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Buried Flexible Pipelines AS2566

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Design of Buried Flexible Pipelines

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Buried Flexible Pipelines AS2566

  1. 1. BURIED FLEXIBLE PIPELINES <ul><li>The Design Process- Boundary Conditions </li></ul><ul><li>Design Fundamentals-AS2566.1 </li></ul><ul><li>Materials </li></ul><ul><li>Installation AS 2566.2 </li></ul><ul><li>Tips, Tricks & Traps </li></ul>Presented by Geoffrey D Stone C.Eng FIMechE; CP Eng FIEAust RPEQ Principal Blenray Pty Ltd ( Design Detail & Development) [email_address] 0402 35 2313
  2. 2. THE DESIGN PROCESS Boundary Conditions <ul><li>Soils & Soil Data </li></ul><ul><li>Trench Width & Depth </li></ul><ul><li>Structural Response to Loading </li></ul><ul><li>Trench Details </li></ul><ul><li>Stiffness </li></ul><ul><li>Thrust Blocks </li></ul><ul><li>Structural Interfaces </li></ul><ul><li>Water Table </li></ul><ul><li>Design Loads Trench & Embankment Fill </li></ul><ul><li>Superimposed Live Loads </li></ul><ul><li>Other Superimposed Loads </li></ul>
  3. 3. Soils & Soils Data <ul><li>Native Soil </li></ul><ul><ul><li>Classify </li></ul></ul><ul><ul><li>Modulus </li></ul></ul><ul><li>Bedding </li></ul><ul><ul><li>Type </li></ul></ul><ul><li>Embedment </li></ul><ul><ul><li>Material </li></ul></ul><ul><ul><li>Compaction </li></ul></ul><ul><ul><li>Geo-textile </li></ul></ul><ul><ul><li>Water Table </li></ul></ul><ul><li>Backfill </li></ul><ul><ul><li>Type </li></ul></ul><ul><ul><li>Compaction </li></ul></ul><ul><li>Piles </li></ul><ul><li>Testing </li></ul><ul><ul><li>Field </li></ul></ul><ul><ul><li>Laboratory </li></ul></ul>
  4. 5. Trench Width & Depth <ul><li>AS 2566.1 Minimum </li></ul><ul><li>Embedment or Embankment </li></ul><ul><li>Shape of trench </li></ul>
  5. 6. Trench Dimensions
  6. 7. Structural Response to Loading
  7. 8. Stiffness AS 2566.1 <ul><li>2 year values of pipe stiffness suitable for good soils </li></ul><ul><li>50 year values of pipe stiffness should be used for poor soils, uncontrolled installations or other higher risk applications </li></ul>
  8. 9. Stiffness AS 2566.1
  9. 10. Thrust Blocks <ul><li>Not required for fully welded systems as in ABS, PP, PVC-U, PB or PE </li></ul><ul><li>Required for rubber ring systems as used for DICL, MSCL, GRP & PVC-U/O/M </li></ul><ul><li>Design basis </li></ul><ul><ul><li>Steady state pressure </li></ul></ul><ul><ul><li>Unsteady state pressure spikes </li></ul></ul><ul><ul><li>Hydrostatic test pressure </li></ul></ul>
  10. 11. Structures Interfaces <ul><li>Differential Settlement </li></ul><ul><li>Soil swelling </li></ul><ul><li>Water Retaining </li></ul><ul><li>Shear Loading </li></ul><ul><li>Thermal Loading </li></ul><ul><li>Chaffing </li></ul><ul><li>Water seal in concrete </li></ul>
  11. 12. Water Table <ul><li>Water hydrostatic level applies load onto pipe-refer AS2566 </li></ul><ul><li>Rising water applies uneven load onto pipe and the pipe may buckle or exceed its strain limit </li></ul><ul><li>Water may cause flotation of empty pipe and special embedment may be necessary </li></ul><ul><li>High water table increases construction difficulty </li></ul><ul><ul><li>Safety </li></ul></ul><ul><ul><li>Dewatering </li></ul></ul><ul><ul><li>Quality </li></ul></ul>
  12. 13. Loading <ul><li>Design loads due to trench & embankment fill </li></ul><ul><li>External hydrostatic loads </li></ul><ul><li>Internal pressure </li></ul><ul><li>Superimposed dead loads </li></ul><ul><li>Superimposed live loads </li></ul><ul><li>Other unsustained loads </li></ul>
  13. 14. Design Loads due to Trench & Embankment Fill
  14. 15. Superimposed Live Loads
  15. 16. Superimposed Live Loads
  16. 17. Other Unsustained Loads <ul><li>Specialist Engineering </li></ul><ul><li>National Codes </li></ul><ul><li>Local Conditions </li></ul><ul><li>Risk </li></ul><ul><ul><li>Likelihood </li></ul></ul><ul><ul><li>Consequences </li></ul></ul><ul><ul><li>Responsibility </li></ul></ul><ul><ul><li>Safeguarding </li></ul></ul><ul><li>Earthquake </li></ul><ul><li>Vibration/Shock </li></ul><ul><li>Differential Settlement </li></ul><ul><li>Thermal Strain </li></ul><ul><li>Subsidence </li></ul><ul><li>Airport runways </li></ul><ul><li>Railways </li></ul>
  17. 18. DESIGN FUNDAMENTALS AS2566.1 Buried Flexible Pipelines-Design <ul><li>Deflection </li></ul><ul><li>Strength </li></ul><ul><li>Internal Pressure </li></ul><ul><li>Combined Loading </li></ul><ul><li>Buckling </li></ul><ul><li>Hoop Stress </li></ul><ul><li>Ring Bending Strain </li></ul><ul><li>Creep </li></ul><ul><li>Temperature </li></ul><ul><li>Other Considerations </li></ul>
  18. 19. Deflection <ul><li>Short term </li></ul><ul><li>Long term </li></ul><ul><li>Vertical & Horizontal </li></ul><ul><ul><li>Considered equal </li></ul></ul><ul><ul><li>Effect of excess side compaction </li></ul></ul><ul><li>Modulus to use </li></ul><ul><li>Acceptance criteria </li></ul><ul><li>Measurement during installation </li></ul>
  19. 20. Strength <ul><li>Loads cause strain in pipe wall </li></ul><ul><li>Ring compression strains << ring bending strains </li></ul><ul><li>AS 2566.1 predicts maximum tensile ring bending strains </li></ul><ul><li>A Shape Factor adjusts strain values </li></ul><ul><ul><li>True Ellipse Shape Factor D f =3.0 </li></ul></ul><ul><ul><li>Δ horizontal < Δ vertical Shape Factor D f > 3.0 </li></ul></ul>
  20. 21. Internal Pressure <ul><li>Steady State </li></ul><ul><li>Unsteady State </li></ul><ul><ul><li>AS 2566.1 Requirements 1.25 </li></ul></ul><ul><ul><li>AS 2885 Requirement 1.10 </li></ul></ul><ul><ul><li>Other codes requirements </li></ul></ul>
  21. 22. Combined Loading <ul><li>Combined external load and internal pressure </li></ul><ul><li>Re rounding effect </li></ul>
  22. 23. Buckling <ul><li>Ovalization </li></ul><ul><li>Buckling </li></ul><ul><li>External Pressure </li></ul><ul><li>No substantial soil support-Timoshenko </li></ul><ul><li>Substantial soil support –I.D. Moore </li></ul>
  23. 24. Hoop Stress <ul><li>Stress in the wall due to pressure </li></ul><ul><li>Only criteria used for pipe class selection </li></ul><ul><li>Does not take into account other stresses </li></ul><ul><li>Basis of the Pipe Class System </li></ul><ul><li>Relaxes with time for thermoplastic pipes </li></ul><ul><li>Never Constant </li></ul>
  24. 25. Ring Bending Strain <ul><li>Importance of Strain </li></ul><ul><li>Comparison of allowable strain in materials </li></ul><ul><li>ABS 1% </li></ul><ul><li>GRP 0.18 to 0.6 % </li></ul><ul><li>PE 4.0% </li></ul><ul><li>PVC-U 1% </li></ul><ul><li>PVC-M 1% </li></ul><ul><li>PVC-O 1.3% </li></ul>
  25. 26. Creep <ul><li>Variation of Properties in Time </li></ul><ul><li>Long term loading/Stress relaxation </li></ul><ul><li>Reverse loading/Stress magnitude </li></ul><ul><li>Repetitive loading/Fatigue </li></ul>
  26. 27. Temperature <ul><li>The design temperature may vary due to:- </li></ul><ul><ul><li>Ambient diurnal temperature variations </li></ul></ul><ul><ul><li>Flow rate </li></ul></ul><ul><ul><li>Fluid temperature range </li></ul></ul><ul><ul><li>Process conditions </li></ul></ul><ul><ul><li>Installation ambient temperature </li></ul></ul><ul><ul><li>Wall thickness </li></ul></ul>
  27. 28. Other Considerations <ul><li>Anchor forces </li></ul><ul><li>Differential Settlement </li></ul><ul><li>Earthquake </li></ul><ul><li>Subsidence </li></ul><ul><li>Testing conditions </li></ul><ul><li>Corrosion </li></ul><ul><li>Mass of pipe contents </li></ul><ul><li>Thermal Strain </li></ul><ul><li>Local buckling </li></ul><ul><li>Fatigue </li></ul><ul><li>Pavement settlement </li></ul>
  28. 29. Materials Selection <ul><li>Types </li></ul><ul><li>Costs </li></ul><ul><li>Class </li></ul><ul><li>Characteristics </li></ul><ul><li>Fittings & Valves </li></ul><ul><li>Modulus GRP </li></ul><ul><li>Modulus Thermoplastic Pipes </li></ul>
  29. 30. Materials - Types <ul><li>GRP </li></ul><ul><li>ABS </li></ul><ul><li>PE </li></ul><ul><li>PVC-U, PVC-M, PVC-O </li></ul><ul><li>DICL </li></ul><ul><li>MSCL </li></ul>
  30. 31. Materials Selection <ul><li>Costs – Supply </li></ul><ul><ul><li>Pipe </li></ul></ul><ul><ul><li>Fittings </li></ul></ul><ul><ul><li>Supports </li></ul></ul><ul><li>Costs – Installation </li></ul><ul><ul><li>Standard of trades </li></ul></ul><ul><ul><li>Equipment </li></ul></ul><ul><ul><li>Jointing </li></ul></ul><ul><ul><li>Access </li></ul></ul><ul><ul><li>Testing </li></ul></ul><ul><li>Costs - Whole of Life </li></ul><ul><ul><li>Safety </li></ul></ul><ul><ul><li>Availability </li></ul></ul><ul><ul><li>Maintenance </li></ul></ul><ul><ul><li>Energy </li></ul></ul><ul><ul><li>Risks </li></ul></ul><ul><li>Costs - Standards </li></ul><ul><ul><li>Authority </li></ul></ul><ul><ul><li>Industry </li></ul></ul><ul><ul><li>Acts </li></ul></ul>
  31. 32. Selection of Pipe Class <ul><li>Design Pressure Steady State </li></ul><ul><li>Design Pressure Unsteady State </li></ul><ul><li>Vacuum Conditions </li></ul><ul><li>Industry Application & Environment </li></ul><ul><li>Soil/Pipe Structure Design </li></ul><ul><li>Standardization </li></ul><ul><li>Risk </li></ul><ul><ul><li>Likelihood </li></ul></ul><ul><ul><li>Consequences </li></ul></ul><ul><ul><li>Responsibilit y </li></ul></ul>
  32. 33. Typical Material Characteristics
  33. 34. Fittings & Valves <ul><li>Valve classes do not meet all pipe classes </li></ul><ul><li>Injection moulded fittings- Size Limitation </li></ul><ul><li>Manufactured fittings-Larger Sizes </li></ul><ul><ul><li>Tees </li></ul></ul><ul><ul><li>Bends </li></ul></ul><ul><li>Jointing </li></ul><ul><li>Gaskets </li></ul><ul><li>Expansion Bellows </li></ul><ul><li>Saddles </li></ul><ul><li>Valves </li></ul><ul><ul><li>Isolation </li></ul></ul><ul><ul><li>Check </li></ul></ul><ul><ul><li>Air release </li></ul></ul><ul><ul><li>Control </li></ul></ul>
  34. 35. Modulus-GRP Pipes <ul><li>Manufacturers establish values by test & calculation </li></ul><ul><li>Axial & longitudinal modulus differs </li></ul><ul><li>Values at various temperatures required for design </li></ul><ul><li>Strain rate changes values </li></ul><ul><li>Standards such as ISO 14692 </li></ul>
  35. 36. Modulus-Thermoplastic Pipes <ul><li>Published figures normally are strain rate at 20 ºC </li></ul><ul><li>Value determined by ASTM test </li></ul><ul><ul><li>Standard dog bone test specimen </li></ul></ul><ul><ul><li>Fixed strain rate </li></ul></ul><ul><li>Values at various temperatures required for design </li></ul><ul><li>Strain rate changes values </li></ul>
  36. 37. INSTALLATION <ul><li>Trench Excavation </li></ul><ul><li>Trench Shields </li></ul><ul><li>Laying & Jointing </li></ul><ul><li>Embedment & Compaction </li></ul><ul><li>Thrust Blocks </li></ul><ul><li>Hydrostatic Testing </li></ul>
  37. 38. Trench Excavation <ul><li>Excavator bucket width </li></ul><ul><li>Excavated depth </li></ul><ul><li>Soil removal, testing and stockpile </li></ul><ul><li>Shape of trench </li></ul><ul><li>Pockets for pipeline projections </li></ul><ul><li>Thrust block preparation </li></ul><ul><li>Dewatering </li></ul><ul><li>Welding machine access </li></ul><ul><li>Adjacent pipes </li></ul>
  38. 39. Trench Shields <ul><li>When to use </li></ul><ul><li>Remove in stages </li></ul><ul><li>Affect on compaction </li></ul><ul><li>Geotextile fabric </li></ul><ul><li>Over excavation </li></ul><ul><li>Wide trench </li></ul>
  39. 40. Trench Shields
  40. 41. Laying and Jointing <ul><li>Join on the bank and lay </li></ul><ul><li>Lay in trench and join </li></ul><ul><li>Rubber ring joints PVC-U, PVC-M, PVC-O, GRP, DICL & MSCL </li></ul><ul><li>Solvent welded joints-ABS, PVC-U & PVC-M </li></ul><ul><li>Fusion butt weld-PE, PB & PP </li></ul><ul><li>Electro-fusion couplings-PE </li></ul><ul><li>Wrapped joints-GRP </li></ul><ul><li>Welded joints-steel </li></ul><ul><li>Flanges & Mechanical Joints-All </li></ul><ul><li>Alignment & Bending </li></ul><ul><li>Adjacent parallel pipes </li></ul><ul><li>Crossing Pipelines </li></ul><ul><li>Removal of temporary pegs and supports </li></ul>
  41. 42. Embedment & Compaction <ul><li>Materials </li></ul><ul><li>Dewatering </li></ul><ul><li>Bedding </li></ul><ul><li>Side Support </li></ul><ul><li>Overlay </li></ul><ul><li>Migration of fines </li></ul><ul><li>Pipeline Protection </li></ul><ul><li>Prevention of floatation </li></ul><ul><li>Compaction trials </li></ul><ul><li>Compaction controls </li></ul><ul><li>Deflection controls </li></ul><ul><li>Gauging </li></ul>
  42. 43. Thrust Blocks
  43. 44. Hydro-testing <ul><li>Establish test pressure </li></ul><ul><li>Test standard </li></ul><ul><li>Prepare test equipment </li></ul><ul><li>Prepare ITP’s </li></ul><ul><li>Prepare test points </li></ul><ul><li>Source of test water </li></ul><ul><li>Disposal of test water </li></ul><ul><li>Selection of test lengths </li></ul><ul><li>Owner’s witness </li></ul><ul><li>Records </li></ul>
  44. 45. Hydrotest Methods <ul><li>Constant pressure test (No water loss) –DICL, MSCL, GRP & PVC </li></ul><ul><li>Constant pressure test (water loss) – PE, ABS, PP & PB </li></ul><ul><li>Pressure decay – PE & PB </li></ul><ul><li>Pressure rebound- DN ≤ DN315 ABS, PB & PE </li></ul>
  45. 46. Tips, Tricks & Traps <ul><li>Design </li></ul><ul><li>Installation </li></ul><ul><li>Testing </li></ul><ul><li>Product quality </li></ul><ul><li>Completion </li></ul><ul><li>In Service leaks </li></ul>
  46. 47. Tips, Tricks & Traps - Design <ul><li>Design pressure may not include surge </li></ul><ul><li>Temperature profile not defined </li></ul><ul><li>Pipeline route/soils not adequately surveyed </li></ul><ul><li>Consultant expects sub contractor or material supplier to do the detail design </li></ul><ul><li>Lower pipe class than necessary specified </li></ul><ul><li>Temporary facilities not designed </li></ul>
  47. 48. Tips, Tricks & Traps - Installation <ul><li>Variations from design not engineered </li></ul><ul><li>Surfaces not cleaned </li></ul><ul><li>Aged solvent cement </li></ul><ul><li>Pipe ends bevelled </li></ul><ul><li>Damaged pipe </li></ul><ul><li>UV degradation </li></ul><ul><li>Physical damage </li></ul><ul><li>Solvent damage to internal surface </li></ul><ul><li>Use of incorrect solvent </li></ul><ul><li>Incorrect slings </li></ul><ul><li>Foreign matter not removed from trench </li></ul>
  48. 49. Tips, Tricks & Traps - Installation <ul><li>No detail drawings </li></ul><ul><li>Insufficient joints for erection </li></ul><ul><li>Incomplete insertion in joints </li></ul><ul><li>Inadequate time for welds or lay ups </li></ul><ul><li>Differential settlement </li></ul><ul><li>Resources </li></ul><ul><li>Poor trench conditions </li></ul><ul><li>Poor native soil </li></ul><ul><li>Soil properties not measured routinely </li></ul><ul><li>Inadequate access </li></ul><ul><li>Water ingress </li></ul><ul><li>Cleanliness </li></ul>
  49. 50. Tips, Tricks & Traps -Testing <ul><li>Lack of planning & procedure </li></ul><ul><li>Standard provisions not understood </li></ul><ul><li>Inexperienced testers </li></ul><ul><li>Test pressure unknown </li></ul><ul><li>Equipment not isolated </li></ul><ul><li>Procedure not agreed beforehand </li></ul><ul><li>Records of test not prepared </li></ul><ul><li>Person to witness test not available </li></ul><ul><li>Resources not available </li></ul><ul><ul><li>Water supply </li></ul></ul><ul><ul><li>Pump </li></ul></ul><ul><ul><li>Gauges </li></ul></ul><ul><ul><li>Data logger </li></ul></ul><ul><ul><li>Temperature instrument </li></ul></ul><ul><ul><li>Trained personnel </li></ul></ul>
  50. 51. Tips, Tricks & Traps - Product Quality – Inspection or QA <ul><li>Non conformance with drawings </li></ul><ul><li>Pipe ovality </li></ul><ul><li>Lining thickness </li></ul><ul><li>Socket dimensions </li></ul><ul><li>Surface defects </li></ul><ul><li>Fabricated fittings </li></ul><ul><ul><li>Cracks at weld </li></ul></ul><ul><ul><li>Dimensions </li></ul></ul><ul><ul><li>Orientation </li></ul></ul>
  51. 52. Tips, Tricks & Traps -Completion <ul><li>Resources & budget </li></ul><ul><li>Site clean up </li></ul><ul><li>Reinstatement </li></ul><ul><li>Handover to owner </li></ul><ul><li>Records </li></ul><ul><li>Work as Executed Drawings </li></ul><ul><li>Quality Assurance Sign-Off </li></ul><ul><li>Certificate of Practical Completion </li></ul>
  52. 53. Tips, Tricks & Traps - In Service Leaks & Failures <ul><li>Pipe burst </li></ul><ul><li>Flanged joints leak </li></ul><ul><li>Solvent welds leak </li></ul><ul><li>Rubber ring joints leak </li></ul><ul><li>Fusion welds leak </li></ul><ul><li>Fittings </li></ul><ul><li>Buckling of thin wall pipe </li></ul><ul><li>Thrust blocks </li></ul><ul><li>Waterhammer </li></ul><ul><li>Over pressure </li></ul><ul><li>Pipe shear </li></ul><ul><li>Fatigue & vibration </li></ul>
  53. 54. Questions <ul><li>Is AS 2566 mandatory? </li></ul><ul><li>Can AWWA M45 be used? </li></ul><ul><li>Is FEA a viable alternative? </li></ul><ul><li>Who designs pipelines Civil, structural or mechanical engineers? </li></ul>

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