Design, Modeling, and Reliability in ROTATING MACHINERY This broad collection of current rotating machinery topics, written by industry experts, is a must-have for rotating equipment engineers, maintenance personnel, students, and anyone else wanting to stay abreast with current rotating machinery concepts and technology.
Rotating machinery represents a broad category of equipment, which includes pumps, compressors, fans, gas turbines, electric motors, internal combustion engines, and other equipment, that are critical to the efficient operation of process facilities around the world. These machines must be designed to move gases and liquids safely, reliably, and in an environmentally friendly manner. To fully understand rotating machinery, owners must be familiar with their associated technologies, such as machine design, lubrication, fluid dynamics, thermodynamics, rotordynamics, vibration analysis, condition monitoring, maintenance practices, reliability theory, and other topics.
The goal of the “Advances in Rotating Machinery” book series is to provide industry practitioners a time-savings means of learning about the most up-to-date rotating machinery ideas and best practices. This three-book series will cover industry-relevant topics, such as design assessments, modeling, reliability improvements, maintenance methods and best practices, reliability audits, data collection, data analysis, condition monitoring, and more.
This first volume begins the series by focusing on rotating machinery design assessments, modeling and analysis, and reliability improvement ideas. This broad collection of current rotating machinery topics, written by industry experts, is a must-have for rotating equipment engineers, maintenance personnel, students, and anyone else wanting to stay abreast with current rotating machinery concepts and technology.
Design, Modeling, and Reliability in Rotating Machinery covers, among many other topics:
- Rotordynamics and torsional vibration modeling
- Hydrodynamic bearing design theory and current practices
- Centrifugal and reciprocating compressor design and analysis
- Centrifugal pump design, selection, and monitoring
- General purpose steam turbine sizing
Table of Contents:
Preface xiii
Acknowledgements xv
Part 1: Design and Analysis 1
1 Rotordynamic Analysis 3
By William D. Marscher
Introduction 3
Rotor Vibration – General Physical Concepts 4
Rotor Vibration – Mathematical Description 6
Natural Frequencies and Resonance 6
Critical Speed Analysis 10
Phase Angle, and Its Relationship to Natural Frequency 15
Gyroscopic Effects 16
Accounting for Bearings 18
Cross-Coupling Versus Damping and “Log Dec” 20
Annular Seal “Lomakin Effect” 21
Fluid “Added Mass” 23
Casing and Foundation Effects 24
Lateral Vibration Analysis Methods for Turbomachinery and Pump Rotor Systems 25
Manual Methods Single Stage 25
Computer Methods 26
Forced Response Analysis 30
Mechanical Excitation Forces 32
Balance 32
Fluid Excitation Forces 37
Impeller Reaction Forces 37
Impeller Active Forces 38
Rotordynamic Stability 43
Subsynchronous Whirl & Whip 43
Stabilizing Component Modifications 47
Vertical Turbine Pump Rotor Evaluation 48
Conclusions 51
Nomenclature 52
Acknowledgements 53
References 53
2 Torsional Analysis 57
By William D. Marscher
Introduction 58
General Concerns in the Torsional Vibration Analysis of Pump and Turbomachinery Rotor Assemblies 58
Predicting Torsional Natural Frequencies 59
Torsional Excitations 63
Torsional Forced Response 68
Case History 72
Conclusions 73
Nomenclature 79
Acknowledgements 79
References 80
3 Hydrodynamic Bearings 83
By John K. Whalen
API Mechanical Equipment Standards for Refinery Service 83
Bearings 84
Hydrodynamic Lubrication 85
Tower’s Experiments 86
Reynolds Equation 88
Stribeck Curve 93
Journal Bearings 94
Dynamic Coefficients 101
Tilting Pad Journal Bearings 103
Pivot Types 107
Lubrication Methods 117
Thrust Bearings 120
A Note on Thrust Bearing Diameters 122
Fixed Geometry Thrust Bearings 122
Pivot Types 127
Lubrication 127
Increasing Load Capacity 130
Babbitt 131
Polymer-Lined Bearings 132
Current and Future Work 134
References 135
4 Understanding Rotating Machinery Data Trends and Correlations 139
By Robert X. Perez
Pattern Recognition 139
Static Versus Dynamic Data 141
Trends 142
Flat Trends 142
Trends with Step Changes 144
Upward and Downward Trends 146
Cyclic Trends 148
Is It the Machine or the Process? 148
Correlations 149
“Correlation Does Not Imply Causation” 151
Combination Trends 154
Exponential Growth Trends 155
Erratic Trends 160
Induced Draft Fan Experiences Unpredictable Vibration 160
Erratic Vibration Related to Rotor Instability 161
Some Rules of Thumb 162
5 An Introduction to Sizing General Purpose Steam Turbines 165
By Robert X. Perez and David W. Lawhon
Why Do We Use Steam Turbines? 165
How Steam Turbines Work 165
Steam Generation 167
Waste Heat Utilization 168
The Rankine Cycle 169
General Purpose Steam Turbine Sizing 170
General Purpose, Back Pressure, Steam Turbines 170
Single Stage Back Pressure Steam Turbine 170
Sizing Procedure 171
Closing Comments 185
6 Making the Business Case for Machinery Upgrades 187
By Robert X. Perez
Payback Time Examples 190
Closing Thoughts 193
Part 2: Compressors 195
7 Selecting the Best Type of Compressor for Your Application 197
By Robert X. Perez
Example of How to Convert from SCFM to ACFM 200
Compressibility Factor (Z) 200
Compressor Selection Example 201
Summary 205
Addendum 207
Demystifying Compressor Flow Terms 207
Ideal Gas Law 208
Examples of How to Convert from SCFM to ACFM 210
Visualizing Gas Flow 211
Compressibility Factor (Z) 212
8 Compressor Design: Range versus Efficiency 215
By James M. Sorokes
Introduction 215
Critical Parameters/Nomenclature 216
Operating Requirements 223
Critical Components 225
Impellers 225
Inlet Guides 232
Diffusers 235
Return Channels 238
Other Components 240
Aerodynamic Matching 243
Stage Components 243
Stage to Stage 245
Operating Conditions 246
Movable Geometry – Optimizing Range and Efficiency 248
Concluding Remarks 251
Disclaimer 251
Acknowledgements 251
References 252
9 Understanding Reciprocating Compressor Rod Load Ratings 255
By Robert X. Perez
Introduction 255
Basic Theory 256
Gas Loads 256
Piston Rod Loads 260
Crosshead Pin Loads 261
Crankpin Loads 262
History of “Rod Loads” 262
Glossary of Terms 265
User’s Perspective 266
Performance Study to Evaluate Compressor Re-Rate 268
Combined Load Exceeds Gas Load 269
Distorted Pressure Measurements = Distorted Rod Loads 269
Conclusions 271
Reference 271
10 How Internal Gas Forces Affect the Reliability of Reciprocating Compressors 273
By Robert Perez, Robert Akins and Bruce McCain
Gas Loads 274
Non-Reversing Gas Loads 277
Non-Reversing Rod Conditions Matrix 279
Non-Reversing Gas Load Examples 281
“One Failure from Disaster” 283
Ways to Protect Your Compressor 285
Closing Remarks 285
Robert Akins 286
Acknowledgements 286
Part 3: Pumps 287
11 Should You Use a Centrifugal Pump? 289
By Robert X. Perez
Net Positive Suction Head - NPSH 296
Ways to Increase the Margin Between the NPSHa and the NPSHr 302
Summary 306
12 Practical Ways to Monitor Centrifugal Pump Performance 307
By Robert X. Perez
Why Use Centrifugal Pumps? 307
Head Versus Pressure 309
Centrifugal Pump Performance 311
Assessing Centrifugal Pump Performance 313
Summary 317
Addendum 319
Determining the Best Two-Parameter Analysis Method for a Centrifugal Pump 319
13 Using Electric Motor Horsepower to Protect Centrifugal Pumps Operating in Parallel Flow Applications: A Case Study 325
By Robert X. Perez and Glenn Everett
The Problem 325
Solution 327
Results 331
Conclusions 332
Addendum 332
A Simplified Method of Determining the Efficiency of a Motor-Driven Centrifugal Pump 332
The Traditional Analysis Method 333
A Simplified Alternative Assessment Method 334
Example 335
14 Mechanical Seals and Flush Plans 337
By Robert X. Perez
Recommendations for Optimizing the Service Lives of Mechanical Seals 337
Liquid Properties 339
Expected Seal Cavity Pressure 340
Sealing Temperature 340
Liquid Characteristics 340
Reliability and Emission Concerns 340
Single or Double Seal? 341
Seal Flush Plans 342
Parting Advice 350
About the Editor 351
About the Contributors 353
Index 357
About the Author :
Robert 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.
