DESIGN AND IN-SERVICE INSPECTIONS

DESIGN AND IN-SERVICE INSPECTIONS

Guy BAYLACTechnical 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)

)4,2

;5,1

min( 20,m2,0, RRf p

)3

;5,1

min( 20,m2,0, RRf p

cycles pressure 1000for eq ncycles pressure 500for eq n

)875,1

;5,1

min( 20,m2,0, RRf p

cycles pressure 500for eq n

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

10000for 3,0

100001000for 5,0

1000500for 8,0 and

500

eqmax

eqmax

eqmax

eq

nD

nD

nD

n

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

cee

ffPP

min

min

t

ast 0,2

min5,0 e

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

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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 progressiona

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

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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

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

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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

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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.