DESIGN AND IN-SERVICE INSPECTIONS

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 legislation • Explicit reference to in-service inspection in EN 13445:2002 • Fatigue (Clauses 18 and 17 of EN 13445-3) • Annex M of EN 13445-3 • 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 of equipment wants the lowest possible price • The User wants to reduce inspection, maintenance and download costs • But it is the total cost (purchase + inspection + maintenance + download) which is to consider

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 13445:2002 • Fatigue (Clauses 18 and 17 of EN 13445-3) • Annex M of EN 13445-3 • Creep and fast closures • Experience feedback • Conclusion

7. Fatigue damage occurs earlier with thickness reduction! • 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 neq 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. HYDFAT RESEARCH PROGRAMME(Institut de Soudure) Typical small scale pressure vessels (MBEL)

14. ANNEX M "Tests during operation" • These tests shall be included in the operating instructions of the Manufacturer

15. 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

16. 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

17. Annex M Measures at end of design lifetime • Vessels of testing group 4 • Complete visual inspection after 500 full or equivalent pressure cycles • Followed by a pressure test at a pressure equal to that used for the initial pressure test. • This sequence may be repeated as long as the visual inspection reveals no evidence of fatigue cracking and the pressure vessel passes the pressure test.

18. Crack progression a 500 Cycles 1 cycle per week ~ 10 years Crack depth No hydrotest in service Danger! Hydrotest in service with crack blunting Time

19. Similar considerations for Creep (EN 13445-3 New Clause 19) • Two safety coefficients versus creep rupture strength • SF=1,5 without monitoring • SF=1,25 with monitoring • Operating instructions shall specify monitoring if it is a design option

20. 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 • Operating instructions available on the site

21. Layout • Introduction: PED and National legislations • Explicit reference to in-service inspection in EN 13445:2002 • Fatigue (Clauses 18 and 17 of EN 13445-3) • Annex M of EN 13445-3 • Creep, fast closures • Experience feedback • Conclusion

22. Experience feedback

23. Experience feedback has beneficial consequences • Product improvement: life extension, easiness of operation, recycling • Improvement of inspectability (possibility to inspect) • Introduction of proven materials e.g. • Composite materials • Spheroidal graphite cast iron (low cost)

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

25. Layout • Introduction: PED and National legislations • Explicit reference to in-service inspection in EN 13445-3:2002 • Fatigue (Clauses 18 and 17) • Annex M • Creep, fast closures • Experience feedback • Conclusion

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

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