Reliability Based Design for Pipelines Canadian Standard Association Approach, Industry Response, and Comparison with ISO 16708

Transcription

1 Reliability Based Design for Pipelines Canadian Standard Association Approach, Industry Response, and Comparison with ISO International ISO Standardization Seminar for the Reliability Technology and Cost Area NEN - Vlinderweg AX Delft 29 th Maher Nessim Francisco Alhanati C-FER Technologies

2 Current Onshore Pipeline Design Approach Pipelines are designed using the Barlow Equation PD 2t SMYS Applied hoop stress Specified Minimum Yield Strength Safety factor (Design factor x location factor) Prevent yielding / rupture of new pipe under internal pressure ISO Standardization Seminar - Delft NL 2

3 Pipeline Failure Stats Reportable Incidents for Natural Gas Pipelines US DOT ( ) 5% 1% 4% 11% 6% 11% 26% 36% External Interference External Corrosion Internal corrosion Manufacturing Defects Geotechnical Hazard Construction Defects Operator Error Other Most failures are associated with mechanical damage by external forces, corrosion and other deterioration mechanisms ISO Standardization Seminar - Delft NL 3

4 Key Limitation Pipeline reliability with respect to the dominant failure mechanisms is far more sensitive to wall thickness than to other parameters, such as hoop stress The current design approach is not the most effective safety control parameter results in widely varying risk levels for different pipelines ISO Standardization Seminar - Delft NL 4

5 Implied Safety Levels Resistance to dominant failure causes is more dependent on the wall thickness than the hoop stress factor Hoop stress design factor not the most effective safety control parameter ISO Standardization Seminar - Delft NL 5

6 Reliability Based Design Key features Design for actual failure mechanisms (limit states) Use reliability as a safety control parameter Evaluate options based on meeting a specified reliability target Benefits Known and consistent safety levels Guidance for all relevant design and assessment conditions Effective allocation of resources to maximize safety Well suited to new situations (new technologies, materials or loads) Limitations Requires probability calculations (data / expertise / effort) Potential for different users to get different answers ISO Standardization Seminar - Delft NL 6

7 Reliability Based Design Standards Reliability based design is permitted in many standards, e.g. ISO / CSA Z662 / IGE TD1 / AS Guidance is provided in a few standards, e.g. CSA Z662 (1995). Oil and gas pipeline systems Annex C: Limit States design IGE/TD/1 (2001) Steel pipelines and associated installations for high pressure gas transmission Appendix 4: Structural reliability analysis ISO (2006) - Petroleum and natural gas industries - Pipeline transportation systems - Reliability-based limit state methods NEN (2006) Requirements for pipeline systems Section 8: Structural design CSA Z662 (2007). Oil and gas pipeline systems Annex O: Reliability based design and assessment of onshore natural gas pipelines ISO Standardization Seminar - Delft NL 7

8 Comparison Between ISO and CSA Topic ISO CSA Scope - pipelines Scope - fluids Reliability targets Loads, load combinations and limit states Reliability estimation Reliability checking All pipelines All oil and gas To be defined by user optional specific guidance given for some cases Generic definitions with illustrative examples Detailed description of distribution and reliability theories implementation left to the user Generic check Buried onshore pipelines (no crossings or above-ground sections) Specific fluids (Natural Gas / non-volatile LVP / more to come) Prescribed defined as function of pipeline and location parameters Comprehensive listing of potentially applicable loads, load combinations and corresponding limit states Reference to reliability texts specific limit state functions and input distributions for key design conditions Specific methodology addressing pipeline segmentation and length averaging ISO Standardization Seminar - Delft NL 8

9 CSA Approach - Highlights Limit States Reliability targets Reliability checking (demonstrating compliance) ISO Standardization Seminar - Delft NL 9

10 Life Cycle Phase Pipe Configuration Primary Load Companion Loads Limit State Limit State Type Stress limit Strain limit Time Dependent Loads and Limit States Transportation Installation All Buried (installed by directional drilling) 1 Cyclic bending Fatigue crack growth SLS Yes 2 Stacking weight Ovalization SLS No 4 Bending during installation 5 Directional drilling tension and bending Plastic collapse SLS No Local Buckling SLS No Girth weld tensile rupture SLS No Local buckling SLS No Testing All 3 Hydrostatic test Excessive plastic deformations SLS No All 6 Internal pressure Burst of defect free pipe ULS No 7 Equipment Impact 6 Burst of a gouged dent 2 ULS No Buried 8 Restrained thermal expansion 6 9 Slope instability, ground movement 6,8,12 10 Frost heave 6, Thaw settlement 6,8,12 Local buckling SLS or ULS 1 No Upheaval buckling SLS or ULS 1 No Local buckling SLS or ULS 1 Yes Girth weld tensile rupture ULS Yes Local buckling SLS or ULS 1 Yes Girth weld tensile rupture ULS Yes Local buckling SLS or ULS 1 Yes Girth weld tensile rupture ULS Yes 12 Seismic loads 13 Loss of soil support (e.g., subsidence) 6,8, 9 or10 or 11 6,8 Local buckling SLS or ULS 1 No Girth weld tensile rupture ULS No Local buckling SLS or ULS 1 Yes Girth weld tensile rupture ULS Yes Operation Buried rail or road crossings, or in farmland 14 Overburden and surface loads 6 Failure of a weld defect ULS Yes Plastic collapse SLS or ULS 1 No Ovalization SLS No Dynamic instability SLS or ULS 1 No Waterway crossings 15 River bottom erosion 6,8,16 Formation of mechanism by yielding SLS or ULS 1 No Local buckling SLS or ULS 1 No Waterway crossing or wetlands Girth weld tensile rupture ULS No 16 Buoyancy 6,8 Floatation SLS or ULS 1 No Formation of mechanism by yielding SLS or ULS 1 No 17 Gravity loads 6 Local buckling SLS or ULS 1 No Above ground 18 Support settlement 6,17 Girth weld tensile rupture SLS or ULS 1 No Local buckling SLS or ULS 1 Yes Girth weld tensile rupture ULS Yes Dynamic instability SLS or ULS 1 No 19 Wind loads 6,17 Burst of crack by fatigue ULS Yes 1 Starts as a serviceability limit state, but could progress to an ultimate limit state ISO Standardization Seminar - Delft NL 10

11 Loads and Limit States Life Cycle Phase Pipe Configuration Primary Load Companion Loads Limit State Limit State Type Stress limit Strain limit Time Dependent Transportation Installation All Buried (installed by directional drilling) 1 Cyclic bending Fatigue crack growth SLS Yes 2 Stacking weight Ovalization SLS No 4 Bending during installation 5 Directional drilling tension and bending Plastic collapse SLS No Local Buckling SLS No Girth weld tensile rupture SLS No Local buckling SLS No Testing All 3 Hydrostatic test Excessive plastic deformations SLS No All 6 Internal pressure Burst of defect free pipe ULS No 7 Equipment Impact 6 Burst of a gouged dent 2 ULS No Buried 8 Restrained thermal expansion 6 9 Slope instability, ground movement 6,8,12 10 Frost heave 6, Thaw settlement 6,8,12 Local buckling SLS or ULS 1 No Upheaval buckling SLS or ULS 1 No Local buckling SLS or ULS 1 Yes Girth weld tensile rupture ULS Yes Local buckling SLS or ULS 1 Yes Girth weld tensile rupture ULS Yes Local buckling SLS or ULS 1 Yes Girth weld tensile rupture ULS Yes 12 Seismic loads 6,8, 9 or10 or 11 Local buckling SLS or ULS 1 No Girth weld tensile rupture ULS No Operation 13 Loss of soil support (e.g., subsidence) Buried rail or road crossings, or in 14 Overburden and surface loads 6 6,8 Local buckling SLS or ULS 1 Yes Girth weld tensile rupture ULS Yes ISO Standardization Seminar Failure of - Delft a weld NL defect ULS Yes 11 Plastic collapse SLS or ULS 1 No

12 Risk Based Reliability Targets ULS Based on benchmarking to current practice Match or exceed average safety associated with a new pipeline network designed to acceptable standards and operated to best industry practices Maintain a uniform safety level for all pipelines ISO Standardization Seminar - Delft NL 12

13 Average 50-yr Risk (per km-yr) Risk Benchmarking Example Total Societal Risk 1E psi, 10 in 1200 psi, 20 in 1400 psi, 42 in 1E-03 1E-04 1E-05 1E-06 1E-07 1E-08 1E-09 1E-10 Class 1 Class 2 Class 3 Class 4 Weighted average risk - 1.6E-5 1.E+05 1.E+06 1.E+07 1.E+08 1.E+09 PD 3 (psi-in 3 ) Calculated Risk Levels for Wide Range of Natural Gas Pipeline Designs and Corresponding Average Risk Level and Length-weighted Average ISO Standardization Seminar - Delft NL 13

14 Allowable Failure Probabilities Natural Gas 1.E-02 Allowable Probability of Failure (per km-yr) 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 1.E-08 1.E-09 1.E+06 1.E+07 1.E+08 1.E+09 1.E+10 1.E+11 1.E+12 1.E+13 rpd 3 (people/ha-mpa-mm 3 ) ISO Standardization Seminar - Delft NL 14

15 Allowable Probability of Failure (per km yr) Allowable Failure Probabilities Non-volatile LVP Liquids 1.E-02 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 b D 1.6 (mm) ISO Standardization Seminar - Delft NL 15

16 Reliability Checking Issues Pipeline segmentation based on potential consequence severity Population density for natural gas Environmental sensitivity for liquids Reliability checking for different threat types Localized threats point source (moving slope) Distributed threats Continuous (internal pressure) Randomly located (equipment impact) Reliability checking for different failure modes Leaks Ruptures ISO Standardization Seminar - Delft NL 16

17 Validation and Scrutiny Developed under PRCI project directed and supervised by industry Tested extensively to evaluate the impact on design and operational decision making Published in a series of 7 conference and 2 journal peer-reviewed papers more to come Reviewed by 3 independent consultants and researchers Presented and debated in multiple sessions of the CSA Z662 Technical Committee Debated in a public forum sponsored by CSA in 2005 Approved unanimously by the Z662 Technical Committee for adoption in 2007 edition of the Standard ISO Standardization Seminar - Delft NL 17

18 Application Adoption initially slow Apprehension about the use of firm reliability targets Skepticism about the required probabilistic calculations Lack of expertise in potential user organizations First applications were for arctic pipeline design against frost heave and thaw settlement loads because the current standards do not provide any guidance in this area Significant momentum over the past 2 to 3 years for application to conventional pipeline issues such as class location changes and management or corrosion and cracks Heightened public awareness of pipeline risk More recognition of the benefits of reliability Improvements in data acquisition techniques ISO Standardization Seminar - Delft NL 18

19 Future Direction Include non-volatile liquid in Annex O of full reliability based design and assessment (2019) Adopt a new version of Annex C on limit states design (2019) Develop a new risk based safety class and design factor system for the main body of the standard (2023?) ISO Standardization Seminar - Delft NL 19

20 Questions? ISO Standardization Seminar - Delft NL 20