Grease Lubrication in Rolling Bearings

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Description

The definitive book on the science of grease lubrication for roller and needle bearings in industrial and vehicle engineering.

Grease Lubrication in Rolling Bearings provides an overview of the existing knowledge on the various aspects of grease lubrication (including lubrication systems) and the state of the art models that exist today. The book reviews the physical and chemical aspects of grease lubrication, primarily directed towards lubrication of rolling bearings.

The first part of the book covers grease composition, properties and rheology, including thermal and dynamics properties. Later chapters cover the dynamics of greased bearings, including grease life, bearing life, reliability and testing. The final chapter covers lubrications systems – the systems that deliver grease to the components requiring lubrication.

Grease Lubrication in Rolling Bearings:

  • Describes the underlying physical and chemical properties of grease.
  • Discusses the effect of load, speed, temperature, bearing geometry, bearing materials and grease type on bearing wear.
  • Covers both bearing and grease performance, including thermo-mechanical ageing and testing methodologies.

It is intended for researchers and engineers in the petro-chemical and bearing industry, industries related to this (e.g. wind turbine industry, automotive industry) and for application engineers. It will also be of interest for teaching in post-graduate courses.

 

Author:

Piet M. Lugt

Published:

2013

Format:

Hardback

Pages:

472

Table Of Contents:

  • Preface xvii
  • List of Abbreviations xix
  • 1 Introduction 1
    • 1.1 Why Lubricate Rolling Bearings? 1
    • 1.2 History of Grease Lubrication 2
    • 1.3 Grease Versus Oil Lubrication 3
  • 2 Lubrication Mechanisms 5
    • 2.1 Introduction 5
    • 2.2 Definition of Grease 6
    • 2.3 Operating Conditions 6
    • 2.4 The Phases in Grease Lubrication 7
    • 2.5 Film Thickness During the Bleeding Phase 8
    • 2.5.1 Ball Bearings 8
    • 2.5.2 Roller Bearings 10
    • 2.6 Feed and Loss Mechanisms During the Bleeding Phase 10
    • 2.7 Film Thickness and Starvation (Side Flow) 11
    • 2.8 Track Replenishment 12
    • 2.9 Grease Flow 13
    • 2.9.1 Non-Newtonian Rheology 14
    • 2.10 Wall-Slip 15
    • 2.11 Oxidation 16
    • 2.12 EP Additives 16
    • 2.13 Dynamic Behaviour 17
    • 2.14 Grease Life 17
    • 2.14.1 Temperature 18
    • 2.14.2 Speed 19
    • 2.14.3 Load 19
    • 2.14.4 Bearing Type 20
    • 2.14.5 Grease Type 20
    • 2.14.6 Environment 21
  • 3 Grease Composition and Properties 23
    • 3.1 Base Oil 24
    • 3.1.1 Natural Triglyceride and Wax Ester Base Oils 26
    • 3.1.2 Mineral Oils 26
    • 3.1.3 Synthetic Oils 30
    • 3.2 Base Oil Viscosity and Density 41
    • 3.2.1 Viscosity–Temperature 44
    • 3.2.2 Viscosity–Pressure–Temperature 45
    • 3.2.3 Density, Compressibility 47
    • 3.3 Thickener 49
    • 3.3.1 Soap Greases, Simple Greases 50
    • 3.3.2 Complex Greases 51
    • 3.3.3 Inorganic Thickeners 52
    • 3.3.4 Mixed Thickeners 52
    • 3.3.5 Mechanical Structure 53
    • 3.3.6 Oil Retention 56
    • 3.3.7 Properties of Different Types of Grease Thickeners 56
    • 3.4 Additives 61
    • 3.4.1 Corrosion Inhibitors 62
    • 3.4.2 Anti-Oxidants 62
    • 3.4.3 EP/AW Additives 63
    • 3.5 Solid Fillers/Dry Lubricants 66
    • 3.5.1 MoS2 and Graphite 66
    • 3.5.2 Nanoparticles 66
    • 3.5.3 ZnO 66
    • 3.5.4 Teflon (polytetrafluoroethylene) 66
    • 3.5.5 Polyethylene 66
    • 3.6 Compatibility 67
    • 3.7 Polymer Grease 67
  • 4 Grease Life in Rolling Bearings 71
    • 4.1 Introduction 71
    • 4.2 Relubrication Intervals and Grease Life 71
    • 4.3 The Traffic Light Concept 72
    • 4.3.1 Low Temperatures 74
    • 4.3.2 Extreme Low Temperature 75
    • 4.3.3 Extreme High Temperature 75
    • 4.4 Grease Life as a Function of Temperature in the Green Zone 75
    • 4.5 SKF Relubrication and Grease Life 76
    • 4.6 Comparison Grease Life/Relubrication Models 78
    • 4.7 Very Low and High Speeds 82
    • 4.7.1 Speed Ratings and Speed Factors 82
    • 4.7.2 High Speed 82
    • 4.7.3 Very Low Speeds 85
    • 4.8 Large Rolling Bearings 85
    • 4.9 Effect of Load 86
    • 4.9.1 Varying Load 86
    • 4.9.2 Direction of Load 89
    • 4.9.3 Very Heavy Loads 89
    • 4.10 Effect of Outer-Ring Rotation 90
    • 4.11 Cage Material 90
    • 4.12 Bearing Type 91
    • 4.12.1 Roller Bearings 91
    • 4.12.2 Hybrid Bearings 91
    • 4.13 Temperature and Bearing Material 92
    • 4.14 Grease Fill 94
    • 4.15 Vertical Shaft 95
    • 4.16 Vibrations and Shock Loads 96
    • 4.17 Grease Shelf Life/Storage Life 97
  • 5 Lubricating Grease Rheology 99
    • 5.1 Visco-Elastic Behaviour 99
    • 5.2 Viscometers 102
    • 5.2.1 Parallel Plate and Cone-Plate Viscometers 103
    • 5.2.2 Errors in Rheometry Measurements 103
    • 5.2.3 Errors in Thin Film Parallel Plate Rheometry Measurements 105
    • 5.3 Oscillatory Shear 108
    • 5.3.1 Theory 108
    • 5.3.2 Application to Grease 110
    • 5.3.3 Effect of Thickener Concentration 112
    • 5.4 Shear Thinning and Yield 112
    • 5.4.1 Grease 112
    • 5.4.2 Lubricating Oil 116
    • 5.5 Yield Stress 118
    • 5.5.1 The Concept 118
    • 5.5.2 Influence of Temperature 119
    • 5.5.3 Consistency 120
    • 5.6 Wall-Slip Effects 122
    • 5.7 Translation Between Oscillatory Shear and Linear Shear Measurements 125
    • 5.7.1 Viscosity 125
    • 5.7.2 Yield Stress 126
    • 5.8 Normal stresses 126
    • 5.9 Time Dependent Viscosity and Thixotropy 128
    • 5.10 Tackiness 133
    • 5.10.1 Introduction 133
    • 5.10.2 Tackifiers 134
    • 5.10.3 Pull-Off Test 135
    • 5.10.4 Other Tests 136
  • 6 Grease and Base Oil Flow 137
    • 6.1 Grease Flow in Pipes 137
    • 6.1.1 Approximation Using the Newtonian Pipe Flow Equations 137
    • 6.1.2 Non-Newtonian Fluid 138
    • 6.1.3 Bingham Rheology 139
    • 6.1.4 Sisko Rheology 140
    • 6.1.5 Power Law Rheology 140
    • 6.1.6 Herschel–Bulkley Rheology 140
    • 6.1.7 The Darcy Friction Factor 142
    • 6.1.8 Transient Effects 144
    • 6.1.9 Air in Grease 144
    • 6.1.10 Entrance Length 145
    • 6.1.11 Solid Particles in Grease Flow 145
    • 6.1.12 Wall-Slip/Slip Layer 145
    • 6.1.13 Impact of Roughness 147
    • 6.1.14 Grease Aging in Pipes 149
    • 6.2 Grease Flow in Rolling Bearings 149
    • 6.2.1 Churning 149
    • 6.2.2 Flow Through Bearing Seals 152
    • 6.2.3 Relubrication 152
    • 6.2.4 Grease Flow Around Discontinuities 153
    • 6.2.5 Creep Flow 153
    • 6.2.6 Flow Induced by Vibrations 155
  • 7 Grease Bleeding 157
    • 7.1 Introduction 157
    • 7.2 Ball Versus Roller Bearings 158
    • 7.3 Grease Bleeding Measurement Techniques 158
    • 7.4 Bleeding from the Covers and Under the Cage 159
    • 7.5 A Grease Bleeding Model for Pressurized Grease by Centrifugal Forces 161
    • 7.5.1 Oil Bleeding Model 162
    • 7.5.2 Quality of the Model 166
  • 8 Grease Aging 171
    • 8.1 Mechanical Aging 172
    • 8.1.1 Softening of Grease in Rolling Bearings 172
    • 8.1.2 Hardening of Grease in Rolling Bearings 179
    • 8.2 Grease Oxidation 179
    • 8.3 The Chemistry of Base Oil Film Oxidation 181
    • 8.3.1 Chemical Reactions 181
    • 8.4 Oxidation of the Thickener 183
    • 8.5 A Simple Model for Base Oil Degradation 184
    • 8.6 Polymerization 186
    • 8.7 Evaporation 186
    • 8.8 Simple Models for the Life of Base Oil 186
    • 8.8.1 Booser’s Oil Life Model 186
    • 8.8.2 Two Phase Model 187
  • 9 Film Thickness Theory for Single Contacts 191
    • 9.1 Elasto-Hydrodynamic Lubrication 192
    • 9.1.1 History 192
    • 9.1.2 The Navier–Stokes Equations 193
    • 9.1.3 The Reynolds and Thin Film Equation 194
    • 9.1.4 Cavitation 198
    • 9.2 Contact Geometry and Deformation 198
    • 9.2.1 Rigid Bodies 199
    • 9.2.2 Elastic Deformation 200
    • 9.3 EHL Film Thickness, Oil 202
    • 9.3.1 Example: 6204 Bearing 205
    • 9.4 EHD Film Thickness, Grease 205
    • 9.4.1 Measurements 205
    • 9.4.2 Film Thickness Models for Grease Rheology 207
    • 9.5 Starvation 212
    • 9.5.1 Starved Oil Lubricated Contacts 212
    • 9.5.2 Starved Lubrication EHL Models 213
    • 9.5.3 Base Oil Replenishment 219
    • 9.5.4 Starved Grease Lubricated Contacts 222
    • 9.6 Spin 225
  • 10 Film Thickness in Grease Lubricated Rolling Bearings 227
    • 10.1 Thin Layer Flow on Bearing Surfaces 228
    • 10.1.1 Contact Replenishment in Bearings 228
    • 10.1.2 Thin Layer Flow Induced by Centrifugal Forces 231
    • 10.1.3 Combining the Thin Layer Flow on the All Bearing Components 233
    • 10.2 Starved EHL for Rolling Bearings 234
    • 10.2.1 Central Film Thickness 234
    • 10.2.2 Combining Lightly Starved and Severely Starved 237
    • 10.3 Cage Clearance and Film Thickness 239
    • 10.4 Full Bearing Film Thickness 241
  • 11 Grease dynamics 245
    • 11.1 Introduction 245
    • 11.2 Grease Reservoir Formation 245
    • 11.3 Temperature Behaviour 246
    • 11.4 Temperature and Film Breakdown 249
    • 11.5 Chaotic Behaviour 249
    • 11.5.1 Reconstruction of the Temperature Dynamics Using Time Delayed Embedding 249
    • 11.5.2 Estimation of the Time Delay t 251
    • 11.5.3 Calculation of the Dimensions d and m 251
    • 11.5.4 Calculation of the Lyapunov Exponents 252
    • 11.6 Quantitative Analysis of Grease Tests 253
    • 11.7 Discussion 254
  • 12 Reliability 257
    • 12.1 Failure Distribution 258
    • 12.2 Mean Life and Time Between Failures 261
    • 12.3 Percentile Life 264
    • 12.4 Point and Interval Estimates 265
    • 12.4.1 Graphical Methods for Point Estimates 265
    • 12.4.2 Suspended Tests, Censored Data 267
    • 12.4.3 Weibull Parameters ? and ß: Maximum Likelihood Method 269
    • 12.4.4 Bias of Point Estimates 272
    • 12.4.5 Confidence Intervals for ß 273
    • 12.4.6 Confidence Intervals and Unbiased Point Estimates
    • for Life Percentiles 273
    • 12.4.7 Estimate Precision 274
    • 12.5 Sudden Death Testing 275
    • 12.5.1 Maximum Likelihood Method for a 3-Parameter Weibull Distribution 280
    • 12.6 System Life Prediction 281
  • 13 Grease Lubrication and Bearing Life 283
    • 13.1 Bearing Failure Modes 283
    • 13.2 Rated Fatigue Life of Grease Lubricated Rolling Bearings 285
    • 13.2.1 Introduction 285
    • 13.2.2 The Lubrication Factor 287
    • 13.2.3 The Contamination Factor ?c 288
    • 13.2.4 The Stress-Life Modification Factor aslf 289
    • 13.3 Background of the Fatigue Life Ratings of Grease Lubricated Bearings 289
    • 13.3.1 Fatigue Life and Endurance Testing in the Period 1940–1960 289
    • 13.3.2 Fatigue Life and Endurance Testing After 1960 291
    • 13.3.3 The Reliability of Grease Lubricated Bearings 292
    • 13.4 Lubricant Chemistry and Bearing Life 296
    • 13.4.1 Anti-Wear Additives 297
    • 13.4.2 EP Additives 297
    • 13.4.3 The Influence of Lubricant Additives on Bearing Life 297
    • 13.5 Water in Grease 304
    • 13.5.1 Introduction 304
    • 13.5.2 Film Thickness 304
    • 13.5.3 Water in Oil and Bearing Life 304
    • 13.5.4 Concentration of Water 305
    • 13.5.5 Water in Grease 306
    • 13.6 Surface Finish Aspects Related to Grease Lubrication 306
  • 14 Grease Lubrication Mechanisms in Bearing Seals 309
    • 14.1 Introduction 309
    • 14.2 Lubrication Mechanisms for Radial Lip Seals 309
    • 14.3 Sealing Action of Grease 312
    • 14.3.1 Migration of Contaminant Particles in the Pocket 313
    • 14.3.2 Migration of Contaminant Particles in the Vicinity of the Sealing Contact 316
    • 14.4 Softening and Leakage 319
    • 14.5 Compatibility 320
    • 14.6 A Film Thickness Model for Bearing Seals 320
    • 14.6.1 Oil Feed 321
    • 14.6.2 Oil Loss 321
    • 14.7 Importance of Sealing Grease Inside the Bearing 324
  • 15 Condition Monitoring and Maintenance 327
    • 15.1 Condition Monitoring 327
    • 15.2 Acoustic Emission 328
    • 15.3 Lubcheck 330
    • 15.4 Consistency Measurement 331
    • 15.5 Oil Bleeding Properties 332
    • 15.6 Oil Content 332
    • 15.7 Particle Contamination 332
    • 15.8 Spectroscopy 333
    • 15.8.1 Infrared (IR) Spectroscopy 333
    • 15.9 Linear Voltammetry 334
    • 15.10 Total Acid Number 335
    • 15.11 DCS – Differential Scanning Calorimetry 335
    • 15.12 Oxidation Bomb 336
    • 15.13 Water 336
  • 16 Grease Qualification Testing 339
    • 16.1 Introduction 339
    • 16.2 Standard Test Methods 339
    • 16.2.1 Penetration/Grease Consistency 339
    • 16.2.2 Worked Penetration 341
    • 16.2.3 Shell Roll Stability 341
    • 16.2.4 Dropping Point 343
    • 16.2.5 Emcor 344
    • 16.2.6 Oil Separation 345
    • 16.2.7 Water Resistance 347
    • 16.2.8 Low Temperature Torque 348
    • 16.2.9 Flow Pressure 349
    • 16.2.10 4-Ball Weld Load 349
    • 16.2.11 4-Ball Wear Scar 350
    • 16.2.12 High Speed Grease Life Testing, RHF1 351
    • 16.2.13 R0F 353
    • 16.2.14 R0F+ 354
    • 16.2.15 R2F, Using the Special Spherical Roller Bearing 356
    • 16.2.16 R2F, Using Standard Bearings 357
    • 16.2.17 V2F 358
    • 16.2.18 FE8 359
    • 16.2.19 FE9 360
    • 16.2.20 A-Frame Cycle Test 360
    • 16.2.21 Cold Chamber Test 361
    • 16.2.22 BeQuiet+ 362
    • 16.2.23 Fafnir Friction Oxidation Test 364
    • 16.2.24 Copper Corrosion Test 365
    • 16.2.25 EP Reaction Test 366
    • 16.2.26 Compatibility with Preservatives/Process Fluids 367
    • 16.2.27 Compatibility Tests for Polymeric Materials 367
    • 16.2.28 Remaining Oil Percentage, or Thickener/Oil Ratio 368
    • 16.2.29 ROF/ROF+ 369
    • 16.2.30 R2F and FE8 Comparison 370
    • 16.2.31 ASTM D 3527 Life Performance of Wheel Bearing Grease 372
    • 16.2.32 ASTM D 5483 Oxidation Induction Time of Lubricating Greases by Pressure Differential Scanning Calometry 372
    • 16.2.33 Linear Sweep Voltammmetry 374
    • 16.3 Some Qualification Criteria for Grease Selection 374
    • 16.3.1 Low Temperature Limit 374
    • 16.3.2 Low Temperature Performance Limit 374
    • 16.3.3 High Temperature Performance Limit 374
    • 16.3.4 High Temperature Limit 375
    • 16.3.5 Minimum Speed 375
    • 16.3.6 Maximum Speed 375
    • 16.4 Pumpability 375
  • 17 Lubrication Systems 377
    • 17.1 Single Point Lubrication Methods 379
    • 17.2 Centralized Grease Lubrication Systems 380
    • 17.3 Pumps 382
    • 17.3.1 Shovel Pump for Pumping High Viscous Grease 382
    • 17.3.2 Method to Create a Positive Head Pressure by Using a Follower Plate 384
    • 17.4 Valves 384
    • 17.5 Distributors 386
    • 17.6 Single-Line Centralized Lubrication Systems 386
    • 17.6.1 Single-Line System and Venting 387
    • 17.6.2 Prelubrication Distributors 387
    • 17.6.3 Relubrication Distributors 390
    • 17.6.4 Strengths and Weaknesses of Single-Line Systems 392
    • 17.7 Dual-Line Lubrication Systems 393
    • 17.7.1 Description 393
    • 17.7.2 Strengths and Weaknesses of the Dual-Line System 394
    • 17.8 Progressive Lubrication Systems 394
    • 17.8.1 Description 394
    • 17.8.2 Strengths and Weaknesses of Progressive Systems 397
    • 17.9 Multi-Line Lubrication System 397
    • 17.10 Cyclic Grease Flow 397
    • 17.11 Requirements of the Grease 398
    • 17.11.1 Grease Pumpability 398
    • 17.11.2 Venting Pressure for Single-Line Systems 399
    • 17.11.3 Oil Separation/Bleeding 400
    • 17.11.4 Cleanliness 400
    • 17.11.5 Compressibility 401
    • 17.11.6 Homogeneity 401
    • 17.11.7 Additives 401
    • 17.11.8 Compatibility 402
    • 17.11.9 Delivery Resistance or Pressure Losses 402
    • 17.12 Grease Pumpability Tests 402
    • 17.12.1 Flow Ability 403
    • 17.12.2 Delivery Test 408
  • A Characteristics of Paraffinic Hydrocarbons 413
  • References 415
  • Index

 

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