Section 2 - Fitness-For-Service Overview

Fitness-for-Service (FFS) Assessment based on API RP579

Section 2 - Fitness-for-Service Overview

Copyright 2005, TWI Ltd 1

Copyright © 2005, TWI Ltd World Centre for Materials Joining TechnologyWorld Centre for Materials Joining Technology

Fitness-For-Service OverviewFitness-For-Service Overview


ContentsContents

•• Why fitnessWhy fitness--forfor--serviceservice•• Definition of fitnessDefinition of fitness--forfor--serviceservice•• Common standards of assessmentCommon standards of assessment•• BS 7910 and API RP 579BS 7910 and API RP 579





Why fitness-for-serviceWhy fitness-for-serviceCommissioning

Time

Forc

ed s

hu

tdow

n f

requ

ency

Designlife

End of life

Classic bath tub curve

Life extension,Fitness-for-service,

Modification,Refurbishment,

Repair

Risk based inspection,Condition

monitoring


Why fitness-for-serviceWhy fitness-for-service

•• Used for equipment managementUsed for equipment management•• Optimisation and life extension of Optimisation and life extension of

assetsassets•• Improve safety Improve safety •• Improve availability of equipmentImprove availability of equipment•• Applicable to all stages of equipment Applicable to all stages of equipment

life, for example:life, for example:–– fabrication flaws fabrication flaws –– inin--service inspection service inspection –– Life extensionLife extension





Definition of FFSDefinition of FFS

“A multi“A multi--disciplinary engineering analysis disciplinary engineering analysis of equipment for continued operation”of equipment for continued operation”

FFSAssessment

MaterialMaterialInformationInformation

StressStressInformationInformation

FlawFlawInformationInformation

Sometimes referred to as the structural Sometimes referred to as the structural integrity triangleintegrity triangle


FFS standardsFFS standards

Regulatory bodies usually require that Regulatory bodies usually require that assessments are conducted to ‘recognised assessments are conducted to ‘recognised and generally accepted good engineering and generally accepted good engineering practice’practice’

This has lead to the formulation of This has lead to the formulation of international standards and proceduresinternational standards and procedures





Common FFS StandardsCommon FFS Standards

BS7910:1999

Incorporating amendment No.1


Common FFS standardsCommon FFS standards

ANSI/API RP 579:2000






ASME B31.G



SINTAP






R6 procedure



R5 procedure








To what are FFS assessments being conducted

59%17%

24%

Published procedures In-house proceduresUnknown or mixture

TWI worldwide industry survey into risked based life management practices and their relationship to FFS.

API 579 (50%) BS 7910 (50%)






Top two reasons for undertaking a FFS:

– Determining remaining life of damaged plant

– Assessment to ensure safe operation beyond design life

Top two equipment types assessed:

– General pressure vessels

– Process piping


Scope of API 579Scope of API 579

•• Prepared by API primarily for equipment Prepared by API primarily for equipment designed to ASME & API codes (Section I/VIII, designed to ASME & API codes (Section I/VIII, B31.1/3, API 650 & 620)B31.1/3, API 650 & 620)

•• Covers wide range of flaw/damage types found Covers wide range of flaw/damage types found in refinery/petrochemical equipmentin refinery/petrochemical equipment

•• Procedures and supporting data relate to ASME Procedures and supporting data relate to ASME design specifications and materialsdesign specifications and materials





Organisation of API 579Organisation of API 579Modular, based around flaw and damage type:Modular, based around flaw and damage type:

•• Brittle fractureBrittle fracture•• General or local metal loss, and pittingGeneral or local metal loss, and pitting•• Blisters and laminationsBlisters and laminations•• Weld misalignment, dents, distortions Weld misalignment, dents, distortions •• CrackCrack--like flawslike flaws•• Fire damageFire damage

•• Extensive annexes containing materials data, Extensive annexes containing materials data, formulae, and reference solutions formulae, and reference solutions


Levels of assessmentLevels of assessmentAPI 579 has three levels, relating to competence API 579 has three levels, relating to competence of assessors, extent of data gathering, of assessors, extent of data gathering, conservatism of analysis method:conservatism of analysis method:

••Level 1 is aimed at inspectors for use onLevel 1 is aimed at inspectors for use on--site for site for quick decisions with minimum dataquick decisions with minimum data

••Levels 2 is intended for qualified engineersLevels 2 is intended for qualified engineers

••Level 3 is an advanced assessment requiring Level 3 is an advanced assessment requiring detailed data and analysis and expert staffdetailed data and analysis and expert staff

••BS 7910: requires qualified engineersBS 7910: requires qualified engineers





Scope of BS 7910Scope of BS 7910•• Prepared by British Standards for all types of Prepared by British Standards for all types of

metallic structuresmetallic structures

•• Originated from BS PD 6493 for defects in fusion Originated from BS PD 6493 for defects in fusion welded structureswelded structures

•• Emphasis on fatigue and fracture assessment of Emphasis on fatigue and fracture assessment of flaws in welded components, and also covers flaws in welded components, and also covers creep cracking and locally thinned areascreep cracking and locally thinned areas

•• Annexes give extra guidance and dataAnnexes give extra guidance and data


SummarySummary

•• FFS is widespread and as manufacturing FFS is widespread and as manufacturing plants continued to age, its usage will growplants continued to age, its usage will grow

•• There are many assessment standards; API There are many assessment standards; API 579 and BS 7910 are most common in the non579 and BS 7910 are most common in the non--nuclear industrynuclear industry

•• API 579 is designed for ASME code equipment API 579 is designed for ASME code equipment and can be used by plant inspectors onand can be used by plant inspectors on--site site

•• API 579 has strengths in corrosion and non API 579 has strengths in corrosion and non crackcrack--like assessment for pressure equipmentlike assessment for pressure equipment

•• BS 7910 is for all welded structures and has BS 7910 is for all welded structures and has strengths in fracture and fatigue assessmentstrengths in fracture and fatigue assessment

Section 2 - Fitness-For-Service Overview

Documents

Transcript of Section 2 - Fitness-For-Service Overview