge: Dispersed sludge shows up as a sharply defined outer boundary of the absorbedoil. A well defined black inner spot indicates dispersing properties of the oil have beenoverwhelmed by sludge.

A more complex version of this test is in Section 5.3.5.

• Examination of Solid Debris: When identifying the source of trouble in a machine, it isimportant to know the nature and source of solid debris in the lubricating oil. Such debris canbe separated from an oil test sample or scraped from machine parts, the oil storage tank,filters, or centrifuge bowls. The debris can then be washed free of oil with a volatilepetroleum solvent from a squeeze bottle (be aware of the fire hazard from the volatilematerial). After drying, a magnet can separate iron-derived matter from the rest. Examinationwith a 10X or stronger pocket magnifying glass or with a higher power scope, if available,will often help in deciding the nature and source of the debris. This material can be related tothe machine and its components. Results can point to needed action.

5.3.3 Diagnostic Laboratory Tests

• Oil Viscosity and Grease Consistency: Both of these can be measured in more complexlaboratory tests. The ASTM D 445 method is preferred for oil measurements and


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D 217 or D 1403 for grease measurements. The grease apparatus involves dropping astandard cone into a standard cup of grease. The depth of penetration is the measure ofconsistency, expressed in 0.1 millimeters. The NLGI has classified greases in grades 000 to6. The grease consistencies versus grade are given in Appendix B.

• Antiscuff and Antiwear: These properties can be measured or studied in a precisionlaboratory-testing device called the Tribometer or pin-on-disk machine (ASTM G 99). A pinis pressed against a rotating disk. Friction coefficients and wear on the pin and on the disk aremeasured. Various metal combinations can be used and various test conditions imposed, forexample load, speed, surface finish, and temperature. (See Section 6, “Lubricating MotorizedValve Actuators,” Table 6-3, for typical data from the Tribometer.)

• Infrared Spectroscopy (IR): In this lab procedure, a beam of infrared light is passedthrough or bounced off a thin film of an organic material, for example a lubricant. Thevarious chemical functional groups within the organic molecule absorb the light atcharacteristic wave lengths. Thus, one chemical group is distinguishable from another in theIR trace. The absorption peak heights relate to the quantity of species present. Table 5-2shows the IR peak regions of interest.

Table 5-2IR Peak Regions of Interest

Functional Group Wave Number, cm -1

HydrocarbonBase Oil

680-7751300-15002800-3050

EP/Antiwear Agents 900-1000

Soap Grease Gelling Agents 1425-1650

Ester Synthetic Base Oils 1720-1730

Oxidation Products, Rust Inhibitors 1720-17303250-3450

Phenolic Oxidation Inhibitors 3600-3660

Note that there are several base oil peak regions. Additives, if their peaks coincide with these,are masked effectively. Hence the term, “dead band regions.” One uses peaks outside thebase oil areas for functional group identification and quantitative work. Even when anadditive peak barely shows up in the full IR spectrum, it can be magnified by modern FourierTransform IR using interferometers and computer enhancement for further identification. If asample of an additive in a product can be obtained (the lubricant supplier can provide asample), concentrations of it in a base oil or grease can be determined for quantitative IRanalysis. Comparison of the known additive peak height with those of the unknown willestablish the additive concentration in the latter.

The most common approach in using IR is to compare the spectrum of a used lubricant withthat of fresh product. It is particularly useful to place both the spectra of the fresh and theused product on the same trace. This makes comparison much easier. The spectra are studiedto identify the reasons for the differences, if any, and how they came about in the lubricationprocess, for example contamination, oxidation, thermal degradation, and so on. Incoming


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fresh products and materials from storage can be studied in this same way to determine theirauthenticity and condition. See examples of these spectra in NMAC Lube Notes, October1999. On page 2, an example of comparing incoming lubricants is shown. On page 5, there isan example of monitoring the depletion of an oxidation inhibitor in a turbine oil.

• Emission Spectroscopy: Spectro Analysis or “Spectro” involves subjecting a lubricantsample to a high-energy spark, plasma, or flame. This treatment excites certain elements inthe sample and they emit or absorb light at characteristic wavelengths. Study of the resultingspectra tells what metals are present. Major changes in the elements versus those in freshlubricant can indicate trouble from wear or contamination from other lubricants, dirt, and soon. Spectro works best with oils. It can be applied to greases, as well, but their semi-solidnature can yield poorer results. Accuracy can be improved by digesting or ashing the oil orgrease sample and taking it up into solution. The test is then run on the solution. However,this complicates the method and sharply increases its cost.

One widely used, routine emission spectro method yields values for some 20 metals in oneshot. It involves a rotating electrode (Rotrode) that dips into the sample and carries it into ahigh-energy spark area for “burning.” This can handle particles in an oil up to about 10microns in size. Another routine method with similar capabilities introduces the sample or adilution of it into an argon plasma (ICP). Higher energy or temperature is involved and themethod lends itself well to automation.

Routine spectro does not “see” particles larger than 10 microns 9. Large metal particles fromscuffing are missed. One has to use the more complex “total” metals or digestion method ofanalysis to see all of the particles. Spectro analysis gives no indication of compounds ofwhich the elements are a part. For example, iron in spectro can be metallic but also ironoxide, hydrated iron oxide (rust), iron sulfide, iron phosphate, and so on. The same is true ofmetal organic species. Atomic absorption is another method; however, it is not widely usedin production analytical laboratories. X ray diffraction is the primary analytical method forthe identification of crystalline compounds. Table 5-3 identifies sources of metals found inlubricants.

9 Rotrode Filter Spectroscopy is a development that extends the particle size detection capabilities to approach thoseof ferrography.


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Table 5-3Sources of Metals in Lubricants

Source Metals

Dirt Al, Ca, Mg, K, Na, Si

Rust Fe (When water is present)

Grease Al, Ba, Ca, Li, Pb, Na, Si + Dirtelements (Clay)

Additives B, Ca, Mg, Ba, Mo, P ,K, Zn, Sb

Wear of bearings,gears

Co, Cu, Sn, Zn, Mn, Fe, Cr, Ni, P

• Ferrography: Figure 5-5 illustrates the importance of wear particle size and quantity indetermining the condition of operating equipment. Note that we need to get at particles abovethe normal 10-micron size detectable with routine emission spectroscopy. This can be donethrough the use of ferrography (or by the digestion method). Note too, in Figure 5-5, thatsome particle sizes (less than 10 microns) in benign wear also involve some of those in theother failure modes. So, a rapid rise in particles less than 10 microns can be indicative of awear problem.

Figure 5-5Wear Particle Size/Concentration and Machine Condition

The ferrograph magnetically separates materials, particularly ferrous metals, from wear,contamination, etc. by size and quantity to reveal their source. Its effectiveness in picking upthe larger particles missed in routine emission spectroscopy is shown in Figure 5-6. Theparticle characteristics from ferrography are often sufficiently specific to determine the wearmode that formed the particle within the machine.


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Figure 5-6Detection of Wear and Other Particles

Direct Reading Ferrography: With this technique, a diluted oil sample flows througha precipitator tube where a magnetic array separates particles according to size.Largersizes separate first, smaller ones further down the tube. Light beams pass through theseparated, collected particles to provide information on the amount deposited.

Analytical Ferrography: This technique involves flowing the diluted oil over a speciallyprepared microscope slide, tilted to provide a known flow rate. A solvent wash removesthe carrier oil and a ferrogram is prepared from the dried residue. This is examined (andphotographed) through an optical microscope. Identifiable solids include several types ofsteel, and, to a lesser extent, associated copper, lead/tin alloys, friction polymers, molysulfide, silica, fibers, and carbon flakes.

Some of the identifiable wear from ferrography and its causes are given in Table 5-4.

Table 5-4Wear and Its Causes

Wear Cause

Mild adhesive Acceptable low wear rates

Severe adhesive Scuffing, usually from excessive loads orspeeds

Abrasive Cutting due to hard particles or hard, roughopposing surfaces

Contact fatigue Wear particles from pitting or spalling due topoint or line contact from rolling elements ingears and ball and roller bearings

Corrosive Corrosive wear products from chemical actionof acids or water to produce fine particles


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Information from the direct reading technique is useful in trending data on the condition of amachine. The more complex analytical ferrogram is effective when more data are needed inanticipated stress situations.

Particle Counting

The importance of monitoring and controlling the concentration of particle contamination inlubricating oils and hydraulic fluids cannot be overstated. Modern lubrication programs in powergeneration use such monitoring and control for hydraulic fluids (for example, EHC fluids),turbine oils, pump lubes, compressor lubricants, crankcase oils, gear oils, and fan/motor bearingoils. In recent years, many case studies have shown how substantial improvements in thereliability of these components can be achieved by monitoring and maintaining cleaner fluids.

The ISO Solid Contaminant Code (ISO 4406:99) is probably the most widely used method forrepresenting particle counts (number of particles/mL) in lubricating oils and hydraulic fluids.The current standard employs a three-range number system. The first range number correspondsto particles larger than 4 microns, the second range number for particles larger than 6 microns,and the third for particles larger than 14 microns (see Table 5-5). As the range numbersincrement up one digit, the associated particle concentration roughly doubles. A typical ISOCode for a turbine oil would be ISO 17/15/12.

While there are numerous different methods used to arrive at target cleanliness levels for oils indifferent applications, most combine the importance of machine reliability with the generalcontaminant sensitivity of the machine. Organizations such as ASTM, Westinghouse, ABB, andGE have published guidelines on turbine oil cleanliness.

Particle counts can be obtained manually using a microscope or by an automatic instrumentcalled a particle counter. There are many different types of automatic particle counters used byoil analysis laboratories. There are also a number of different portable and online particlecounters on the market. The performance of these instruments can vary considerably dependingon the design and operating principle. Optical particle counters deploying laser or white light arewidely used because of their ability to count particles across a wide range of sizes. ISO 11500and ISO 11171 are published standards related to the use of optical particle counters. Poreblockage type particle counters have a more narrow size range sensitivity. They are popularbecause of their ability to discriminate between hard particles and other impurities in the oil suchas water, sludge, and air bubbles. More than ten different automatic particle counters areavailable for fluid monitoring purposes.


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Table 5-5Particle Count Range Numbers

Number of Particles per mL

More than Up to andincluding

Range number (R)

80,000 160,000 24

40,000 80,000 23

20,000 40,000 22

10,000 20,000 21

5,000 10,000 20

2,500 5,000 19

1,300 2,500 18

640 1,300 17

320 640 16

160 320 15

80 160 14

40 80 13

20 40 12

10 20 11

5 10 10

2.5 5 9

1.3 2.5 8

.64 1.3 7

.32 .64 6

.16 .32 5

.08 .16 4

.04 .08 3

.02 .04 2

.01 .02 1


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5.3.4 Standard Laboratory Tests

Over the years ASTM has developed standard test methods for a variety of materials, includingoils and greases. Committee D-2 oversees activities on lubricants. To standardize tests, severallaboratories perform them then compare notes in a “round robin” approach. Proceduraldifferences are gradually worked out until laboratories can duplicate one another. Once everyoneis satisfied, the procedure is considered to be “standardized” and is given a “D” number. A keypart of the method development is the statistical analysis of the test results according torepeatability (one operator, one laboratory) and reproducibility (different operators, differentlaboratories).

Important ASTM tests for lubricants with their designations and precision are given in Table 5-6.The numbers given under repeatability and reproducibility columns show the expected toleranceof the test results 95% of the time. Note that results from any laboratory, with even these mostcarefully developed test methods, are not absolute – they have pluses and minuses attached tothem. The ASTM precision values are the most accurate available.

Two appropriate ASTM test methods that address this repeatability and precision, relative topower plant maintenance, are:

• ASTM D 4378, “In-Service Monitoring of Mineral Turbine Oil for Steam or Gas Turbine.”

• ASTM D 6224, “In-Service Monitoring of Lubricating Oil for Auxiliary Power PlantEquipment.”


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Table 5-6Key Tests for Lubricants

Property ASTM Method Units Repeatability (Ir) Reproducibility (IR)

Greases

D217 0.1 mm 7* 20Consistency

D1403 0.1 mm 11 26

D566 °C 7 13DroppingPoint

D2265 °C 6* 15*

Oxidation D942 Psi drop 5* 9*

Bleeding D1742 Wt. % 10 17

Bearing Life D3336 Hrs. NA NA

Oils

Timken EP D2509 % of Value 23* 59*

Flash Point D92 °F (°C) 15(8) 30(17)

Pour Point D97 °F (°C) 5(3) 10(6)

Viscosity D445 cSt 0.35% mean 0.70% mean

D664 mgKOH/g 6% mean 30% meanNeut. No.

D2896 mgKOH/g 31-242% mean 71-322% mean

OxidationRPVOT

D2272 Min. to 25Psi drop

10% mean 20% mean

Both Oils andGreases

Friction andWear

G99-95A Friction Coefficientand Wear

+ 10% —

Notes:An asterisk (*) indicates that the values vary with the level of data.NA indicates that data are not available.1 Fresh oil2 Used oil


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5.3.5 Analytical Test Methods

An assortment of specific analytical techniques and procedures is available to the laboratorychemist for studying lubricants. These include:

• Gas chromatography (GC)

• Scanning electron microscopy (SEM) (for wear surfaces)

• Thermogravimetric analysis (TGA)

• Differential scanning calorimetry (DSC)

• Rotating Pressure Vessel Oxidation Test (RPVOT)

• Remaining Useful Life Evaluation Routine (Ruler™)

• Thin-layer chromatography

A brief description of the last five methods will be given here. These tests are not alwaysstandard and depend on the skill of the operator. Validity and usefulness of the results can beenhanced by direct comparison with results on a known material tested in the same way.

TGA is a promising tool for thermally separating certain greases into their component parts, forexample:

Highly volatiles 50-150°C (122-302°F)Medium volatiles 150-650°C (302-1202°F)Combustibles 650-750°C (1202-1382°F)Inert & ash Remainder

This ASTM (E 1131) method uses 10 mg of sample in the balance setup shown in Figure 5-7.The procedure is what might be termed a destructive distillation. A heating cycle is programmedover 25 minutes from 50 to 750°C (122-1382°F), first in nitrogen and then in air. The residuenumber correlates with the gelling agent content of metal-containing greases (most products). Itdoesn't work with ashless greases such as polyurea-gelled materials.


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Figure 5-7Schematic of TGA Setup

DSC is a thermal analysis technique that measures the heat flow associated with certain physicaland chemical changes in a lubricant. Of most interest is stability to oxidation, which shows up asthe time delay to the onset of the oxidative exothermal reaction. The method uses a fewmilligrams of the test lubricant in the apparatus shown in Figure 5-8. One copper (catalytic) cellor pan on a sensitive thermocouple contains the lubricant and the other is an empty reference cellon its own thermocouple.

Figure 5-8Schematic of DSC Apparatus

The apparatus is placed in an oven heated to a set temperature, for example, 200°C (392°F).Oxygen is then passed over the two cells. When the antioxidant in the sample can no longerafford protection, oxidation of the lubricant takes place and is detected by a temperature rise inthe cell containing the sample. Results correlate roughly with those from the standard RPVOT(Rotating Pressure Vessel Oxidation Test) method, ASTM D 2272 (see Table 5-5).


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HP-DSC is a variant of DSC in which the oxidation takes place under 500 psi pressure. Thisreduces volatilization of the test sample during thermal stress. This ASTM Method(D 5483) is more complex than the atmospheric method and is not needed unless volatilecomponents are involved.

RPVOT (ASTM D 2272), formerly RBOT (Rotating Bomb Oxidation Test), measures theoxidation stability of turbine oil and is a principal way to determine the remaining useful life ofthe oil. Oils deteriorate through oxidation, which, if allowed to go too far, results in depositformation and ultimate equipment failure. The traditional test for evaluating turbine oil oxidationstability has been the ASTM D 943 test. This test is unworkable for maintenance evaluations ofturbine oils in service. For example, some top-of-the-line turbine oils can go over 20,000 hoursto reach the end point; over 8,000 hours is common in this top group. Lesser quality “standard”materials go for 3,000-5,000 hours. These are very long times for research and evaluation.

The RPVOT overcomes this difficulty. Top oils reach the end point in only 2,000 minutes;second quality materials go for 400-600 minutes. The RPVOT is run at 302°F (150°C) in astainless steel vessel with water and a copper metal catalyst present. The vessel is pressurizedwith oxygen to 90 psi (620.5 kPa) at 77°F (25°C) and the end point is to a drop of 25 psi (172.4kPa) in the oxygen pressure. Good correlations between TOST (ASTM D-943) and RPVOT havebeen made. For these results and more details, see Note No. 8, NMAC Lube Notes, October 1999.

RULER™ is a technique to measure the antioxidant levels in lubricants. The small, hand-helddevice employs a cyclic voltameter to measure the electrochemically active species in thelubricant (see Figure 5-9).

Figure 5-9Ruler™ (Remaining Useful Life Evaluation Routine) Instrument

A small sample of lubricant is diluted with a select solvent and a voltage is applied to thesolution using a glassy carbon electrode. The resulting current flow depends on the concentrationof the active species, that is, antioxidant. Comparison of results with those from fresh lubricantand other samples from the lubricated equipment allows an appraisal of remaining useful life.


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The choice of solvent in the RULER™ test depends on the oil and additive types. For example,esters are polar materials that are soluble in polar solvents, for example, acetone. Hydrocarbonsare not in this category. Also, there are three main types of oxidation inhibitors to consider:

• Aromatic amines

• Hindered phenols

• Metallic dithiophosphates

Each type can require modification in technique and/or solvent.

A varying voltage (0.0-1.0 volt) is applied to the electrodes in the prepared sample. Current flowbetween the working and other electrodes at certain potentials is a function of type andconcentration of the additives. Current flow changes as electrochemical oxidation of theadditives takes place at the working electrode. The current flow creates mounds (rounded peaks)in the current/applied voltage curve. Figure 5-10 illustrates this for three oxidation inhibitors.Note that all three can be picked up by this method at the same time.

Figure 5-10Example of Three Additives and Voltammeter Response

The heights of the rounded peaks relate to additive concentrations. Values for the fresh lubricantare used as the 100% standard; the values for the solvent/base oil/electrolyte alone serve as the0% standard. Various in-between points can be arrived at accurately by testing knownconcentrations of the additives in question in base oil. With careful work, repeatability of +/- 5%is claimed for determining the percentage of remaining antioxidant. For more details, see NoteNo. 5, NMAC Lube Notes, July 1995.


Tests and Analyses

5-18

Thin-Layer Chromatography (Herguth Laboratories, Inc.) Chromatography is a techniquefor separating a sample into its components for study. This separation involves two mutuallyimmiscible phases, one of which is stationary. The latter is sometimes a solid, as in thin-layerchromatography. The stationary phase is attached to a solid support material, for example, aplate. The sample, when dropped or smeared on the coated plate, moves across or through thisstationary phase by capillary action and is separated by the differences in the chemical andphysical properties of the components. These differences also govern the rate of movement ormigration of the individual components. The components emerge or are eluted from the systemin the order of their interaction with the stationary phase. This technique is called radial planerchromatography. Separation of components occurs through adsorption or similar processes. TheBlotter Spot Test (Section 5.3.2) is a simple version of this chromatography. However, theblotter test relies only on diffusion around an initial spot on blotter or filter paper. There is nospecial solid phase. Figure 5-11 illustrates radial planer chromatographs of fresh and used gearoils.

Figure 5-11Chromatographs of Fresh and Used Gear Oils

When thin-layer chromatography is used as an oil analysis tool, various machine/oilcombinations will show unique trends during the life of the machine and oil. These trends areindicated by bands or zones of different colors and/or densities of the chromatographs. Evenunwanted wear metals and debris can be observed, as can the presence of an incorrect oil used asmakeup.


Tests and Analyses

5-19

Ideally, a reference oil is tested to establish the baseline of fresh, clear new oil. Used oils fromthe machine are then spotted on the chromatographic substrate at regular, time-based intervals.Changes in the appearance of the bands/zones are a clear indication that something has changedin the machine or oil. A close look at the zones with the unaided eye or, if needed, with a 10-power magnifying glass can even be correlated with the ISO Particle Code, water contamination,or wear debris. As with most analytical methods, this method is not a predictor of futureperformance, but rather is a measurement of the situation at the time of sampling. For moredetails on this topic, see Note No. 5, NMAC Lube Notes, November 2000.

5.4 Using Test Results

A single test result on a lubricant cannot be considered as definitive, even though it might be ona properly collected sample with a carefully performed procedure. This is because of the inherentvariability of any test. The only available statistical appraisal of test precision is for ASTMprocedures. That is one of the reasons they are so widely used when standard tests are required.Table 5-5 lists these data for some key procedures. To cite an example, the repeatability of thel/4-scale grease penetration test, D 1403, is listed as 11 points. This means that 95% of the time aresult by this procedure will fall within +/- 11 points of the true value. Some 5% of the time theresult will fall outside this envelope. So, +/- tolerances are attached to any result.

When a result seems outside the acceptable variability band, begin again with a new sample anda new test. If the second result checks the first, it might truly be showing a problem. The cause ofthis problem should receive attention. If the two results diverge, additional testing is needed toresolve the disparity.

Non-standard tests (that is, test methods without an ASTM-type statistical matrix) present adifferent picture. There, test credibility needs to be established. Replicate tests will determinerepeatability, but not reproducibility. However, repeatability data should be enough to allowreliable tests. Merely compare results on an unknown or used lubricant with those for freshmaterial. Use this approach particularly with shortened or special tests conducted at low cost bymany commercial laboratories.

5.5 Trending

Enough cannot be said for having in hand samples of the unused lubricant that wasoriginally charged to a piece of equipment under study. At the least, one should have storeddata on tests run on the fresh material when it was introduced. Then, as data are obtained onused material, they can be compared directly with the stored information. Essentially all testprocedures profit from such comparisons.

A lubricant analysis program should feature periodic sampling and testing. The test data can thenbe plotted on a continuing graph, as in Figure 5-12 10, to establish a trend. Place test variablelimits above and below the trend line. Thus, minor variations will not affect the equipmentoperation but results outside these limits will be noticeable. If, on resample and retest, the results



Tests and Analyses

5-20

return to the trend line, all is well. If not, then a problem exists that needs attention. At somepoint, the trend line will break away and a preset warning limit or flag is up. When this occurs,retest to verify results, then go for changeout, makeup addition, adding inhibitor, etc., and studyfurther if needed. Note the warning limit line in Figure 5-12.

Figure 5-12Sample Plot of Lubricant Properties

5.6 Warning Limits

Classic warning limits for oils and greases are given in Table 5-711. The following discussionsabout these limits are for clearer understanding.

• Determine which property test limit of the lubricant is the most critical and trend it. Forexample, for turbine oils this will be oxidation inhibitor content. The inhibitor is sacrificed inprotecting the oil (or grease). When its concentration is reduced sharply, oxidation of thelubricant takes place to form acids and eventually polymers that increase viscosity. But acidformation and viscosity increases occur late; a decrease in inhibitor content is an earlywarning sign or leading indicator of deterioration.

• Sometimes accelerated performance tests are needed to assess remaining performanceproperties. For example, DSC or RPVOT (ASTM D 2272) are useful for antioxidationperformance. The sacrificed inhibitor might generate oil-soluble species that acceleratelubricant breakdown.

• The application involving a lubricant also impacts its warning limit. A 50% additivedepletion with an oil in a turbine system might mean that years of service still remain for theproduct. A similar drop in inhibitor content with a reactor cooling pump oil might dictateaction soon.



Tests and Analyses

5-21

Table 5-7Typical Warning Limits1 for Certain Lubricant Services

ServiceOils GreasesProperty

DieselEngine

Steam/GasTurbine

HydraulicSystem

Gear AirCompressor

Bearings,Gears,Actuators

AppearanceColor/Odor

Unusual Change from Original

Wear Metals ContentBy Emission/AbsorptionSpectroscopy

Unusual Change from Original

Calcium ContentBy Absorption, ASTM D4626T, ppm, Max.

NA4 20 NA NA NA NA

ConsistencyViscosity at 40°C(100°F) (ASTM D 445),Change, %.

Max. Penetration(ASTM D 217). NLGIGrade Change, Max.

10-25

NA

103

NA

103

NA

103

NA

103

NA

NA

1 Grade(30 points)

Water Content% Vol. Max.(ASTM D 95)6

0.2 0.05-0.25 0.05 0.03-0.15 0.1 NA

Total Acid Numbermg KOH/g, Max.(ASTM D 664)

NA 0.3 NA NA NA NA

Oxidation Inhibitor2

% of New Lube, Min.NA 50 50 NA NA NA

EP Additive2

% of New Lube, Min.NA NA NA 50 50 NA

Rust TestOil (ASTM D 665)

NA Fail Test Fail Test NA NA NA

Base No.mg KOH/g, Min.

>3 NA NA NA NA NA

Fuel DilutionVol. %, Max.

3 NA NA NA NA NA

Notes:1 These warning limits are derived from past experience. No definitive studies have been conducted to ascertain these points.2 These points can be determined by Infrared analysis. Also, the atomic absorption procedure can be used for EP additives.3 This is not a sensitive criterion. Other limits should be used for early warning. If original viscosity is known, apply the 10%increase to it to arrive at the warning limit.4 NA = Not Applicable.5 Depending on the application.6 Based on experience and ASTM D 6224 and D 4378.


Tests and Analyses

5-22

5.7 Cleanup Considerations

A lubricant is changed because the maintenance plan is being followed or because there is apossible problem to resolve. In the latter case, cleanup is essential even if the replacementlubricant is the same type as the old. This is because the old lubricant has either had a problem orbeen the indicator of a problem. The old lubricant becomes a contaminant in the new lubricantand is best removed, if possible.

The principal way to ensure cleanliness in the system being changed is to drain the system, addfresh lubricant, drain again, and repeat until the debris is removed. Sampling and sensory testing,as already discussed, should suffice for determining when flushing is sufficient. This procedureshould also be followed when making a change to an updated product. Such a change might takeplace even though no equipment or lubricant distress has been noted.

Greases are more of a problem with cleanup than are oils. The general pattern is to introduce newlubricant and expel old grease at the same time until sufficient old product has emerged. This isgenerally accomplished with the machine in operation to prevent over-filling. Open rollingelement bearings can be handled in this fashion. Double-shielded bearings are another problemand attempts to regrease them may or may not be successful depending on prevailing conditions.For a further discussion of this, see Note No. 1 of the June 1998 NMAC Lube Notes.


6-1

6 LUBRICATING MOTORIZED VALVE ACTUATORS

Limitorque valve actuators have four major areas requiring lubrication. Three, if one eliminatesthe common motor bearings that come lubricated for life. These three areas are:

• Main gear box

• Limit switch gear box

• Stem and stem nut

To minimize oil leakage, all of these are lubricated with greases. Selection of grease for the limitswitch gearbox is the easiest because it involves mostly brass gears at low load. Selection for themain gearbox with its carbon steel worm against a manganese bronze (Limitorque bronze) wormgear is slightly more difficult. It requires a mild antiscuff (formerly called EP) product. Selectionfor the stem/stem nut interface is the most difficult because it has a Limitorque bronze nutdriving a stainless steel stem, which requires a more effective antiscuff product.

Table A-9 in Appendix A, “Limitorque Valve Actuator Lubricants”, details the products in useand some proposed for use for these applications. However, these are not the only products thatwill work satisfactorily; any product that meets the Limitorque specifications can be used. TableA-11 in Appendix A, “General Purpose Greases,” shows equivalent products. Data are availableto justify substitutions. Requirements for the main gearbox include antiscuff properties, bleedresistance, temperature and water stability, compatibility with seal elastomers, andnoncorrosivity. Antiscuff ability, along with bleed and heat resistance, are the key properties.

As noted in Table A-9, the greases in use are much different in composition. This can create acompatibility problem if the products get mixed. With this in mind and from the viewpoint ofproduct consolidation, it would be preferable to have a single grease to do the job in all threeareas of the actuator. This, of course, means that the new product would have to be powerfulenough to do the toughest job (stem and stem nut lubrication) and yet be satisfactory for otherareas. Thus, it needs to be a low-bleeding-type grease with good antiscuff properties andcompatibility with brass. The calcium sulfonate complex greases (CCS - calciumcarbonate/sulfonate) have now emerged as the best candidates for this single grease.

This possibility of using a single grease was studied under the EPRI MOV PerformancePrediction Program (see EPRI report TR-102135). During the course of this study anotherobjective emerged – studying the friction and wear performance of off-the-shelf greases andsolid lubricants for the stem/stem nut alone. These two investigations were carried onsimultaneously.


Lubricating Motorized Valve Actuators

6-2

6.1 Stem Nut Friction and Wear – Off-the-Shelf Products

Friction at the stem/stem nut interface is a key factor influencing the conversion of motor-operated valve (MOV) operator torque to valve stem thrust. One of the factors affecting thisvalue is the lubricant employed at this interface. Wear of the stem nut, of course, relates tofriction and is an important item in maintenance.

Some 13 commercial greases were tested in an SMB-0 actuator, coupled to a globe valve, forabout 250 opening and 250 closing strokes (500 strokes). All the products tested were eitherpresently in use or proposed for use. The effects of stroke number and load (0-17,000 lb.) onfriction and on wear of the stem nut were determined. A new, premeasured Limitorque bronzenut was employed for each test and it drove a type 410 stainless steel valve stem. The tests wereperformed at room temperature. Table 6-1 shows the results obtained.

Note that eight of the first thirteen listed show friction coefficients of below 0.15 at thebeginning of the 500 stroke run (generally the highest point). Six of them exhibit only smallvariations in friction with stroke. Those greases with the best antiscuff properties showed thelowest wear, for example Mobilux EP, Multifak EP, and so on. There is little correlation betweenlow friction and low wear. The last two lubricants with special additives will be discussed in alater section.



6-3

Table 6-1Friction and Wear Performance Summary(500 Stroke Stem/Stem Nut Lubricant Tests with SMB-0)

Coefficient of Friction UnderDynamic Loading @ 10,000 Lbs.

Tooth Wear in MilsLubricants

AverageCOF

COFBeginningof Run

COFEnd ofRun

0.05 in.AboveToothRoot

0.10 in.AboveToothRoot

Moly 1011 0.13 0.12 0.13 2 3

SRI1 0.13 0.12 0.14 4 0

Mobilux EP-1 0.13 0.13 0.13 1 0

Never-Seez 1653 0.14 0.17 0.10 4 4

Fel-Pro (Loctite) N-5000 0.10 0.14 0.08 2 3

Never-Seez 1603 0.12 0.19 0.08 3 4

Dura-Lith EP-1 0.12 0.13 0.12 1 2

Multifak EP-11 0.12 0.12 0.12 1 0

Lubriplate 930 AA 0.13 0.15 0.13 1 1

RF Graphite3 0.12 0.22 0.09 4 5

Dow Corning 44 0.14 0.18 0.10 1 3

Multi-Motive 13 0.09 0.11 0.07 1 1

Nebula EP-13 0.08 0.10 0.07 2 2

Darina EP-1 + additives2 0.09 0.10 0.07 1 1

Shear Magic + additives2 0.10 0.13 0.08 1 1

1 Also in 2000 stroke runs (see Section 6.4).2 Additives are polymer tackiness agent and antimony/sulfur/phosphorus antiscuff (EP) agent.3 Obsolete products.

Figure 6-1 is a plot of friction coefficient at 10,000 lb. dynamic closure load versus number ofstrokes for three typical lubricant types from Table 6-1. A preferred lubricant will have theproperty of low friction coefficient with little or no change with number of strokes.

The data in Table 6-1 show a decrease in friction in many cases as the test progresses. This mightbe a result of break-in of the stem nut, because each test was started with a new nut. However,this effect was not universal. For example, no change was noticed in Mobilux EP or Multifak EP.



6-4

Figure 6-1Composite of Friction Coefficient (@10,000 lbs) Versus Number of Strokes

6.2 Stem Nut Friction & Wear – Solid Lubricants and Improved Nut Cutting Procedure

A permanent solid lubricant for the stem/stem nut and a single grease for the other two areas ofan MOV is an attractive alternative to a single lubricant for the whole actuator. Very low stem/stem nut friction could theoretically be obtained through the use of effective solid lubricants.However, one problem with the solids is their poor durability. This prompted a closer look at thequality of the stem nut threads to which the solid lubricants would be applied. Application ofsolid lubricant to the nut threads was considered to be the only practical approach as the nuts aremore frequently and easily replaced than the valve stems.

Our examination showed that the stem nut quality is generally poor, irrespective of whether thenut is made at the utility machining facility or at that of the valve vendor. Figure 6-2 illustrates autility-made new SMB-O nut tooth with a damaged upper area. Scuffing of the surfaces is alsoprevalent as a result of machining. There are even instances of the threads not being concentricwith the outside body of the nut. This would cause the nut to wobble on the stem. This shouldincrease friction and wear. In short, making the threads out of Limitorque bronze is not an easyjob and should receive careful attention so that stem nut durability can be improved and frictionand wear reduced.



6-5

Figure 6-2Cross-Section of Macrograph of New SMB-O Stem Nut Thread – Standard Machining

An improved thread cutting procedure was developed for both SMB-O and -000 nuts. Thisinvolved starting with standard Limitorque drilled blanks and using a high quality lathe. (It wasassumed that such a lathe would be available at any utility maintenance facility.) A specialfloating tap holder was used to avoid non-concentric boring and tapping. A reamer and three tapswere used to cut the threads – a rougher, semi-finisher, and a finisher. Using this method, largecuts that can yield thread damage are avoided. To determine the optimum production of highquality threads, cutting fluids and methods of application were investigated. This new procedurewas used to make all of the nuts for the 500-stroke actuator test program.

The following solid lubricants were applied to separate stem nuts and then run in the actuator:

• Sputtered Molybdenum Disulfide

• Bonded Molybdenum Disulfide -1

• Bonded Molybdenum Disulfide - 2

• Plated Paladium Silver/Indium

• Graphite Insert

• Graphite/Resin in Solvent

All of these solid lubricants failed after only a few strokes, exhibiting very high friction andwear. The graphite insert was graphite/resin cast into the thread form and fitted into a drilled outLimitorque bronze nut. It failed quickly due to lack of mechanical strength under load. Thus, thepromise of solid lubricants for the stem nut application did not materialize in practice.



6-6

6.3 Search for Improved Actuator Lubricants

There are two important grease performance elements for Limitorque actuators – bleeding andantiscuff properties. Low bleeding relates to reduced leakage through seals and high loadcarrying capacity to the ability to handle the tough stem/stem nut lubrication task. Bleeding testsand tests with the pin-on-disk machine were used to study these properties.

Table 6-2 shows the results of the bleeding tests. There are large differences between variousgrease types in bleeding tendencies. The first three types listed, being the lowest in bleeding,were chosen for further study. Small amounts of tackiness agents (polymers) are effective inlowering bleeding.

Table 6-2Bleeding Tests¹ on Grade 1 Greases (including effects of gelling agents)

Gelling Agent Percent Oil Bleed

Calcium Complex2 3-8

Calcium Sulfonate Complex2,3

(CCS - Ca Carbonate/Sulfonate)<0.2

Clay2 2-6

Polyurea2 3-14

Lithium Complex 10-20 (48)

Aluminum Complex 10 (48)

Lithium Soap 20-35 (48)

1 Bleeding tests per ASTM D 1742, at 135°F (57°C), 128 hr. or 48 hr. The number (48) indicates that the test was conducted for48 hours.2 Greases chosen for further study.3 Data obtained subsequent to the original study. See NMAC Lube Notes, July 1996, p. 144.



6-7

The pin-on-disk machine (Tribometer - ASTM D 99) is illustrated in Figure 6-3. Here, a 1/4-inchdiameter Limitorque bronze pin is pressed by the applied load against a rotating stainless steeldisk. Friction coefficients and wear on the pin and disk are determined. In our study, a load ofl Kg (about 20,000 psi initial) at a temperature of 200°F (93°C) was used in a one hour run.

Figure 6-3Pin-On-Disk Machine Schematic (Tribometer)

The data obtained on the pin-on-disk machine are tabulated in Table 6-3 for several greasetypes. Average friction coefficients range from 0.11 to 0.24 for the most severe of the metalscombinations, that is, bronze on type 310 stainless steel. The friction and wear evaluations, on a0-200 scale, are 20-25 for the products having excellent antiscuff properties and 65-100 for thegreases with no or less effective antiscuff properties.

Results with the less severe bronze/410 stainless and bronze/17-4PH are also shown in Table6-3. The metal choices make little difference if the lubricant has excellent antiscuff properties. Ifthe lubricant has poor antiscuff capability, it will not lubricate bronze with SS310 very well,though it might be acceptable with the other metal combinations. There is a rough correlationbetween the pin-on-disk results and those from the actuator tests. Therefore, if one has a choice,selection of 410 or 17-4PH valve stems over the 300 series materials is recommended.



6-8

Table 6-3Pin-on-Disk Tribometer Data for Some Grease Types

Coefficient of Friction (COF) and F/W Wear Ratings1

Bronze Pin/SS310Disk

BronzePin/SS410 Disk

Bronze Pin/SS17-4PH Disk

Grease Type

COF F/W COF F/W COF F/W

Calcium Complex-GelledAntiscuff (EP) – Type 1

0.19 75 0.12 105 0.11 75

Same as above – Type 2 0.11 25 0.10 20 .11 25

Calcium SulfonateComplex (CCS - CalciumCarbonate/Sulfonate)2

0.10-0.12 20-60

Lithium Soap-GelledAntiscuff (EP)

0.12 20 0.12 20

Lithium Complex Soap-Gelled

0.19 65

Clay-Gelled 0.16 60

Same as above –Synthetic

0.13 75 0.12 25

Clay-Gelled Antiscuff (EP) 0.17 60 0.11 35

Same as above + Graphite+ MoS2

0.15 60 0.12 35

Polyurea-Gelled 0.19 80 0.10 20 0.09 25

Nickel Antiseize 0.16 70 0.11 35

Copper Antiseize 0.24 100 0.10 35

Clay Gelled + Tackinessand Strong Antiscuff (EP)Agents

0.12 25 0.12 25

Polyurea + Tackiness andStrong Antiscuff (EP)Agents

0.12 25 0.13 25

1 Wear ratings are measured on a scale of 0-200, excellent to terrible.2 Data obtained subsequent to the original study.



6-9

The last two grease types in Table 6-3 came from the studies to find products good in bleedingand outstanding in friction and wear. In both cases, commercial greases were improved byintroducing additives as indicated. Specific materials from these classes of grease were run in500 stroke cycle actuator tests. Results shown at the lower portion of Table 6-1 indicate lowfriction and low wear for these products.

6.4 Long-Term Thermal Effects On Greases

After running the 500 cycle actuator tests, there was, of course, wear debris in the lubricants. Theamount of debris depended on the stem nut wear. Otherwise, the greases showed only minorchanges in consistency – nothing that would impact their continued usability. The same wasfound to be true in more lengthy, 2000 stroke actuator tests. Two SMB-000s and one SMB-0were involved in this work. These tests included studies of greases from the main and limitswitch gearboxes as well as those from the stem/stem nut interface. However, all these tests wereof short duration – up to a week. Longer-term thermal tests give a partial view of what happensin an extended period of operation.

Two sets of tests were conducted on selected greases to show thermal effects – the first at roomtemperature for five months and the second at 130°F (54°C) and at 180°F (83°C) for six months.Consistency changes were observed along with bleeding and evaporation. Only consistencychanges were of any significance in the room temperature test — percent of bleed ran from 0.1 to0.7 and the percent evaporation from 0 to 0.4. In the higher temperature tests, bleeding washigher at 0 - 4% at 130°F and 0 - 6% at 180°F. Table 6-4 shows the observed consistencychanges.



6-10

Table 6-4Grease Consistency Changes in Long-Term Thermal Tests

Consistency After 5 Months at65-85°F (18-29°C)

(grease placed on plain screen)

Change in Penetration3, P60 After 6Months at Temp. (grease placed on

fine screen, loosely covered)Grease

Surface Film1 Bulk2 130°F (54°C) 180°F (83°C)

Nebula EP-14 5 5 -17 +6

Nebula EP-04 — — +18 +3

Dura-LithEP-1 1 1 — —

Mobilux EP-1 2 1 +28 +37

Multifak EP-1 1 1 — —

Ronex EP-1 1 1 — —

Mobilgrease 28 1 1 -38 -58

Moly 101 — — +14 -6

Polyurea EP-15 1 1 — —

Darina EP-1 +Additives

1-3 1-2 -3 -43

Multi-MotiveEP-15 + Additives

2 1 +30 +40

1 Surface film: 1 = minimum, 5 = tough2 Bulk: 1 = like original, 5 = much thickening3 – = harder; + = softer4 Now being phased out but still in use5 Obsolete product

The most notable result in the 65-85°F (18-29°C) tests is the performance of Nebula EP. It had atough surface film and much thickening after exposure. This is similar to what has often beenobserved in the field. The nature of Nebula EP is such that it gets harder on standing aroundunworked and this is not due to bleeding or evaporation. The 0-grade is less prone to hardening,as shown in the 130°F (54°C) tests. This advantage of the softer grade is likely due to lowerconcentration of the gelling agent in it.

The 180°F (83°C) temperature featured mostly grease softening. Another widely used materialgot as much as two grades harder on exposure. Working during use would perhaps have madethese changes less severe. Greases like to be worked. This is the reason for the recommendationthat greased equipment be operated now and then.



6-11

6.5 Conclusions

• 500 stroke actuator tests, using Limitorque bronze stem nuts and type 410 stainless steelvalve stems, show it is possible for existing greases to have friction coefficients consistentlyless than 0.15. They can also have low stem nut wear.

• A low change of friction with stroke number can be achieved through the proper choice ofgrease. This can also result in low wear.

• Antiseize compounds might allow operation at moderate friction but will result in high stemnut wear, as shown in 500 stroke actuator tests.

• Good quality greases were not overstressed in either 500 stroke or 2000 stroke actuator testsunder load. Aside from the presence of wear debris, changes in the greases would not haveprevented continued use of the equipment.

• Bench tests show that the stem/stem nut interface, with its bronze on stainless steel, is thehardest to lubricate. Type 410 or 17-4PH stems are easier to lubricate than 300 seriesmaterials.

• Solid lubricants for the stem nut proved to be grossly inadequate in durability in actuatortests. Their study has now been abandoned for this use.

• In the original work, no grease was found to have all the properties desired in a singlelubricant for all the areas of the actuator. Many existing products need anti-bleedingadditives. They also need increased load carrying capacity. Recent work has shown selectedcalcium sulfonate complex (calcium carbonate/sulfonate) greases to have the desiredproperties for a single actuator grease.

• Calcium complex-gelled greases tend to harden in use. The 0-grade shows less of this traitthan the 1-grade, but at a sacrifice in bleeding tendency.


A-1

A APPENDIX A

A.1 Lubricant Property TablesTable A-1Turbine OilsISO Viscosity Grades 32, 46, 68a

Operating Limit Range

Profile Application Products Temperatureb

°C (°F)Radiationc

Rads

Products aremade from highlyrefined mineraloils plus oxidationand corrosioninhibitors.Products providerust protection,foamsuppression, andrelease ofentrained water.

Main steamturbines andauxiliaries

• Main bearings• Pump bearings• Small gear sets• Circulating

systems• Compressor

crankcases• Control

systems

• Castrol Paradine R&O• Chevron Authentic

Industrial Oil• Conoco Hydroclear

Turbine• Exxon Teresstic• Lyondell Ideal• Mobil DTE–

797, 798, 799• Pennzoil Pennzbell RO• Shell Turbo T• Texaco Regal R&O

60-95(140-200)

5x106-5x107

Same as aboveplus increasedoxidation andthermal stabilities

Same plus gasturbines

• BP Turbinol Select• Castrol Perfecto HPT• Chevron GST Oil Series,

TR ISO 32• Conoco Hydroclear

Diamond Class• Exxon Teresstic GT,

GTC 32• Lyondell Ideal Plus• Mobil DTE 724, 823;

SHCd 824, 825• Pennzbell TO• Shell Turbo IG Oil 32,

CC 32• Texaco Gas Turbine

65-107(150-225)

7 x106-108

Note: Lettered superscripts refer to “Footnotes” defined in Appendix A, Section A.2.


Appendix A

A-2

Table A-2Engine Oils for Large Dieselsu

Profile Application Products

High Base Reserve (True Base No. - TBN > 10 mg KOH/g)

Products are made frompremium base oils plusadditives to providedetergency and resistanceto wear, corrosion,oxidation, and foaming.Typically, products havehigh base reserve toaccommodate high sulfurfuels (>0.5% sulfur).Another group willaccommodate low sulfurfuels. Many oils (no zinc)are compatible with silver-lined sleeve bearings.

Crankcases of auxiliary Dieselengines — railroad/marine type— used for emergency power.

• BP Energol REO• Chevron Diesel Engine Oils

Delo 6170 CFO, Marine 1000• Exxon Diol 13D, 17D• Lyondell Gascon Supreme

Plus• Mobil Mobilgard 450 NC• Pennzoil RR513, RR517• Shell Caprinus XR• Texaco Diesel Engine

Low Base Reserve (TBN 7-9)

Products recommended formodern low sulfur diesel fuel (seeLube Note No. 4, July 1996).Most oils contain zinc additivesand likely will not be compatiblewith silver-lined bearings in EMDengines. However, such silverbearings should be phased outby 2006. Also, silver bearings canbe retrofitted with bronze (at acost).

• Chevron Marine Engine OilDelo 194 (no zinc), Delo 100,Delo 400

• Exxon XD-3 Extra• Mobil Delvac• Pennzoil Long Life Heavy

Duty Engine Oil• Phillips Super HD II Motor Oil• Shell Rotella T• Texaco Ursa Premium TDX



Appendix A

A-3

Table A-3Low-Pressure Hydraulic OilISO Viscosity Grades 32, 46, 68, 100


Profile Application Productse Temperatureb

°C (°F)Radiationc

Rads

Products are madefrom refinedmineral oils plusoxidation andcorrosion inhibitors,antiwear/antiscuffagents, and foamsuppressants. Theycontain lower levelsof additives than inhigh-pressurehydraulic oil.

• Moderate dutyhydraulic systemsgeneral machinery

• Reciprocating aircompressors

• Circulating systemsand bearings (plainand rolling element)where loads andtemperatures aremoderate

• Reduction gears,speed reducers,and high speedspindles atmoderate loads

• BP AW• Castrol Hyspin

AW• Chevron

Machine AW• Conoco

HydroclearMultipurposeR&O

• Exxon HumbleHydraulic H

• Lyondell Duro;Polarvis

• Mobil HydraulicISO

• Texaco AWHydraulic

65-105(150-220)

107-5x107



Appendix A

A-4

Table A-4High-Pressure Hydraulic Oile

ISO Viscosity Grades 32, 46, 68, 100



°C (°F)Radiationc

Rads

Products aremade from refinedmineral oils plusoxidation andcorrosioninhibitors,antiwear/antiscuffagents, and foamsuppressants.

• Vane, gear, andpiston-type pumpsoperating in heavy-duty hydraulicsystems above1000 psi. Operatingtemperatures areabove those typicalof low-pressuresystems.

• Hydraulicallyactivatedequipment.

• Machine tools andpresses.

• BP Energol HLP-HM

• Castrol ParadineAW, Tribol943AW

• ChevronHydraulic AW,ECO HydraulicAW, RykonPremium

• ConocoHydroclear AW

• Exxon Nuto H• Lyondell Duro

AW• Mobil DTE 10M,

20 series; SHCd

500 series• Pennzoil

Pennzbell AW• Shell Tellus• Texaco Rando

HD, HDZ

70-115(160-240)

5x107-108



Appendix A

A-5

Table A-5Compressor Oils



°C (°F)Radiationc

Rads

Premium qualitymultipurposeindustrial oilsmade fromspecially refinedmineral oils; cancontainantioxidant,antiscuff agent,alkalinity, rustinhibitor, metaldeactivator, foamsuppressant,and/or mist controlagent.

• Reciprocatingand rotary aircompressors

• Mild dutyindustrial gearsets

• Oil mist systems• Hydraulic

systems• Multi-stage

compressors

• BP Turbinol – T• Castrol

ReciprocatingCompressor Oil,Tribol 1750d

• ChevronCompressor Oil260 R&O, MachineR&O LVI

• ConocoHydroclear-Diamond Class

• Exxon Exxcolub 77• Lyondell

Compressor 7585• Mobil Rarus 427,

800d series; SHC1024, 1026d

• PennzoilPennzcom

• Shell Corena S• Texaco Cetus DEd,

Cetus PAOd

71-115(160-240)

107-5x107



Appendix A

A-6

Table A-6High Load Extreme Pressure(EP) Gear Lubricants



°C (°F)Radiationc

Rads

Products aremade from highlyrefined mineraloils plus sulfur-phosphorusantiscuff (EP)agents. They canalso containantiwear agents,antioxidants,corrosioninhibitors, andfoamsuppressants.These lubes arelead-free.

• Enclosed gearsystems

• Chain drives,sprockets,bearings, andcouplings

• High horsepowergear drives andreducers

• Spur, bevel, andworm gears

• Hypoid gears atmoderatetemperatures,loads, and speeds

• Worm drive axles• Heavy, suddenly

(shock)-loadedequipment

• Applications whereAGMA specifies an“extreme pressure”(antiscuff) lubricant

• BP Energol - GR- XP

• Castrol EP GearLubricant; AlphaGear, Tribol 1100

• Chevron GearCompound EP

• ConocoHydroclear EP

• Exxon SpartanEP; SpartanSynthetic EPd

• Lyondell PennantNL

• Mobil Mobil Gear600 series; SHCd

series• Pennzoil Super

Maxol EP• Shell Omala• Texaco Meropa

60-95(140-200)

107-108



Appendix A

A-7

Table A-7Open Gear Lubricants



°C (°F)Radiationc

Rads

Products arehigh viscositymineral oils,sometimesgelled to giveblack, tackygreases.Generallythey containspecial fillerssuch asmolybdenumsulfide and/orgraphite.They alsocontain rustinhibitors andwettingagents.Products arestringy.

• Antiscuff(extremepressure) filmfor slowlymoving parts.

• Industrialequipment suchas slow moving,heavily loadedgears, hoists,and cranes.

• Wire rope

Lithium soap-gelled

• Conoco Tacna M 5• Exxon Dynagear,

Dynagear Extra• Mobil Mobilux EP III• Shell Retinax AM• Texaco Molytex EP

Calcium Complex-Gelled

• Chevron OpenGear Grease; NC;Aerosolh

• Texaco Texcladj 2

Ungelled

• Castrol Open Gear800, Molub-Alloy936 SF Open Gear

• Chevron MillLubricants

• Exxon Suretth

• Mobil Mobiltach

Series• Pennzoil Open

Gear and WireRope Spray

65-120i

(150-250i)5x107-2x108



Appendix A

A-8

Table A-8Antiseizure Compounds

Profile Application Productsn Carrier/Solid*

Temp.b

°C (°F)Radiationc

Rads

Acheson DAG 154Graphite Lube

So/G, R 455 (850) >109

Bostik 980 (1800) >109

Never-SeezRegular

Gr/Cu

Nuclear NiGrade Gr/N

Chesterton NickelAntiseizeCompound 772

Gr/N 1430 (2600) >109

Chevron ToolJoint Compound

Gr/G, Cu 400 (750) >109

Dow Corning

1000 Gr/G, Cu 1150 (2100) >109

G-N Gr/G, M 400 (750) >109

Molykote P37 Gr/G, Zr 1400 (2550) >109

Huron

Neolube No. 1, 2 So/G, R 200 (400) >109

Neolube No. 650 Gr/G 635 (1200) >109

Jet Lube SS-30 Gr/Cu, R 980 (1800) >109

Loctite

N1000 O/G, Cu 980 (1800) >109

N5000 O/G, N 1430 (2600) >109

N7000 Gr/G 464 (850) >109

550 Moly Gr/G, M 400 (750) >109

Nikal Gr/N, R 1430 (2600) >109

Nuclear Non-Metallic

Gr/G 1315 (2400) >109

Texaco ThreadCompound

Gr/Cu 980 (1800) >109

Products aretypicallydispersions ofsolids in apetroleumcarrier. Solidscan be graphite,molybdenumsulfide, copper,or nickel flakes.Products areusually specificto an applicationand are NOTinterchangeableor compatible.Usually appliedby spray orbrush.

• Threads• Keyways• Valve

components• Studs and

bolts• Cable and

rods

Zinc Gr/Z 350 (660) >109


*Key for Carrier/Solid

Carrier:SO = SolventGR = GreaseO = Oil

Solid:G = GraphiteM = MoS2

Cu = CopperN = NickelR = ResinZ = Zinc, Zinc OxideZr = Zerconium DioxideA = Aluminum


Appendix A

A-9

Table A-9Limitorque Valve Actuator Lubricants


Profile Application Products k Temp.b

°C (°F)Radiationc

Rads

Calcium sulfonatecomplex (CCS) gelledgrease (see Table A-11).

Cor-Tek MOV Plus,Long Life

95-150(200-300)

5x107-3x108

Calcium complex-gelledmineral oil plusadditives for wide rangeof load, speed,temperature, andmoisture conditions.

Exxon Nebula EP-0*Exxon Nebula EP-1*

95-150(200-300)

5x107-2x108

Lithium complex-gelled(see Table A-11).

Main gearcase

Mobilith AW 95-150(200-300)

5x107-2x108

Calcium sulfonatecomplex-gelled grease(see Table A-11).

Cor-Tek MOV Plus,Long Life

95-150(200-300)

5x107-3x108

Ester-based, lithiumsoap-gelled product,formulated for use overa wide temperaturerange.

Exxon Beacon 325l 95-120(200-250)

107-2x108

Synthetic hydrocarbon-based, clay-gelledproduct. Designed foruse over a widetemperature range.

Geared limitswitch

Mobil Mobilgrease 28 95-163(200-325)

108-5x108

Lubricated for motorlife, as supplied.

Motorbearings

Long Life Productm NA NA

Greases, SolidLubricants

Valve stem/stem nut

Many with variedsuccess.

NA NA

* Still in use but now being phased out by ExxonNA = Not applicableNote: Lettered superscripts refer to “Footnotes” defined in Appendix A, Section A.2.


Appendix A

A-10

Table A-10Fire Resistant Hydraulic Fluids



°C (°F)Radiationc

Rads

Three types arecommerciallyavailable (thetypes areNOTinterchangeableor compatible)

• Industrialhydraulicand controlapplicationswherehazardousconditionsrequire theuse of a fire-resistantfluid.

Note: DO NOTMIX FLUIDTYPES.

Water-Glycol

• BP Energol – FRG-46• Castrol Premium Fluid 200• Exxon Firexx HF-C46• Houghto-Safe 400-600

Series• Mobil FR 200D Fluid• Pennzoil Glycol FR• Texaco Hydraulic Safety

Fluid

Water-in-Oil Emulsion

• Conoco FR• Exxon Fyrexx HF-B• Lyondell Duro FR-HD• Mobil Pyrogard D• Pennzoil Maxmul FRP/G

Oil-in-Water Emulsion

• Pennzbell HWCF

Phosphate Ester

• Akzonobel Fyrquel EHC,MTL

• Forsythe (FMC) Reolube• Houghton International

Houghto-Safe 1000 Series• Mobil Pyrogard 53• Pennzoil Pennzsafe FE

95 (200)

80 (180)

80 (180)

95 (200)

5x107-2x108

5x106-5x107

5x106-5x107

106-107



Appendix A

A-11

Table A-11General Purpose Greases—Grades 00, 0, 1, 2, 3



°C (°F)Radiationc

Rads

Lithium soap-gelled

• BP Energrease-LS-EP

• Castrol Longtime PD• Chevron Dura-Lith EP

• Conoco EP Conolith• Exxon Lidok EP

• Lyondell Litholine HE-P• Mobil Mobilux EP

• Pennzoil Pennlith• Shell Alvania EP

• Texaco Multifak EP; Premium RBg

95-135(200-275)

107-108

Products aremade fromrefined mineraloils plus gellingagent,oxidation andcorrosioninhibitors, andantiscuff (EP)agents.

Bearings

• Motor

• Pump

• Fan

• Compressor

• Couplings

Lithium complex-gelled

• BP Energrease LC-EP

• Castrol Pyroplex Blue, Molub-alloy860 ES

• Chevron Ulti-Plex EP; Ulti-PlexSyntheticd EP, RPM AutomotiveLC EP

• Conoco Conolith HT• Exxon Unirex N

• Lyondell Litholine Complex EP• Mobil Mobilith AW, SHCd 15, 100

• Pennzoil Premium LithiumComplex

• Texaco Starplex

95-150(200-300)

5x107-108

Calcium complex-gelled• Exxon Nebula EP*

95-150(200-300)

5x107-108

Calcium sulfonate complex (Calciumcarbonate/sulfonate - CSS)-gelled

• Castrol SFG

• Compton G-2000 Series

• Cor-Tek MOV Plus, Long Life

• Petro-Canada Peerless LLG

95-150(200-300)

5x107-3x108

Polyurea-gelled

• Chevron Rykon Premium EPg,Black Pearl EP; SRIg

• Conoco Polyureag, EP Polyurea

• Exxon Polyrex EMg, EP

• Shell Dolium BRBg

• Texaco Polystar RBg

120-175(250-350)

5x107-3x108

* Obsolete productNote: Lettered superscripts refer to “Footnotes” defined in Appendix A, Section A.2.


Appendix A

A-12

Table A-12Coupling Greases



°C (°F)Radiationc

Rads

Products aremade from highviscosity mineraloils, gelled with asoap and/or apolymer. Mostcontainantioxidants andantiscuffing (EP)agents. Productsare designed toresist separationby centrifugalforce.

Couplings

• Flexible

• Geared

• High speed

• High load

• ChevronCoupling

• Exxon RonexExtra Duty*

• Falk LTG

• KOP-FLEXKSGKHP 1

• Mobil MobiluxEP 111

• TexacoCoupling

66-95(150-200)

107-108

* Below 3600 rpmNote: Lettered superscripts refer to “Footnotes” defined in Appendix A, Section A.2.


Appendix A

A-13

Table A-13Grease Types and Performanceq

DroppingPoint

°C (°F)

Condition AfterHeating to 200°C

(400°F) andCooling

Max.Temp. forProlongedUse °C (°F)

WaterEffects

Stability ofPenetrationon Working

BleedingTendency

GellingAgents

Calciumsoapr

85-150(185-300)

Oil and soapseparate

70-120(160-250)

Highlyresistant

Good toexcellent

Medium

Calciumcomplex

260-300(500-570)

Hardens; OK afterworking

120-150(250-300)

Highlyresistant

Excellent Low

CalciumSulfonatecomplex[Calciumcarbonate/sulfonate(CCS)]

300-320(570-610)

Little change afterworking

150-175(300-350)

Highlyresistant

Excellent Low

Lithiumsoaps

170-200(340-390)


120-135(250-275)

Someemulsificationto resistantt

Poor toexcellentt

High

Lithiumcomplex

260-300(500-570)


150-175300-350

Resistant Excellent Medium

Polyurea,Polyureacomplex

240-260(465-500)


150-175(300-350)

Highlyresistant

Fair toexcellent

Low

Inorganics 260+(500+)


120-140(250-285)

Resistant Fair toexcellent

Low

Sodiumsoap

175-300(350-570)

Hardens; OK afterworking

120-150(250-300)

Emulsifies Fair Medium

Bariumsoap

200-260(390-500)


120-140(250-285)

Highlyresistant

Good Low

Aluminumcomplex

240-270(465-520)

Slight hardening 110-135(230-275)

Resistant Good toexcellent

Low



Appendix A

A-14

A.2 Footnotes

a Higher viscosity grades are available in many cases for use as non-EP (antiscuff) gear oils.

b Quite long life (years) can be expected at the lower value. Life is about halved by each

increase of 10°C (18°F) in operating temperature. Oil change-outs should be expected withprolonged use at the upper temperature values.

c Lower value is the point at which no significant change is expected. Lubricant should be

replaced at the upper value or its performance watched closely. 1 RAD ≅ 0.01 gray ≅ 100ergs/g ≅ 0.01 joule/kg ≅ 4.30 x 10-6 btu/lb.

d Synthetic base oils.

e High-pressure hydraulic oils also function satisfactorily in low-pressure systems.

f Designed for maximum radiation-resistance.

g Designed primarily for ball and roller bearings. Contains no EP additive.

h Some contain a nonflammable solvent (often halogenated), usually packaged in aerosol

form or in cartridges for ease of application.

i Might be used at higher temperatures in situations where the hydrocarbon carrier isevaporated and the solids remain as the lubricant.

j Calcium soap-gelled. Temperature limit 80°C (175°F).

k Do NOT mix products. Acceptable substitutes may be made if they meet or exceed Limitorque lubricant

specifications and plant EQ requirements.

l The ester base oil may soften or swell certain paints and elastomers.

m Limitorque is not responsible for continued 1E qualification unless motors are returned to

Limitorque for repair. If return is not possible, the user assumes this responsibility.

n Not intended as a complete list.

o Products contain no solids other than gelling agent.

p Contains graphite and molybdenum sulphide residual lubes.


Appendix A

A-15

q Taken in part from Chevron Research Bulletin, “Grease” 1976, 1983; “Automotive

Engine Oils,” 1989; “Testing Used Engine Oils,” 1983; “Industrial Oil,” 1985.

r Includes calcium hydroxystearate-gelled products.

s Includes lithium hydroxystearate-gelled products.

t The better products are lithium hydroxystearate-gelled.

u Many can be used for smaller diesels, too (API CD Classification). Oils exclusively for

smaller diesels are many and varied and are beyond the scope of this report.


B-1

B APPENDIX B

B.1 Glossary

AGMA American Gear Manufacturers' Association.

Alkylaromatic Alkyl (paraffinic) side chain on an aromatic (that is,benzene, naphthalene, and so on) ring.

Antiscuff Formerly called extreme pressure (EP). Antiscuffadditives enhance scuff-resistance of lubes andreduce metal-to-metal contact. This decreasestendency toward seizing and galling.

ASTM American Society for Testing and Materials.

Atomic Absorption Spectroscopy An analytical method in which a small quantity of asample is introduced into a flame. The absorptionspectra are characteristic of some materialspresent, for example metals.

AW Antiwear. Denotes the presence of an antiwearadditive in an oil to minimize wear.

Consistency General term: viscosity in oils; penetration ingreases.

Emission spectroscopy An analytical method in which a small quantity of asample is “sparked.” The spectrum of light emittedis characteristic of some materials present, forexample, metals present as elements.

Ester Reaction product between an organic acid and analcohol [RC(O)OR].

Ferrography An analytical method whereby magnetic material,for example iron and chromium, under the influenceof a magnetic field, are isolated and studiedoptically. Yields information on large as well assmall particles and their possible source.

FTIR Fourier Transform Infrared Spectroscopy.


Appendix B

B-2

Grade, Penetration Standard NLGI grease consistency classes(grade definitions) are as follows:

NLGI ASTM (D 217) Penetration,Grade No. 60 Stroke,

Worked, 25° C (77°F), 0.1 mm

000 445-475

00 400-430

0 355-385

1 310-340

2 265-295

3 220-250

4 175-205

5 130-160

6 85-115

Grade, Viscosity Standard viscosity classifications by ISO. Gradesare matched to centistoke viscosities at 40°C(104°F); for example, 32 grade is about 32 cSt at40°C. Grades range from 2 to 1500.

HD Heavy Duty. HD oils are extra inhibited withantioxidation and antiwear additives to withstandunusually high stresses.

Highly Refined Mineral Oil Refined to the point that all or most of the naturallyoccurring inhibitors or impurities are removed, forexample, a white oil or a near white oil, alsohydrorefined or hydrocracked oils.

Hydrolysis Interaction with water.

Infrared (IR) An analytical method whereby infrared light ispassed through, or bounced off, a sample. Manyorganic substances have characteristicabsorbencies at specific wavelengths.

Inhibitor A chemical naturally present or added to lubricantsto enhance or to suppress certain properties orcharacteristics.

ISO International Standards Organization.

Lubricant A material, usually an oil or a grease, designed toreduce friction and wear between moving machineelements, acts as an hydraulic medium to removeheat, and so on.

Molysulfide A laminar solid powder of sulfides of molybdenumadded to lubricants to enhance antiscuffperformance.


Appendix B

B-3

NL Non-lead. In most gear lubricants lead has beendisplaced by other additives.

NLGI National Lubricating Grease Institute.

OEM Original Equipment Manufacturer.

Penetration(ASTM D 217; D 1403)

In a grease, the depth of entry in 1/10 millimeters ofa dropped standard cone into a grease sample. Ameasure of consistency (the higher the penetration,the lower consistency of the grease).

Pyrolysis Interaction with heat.

R & O Rust and oxidation-inhibited.

Radiolysis Treatment with radiation; interaction with radiation.

Viscosity Property of a fluid or semi-fluid that offerscontinuous resistance to flow. Usually measured asthe time of flow through a calibrated orifice,expressed as centistokes (cSt, mm²/sec.). Othermeans of expression are also used. Theinterrelationships of these are shown in Table B-1.

Worked Penetration(ASTM D 217; D 1403);Working

Penetration (or consistency) of a grease measuredafter a number of double strokes, for example 60 ina standard apparatus that provides shear.Expressed as P 60, P 10,000 and so on.


Appendix B

B-4

Table B-1Viscosity Equivalents

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