DESIGN AND IN-SERVICE INSPECTIONS Guy BAYLAC Technical Advisor to EPERC TAIEX Workshop, Working Group 4 Bratislava – 12 April 2005

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

3 Classical error n°1 Legal 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°2 Lack 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 :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 >D max

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 Crack depth Time 500 Cycles 1 cycle per week ~ 5 years Hydrotest Danger

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

18 Fast closures : EN , 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 :2002 –Fatigue –Annex M –Creep, fast closures Experience feedback Conclusion

20 Experience feedback Operation Experience feedback Design

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 :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.