A Practical Guide to Compressor Technology

A Complete overview of theory, selection, design, operation, and maintenance This text offers a thorough overview of the operating characteristics, efficiencies, design features, troubleshooting, and maintenance of dynamic and positive displacement process gas compressors. The author examines a wide spectrum of compressors used in heavy process industries, with an emphasis on improving reliability and avoiding failure. Readers learn both the theory underlying compressors as well as the myriad day-to-day practical issues and challenges that chemical engineers and plant operation personnel must address. The text features: Latest design and manufacturing details of dynamic and positive displacement process gas compressors Examination of the full range of machines available for the heavy process industries Thorough presentation of the arrangements, material composition, and basic laws governing the design of all important process gas compressors Guidance on selecting optimum compressor configurations, controls, components, and auxiliaries to maximize reliability Monitoring and performance analysis for optimal machinery condition Systematic methods to avoid failure through the application of field-tested reliability enhancement concepts Fluid instability and externally pressurized bearings Reliability-driven asset management strategies for compressors Upstream separator and filter issues The text's structure is carefully designed to build knowledge and skills by starting with key principles and then moving to more advanced material. Hundreds of photos depicting various types of compressors, components, and processes are provided throughout. Compressors often represent a multi-million dollar investment for such applications as petrochemical processing and refining, refrigeration, pipeline transport, and turbochargers and superchargers for internal combustion engines. This text enables the broad range of engineers and plant managers who work with these compressors to make the most of the investment by leading them to the best decisions for selecting, operating, upgrading, maintaining, and troubleshooting.

Table of Contents:
PREFACE xiii ACKNOWLEDGMENTS xv PART I POSITIVE DISPLACEMENT COMPRESSOR TECHNOLOGY 1 1 Theory 3 1.1 Symbols 3 1.2 How a Compressor Works 4 1.3 First Law of Thermodynamics 8 1.4 Second Law of Thermodynamics 8 1.5 Ideal or Perfect Gas Laws 9 1.5.1 Boyle’s Law 9 1.5.2 Charles’ Law 9 1.5.3 Amonton’s Law 9 1.5.4 Dalton’s Law 9 1.5.5 Amagat’s Law 10 1.5.6 Avogadro’s Law 10 1.5.7 Perfect Gas Formula 10 1.6 Vapor Pressure 11 1.7 Gas and Vapor 11 1.8 Partial Pressures 11 1.9 Critical Conditions 13 1.10 Compressibility 13 1.11 Generalized Compressibility Charts 14 1.12 Gas Mixtures 15 1.13 The Mole 15 1.14 Specific Volume and Density 16 1.15 Volume Percent of Constituents 16 1.16 Molecular Weight of a Mixture 16 1.17 Specific Gravity and Partial Pressure 17 1.18 Ratio of Specific Heats 17 1.19 Pseudo-critical Conditions and Compressibility 18 1.20 Weight-Basis Items 18 1.21 Compression Cycles 19 1.22 Power Requirement 20 1.23 Compressibility Correction 21 1.24 Multiple Staging 22 1.25 Volume References 23 1.26 Cylinder Clearance and Volumetric Efficiency 24 1.27 Cylinder Clearance and Compression Efficiency 27 Reference 27 2 Reciprocating Process Compressor Design Overview 29 2.1 Crankshaft Design 33 2.2 Bearings and Lubrication Systems 37 2.3 Connecting Rods 37 2.4 Crossheads 38 2.5 Frames and Cylinders 39 2.6 Cooling Provisions 45 2.7 Pistons 47 2.8 Piston and Rider Rings 47 2.9 Valves 48 2.10 Piston Rods 51 2.11 Packings 55 2.12 Cylinder Lubrication 55 2.13 Distance Pieces 56 2.14 Reciprocating Compressor Modernization 57 2.14.1 Cylinder Upgrades 59 2.14.2 Design for Easy Maintenance 59 2.14.3 Crosshead Designs and Attention to Reliable Lubrication 61 2.14.4 Materials 62 3 Reciprocating Compressor Performance and Monitoring Considerations 63 3.1 Capacity Control 63 3.1.1 Recycle or Bypass 64 3.1.2 Suction Throttling 64 3.1.3 Suction Valve Unloading 65 3.1.4 Clearance Pockets 67 3.2 More About Cylinder Jacket Cooling and Heating Arrangements 70 3.2.1 Methods of Cooling 71 3.3 Comparing Lubricated and Nonlubricated Conventional Cylinder Construction 73 3.3.1 Lubricated Cylinder Designs 73 3.3.2 Nonlubricated Cylinder Design 75 3.4 Compressor Vent and Buffer Systems 76 3.5 Compressor Instrumentation 77 3.5.1 Electric vs. Pneumatic Switches 82 3.5.2 Switch Set Points 82 3.5.3 Control Panels 82 3.5.4 Valve-in-Piston Reciprocating Compressors 83 3.5.5 Barrel-Frame Reciprocating Compressors 84 3.6 Condition Monitoring of Reciprocating Compressors 85 3.6.1 Maintenance Strategies 86 3.6.2 Justification for Machine Monitoring 86 3.6.3 What to Monitor and Why 87 References 97 4 Labyrinth Piston Compressors 99 4.1 Main Design Features 99 4.2 Energy Consumption 101 4.3 Sealing Problems 104 5 Hypercompressors 109 5.1 Introduction 109 5.2 Cylinders and Piston Seals 111 5.3 Cylinder Heads and Valves 115 5.4 Drive Mechanism 117 5.5 Miscellaneous Problems 119 5.6 Conclusions 120 6 Metal Diaphragm Compressors 121 6.1 Introduction 121 6.2 Terminology 121 6.3 Description 122 7 Lobe and Sliding Vane Compressors 129 8 Liquid Ring Compressors 135 9 Rotary Screw Compressors and Filter Separators 141 9.1 Twin-Screw Machines 141 9.1.1 Working Phases 141 9.1.2 Areas of Application 145 9.1.3 Dry vs. Liquid-Injected Machines 145 9.1.4 Operating Principles 145 9.1.5 Flow Calculation 147 9.1.6 Power Calculation 147 9.1.7 Temperature Rise 150 9.1.8 Capacity Control 150 9.1.9 Mechanical Construction 153 9.1.10 Industry Experience 154 9.1.11 Maintenance History 158 9.1.12 Performance Summary 158 9.2 Oil-Flooded Single-Screw Compressors 160 9.3 Selecting Modern Reverse-Flow Filter-Separator Technology 163 9.3.1 Conventional Filter-Separators vs. SCCs 164 9.3.2 Removal Efficiencies 165 9.3.3 Filter Quality 165 9.3.4 Selecting the Most Suitable Gas Filtration Equipment 166 9.3.5 Evaluating the Proposed Configurations 167 9.3.6 Life-Cycle-Cost Calculations 168 9.3.7 Conclusions 169 10 Reciprocating Compressor Performance and Sizing Fundamentals 171 10.1 Theoretical Maximum Capacity 172 10.2 Capacity Losses 173 10.3 Valve Preload 174 10.4 Valve and Gas Passage Throttling 174 10.5 Piston Ring Leakage 176 10.6 Packing Leakage 177 10.7 Discharge Valve Leakage 177 10.8 Suction Valve Leakage 178 10.9 Heating Effects 178 10.10 Pulsation Effects 180 10.11 Horsepower 181 10.12 Horsepower Adders 181 10.13 Gas Properties 182 10.13.1 Ideal Gas 182 10.13.2 Real Gas 182 10.14 Alternative Equations of State 183 10.15 Condensation 183 10.16 Frame Loads 183 10.17 Compressor Displacement and Clearance 184 10.18 Staging 186 10.19 Fundamentals of Sizing 187 10.19.1 Number of Stages 187 10.19.2 Approximate Horsepower 187 10.19.3 Cylinder Bore Requirements 188 10.19.4 Frame Load 188 10.19.5 Vendor Confirmation 189 10.20 Sizing Examples 189 PART II DYNAMIC COMPRESSOR TECHNOLOGY 197 11 Simplified Equations for Determining the Performance of Dynamic Compressors 205 11.1 Nonoverloading Characteristics of Centrifugal Compressors 205 11.2 Stability 205 11.3 Speed Change 207 11.4 Compressor Drive 207 11.5 Calculations 208 12 Design Considerations and Manufacturing Techniques 215 12.1 Axially vs. Radially Split 215 12.2 Tightness 215 12.3 Material Stress 215 12.4 Nozzle Location and Maintenance 216 12.5 Design Overview 217 12.5.1 Casings 217 12.5.2 Flow Path 230 12.5.3 Rotors 234 12.5.4 Impellers 234 12.5.5 Axial Blading 242 12.5.6 Seals 242 12.6 Bearing Configurations 250 12.6.1 Radial Bearings 250 12.6.2 Thrust Bearings 251 12.6.3 Flexure Pivot Tilt Pad Bearings 253 12.7 Casing Design Criteria 257 12.8 Casing Manufacturing Techniques 265 12.9 Stage Design Considerations 273 12.10 Impeller Manufacturing Techniques 282 12.11 Rotor Dynamic Considerations 286 12.12 Fouling Considerations and Coatings 292 12.12.1 Polymerization and Fouling 292 12.12.2 Fouling and Its Effect on Compressor Operation 293 12.12.3 Coating Case Study 294 12.12.4 SermaLon Coating 296 12.12.5 Results 297 13 Advanced Sealing and Bearing Systems 299 13.1 Background 299 13.2 Dry Seals 300 13.2.1 Operating Principles 300 13.2.2 Operating Experience 302 13.2.3 Problems and Solutions 303 13.2.4 Dry Seal Upgrade Developments 304 13.2.5 Dry Gas Seal Failures Avoided by Gas Conditioning 304 13.3 Magnetic Bearings 308 13.3.1 Operating Principles 308 13.3.2 Operating Experience and Benefits 310 13.3.3 Problems and Solutions 311 13.4 Development Efforts 311 13.4.1 Thrust-Reducing Seals 312 13.5 Integrated Designs 314 13.6 Fluid-Induced Instability and Externally Pressurized Bearings 318 13.6.1 Instability Considerations 318 13.6.2 Fluid-Induced Instability 318 13.6.3 Eccentricity and Stiffness 320 13.6.4 Externally Pressurized Bearings and Seals 321 13.6.5 Practical Applications 324 13.6.6 Rotor Model, Dynamic Stiffness, and Fluid Instability 325 13.6.7 Root Locus Stability Analysis 327 13.6.8 More About Externally Pressurized Bearings 328 13.6.9 Field Data Collection 331 13.6.10 Test Stand Data 334 13.6.11 Conclusions 336 References 336 Suggested Reading 336 14 Couplings, Torque Transmission, and Torque Sensing 339 14.1 Coupling Overview 339 14.1.1 Low Overhung Moment 341 14.1.2 Low Residual Unbalance Desired 343 14.1.3 Long Life and Maintainability 344 14.1.4 Continuous Lubrication Not a Cure-All 345 14.1.5 Contoured Diaphragm Coupling 345 14.2 Coupling Retrofits and Upgrades 347 14.3 Performance Optimization Through Torque Monitoring 349 15 Lubrication, Sealing, and Control Oil Systems for Turbomachinery 357 15.1 Considerations Common to All Systems 357 15.2 Seal Oil Considerations 359 16 Compressor Control 363 16.1 Introduction 363 16.2 Control System Objectives 363 16.3 Compressor Maps 364 16.3.1 Invariant Coordinates 366 16.4 Performance Control 368 16.4.1 PI and PID Control Algorithms 370 16.4.2 Stability Considerations 372 16.4.3 Integral or Reset Windup 373 16.5 Performance Limitations 373 16.5.1 Surge Limit 374 16.5.2 Stonewall 375 16.6 Preventing Surge 376 16.6.1 Antisurge Control Variables 376 16.6.2 Antisurge Control Algorithms 378 16.6.3 Controlling Limiting Variables 378 16.7 Loop Decoupling 379 16.8 Conclusions 380 Reference 380 17 Head-Flow Curve Shape of Centrifugal Compressors 381 17.1 Compressor Stage 381 17.2 Elements of the Characteristic Shape 382 17.2.1 Basic Slope 382 17.2.2 Blade Angle 384 17.2.3 Fan Law Effect 385 17.2.4 Choke Effect 386 17.2.5 Mach Number 387 17.2.6 Significance of Gas Weight 387 17.2.7 Inducer Impeller Effects on Head Output 388 17.2.8 Surge 389 17.2.9 Vaned Diffusers 390 17.2.10 Vaneless Diffusers 390 17.2.11 Equivalent Tip Speeds 391 17.3 Conclusions 393 18 Use of Multiple-Inlet Compressors 395 18.1 Critical Selection Criteria 395 18.1.1 Head Rise to Surge, Surge Margin, and Overload Margin 396 18.1.2 Head per Section 397 18.1.3 Compressor Parasitic Flows 398 18.1.4 Excess Margins on Other Process Equipment 399 18.1.5 Representing Compressor Performance 399 18.1.6 Practical Levels of Critical Operating Parameters 399 18.2 Design of a Sideload Compressor 401 18.2.1 Mixing Area 402 18.2.2 Aerodynamics 403 18.2.3 Temperature Stratification 405 18.3 Testing 405 18.3.1 Test Setup 406 18.3.2 Instrumentation 406 18.3.3 Testing Procedure 406 18.3.4 Accuracy of Test Results 407 18.3.5 Evaluation of Results 407 19 Compressor Performance Testing 409 19.1 Performance Testing of New Compressors 409 19.1.1 Re-rate Options 410 19.1.2 General Guidelines 410 19.1.3 Gas Sampling 411 19.1.4 Instrumentation 412 19.1.5 Sideload Compressors 414 19.1.6 Calculation Procedures 416 19.2 Shop Testing and Types of Tests 418 19.3 Field Testing 420 19.4 Predicting Compressor Performance at Other Than As-Designed Conditions 432 19.4.1 How Performance Tests Are Documented 434 19.4.2 Design Parameters: What Affects Performance 434 19.4.3 What to Seek from Vendors’ Documents 435 19.4.4 Illustrations and Example 436 References 441 20 Procurement, Audit, and Asset Management Decisions 443 20.1 Incentives to Buy from Knowledgeable and Cooperative Compressor Vendors 443 20.2 Industry Standards and Their Purpose 444 20.2.1 Typical Scope of Standards 444 20.2.2 Disclaimers in Standards 447 20.2.3 Going Beyond the Standards 447 20.3 Disadvantages of Cheap Process Compressors 448 20.4 Audits vs. Reviews 449 20.4.1 Staffing and Timing of Audits and Reviews 450 20.4.2 Use of Equipment Downtime Statistics 450 20.5 Auditing and Reviewing Compressors 451 20.6 Compressor Inspection: Extension of the Audit Effort 465 20.6.1 Inspection of a Welded Impeller (Wheel) and the Entire Rotor 466 20.7 Compressor Installation Specifications 474 20.7.1 Field Erection and Installation Specifications for Special-Purpose Machinery 475 References 476 21 Reliability-Driven Asset Management Strategies 477 21.1 Strategy for Reciprocating Compressors 477 21.1.1 Process Operating Window 478 21.1.2 Breakdown Maintenance 478 21.1.3 Time-Based Maintenance 478 21.1.4 Equipment Health Monitoring 479 21.1.5 Reliability and Maintenance 479 21.1.6 Asset Management Strategy 479 21.2 Achieving Compressor Asset Optimization 486 21.2.1 Input Obtained from Workshops 486 21.2.2 Conclusions 496 References 497 APPENDIX A PROPERTIES OF COMMON GASES 499 APPENDIX B SHORTCUT CALCULATIONS AND GRAPHICAL 507 COMPRESSOR SELECTION PROCEDURES APPENDIX C BIBLIOGRAPHY AND LIST OF CONTRIBUTORS 551 INDEX 557

About the Author :
HEINZ P. BLOCH, MS, is a Consulting Engineer. Previously, Mr. Bloch held the position of regional machinery specialist for the United States at Exxon Chemical. He has authored seventeen books and more than 330 papers and articles and conducted more than 500 technical courses on such issues as practical machinery management, failure analysis and avoidance, turbomachinery, oil mist lubrication, and practical lubrication for industrial facilities.