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DESIGN AND IN-SERVICE INSPECTIONS

DESIGN AND IN-SERVICE INSPECTIONS. Guy BAYLAC Technical Advisor to EPERC guy.baylac@wanadoo.fr TAIEX Workshop, Working Group 4 Bratislava – 12 April 2005. Layout. Introduction: PED and National legislations Explicit reference to in-service inspection in EN 13445-3:2002 Fatigue Annex M

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DESIGN AND IN-SERVICE INSPECTIONS

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  1. DESIGN AND IN-SERVICE INSPECTIONS Guy BAYLAC Technical Advisor to EPERC guy.baylac@wanadoo.fr TAIEX Workshop, Working Group 4 Bratislava – 12 April 2005

  2. Layout • Introduction: PED and National legislations • Explicit reference to in-service inspection in EN 13445-3:2002 • Fatigue • Annex M • Creep, fast closures • Experience feedback • Conclusion

  3. Classical error n°1Legal texts • PED applies to design, manufacture and conformity assessment of PE • National legislation to in-service inspection • Thus design and in-service inspection would be two completely different domains

  4. Classical error n°2Lack of dialogue • The Purchaser wants the lowest possible price • The User wants to reduce inspection, maintenance and download costs

  5. Warnings • PED, Annex 1 • "The manufacturer is under an obligation to analyse the hazards …" • Operating instructions: use, maintenance • Requirements contained in product standards: e.g. EN 13445:2002 "Unfired pressure vessels"

  6. Layout • Introduction: PED and National legislations • Explicit reference to in-service inspection in EN 13445-3:2002 • Fatigue • Annex M • Creep and fast closures • Experience feedback • Conclusion

  7. Fatigue occurs earlier! • Higher nominal stresses • Yesterday • Today (DBF) • Today (DBA) • Fatigue analysis required • Yesterday • Today (DBF) • Today (DBA)

  8. Design conditions for fatigue critical areas • Accessible for inspection and non-destructive testing • Instructions for appropriate maintenance are included in the operating instructions • Valid procedures are given in Annex M "Measures to be adopted in service"

  9. Fatigue critical areas are those for which • The number of full range or equivalent pressure cycles is greater than 500 • And the design fatigue damage D >Dmax

  10. Definition of critical zones in formulae

  11. Special case of testing group 4 vessels • Vessels produced in large series, no NDT except visual inspection • 500 full pressure cycles • Higher pressure test at the end of fabrication to ensure safety • Measured peaking limited to

  12. Outward peaking

  13. TESTS Typical small scale pressure vessels (MBEL)

  14. Annex M Tests during operation • Internal and external inspection at 20 % allowable lifetime • Record of number of load cycles • For vessels subject to cyclic loading internal inspections to be supplemented by non-destructive tests • If operating conditions deviate from those assumed in calculation, inspection intervals should be shortened

  15. Annex M Measures at end of design lifetime • Vessels of testing groups 1, 2 and 3 • Complete NDT • No cracks or crack-like defects: • Continued operation may be allowed • If cracks or crack-like defects: • Removal of cracks by grinding … • Change in mode of operation • Vessels of testing group 4

  16. Crack progression a 500 Cycles 1 cycle per week ~ 5 years Crack depth Danger Hydrotest Time

  17. Similar considerations for Creep Two safety coefficients • SF=1,5 without monitoring • SF=1,25 with monitoring

  18. Fast closures : EN 13445-5, Annex C Operating instructions shall deal with • Service-maintenance intervals • Conservation of records • Checks of closing mechanism • Tolerances for parts subject to wear and parts to replace • Other materials to be used with manufacturer consultation • Operating personnel adequate instructions • Opearting instructions available …

  19. Layout • Introduction: PED and National legislations • Explicit reference to in-service inspection in EN 13445-3:2002 • Fatigue • Annex M • Creep, fast closures • Experience feedback • Conclusion

  20. Experience feedback

  21. Experience feedback: positive aspects • A better product • Use of new materials • Composite materials • Spheroidal graphite cast iron • Improvement of inspectability

  22. Experience feedback: negative aspects • Old inspection rules influence the design without being justified by integrity • A design against time intervals of inspection and not against design fatigue curves: unnecessary increase in thickness

  23. Layout • Introduction: PED and National legislations • Explicit reference to in-service inspection in EN 13445-3:2002 • Fatigue • Annex M • Creep, fast closures • Experience feedback • Conclusion

  24. Conclusion • This presentation has covered • Interaction of fatigue design and in-service inspection • Interaction for creep design and fast closures • This presentation is far from being exhaustive

  25. Conclusion (Continued) • It raises questions, such as: • A better dialogue between involved parties, e.g. the User and the Manufacturer, is a source of new profits • An organised feedback, e.g. a data base on accidents at European scale to improve design and operation efficiency.

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