Maintenance, Reliability and Troubleshooting in Rotating Machinery

Preface xvii Acknowledgements xix Part I: General Reliability Advice 1 1 Machinery Reliability Management in a Nutshell 3 By Robert X. Perez Criticality 4 Environmental Consequences 6 Safety Consequences 6 Equipment History 7 Safeguards 12 Compressor Operating Limits 12 Compressor Flow Limits 12 Critical Speeds 14 Horsepower Limits 15 Temperatures 16 Layers of Machinery Protection 19 Machinery Reliability Assessment Example 20 Background 20 History 22 Safeguards 22 Conclusion 22 Closing Remarks 23 2 Useful Analysis Tools for Tracking Machinery Reliability 25 By Robert X. Perez Commonly Used Metrics for Spared Machinery 28 Mean Time to Repair (MTTR) 28 Mean Time Between Failure (MTBF) 28 Additional Reliability Assessment Tools for Spared Machines 29 Pareto Charts & 80-20 Rule 33 Cumulative Failure Trends 33 Metrics for Critical Machines 36 Availability 37 Critical Machine Events 38 Process Outage Trends 38 Process Outage Related to Machinery Outages 40 Planned Maintenance Percentage (PMP) 41 Reliability Analysis Capabilities of your CMMS Software 43 3 Improving the Effectiveness of Plant Operators 45 By Julien LeBleu Look, Listen and Feel 47 Applying Look, Listen, and Feel Techniques to Troubleshooting 47 Why the Operator's Input is Important to the Troubleshooting Process 47 Operator Tools 48 Understanding the Equipment - Pumps, Seals and Sealing Support Systems 50 Centrifugal Pump Relationships to Remember 51 Positive Displacement Pump Relationships to Remember 52 Mechanical Seals 54 Capital Projects 55 Writing Quality Work Request 55 Procedures (Procedures and Decision Trees) 56 Must Give Operators Feedback 56 Must be Required to Use their Training 58 Discipline 58 Conclusion 59 Appendix A References 59 4 Spare Parts Strategies for Optimizing Rotating Machinery Availability 61 By Robert X. Perez Some Stocking Examples 67 Capital Spares 70 Insurance Spares 71 Analyzing Spare Part Inventories Using Monte Carlo Simulations 72 Closing 72 Some Definitions Related to Spare Parts 73 5 Switch-Over Methodology and Frequency Optimization for Plant Machinery 75 By Abdulrahman Alkhowaiter Machinery Switchover Frequency Optimization Benefits 76 Time-Dependent Issues Involved in Setting Switchover Frequency for Standby Machines 76 Frequent Switchover Introduces the Following Negative Impact to Rotating Equipment 79 Calculation of Start-Stop Damaging Cycles for A, B Configured Equipment: See Definitions Below for More Information 81 Definitions 82 Examples of Short Start-Stop Intervals in Process Machinery 83 Philosophy of Reliability-Centered Switchover Strategy 84 Part II: Design Audits and Improvement Ideas 87 6 Evaluating Centrifugal Pumps in Petrochemical Applications 89 By Robert X. Perez Crude Oil Processing 92 Desalting 94 Crude Oil Distillation 94 Properties of Distillation and Fractionator Fractions 98 Defining NPSHr, NPSH3, and NPSH Margin 101 Natural Gas Processing: NGL Processing 101 Centrifugal Pump Design Audits 104 Design Standards 105 The Materials of Construction 107 The Hydraulic Fit 108 The NPSH Margin 110 Seal and Seal Flush Design 111 Challenging Pump Applications 113 Pumps Operating in Parallel 114 Pump Liquids with Low Densities 117 Low NPSH Services 120 How an Impeller's Suction Specific Speed Affects the Required NPSH 122 Pumps Handling a Liquid with Varying Densities 124 Slurry Pumps 125 FCC Slurry Pumps 127 Bottoms Pumps 127 Hot Pumps with Galling Tendencies 130 Starting Hot Pumps 131 High Temperature Concerns 132 Gaskets 132 O-Rings 135 How Processing Issues Can Affect Pump Reliability 136 Summary 138 Acknowledgement 139 References 139 7 Practical Ways to Improve Mechanical Seal Reliability 141 By Robert X. Perez Seal Reliability Tracking 142 MTBR Data from Across the Industry 143 Reliability Tracking Tools 144 Bad Actors 145 Mechanical Seal Best Practices 150 Improved Mechanical Seal Support System Designs 153 Reducing Potential Leak Points 154 Simplifying Operation and Maintenance 155 Building Better Seal Support Systems 157 Common Mechanical Sealing Design Challenges 157 Sealing Light Hydrocarbon Liquids 157 Sealing Hazardous Organic NESHAP Liquids 159 Buffer Gas Absorption 160 Excessive Solids 160 Seal Cooler Issues in Hot Applications 162 Piping Plan 21 162 Advantages 163 Disadvantages 163 Piping Plan 23 164 Advantages 165 Disadvantages 165 Common Considerations for Flush Plans 165 General Seal Piping Plan Recommendations 166 Ways to Improve Seal Reliability Performance 167 Seal Failure Analysis 167 Common Seal Failure Modes 168 Seal Failure Inspection Notes 174 Possible Causes 175 Meeting with Manufacturer 175 Writing the Seal Failure Report with Recommendations 175 Post-Analysis Activities 175 Justifying Seal Upgrades 175 Closing Thoughts 179 References 180 8 Proven Ways to Improve Steam Turbine Reliability 181 By Robert X. Perez and David W. Lawhon Repairs versus Overhauls 181 Expected Lifetimes of Steam Turbines and Their Components 181 Common Failure Modes 184 Steam Turbine Leaks 184 Bearing and Lubrication Failures 184 Governor Failures and Sticking T&T Valves 184 Improvement Reliability by Design 185 Acknowledgements 187 9 General Purpose Steam Turbine Reliability Improvement Case Studies 189 By Abdulrahman Alkhowaiter Governor Valve Packing Gland Leakage: Sealing & Reliability Improvements 190 Steam Turbines Carbon Seals Upgrade to Mechanical Seals 192 Typical Benefits of Dry Gas Seal in a 1500 HP Turbine 193 Modification of GP Turbines for Fast Start without Slow Rolling 195 How the GP Turbine Fast Startup Modification Works 195 Dry Flexible Metal Coupling Upgrade with Split Spacer, for Short Coupled Turbines with Insufficient ength Coupling Spacers 196 General Purpose Lube Oil System Upgrade for Self-Contained Bearing Housings to Eliminate Overheating & Bearing Failures 198 Governor and Trip System Upgrade from Hydraulic to Electronic-Pneumatic 198 Governor Requirements 198 Electronic Governor with Pneumatic Actuator & Pneumatic Trip System 199 Governor and Trip Requirements 200 Overview of All-Electronic Trip and Overspeed Protection System 201 Outboard Bearing Improved Flex Foot: Higher Turbine Reliability & Lower Vibration 201 Results 203 Part III: Maintenance Best Practices 205 10 Rotating Machinery Repair Best Practices 207 By Robert X. Perez World-Class Reliability Performance Should be the Goal of Every Repair Facility 207 Cutting Corners = Unreliability 208 The Importance of Alignment 209 Alignment Tolerances 210 Alternative Alignment Guidelines 210 Alignment Calculation Example 211 Rotor Balance 211 Imperial Units 212 Metric Units 213 Static Unbalance 213 Dynamic Unbalance 213 Balancing 213 Common Causes of Rotor Unbalance 214 Balancing Grades 215 The Importance of Fit, Clearance & Tolerance 217 Fits, Clearances and Tolerances 217 Tolerance 217 Clearance 218 Coupling Hub Fits 219 Keyed Interference Fits 219 Keyless Interference Fits 219 Effects of Excessive Looseness 220 Rotating Element Looseness 221 Effects of Internal Looseness 222 Structural Looseness 223 As Found and As Left Measurements 223 Closing Thoughts 225 References 225 11 Procedures + Precision = Reliability 227 By Drew Troyer 12 The Top 10 Behaviors of Precision-Maintenance Technicians 231 By Drew Troyer 13 Optimizing Machinery Life Cycle Costs through Precision and Proactive Maintenance 235 By Drew Troyer Precision Maintenance 101 235 Life-Extension Equations 237 Worked Example 238 Life Cycle Costs 239 Considering Energy Consumption 239 Life Cycle Inventory Analysis 242 Justifying Precision Maintenance 242 Estimating the Benefits 242 Now for the Cost-Benefit Analysis 245 14 Optimum Reference States for Precision Maintenance 253 By Drew Troyer Fasteners 254 Lubrication 255 Alignment 257 Balance 258 Flab Management 260 Conclusion 261 15 Writing Effective Machinery Work Order Requests 263 By Drew Troyer Part IV: Analyzing Failures 269 16 Improving Machinery Reliability by Using Root Cause Failure Analysis Methods 271 By Robert X. Perez Introduction 271 What Is a Root Cause Failure Analysis? 272 Root Cause Failure Analysis Example #1: Ill-Advised Bearing Replacement 273 History 273 Corrective Measures 273 Comments 273 Root Cause Failure Analysis Example #2: Reciprocating Compressor Rod Failure 274 Background 274 Physical Root Cause 274 Latent Root Causes 274 Comments 275 RCFA Steps 275 Step 1: Define the Problem 275 Step 2: Gather Data/Evidence 276 Identifying the Physical Root Cause of the Primary Failure 276 Fatigue Example: Fin-Fan Cooler Shaft Failures 279 Preserving Machine Data 282 Step 3: Ask Why and Identify the Causal Relationships Associated with the Defined Problem 283 Causal Chains 283 Bearing Failure Sequence of Events with Descriptions 284 Five Why RCFA Example 286 Cause Mapping 287 Cause Map Example #2 289 Single Root Cause versus Multiple Causes 290 Cause Mapping Steps 290 Inhibitors to Effective Problem Solving 297 When Is a Root Cause Failure Analysis Justified? 297 RCFA Levels 300 Closing Thoughts 301 Appendix A 301 No Magic Allowed 301 Identifying Sequence of Events and Causal Chains 301 5-Why Method of Investigation 304 Advice on Failure Sequences 306 Appendix B 307 Analyzing Component Failure Mechanisms 307 Common Mechanical Failure Modes 309 Foreign Object Damage (FOD) 309 Stress Corrosion Cracking 309 Erosion 310 Cavitation 310 Hydrogen Embrittlement 310 Galling 311 Fretting 311 Hot Corrosion (Gas Turbines) 312 Common Hydrodynamic Bearing Failure Modes 313 Rolling Element Bearing Failure Characteristics 318 Tips for Analyzing Mechanical Seal Failures 320 Common Seal Failure Modes 321 Appendix C 323 Common Machinery Failure Modes 323 Pluggage 325 Erosive Wear 326 Fatigue 326 Compressor Blade Fatigue Example 327 Hydrodynamic Bearing Failure Examples 328 Rubbing 329 Unique Failure Modes 330 References 331 17 Investigation and Resolution of Repetitive Fractionator Bottom Pump Failures 333 By Abdulrahman Alkhowaiter Introduction 333 List of Additional Failure Inherent Causes to Be Rectified 334 Key Shop and Field Pump Measurements 336 Conclusion 340 Actual Findings 340 Effect of Improvements on Pump Radial Shaft Vibration 342 Reference 342 18 Reliability Improvements Made to 6000 KW Water Injection Pumps Experiencing Wear Ring Failures 343 By Abdulrahman Alkhowaiter Summary 343 Sequence of Events 344 New Design Proposal of Eliminating Grub Screws or Flash Butt Welding 346 Example: Wear ring ID = 8.0 inches. Apply Taper Fit Principle 346 Upgrade Options 347 Detailed Analysis of Problem & Solution Related to All Pump Wear Rings 348 Discussion on Reliability Improvements Added to Achieve High Reliability 349 The Five Root Causes of Machinery Failure 350 Design Errors 350 Manufacturing Errors: None Found 351 User Specification Errors 351 User Maintenance Errors: None Found 351 About the Editor 353 About the Contributors 355 Index 357