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DESIGN AND IN-SERVICE INSPECTIONS. Guy BAYLAC Technical Advisor to EPERC [email protected] 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 - PowerPoint PPT Presentation
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DESIGN AND IN-SERVICE INSPECTIONS
Guy BAYLACTechnical 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 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
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 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
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
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 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.
