Operator's Guide to Process Compressors

The perfect primer for anyone responsible for operating or maintaining process gas compressors. Gas compressors tend to be the largest, most costly, and most critical machines employed in chemical and gas transfer processes. Since they tend to have the greatest effect on the reliability of processes they power, compressors typically receive the most scrutiny of all the machinery among the general population of processing equipment. To prevent unwanted compressor failures from occurring, operators must be taught how their equipment should operate and how each installation is different from one another. The ultimate purpose of this book is to teach those who work in process settings more about gas compressors, so they can start up and operate them correctly and monitor their condition with more confidence. Some may regard compressor technology as too broad and complex a topic for operating personnel to fully understand, but the author has distilled this vast body of knowledge into some key, easy to understand lessons for the reader to study at his or her own pace. This groundbreaking new work is a must-have for any engineer, operator, or manager working with process compressors. The main goals of this book are to: Explain important theories and concepts about gases and compression processes with a minimum of mathematics Identify key compressor components and explain how they affect reliability Explain how centrifugal compressors, reciprocating compressors, and screw compressors function. Explain key operating factors that affect reliabilityIntroduce the reader to basic troubleshooting methodologies Introduce operators to proven field inspection techniques Improve the confidence of personnel operating compressors by teaching them the basics of compressor theory Improve compressor reliability plantwide by teaching operating and inspection best practices Improve communication between operating and supporting plant personnel by providing a common vocabulary of compressor terms Help processing plants avoid costly failures by teaching operators how to identify early compressor issues during field inspections

Preface xv 1 Introduction to Gases 1 1.1 Ideal Gases 4 1.2 Properties of Gases 5 1.3 Temperature 5 1.4 Pressure 6 1.5 Gas Laws 7 1.6 Gas Mixtures 10 1.6.1 Dalton’s Law of Partial Pressures 10 1.7 Molecular Weight of a Gas Mixture 11 1.8 Gas Density 13 1.9 Density of Mixtures 14 1.10 Heat of Compression 15 2 Commonly Used Compressor Flow Terms 19 2.1 Ideal Gas Law 20 2.1.1 Example of How to Convert from SCFM to ACFM 22 2.2 Visualizing Gas Flow 23 2.3 Compressibility Factor (Z) 25 2.4 Sizing Compressors 27 3 Compression Processes 31 3.1 Adiabatic Compression 33 3.2 Polytropic Compression 37 3.2.1 Polytropic Example #1 40 3.2.2 Polytropic Example 2 40 4 What Role the Compression Ratio Plays in Compressor Design and Selection 43 4.1 Compression Ratio versus Discharge Temperature 44 4.2 Design Temperature Margin 46 4.2.1 Design Trade-Offs 49 5 An Introduction to Compressor Operations 53 5.1 Compression Basics 53 5.2 Defining Gas Flow 55 5.3 Compressor Types 56 5.4 Multistaging 59 5.5 Key Reliability Indicators 60 6 Centrifugal Compressors 63 6.1 Centrifugal Compressor Piping Arrangements 66 6.2 Start-Up Configuration 68 6.3 Centrifugal Compressor Horsepower 68 6.4 Troubleshooting Tips 70 6.5 Centrifugal Compressor Start-Ups 71 6.6 Centrifugal Compressor Checklist 72 7 How Process Changes Affect Centrifugal Compressor Performance 75 7.1 Baseball Pitcher Analogy 75 7.2 How Gas Density Affects Horsepower 78 7.3 Theory versus Practice 80 8 How to Read a Centrifugal Compressor Performance Map 83 8.1 The Anatomy of a Compressor Map 85 8.1.1 Flow Axis (See Figures 8.2 and 8.3) 85 8.1.2 Head or Pressure Ratio Axis (See Figures 8.2 and 8.3) 86 8.1.3 Predicted Surge Line (See Figures 8.2 and 8.3) 86 8.1.4 Predicted Capacity Limit (Figures 8.2 and 8.3) 86 8.1.5 Surge Margin (See Figure 8.2) 87 8.1.6 Speed Lines (See Figures 8.2 and 8.3) 88 8.2 Design Conditions 88 9 Keeping Your Centrifugal Compressor Out of Harm’s Way 91 9.1 Compressor Operating Limits 93 9.2 Compressor Flow Limits 93 9.3 Critical Speeds 95 9.4 Horsepower Limits 96 9.5 Temperatures 97 10 Troubleshooting Centrifugal Compressors in Process Services 101 10.1 The Field Troubleshooting Process—Step by Step 105 10.1.1 Step 1: Define the Problem 105 10.1.2 Step 2: Collect All Pertinent Data 105 10.1.3 Step 3: Analyze the Body of Data as a Whole 106 10.1.4 Step 4: Act and Confirm 106 10.2 The “Hourglass” Approach to Troubleshooting 108 10.3 Thinking and Acting Globally 109 10.4 Troubleshooting Matrix and Table 110 10.5 Centrifugal Compressor Troubleshooting Example 110 11 Reciprocating Compressors 117 11.1 Reciprocating Compressor Installations 124 11.1.1 How Process Conditions Affect Reciprocating Compressor Performance 126 11.2 Reciprocating Compressor Start-Ups 128 11.3 Reciprocating Compressor Checklist 129 11.4 Criticality 131 12 Troubleshooting Reciprocating Compressors in Process Services 133 12.1 The Field Troubleshooting Process—Step by Step 137 12.1.1 Step 1: Define the Problem 137 12.1.2 Step 2: Collect All Pertinent Data 137 12.1.3 Step 3: Analyze the Body of Data as a Whole 138 12.1.4 Step 4: Act and Confirm 138 12.1.5 Troubleshooting Matrix and Table 140 12.1.6 Reciprocating Compressor Troubleshooting Example 140 13 Screw Compressors 147 13.1 Oil Injected Screw Compressors 150 13.2 Screw Compressor Modulation 151 13.3 Pressure Pulsation Issues 152 13.3.1 Absorptive Type Dampeners 154 13.3.2 Reactive Type Dampeners 154 13.3.3 Combination Type (Reactive and Absorptive) 154 13.3.4 Oil Contamination 155 13.3.5 How Process Conditions Affect Screw Compressor Performance 156 13.4 Troubleshooting Screw Compressors 156 14 Compressor Start-Up Procedures 159 14.1 Compressor Start-Up Risks 160 14.2 Generic Start-Up Procedure 162 14.3 Centrifugal Compressor Start-Ups 165 14.4 Reciprocating Compressor Start-Ups 167 14.5 Screw Compressor Start-Ups 170 15 Compressor Trains: Drivers, Speed Modifiers, and Driven Machines 173 15.1 Driven Process Machines 174 15.1.1 Drivers 175 15.1.1.1 AC Electric Motors 176 15.1.2 Steam Turbines 177 15.2 Gas Turbines 178 15.2.1 Natural Gas Engines 179 15.2.2 Speed Modifiers 180 15.2.2.1 Gear Boxes 180 15.3 Useful Gearbox Facts 182 15.4 Combination Machines 182 15.4.1 Turboexpanders 182 16 Compressor Components 185 16.1 Bearing Types 185 16.2 Rolling Element Bearings 187 16.3 Plain Bearings 188 16.4 Compressor Bearings 189 16.5 Modeling Fluid Film Bearings 190 16.6 Thrust Loads 192 16.7 Kingsbury Thrust Bearing 193 16.8 Compressor Seals 194 16.8.1 Labyrinth Seals 194 16.8.2 Oil Film Seal 194 16.8.3 Face Contact Wet Seals 196 16.9 Seal Oil System 197 16.10 Dry Gas Seals 197 16.11 Seal Gas Quality and Control 198 16.12 Reciprocating Compressors – Packing 199 17 The Importance of Lubrication 201 17.1 Lubrication Regimes 203 17.2 Lubricating Oils 206 17.3 Compressor Lubricating Oil Systems 206 17.3.1 Lubrication Monitoring 209 17.4 Oil Foaming 210 17.4.1 Excessive Foam 211 18 Inspection Ideas for Operators and Field Personnel 213 18.1 Equipment Field Inspections 213 18.1.1 Audible Inspections 215 18.1.2 Visual Inspections 216 18.1.3 Tactile Inspections 217 18.1.4 Smell 219 18.2 Tools Available to Quantify What You Have Detected 220 18.2.1 Audible Inspection Methods 220 18.2.1.1 Ultrasonic Gun 220 18.2.1.2 Stethoscope 220 18.2.1.3 Metal Rod 220 18.3 Visual Inspection Methods 221 18.3.1 Infrared or IR Gun 221 18.4 IR Camera 222 18.4.1 Strobe Light 223 18.5 Inspection Methods Using Vibration and Temperature Measurement Equipment 224 18.5.1 Vibration Meter with Accelerometer 224 18.5.2 Temperature Measurement Equipment 226 18.6 Generic Monitoring Guidelines 227 19 Addressing Reciprocating Compressor Piping Vibration Problems: Design Ideas, Field Audit Tips, and Proven Solutions 229 19.1 Piping Restraints 232 19.2 Pipe Clamping Systems 233 19.3 Guidelines 233 19.4 Piping Assessment Steps 235 19.4.1 First, Perform the Following Pre-Field Analysis Steps 235 19.4.2 Next 235 19.4.3 Problem Locations 236 19.5 Attaching Pipe Clamps to Structural Members 237 19.5.1 Installation Examples 240 19.5.2 Here Are a Few More Pipe Clamp Tips 240 20 Collecting and Assessing Piping Vibration 243 20.1 Piping Analysis Steps 245 20.2 Piping Vibration Examples 246 Appendix A: Practice Problems Related to Chapters 1 Through 4 Topics 249 Appendix B: Glossary of Compressor Technology Terms 261 Index 273