Page 19 - Pipelines and Risers

XVI Contents

Chapter 14 Remaining Strength of Corroded Pipes 229
14.1 Introduction .......................................................................................................................................... 229
14.2 Review of Existing Criteria .................................................................................................................. 230
14.2.1 NG-18 Criterion ........................................................................................................................... 230
14.2.2 B3 1G Criterion ............................................................................................................................. 231
14.2.3 Evaluation of Existing Criteria ..................................................................................................... 232
14.2.4 Corrosion Mechanism .................................................................................................................. 232
14.2.5 Material Parameters ..................................................................................................................... 235
14.2.6 Problems excluded in the B3 1G Criteria ...................................................................................... 236
14.3 Development of New Criteria .............................................................................................................. 237
14.4 Evaluation ofNew Criteria .................................................................................................................. 240
14.5 Reliability-based Design ...................................................................................................................... 240
14.5.1 Target Failure Probability ............................................................................................................ 241
14.5.2 Design Equation and Limit State Function .................................................................................. 241
14.5.3 Uncertainty ................................................................................................................................... 243
14.5.4 Safety Level in the B31G Criteria ................................................................................................ 245
14.5.5 Reliability-based Calibration ........................................................................................................ 245
14.6 Example Applications .......................................................................................................................... 246
14.6.1 Condition Assessment .................................................................................................................. 249
14.6.2 Rehabilitation ............................................................................................................................... 254
14.7 Conclusions .......................................................................................................................................... 254
14.8 References ............................................................................................................................................ 254
Chapter 15 Residual Strength of Dented Pipes with Cracks 257
15.1 Introduction .......................................................................................................................................... 257
15.2 Fracture of Pipes with Longitudinal Cracks ......................................................................................... 258
15.2.1 Failure Pressure of Pipes with Longitudinal Cracks .................................................................... 258
15.2.2 Burst Pressure of Pipes Containing Combined Dent and Longitudinal Notch ............................. 259
15.2.3 Burst Strength Criteria ................................................................................................................. 261
15.2.4 Comparisons with Test ................................................................................................................. 261
15.3 Fracture of Pipes with Circumferential Cracks .................................................................................... 262
15.3.1 Fracture Condition and Critical Stress ......................................................................................... 262
15.3.2 Material Toughness, K, ............................................................................................................. 263
15.3.3 Net Section Stress, Q ................................................................................................................... 263
15.3.4 Maximum Allowable Axial Stress ............................................................................................... 263
15.4 Reliability-based Assessment and Calibration of Safety Factors ......................................................... 263
15.4.1 Design Formats vs . LSF ............................................................................................................... 264
15.4.2 Uncertainty Measure .................................................................................................................... 265
15.4.3 Reliability Analysis Methods ....................................................................................................... 266
15.4.4 Target Safety Level ...................................................................................................................... 267
15.4.5 Calibration .................................................................................................................................... 267
15.5 Design Examples .................................................................................................................................. 267
15.5.1 Case Description .......................................................................................................................... 267
15.5.2 Parameter Measurements ............................................................................................................. 268
15.5.3 Reliability Assessments ............................................................................................................... 268
15.5.4 Sensitivity Study .......................................................................................................................... 272
15.5.5 Calibration of Safety Factor ......................................................................................................... 273
15.6 Conclusions .......................................................................................................................................... 274
1 5.7 References ............................................................................................................................................ 274

Chapter 16 Risk Analysis applied to Subsea Pipeline Engineering 277
16.1 Introduction .......................................................................................................................................... 277
16.1.1 General ...................................... ...................................................................................... 277