Operator's Guide to General Purpose Steam Turbines An Overview of Operating Principles, Construction, Best Practices, and Troubleshooting

When installed and operated properly, general purpose steam turbines are reliable and tend to be forgotten, i.e., out of sound and out of mind.  But, they can be sleeping giants that can result in major headaches if ignored.  Three real steam turbine undesirable consequences that immediately come to mind are:

• Injury and secondary damage due to an overspeed failure.  An overspeed failure on a big steam or gas turbine is one of the most frightening of industrial accidents.
• The high cost of an extensive overhaul due to an undetected component failure.  A major steam turbine repair can cost ten or more times that of a garden variety centrifugal pump repair. 
• Costly production loses due an extended outage if the driven pump or compressor train is unspared.   The value of lost production can quickly exceed repair costs. 

A major goal of this book is to provide readers with detailed operating procedure aimed at reducing these risks to minimal levels.  Start-ups are complicated by the fact that operators must deal with numerous start-up scenarios, such as:

1. Commissioning a newly installed steam turbine
2. Starting ups after a major steam turbine repair
3. Starting up a proven steam turbine after an outage
4. Overspeed trip testing

It is not enough to simply have a set of procedures in the control room for reference.  To be effective, operating procedures must be clearly written down, taught, and practiced—until they become habit.

Robert X. Perez has 30 years of rotating equipment experience in the petrochemical industry.  He earned a BSME degree from Texas A&M University (College Station), a MSME degree from the University of Texas at Austin, and is a licensed professional engineer in the state of Texas. Mr. Perez has recently published his sixth book titled, "How to Select the Right Centrifugal Pump: A Brief Survey of Centrifugal Pump Selection Best Practices."

David W. Lawhon is a Principal Rotating Equipment Engineer currently employed by Societe des Petroles Shell in France.  He has over 30 years of experience with various aspects of rotating equipment.  He has engaged in multiple working environments ranging from oil refineries to chemical plants and for the past 15 years, has worked extensively on offshore deep water projects in various parts of the world. Mr. Lawhon received his B.S. degree in Mechanical Engineering from Texas A & I University in 1985, and his Master's in Business Administration from Texas A & M Corpus Christi in 1997.

Acknowledgements xix

1 Introduction to Steam Turbines 1

1.1 Why Do We Use Steam Turbines? 1

1.2 How Steam Turbines Work 2

1.2.1 Steam Generation 5

1.2.2 Waste Heat Utilization 5

1.2.3 The Rankine Cycle 7

1.3 Properties of Steam 8

1.3.1 Turbine Design Confi gurations 11

1.4 Steam and Water Requirements 13

1.4.1 Steam Conditions for Steam Turbines 13

1.4.2 Water Conditions for Steam Turbines 13

1.4.3 Advantages of Steam Turbine Drives 14

1.4.4 Speed Control 16

1.4.5 Turbine Overspeed Protection 17

Questions 18

Answers 19

2 General Purpose Back Pressure Steam Turbine 21

2.1 Single-Stage Back Pressure Steam Turbine 22

2.1.1 Steam Flow Path 23

2.2 Mechanical Components in General Purpose Back Pressure Steam Turbines 31

2.2.1 Radial and Th rust Bearings 31

2.2.2 Bearing Lubrication 33

2.2.3 Force Lubrication Systems 37

2.2.4 Lubrication 38

2.2.5 Bering Housing Seals 40

2.2.6 Lip Seals 41

2.2.7 Labyrinth Seals 42

2.2.8 Steam Packing Rings and Seals 44

Questions 48

Answers 49

3 Routine Steam Turbine Inspections 51

Questions 56

Answers 56

4 Steam Turbine Speed Controls and Safety Systems 59

4.1 Introduction 59

4.2 Speed Controls 60

4.3 Governor Classes 68

4.4 Overspeed Trip System 77

4.5 Overpressure Protection 81

4.6 Additional Advice 83

Questions 83

Answers 84

5 The Importance of Operating Procedures 85

5.1 Steam Turbine Start-up Risks 87

5.2 Starting Centrifugal Pumps and Compressors 91

5.3 Steam Turbine Train Procedures 93

5.4 Training Options 95

Questions 97

Answers 98

6 Overspeed Trip Testing 101

6.1 Overspeed Trip Pre-test Checks 104

6.2 Uncoupled Overspeed Trip Test Procedure 106

6.3 Acceptance Criteria for Overspeed Trip Test 110

Questions 113

Answers 114

7 Centrifugal Pump and Centrifugal Compressor Start-ups with a Steam Turbine Driver 115

7.1 Centrifugal Pump and Steam Turbine Start-up 117

7.2 Centrifugal Compressor and Steam Turbine Start-up 125

Questions 134

Answers 134

8 Centrifugal Pump and Centrifugal Compressor Shutdowns with a Steam Turbine Driver 137

8.1 Centrifugal Pump Steam Turbine Shutdown 139

8.2 Centrifugal Compressor Steam Turbine Shutdown 141

Questions 144

Answers 145

9 Installation, Commissioning and First Solo Run 147

9.1 Introduction 147

9.2 Equipment Installation 148

9.2.1 Foundations 148

9.2.2 Grouting 150

9.2.3 Piping 157

9.3 Commissioning 160

9.3.1 Steam Blowing 162

9.3.2 Strainers 165

9.3.3 Lubrication 167

9.3.4 Oil Sump Lubrication 167

9.3.5 Flushing Pressure Lubricated System 169

9.3.6 Hydraulic Governors 172

9.4 Turbine First Solo Run on Site 174

9.4.1 First Solo Run Pre-checks 175

9.4.2 Steam Turbine First Solo Run Procedure 179

Questions 186

Answers 187

10 Reinstating Steam Turbine after Maintenance 189

10.1 Turbine Reinstatment after Maintenance 189

10.2 Reinstatement after Maintenance Check List 190

10.3 Steam Turbine Reinstatement after Maintenance Procedure 194

Questions 201

Answers 202

11 Steam Turbine Reliability 205

11.1 Repairs versus Overhauls 205

11.2 Expected Lifetimes of Steam Turbines and Their Components 206

11.3 Common Failure Modes 207

11.4 Improvement Reliability by Design 211

Questions 214

Answers 215

12 Introduction to Field Troubleshooting 217

12.1 Common Symptoms 219

12.2 Common Potential Causes 219

12.3 Troubleshooting Example #1 222

12.4 Troubleshooting Example #2 223

12.5 Steam Turbine Troubleshooting Table 225

12.6 Other Troubleshooting Approaches 229

Questions 231

Answers 232

13 Steam Turbine Monitoring Advice 235

13.1 What Is the Steam Turbine Speed Telling You? 236

13.1.1 Is the Steam Turbine Running at the Correct Speed? 236

13.1.2 Is the Speed Steady? 237

13.1.3 Is a Speed Swing Acceptable? 237

13.2 Assessing Steam Turbine Vibrations 238

13.2.1 What is Normal? 238

13.2.2 What are Some Causes of Vibration in Steam Turbines? 239

13.3 Steam Turbine Temperature Assessments 243

13.3.1 Bearing Temperatures 243

13.3.2 Oil Temperatures 243

13.4 Common Governor Control Problems 244

13.4.1 Steam Turbine Loss of Power 245

13.4.2 Steam Turbine Sealing 245

13.4.3 Oil Analysis as it Applies to Steam Turbines 247

13.4.4 Formation of Sludge and Varnish 248

13.4.5 Steam Piping and Supports 249

13.4.6 Steam Turbine Supports 250

13.4.7 Overspeed Trip Systems 251

13.5 Other Inspections 252

13.6 Good Rules of Th umb for Steam Turbines 253

Questions 255

Answers 256

14 Beyond Start-ups, Shutdowns, and Inspections 257

Appendix A: An Introduction to Steam Turbine Selection 261

Appendix B: Glossary of Steam Turbine Terms 289

Appendix C: Predictive and Preventative Maintenance Activities 299

Appendix D: Properties of Saturated Steam 301

Index 305

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