Condition Monitoring, Troubleshooting and Reliability in Rotating Machinery

Robert X. Perez is a mechanical engineer with more than 40 years of rotating equipment experience in the petrochemical industry. He has worked in petroleum refineries, chemical facilities, and gas processing plants. He earned a BSME degree from Texas A&M University at College Station, an MSME degree from the University of Texas at Austin and holds a Texas PE license. Mr. Perez has written numerous technical articles for magazines and conferences proceedings and has authored five books and coauthored four books covering machinery reliability, including several books also available from Wiley-Scrivener.

Preface xix

Acknowledgements xxi

Part 1: Condition Monitoring 1

1 An Introduction to Machinery Monitoring 3
By Robert X. Perez

2 Centrifugal Pump Monitoring, Troubleshooting and Diagnosis Using Vibration Technologies 15
By William D. Marscher

Introduction 15

Vibration Definitions 16

How Vibration vs. Time Relates to a Vibration vs. Frequency “Spectrum” 18

What are Reasons for Excess Vibration? 19

Relationship of Vibration to Centrifugal Pump Acceptability and Reliability 20

Vibration Standards, Informal and Formal: Intent and Basis 21

Vibration Measurement Form 22

Vibration Detection Sensors 25

Accelerometers 26

Proximity Probes 27

Motion Magnified Video (aka Vibration Video Amplification) 28

International Vibration Acceptance Standards 30

Pump Components Playing Key Roles in Vibration Diagnostics 33

Rotor Support by Bearings: Fluid Film Journal Bearings vs. Rolling Element Bearings 33

Rotor Support by Seals: Annular Seal “Lomakin Effect” 35

Couplings 38

Bearing Housings and Attachment Bolts 39

Pump Casing, Feet, and Foot Attachment Bolts 39

Pump Pedestals, Baseplate, and Foundation 40

Piping, Suction, and Discharge 40

Pump Drivers 43

Evaluating Causes of Excess Vibration: Excitation vs. Amplification 43

Process of Resonant Amplification due to Coincidence of Excitation and Natural Frequencies 45

Impact Test Method of Determining Natural Frequencies 46

Specific Forces in Centrifugal Pumps 48

Mechanical Excitation Forces 48

Balance 48

Misalignment 50

Mechanical Forces Due to Dry Running Pump, Dry Running Seal, Overtightened Seal 52

Hydraulic Forces and Blade Passing Frequency 52

Hydraulic Vibration Forces Below Running Speed, Including Subsynchronous Whirl 54

Detection of Effects of Cavitation 57

Torsional Excitations 59

Vibrations Particular to Various Centrifugal Pump Types 62

Vertical Turbine Pump Evaluation 62

Vertical Dry Pit Pump Vibration Issues 65

Submersible Pump Vibration Issues 65

End Suction Overhung Single Stage Pump Vibration Issues 66

Between Bearing Double Suction Single Stage Pump Vibration Issues 66

Horizontal Multistage Pump Vibration Issues 67

Steps in Pump Evaluation through Vibration Monitoring 68

Use of the Bode and Nyquist Plots to Confirm Natural Frequencies 70

Operating Deflection Shapes (ODS) 71

Conclusions 73

Nomenclature 73

References & Bibliography 74

Acknowledgements 75

3 Proximity Probes are a Good Choice for Monitoring Critical Machinery with Fluid Film Bearings 77
By Robert X. Perez

Proximity Probe Benefits 77

Theory of Operation 78

Runout Concerns 80

Grounding and Noise 80

Shaft Orbits 81

General Machinery Monitoring Recommendations 82

Final Thoughts 85

References 86

4 Optimizing Lubrication and Lubricant Analysis 87
By Jim Fitch and Bennett Fitch

Introduction 87

Optimum Reference State 88

Lubrication Excellence and the Ascend Chart 91

Bringing Awareness to Lubrication, Contamination, and Oil Analysis 94

What You Might Not Know About Lubrication 94

Machine Surface Interaction 94

The Lubricant Film 95

Film Strength 96

Unlubricated Surface Interactions 96

Friction and Wear Generation 96

Mitigating Surface Interactions 97

Physics and Chemistry 97

Contamination: The Antagonist to Lubrication 98

Contamination Control and Condition Monitoring is More Often about Training than Advanced Technology 98

Contamination Control 99

Don’t Leave It to Instinct 99

Creating a Balance Between Exclusion and Removal 100

Why Perform Oil Analysis 102

Fluid Properties Analysis 102

Contamination Analysis 103

Wear Debris Analysis 103

Achieving Oil Analysis Success by Looking Holistically 103

Obtaining a Representative Oil Sample 105

Select the Right Machines for Oil Analysis 105

Clean and Correct Sampling Containers and Extraction Tools 105

Correctly Located Sampling Ports 106

Proper Sampling Frequency 107

Proper and Consistent Sampling Procedures 107

Forward Samples Immediately to the Laboratory 108

Ensuring Reliable Testing 108

Certified Training of Laboratory Technicians 108

Optimized Selection of Tests 109

Onsite Oil Analysis 109

Determining the Optimum Course of Action 110

Effective Organization of Analysis with Proper Trending 110

Accurate Data Interpretation by the Laboratory 110

Enhanced Data Interpretation by the End-User 111

Take Corrective Action and Determine the Root Cause 112

Continuous Improvement and Key Performance Indicator (KPI) 112

Oil Analysis Tests 112

Viscosity 113

Acid Number and Base Number 113

Ftir 114

Elemental Analysis 114

Particle Counting 114

Moisture Analysis 115

Interpreting Oil Analysis Reports 116

Following the Data Trends 118

Looking Back at the Past 123

Inspection 2.0: Advances in Early Fault Detection Strategy 124

Low-Hanging Fruit 124

Inspection Frequency Trumps High Science 125

Beware of Short P-F and Sudden-Death Failures 127

Inspection Windows and Zones 128

Inspection 2.0 is a Nurturing Strategy 129

Final Tips to Help Error-Proof Your Lubrication Program 130

References 134

5 Troubleshooting Temperature Problems 135
By Robert X. Perez

Temperature Assessments 135

How do Infrared Thermometers Work? 136

Bearing Temperature Trending 137

Rolling Element and Sleeve Bearing Temperature Guidelines 139

Rule of Thumb for Rolling Element Bearings: 142

Bearing Temperature Guidelines for Instrumented Hydrodynamic Bearings 142

Recommended Guidelines for Babbitt Bearings 142

Bearing Temperature Sensor Placement 143

Sleeve Bearings 143

Tilting Pad Journal (TPJ) Bearings-Load on Pad 144

Tilting Pad Journal Bearings-Load between Pads 144

Thrust Bearings-Tilting Pad 144

General Temperature Probe Installation Guidelines 145

Compressor Discharge Temperature Assessments 146

Heat of Compression 146

Types of Compression Processes 147

Adiabatic Compression 148

Polytropic Compression 152

Polytropic Example 1: 154

Polytropic Example 2: 154

Why Compression Ratio Matters 155

What Role It Plays in Compressor Design and Selection 155

Compression Ratio versus Discharge Temperature 155

Design Temperature Margin 158

Design Tradeoffs 159

Reciprocating Compressor Temperature Monitoring 160

Valve Temperature Monitoring 162

Temperature Monitoring Example 164

Summary 165

References 165

6 Assessing Reciprocating Compressors and Engines 167
By Robert X. Perez

Overview of Reciprocating Compressors 169

General Monitoring Guidelines for Reciprocating Compressors 174

Impact Monitoring 177

Rod Drop Monitoring 178

Using Ultrasonics to Assess Reciprocating Machinery 178

Mystery Reciprocating Compressor Knock 179

Natural Gas Engines 181

How Accurate are Rotating Equipment and Reciprocating Equipment Analyst Findings? 190

References 193

7 Managing Critical Machinery Vibration Data 195
By Robert X. Perez

Beware of False Positives and False Negatives 195

Vibration Analysis Strategies 197

Part 2: Troubleshooting 201

8 Addressing Reciprocating Compressor Piping Vibration Problems: Design Ideas, Field Audit Tips, and Assessment Methods 203
By Robert X. Perez

Piping Restraints 205

Pipe Clamping Systems 207

Guidelines 207

Preloading Clamp Bolts 209

Piping Assessment Steps 210

Small-Bore Piping 211

Attaching Pipe Clamps to Structural Members 212

The Ideal Pipe Clamp Installation 213

Installation Examples 214

Collecting and Assessing Piping Vibration 217

Piping Analysis Steps 220

Piping Vibration Examples 221

Bolt Torque Tables 223

Chapter Glossary 224

9 Remember to Check the Rotational Speed When Encountering Process Machinery Flow Problems 227
By Robert X. Perez

10 Troubleshooters Need to be Well Versed in the Equipment They are Evaluating 233
By Robert X. Perez

What is the Difference Between Troubleshooting and Conducting a Failure Analysis? 236

Equipment Details 237

Performance Characteristics 238

Centrifugal Compressors 238

Reciprocating Compressors 239

Basic Fluid Film Bearing Troubleshooting Tips 240

Design Basis: Speed, Pressures, Flows 241

System Design Details 243

OEM Recommendations 244

History 244

Putting it All Together 245

11 Precise Coupling Properties are Required to Accurately Predict Torsional Natural Frequencies 247
By Robert X. Perez

Introduction 247

Case Study 247

Start-Up Issues 249

Field Vibration Study 249

Lesson Learned 252

Final Thoughts 253

12 Is Vibration Beating on Machinery a Problem? 255
By Robert X. Perez and Andrew P. Conkey

What is Vibration Beating? 255

Zoom FFT (Fast Fourier Transform) Analysis 257

Electric Motor Zoom Analysis 258

Field Case Study: “Beating” Effect Caused by Two Closely Spaced Mechanical Frequencies Observed on Two-Shaft, Gas Turbine Drive 259

Background Information 260

Vibration Response Analysis 261

Investigation of System and Analysis 261

Frequency Analysis 262

Case Study Solution 263

Case Study Conclusions and Lessons Learned 263

Final Comments 263

References 264

Part 3: Reliability 265

13 Using Standby Machinery to Improve Process Reliability 267
By Robert X. Perez

Introduction 267

Basic Reliability Theory 267

Exercising Spared Machinery 273

Alternating Twin, Non-Critical, Process Pumps 273

Recommended Swapping Procedures for Critical Motors, Pumps, Blowers, Compressors, Generators, and Steam Turbines 274

Recommended Swapping Procedures for Reciprocating Process Plant Machinery above 200 HP 275

Raptor Modeling Software 276

Modeling Examples 277

Example 1: Unspared Compressor 278

Example 2: Main and Spare Compressor Installation 279

Example 3: Two out of Three (2oo3) Compressor Configuration 280

The Cost of Redundancy 282

Example 4: Cost of Unreliability 283

Economics 284

Justifying of a Spare Compressor 285

Closing Thoughts 287

References 287

14 Gas Turbine Drivers: What Users Need to Know 289
By Robert X. Perez

Overview 289

Theory of Operation 292

How Does a Gas Turbine Work? 292

Air Compressor 294

Combustors 296

Transition Pieces 297

Expansion Turbine 298

Turbine Section Challenges and Solutions 299

Two Shaft Gas Turbine Construction Details 301

Gas Producer 301

Lower Pressure Power Turbine (LP) 301

Typical Conditions Inside an Industrial Gas Turbine 303

Effect of Atmospheric Conditions 304

Gas Turbine Controls 305

Protection 305

Fuel and Fuel Treatment 306

Gas Fuels 306

Degradation and Water Washing 306

Advanced Materials for Land Based Gas Turbines 307

Blade Degradation 308

Condition Monitoring Approaches 309

Aerothermal Performance Analysis 309

Vibration Analysis 310

Transient Analysis 311

Mechanical Transient Analysis 311

Dynamic Pressure Analysis 312

Lube Oil Debris Analysis 312

Borescope Inspection 312

Condition Monitoring as a System 313

Gas Turbine Maintenance Inspections 313

Standby Inspections 314

Running Inspections 314

Combustion Inspections 316

Hot Gas Path Inspections 316

Major Inspections 316

Life Cycle Management 318

Non-Destructive Testing (NDT) 320

Spare Parts 321

Final Words of Advice 322

References 323

15 Reliability Improvement Ideas for Integrally Geared Plant Air Compressors 325
By Abdulrahman Alkhowaiter

Integrally Geared Plant Air Compression Packages 325

Reliability Concerns 327

Developing Enhancements for Air Compressor Reliability and Performance 330

Reliability Improvement Program to Achieve Reliability and Eliminate Frequent Failures 330

Reliability Improvements (based on 2008 Report) Made to Five (5) 850 HP Air Compressor Failures by Engineering and Maintenance: 331

16 Failure Analysis & Design Evaluation of a 500 KW Regeneration Gas Blower 341
By Abdulrahman Alkhowaiter

Introduction 341

Detail Design Analysis 343

Conclusion 349

Needed Action by Repair Shop 350

Action Required by Refinery 350

17 Operating Centrifugal Pumps with Variable Frequency Drives in Static Head Applications 353
By Robert X. Perez

VFD Advantages 354

Static Head Systems 356

Recommended Startup Sequence 359

Final Thoughts 362

References 362

18 Estimating Reciprocating Compressor Gas Flows 363
By Robert X. Perez

Swept Volume 364

Clearance Volume 365

Volumetric Efficiency 365

Flow Calculation Example 370

Factors Affecting Compressor Flow 371

Final Words 371

19 Use Your Historical Records to Better Manage Time Dependent Machinery Failure Modes 373
By Robert X. Perez

Part 4: Professional Development 379

20 Soft Skills and Habits that All Machinery Professionals Need to Develop 381
By Robert X. Perez

Asking Probing Questions 383

Listening More Carefully 384

Observing 385

Continuously Learning 386

Praising 387

Teaching 388

Closing Remarks 390

21 Developing Rotating Machinery Competency 391
By Robert X. Perez

Part I: Preparing Students to Work with Rotating Machinery 391

Rotating Machinery Related Job Functions 391

Part II: Steps to Improving Rotating Machinery Competency: Study-Practice-Share 396

About the Editor 403

About the Contributors 405

Index 409