Machinery Failure Analysis and Troubleshooting Practical Machinery Management for Process Plants Volume 2 Fourth Edition n Heinz P. Bloch Fred K. Geitner AMSTERDAM(cid:129)BOSTON(cid:129)HEIDELBERG(cid:129)LONDON NEWYORK(cid:129)OXFORD(cid:129)PARIS(cid:129)SANDIEGO SANFRANCISCO(cid:129)SINGAPORE(cid:129)SYDNEY(cid:129)TOKYO Butterworth-HeinemannisanimprintofElsevier Butterworth-HeinemannisanimprintofElsevier TheBoulevard,LangfordLane,Kidlington,Oxford,OX51GB,UK 225WymanStreet,Waltham,MA02451,USA OriginallypublishedbyGulfPublishingCompany,Houston,Texas,USA ThirdeditionpublishedbyGulfProfessionalPublishing(animprintofElsevier),1999 FourtheditionpublishedbyButterworth-Heinemann(animprintofElsevier)2012 Copyright(cid:1)2012ElsevierInc.Allrightsreserved. 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Failure prevention can be achieved by sound specification, selection, review, and design audit routines. When failures do occur, accurate definition of the root cause is an absolute prerequisite to the prevention of future failure events. Thisbookconcernsitselfwithprovenapproachestofailuredefinition.Itpresentsaliberalcross sectionofdocumentedfailureeventsandanalyzestheproceduresemployedtodefinethe sequenceofeventsthatledtocomponentorsystemsfailure.Becauseitissimplyimpossibleto dealwitheveryconceivabletypeoffailure,thisbookisstructuredtoteachfailureidentification andanalysismethodsthatcanbeappliedtovirtuallyallproblemsituationsthatmightarise. Auniformmethodologyoffailureanalysisandtroubleshootingisnecessarybecauseexperience showsthatalltoooftenprocessmachineryproblemsareneverdefinedsufficiently;theyare merely“solved”to“getbackonstream.”Productionpressuresoftenoverridetheneedtoanalyze asituationthoroughly,andtheproblemanditsunderlyingcausecomebackandhauntuslater. Equipmentdowntimeandcomponentfailureriskcanbereducedonlyifpotentialproblemsare anticipated and avoided. Often, this is not possible if we apply only traditional methods of analysis.Itisthusappropriatetoemployothermeansofprecludingorreducingconsequential damagetoplant,equipment,andpersonnel.Thisobjectiveincludes,amongothers,application of redundant components or systems and application of highly computerized analysis techniques for electrical/electronic systems. The organizational environment and management style found in process plants often permits a “routine” level of machinery failures and breakdowns. This book shows how to arrive at a uniform method of assessing what level of failure experience should be considered acceptable and achievable. In addition, it shows how the organizational environment can be betterpreparedtoaddressthetaskofthoroughmachineryfailureanalysisandtroubleshooting, with resulting maintenance incident reduction. Finally, by way of successful examples, this bookdemonstrateshowtheprogressandresultsoffailureanalysisandtroubleshootingefforts can be documented and thus monitored. H.P. Bloch Westminster, Colorado F.K. Geitner Brights Grove, Ontario xv Contents Acknowledgments ............................................................................................xiii Preface............................................................................................................xv Chapter 1: The Failure Analysis and Troubleshooting System.................................1 Troubleshooting as an Extension of Failure Analysis.......................................................1 Causes of Machinery Failures............................................................................................3 Root Causes of Machinery Failure.....................................................................................7 References...........................................................................................................................9 Chapter 2: Metallurgical Failure Analysis..........................................................11 Types of Failures..............................................................................................................15 Metallurgical Failure Analysis Methodology..................................................................15 Failure Analysis of Bolted Joints.....................................................................................21 Shaft Failures....................................................................................................................28 The Case of the Boiler Fan Turbine................................................................................46 Analysis of Surface-Change Failures...............................................................................48 Analyzing Wear Failures..................................................................................................56 Preventive Action Planning Avoids Corrosion Failure....................................................65 Case Studies......................................................................................................................69 Summary...........................................................................................................................84 References.........................................................................................................................85 Chapter 3: Machinery Component Failure Analysis.............................................87 Bearings in Distress..........................................................................................................90 Rolling-Element Bearing Failures and Their Causes......................................................96 Patterns of Load Paths and Their Meaning in Bearing Damage.....................................98 Troubleshooting Bearings...............................................................................................131 Journal and Tilt-Pad Thrust Bearings............................................................................150 Gear Failure Analysis.....................................................................................................172 Preliminary Considerations............................................................................................173 Analytical Evaluation of Gear Theoretical Capability..................................................176 vii viii Contents Metallurgical Evaluation................................................................................................177 General Mechanical Design...........................................................................................178 Lubrication......................................................................................................................178 Defects Induced by Other Train Components...............................................................178 Wear................................................................................................................................179 Scoring............................................................................................................................186 Surface Fatigue...............................................................................................................192 Failures from the Manufacturing Process......................................................................197 Breakage.........................................................................................................................202 Lubricated Flexible/Coupling Failure Analysis.............................................................205 Gear-Coupling Failure Analysis.....................................................................................206 Gear-Coupling Failure Mechanisms...............................................................................208 Determining the Cause of Mechanical Seal Distress....................................................218 Troubleshooting and Seal-Failure Analysis...................................................................219 Summary of Mechanical Seal Failure Analysis.............................................................240 Avoiding Common Causes of O-ring Failures...............................................................241 Failure Without Visible Evidence on Seal.....................................................................241 Compression Set.............................................................................................................242 Lubricant Considerations................................................................................................248 Lubrication Failure Analysis..........................................................................................248 Why Lube Oil Should Be Purified.................................................................................250 Six Lube-Oil Analyses Are Required............................................................................263 Periodic Sampling and Conditioning Routines Implemented.......................................267 Calculated Benefit-to-Cost Ratio...................................................................................271 Wear-Particle Analysis...................................................................................................272 Grease Failure Analysis..................................................................................................275 Magnetism in Turbomachinery......................................................................................278 References.......................................................................................................................292 Chapter 4: Machinery Troubleshooting............................................................295 Competing Approaches..................................................................................................297 The Professional Problem Solver’s (PPS) Approach.....................................................301 The Matrix Approach to Machinery Troubleshooting...................................................304 Troubleshooting Pumps..................................................................................................312 Making Good Choices....................................................................................................344 Troubleshooting Centrifugal Compressors, Blowers, and Fans....................................346 Troubleshooting Reciprocating Compressors................................................................347 Troubleshooting Engines................................................................................................361 Troubleshooting Steam Turbines....................................................................................368 Troubleshooting Gas Turbines.......................................................................................369 Contents ix Troubleshooting Electric Motors....................................................................................373 Electrical Motor Bearing Failures..................................................................................373 Troubleshooting the Process...........................................................................................379 Apply Proven Machinery Problem Solving Strategies..................................................383 References.......................................................................................................................389 Chapter 5: Vibration Analysis........................................................................391 Machine History.............................................................................................................394 Machine Characteristics.................................................................................................394 Interpretation of Collected Data.....................................................................................402 Aerodynamic Flow-Induced Vibrations.........................................................................421 Establishing Safe Operating Limits for Machinery.......................................................463 Appendix.........................................................................................................................466 Formulas.........................................................................................................................475 References.......................................................................................................................477 Chapter 6: Generalized Machinery Problem-Solving Sequence............................479 Situation Analysis...........................................................................................................480 Cause Analysis................................................................................................................485 Action Planning and Generation....................................................................................496 Planning for Change.......................................................................................................518 References.......................................................................................................................524 Chapter 7: Statistical Approaches in Machinery Problem Solving........................525 Machinery Failure Modes and Maintenance Strategies.................................................526 Machinery Maintenance Strategies................................................................................542 Method to Identify Bad Repairs from Bad Designs......................................................549 References.......................................................................................................................557 Quantifying Reliability Performance to Meet Process Safety Expectations.................558 How Equipment Reliability has an Impact on Process Safety......................................558 Case Histories in Responsive Risk Mitigation..............................................................559 Conservative, but Reasonable?.......................................................................................562 What Does “Good” Look Like?.....................................................................................564 A Standardized Approach to Assessing Pump Failure Risk.........................................564 Conclusions.....................................................................................................................575 References.......................................................................................................................575 Chapter 8: Formalized Failure Reporting as a Teaching Tool.............................577 Examining the Sample Reports......................................................................................579 The Case of the High-Speed, Low-Flow Pump Failure................................................580 References.......................................................................................................................614 x Contents Chapter 9: The “Seven Cause Category Approach” to Root-Cause Failure Analysis............................................................................615 Checklists and Failure Statistics Can be Helpful..........................................................616 Systematic Approaches Always Valuable......................................................................616 Faulty Design Causes Premature Bearing Failures........................................................617 Fabrication and Processing Errors Can Prove Costly....................................................619 Operations Errors Can Cause Pumps to Malfunction....................................................621 Maintenance Omissions Can Cause Loss of Life..........................................................622 Awareness of Off-Design and Unintended Service Conditions Needed to Prevent Failures........................................................................................................................630 Reduced Life and Catastrophic Failure of Electric Motor Bearings.............................634 References.......................................................................................................................635 Chapter 10: A Principle Based Problem Solving Process....................................637 Traditional Problem-Solving Strategies.........................................................................638 Linear Thinking..............................................................................................................638 Categorization.................................................................................................................638 Storytelling......................................................................................................................640 Root Cause Myth............................................................................................................644 Principles of Causation...................................................................................................645 Seven Steps to Effective Problem Solving....................................................................647 RealityCharting...............................................................................................................648 Continuous ImprovementdThe Essence of Quality.....................................................648 Additional Resources......................................................................................................648 References.......................................................................................................................649 Chapter 11: Knowledge-Based Systems for Machinery Failure Diagnosis.............651 Examples of Knowledge-Based Systems.......................................................................653 Identification and Selection of Knowledge-Based System Applications......................654 Project Implementation..................................................................................................659 Expert-System Questionnaire.........................................................................................662 References.......................................................................................................................668 Chapter 12: Training and Organizing for Successful Failure Analysis and Troubleshooting....................................................................669 Available Choices and When to Make Them................................................................670 Why Shared Learning and a Measure of Specialization are Important........................671 Specific Steps in the Training and Learning Process....................................................672 Favorable Results Anticipated........................................................................................674 Contents xi Professional Growth: The Next Step..............................................................................675 Organizing for Failure Analysis and Troubleshooting..................................................677 Setting Up a Centrifugal Pump Failure Reduction Program.........................................677 Definition of Approach and Goals.................................................................................678 Action Steps Outlined....................................................................................................679 Development of Checklists and Procedures...................................................................680 Program Results and Conclusions..................................................................................688 References.......................................................................................................................689 Appendix A: Databases, Surveys and mean-time-between-failure expectations derived from literature and from authors’ observations....................691 Appendix B: Probability Plotting of Life Data...................................................713 Appendix C: Glossary of Problem-Solving and Decision-Making Terms.................723 Appendix D: Gear Nomenclature.....................................................................725 Subject Index................................................................................................727 CHAPTER 1 The Failure Analysis and Troubleshooting System Chapter Outline Troubleshooting as an Extension of Failure Analysis 1 Causes of Machinery Failures 3 Root Causes of Machinery Failure 7 References 9 Troubleshooting as an Extension of Failure Analysis Foryears,theterm“failureanalysis”hashadaspecificmeaninginconnectionwithfracture mechanics and corrosion failure analysis activities carried out by static process equipment inspection groups. Figure 1-1 shows a basic outline of materials failure analysis steps.1 The methodsappliedinourcontextofprocessmachineryfailureanalysisarebasicallythesame; however, they are not limited to metallurgic investigations. Here, failure analysis is the determination of failure modes of machinery components and their most probable causes. Figure1-2illustratesthegeneralsignificanceofmachinerycomponentfailuremodeanalysis as it relates to quality, reliability, and safety efforts in the product development of a major turbine manufacturer.2 Very often, machinery failures reveal a reaction chain of cause and effect. The end of the chainis usuallyaperformancedeficiencycommonlyreferredto asthesymptom,trouble,or simply“theproblem.”Troubleshootingworksbackwardtodefinetheelementsofthereaction chainandthenproceedstolinkthemostprobablefailurecausebasedonfailure(appearance) analysis with a root cause of an existing or potential problem. For all practical purposes, failureanalysisandtroubleshootingactivitieswillquiteoftenmeshwithoneanotherwithout any clear-cut transition. However,aswewillseelater,therearenumerouscaseswheretroubleshootingalonewillhave tosufficetogettotherootcauseoftheproblem.Thesearethecasesthatpresentthemselves as performance deficiencies with no apparent failure modes. Intermittent malfunctions and faults are typical examples and will tax even the most experienced troubleshooter. In these 1 2 Chapter 1 Figure 1-1: Failure analysis stepsdmaterials technology (modified from Ref. 1). cases, troubleshooting will be successful only if the investigator knows the system he is dealing with. Unless he is thoroughly familiar with component interaction, operating or failure modes, and functional characteristics, his efforts may be unsuccessful. There are certain objectives of machinery failure analysis and troubleshooting: 1. Prevention of future failure events. 2. Assurance of safety, reliability, and maintainability of machinery as it passes through its life cycles of: a. Process design and specification. b. Original equipment design, manufacture, and testing. c. Shipping and storage. d. Installation and commissioning. e. Operation and maintenance. f. Replacement. From this it becomes very obvious that failure analysis and troubleshooting are highly co- operativeprocesses.Becausemanydifferentpartieswillbeinvolvedandtheirobjectiveswill sometimes differ, a systematic and uniform description and understanding of process machinery failure events is important.