Ipea api579

The API 579 Fitness-for-Service Standard – The Current State of Technology and a Ten Year Look

Ahead

Robert Brown, P.E.

10th Annual IPEIA (formerly NPEC) Conference Banff Centre in Banff Alberta, Canada

February 1 – 3, 2006

2

Presentation Outline• Introduction• API 579 Development Background• Overview of API 579• New Joint API and ASME FFS Standard• Planned Developments for API/ASME 579• Overview of API/ASME 579-2006• Future Enhancements Following the 2006 Publication of

API/ASME 579• Technical Basis and Validation of API/ASME 579 FFS

Assessment Methods• Understanding of Damage Mechanisms• In-Service Inspection Codes and Fitness-For-Service• Fitness-For-Service and RBI - Complementary Technologies• Harmonizing Pressure Vessel Design and Fitness-For-Service• Summary

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Introduction

• The ASME and API construction codes do not provide rules to evaluate a component containing a flaw or damage that results from operation after initial commissioning

• Fitness-For-Service (FFS) assessments are quantitative engineering evaluations that are performed to demonstrate the structural integrity of an in-service component containing a flaw or damage

• API 579 was developed to evaluate flaws and damage associated with in-service operation

• API 579 assessment procedures were not originally intended to evaluate fabrication flaws; however, these procedures have been used for this purpose by many Owner-Users

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Introduction

• If the damage mechanism cannot be identified, then a FFS assessment should not be performed per API 579

– Identification of damage mechanism is the key component in the FFS assessment

– Firm understanding of the damage mechanism is required to evaluate the time-dependence of the damage

– Time-dependence of damage is required to develop a remaining life and inspection plan

• API 579 provides guidance for conducting FFS assessments using methods specifically prepared for equipment in the refining and petrochemical industry; however, this document is currently being used in other industries such as the fossil utility, pulp & paper, food processing, and non-commercial nuclear

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API 579 Development Background API’s Definition of Fitness-For-Service

• An FFS assessment is a multi-disciplinary engineering analysis of equipment to determine whether it is fit for continued service, typically until the next shutdown

• The equipment may contain flaws, not met current design standards, or be subjected to more severe operating conditions than current design

• The product of a FFS assessment is a decision to run as is, monitor, alter, repair, or replace; guidance on an inspection interval is also provided

• FFS assessments consist of analytical methods (mainly stress analysis) to assess flaws and damage

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API 579 Development Background Need for FFS Standardization

• Plant safety and Compliance with US OSHA 1910 Process Safety Management (PSM) Legislation

• Operation of aging facilities

• Maintaining safe, reliable operations with an increase in run-lengths, increase in severity of operations and/or decrease in shut-down periods

• Rationalizing flaws found by more rigorous in-service inspections than those conducted during original construction

• Refining and petrochemical industry is unique due to the wide variety of processes and operating conditions, materials of construction, and damage mechanisms

• Standardization facilitates acceptance by jurisdictions

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API 579 Development Background MPC FFS JIP Program Overview

• Joint Industry Project (JIP) started in 1990 under The Materials Properties Council (MPC)

• Technology development focus

• Base resource document and computer software developed

• Information disseminated to public through technical publications and symposia

• Technology developed provides basis for API 579

• Continued sponsorship by owner-users and funding support from API indicates high level of interest in FFS

• MPC FFS JIP continues to develop new FFS technology that is subsequently incorporated into API 579

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Overview of API 579General

• Applicable to pressurized components in pressure vessels, piping, and tankage (principles can also be applied to rotating equipment)

• Highly structured document with a modular organization based on flaw type/damage condition to facilitate use and updates

• Multi-level assessment - higher levels are less conservative but require more detailed analysis/data

– Level 1 - Inspector/Plant Engineer

– Level 2 - Plant Engineer

– Level 3 - Expert Engineer

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Overview of API 579 General

• Identifies data requirements, applicability and limitations of assessment procedures, and acceptance criteria

• Contains flow charts, figures, and example problems to simplify use of the assessment procedures

• Provides recommendations for in-service monitoring and/or remediation for difficult situations

• Provides recommendations for stress analysis techniques, NDE, and sources for materials properties

• Requires a remaining life to be evaluated; remaining life is the basis for the inspection interval

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Overview of API 579 General

• General FFS assessment procedure used in API 579 for all flaw types is provided in Section 2 that includes the following steps:– Step 1 - Flaw & damage mechanism identification– Step 2 - Applicability & limitations of FFS procedures– Step 3 - Data requirements– Step 4 - Assessment techniques & acceptance criteria– Step 5 - Remaining life evaluation– Step 6 - Remediation– Step 7 - In-service monitoring– Step 8 - Documentation

• Some of the steps shown above may not be necessary depending on the application and damage mechanism

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Overview of API 579 Contents

• API 579 originally released in 2000: Nine flaws and damage conditions are covered with supporting appendices

• Organized to facilitate use and updates– Section covering overall assessment procedure

– Separate sections for each flaw type/condition

– Consistent organization within each section

– Information common to more than one section placed in appendices

• Self-contained document - do not need to purchase other API standards to perform an assessment

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Main Sections• Section 1 - Introduction

• Section 2 - FFS Engineering Evaluation Procedure

• Section 3 - Assessment of Equipment for Brittle Fracture

• Section 4 - Assessment of General Metal Loss (tm < tmin - large area)

• Section 5 - Assessment of Localized Metal Loss (tm < tmin - small area)

• Section 6 - Assessment of Pitting Corrosion

• Section 7 - Assessment of Blisters and Laminations

• Section 8 - Assessment of Weld Misalignment and Shell Distortions

• Section 9 - Assessment of Crack-Like Flaws

• Section 10 - Assessment of Equipment Operating in the Creep Regime (Draft version)

• Section 11 - Assessment of Fire Damage

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Appendices• Appendix A - Thickness, MAWP, and Stress Equations for a FFS

Assessment

• Appendix B - Stress Analysis Overview for a FFS Assessment

• Appendix C - Compendium of Stress Intensity Factor Solutions

• Appendix D - Compendium of Reference Stress Solutions

• Appendix E - Residual Stresses in a FFS Evaluation

• Appendix F - Material Properties for a FFS Assessment

• Appendix G - Deterioration and Failure Modes

• Appendix H - Validation

• Appendix I - Glossary of Terms and Definitions

• Appendix J - Technical Inquires

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Overview of API 579 Relationships to Other FFS Standards

• The API Committee on Refinery Equipment (CRE) Task Group responsible for development of API 579 reviewed internal corporate methods, international standards and publications, and incorporated appropriate technology

• In most cases, modifications to existing or development of new FFS methods were required

• API Level 3 Assessments permit use of alternative FFS procedures. For example, Section 9 covering crack-like flaws provides reference to British Energy R-6, BS-7910, EPRI J-integral, and other published methods

• The API Task Group is working to set up technical liaisons with other international FFS standard writing bodies (e.g. FITNET)

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New Joint API and ASME FFS Standard

• API and ASME have agreed to form a joint committee to produce a single FFS Standard that can be used for pressure-containing equipment

• API 579 will form the basis of the new co-branded API/ASME standard that will be produced by this committee

• The initial release of the new co-branded standard designated as API/ASME 579 will occur in June, 2006

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• The second edition of API 579 and the new API/ASME joint standard will include all topics currently contained in API 579 and will also include new parts covering FFS assessment procedures that address unique damage mechanisms experienced by other industries

• The agreement to produce a joint standard on FFS technology is a landmark decision that will permit the focusing of resources in the US to develop a single document that can be used by all industries

• In addition, a joint FFS standard will help avoid jurisdictional conflicts and promote uniform acceptance of FFS technology

New Joint API and ASME FFS Standard

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New Developments for API/ASME 579

• To avoid confusion with other ASME B&PV Codes and Standards, Sections in API 579 are being renamed to Parts

• New Enhancements – Existing Sections and New Parts– Part 5 – Assessment of Local Thin Areas, assessment procedures

for gouges being relocated to Part 12– Part 7 – Assessment of Blisters and HIC/SOHIC Damage,

assessment procedures for HIC/SOHIC damage have been added– Part 8 – Assessment of Weld Misalignment and Bulges,

assessment procedures for bulges being modified (in progress), assessment procedures for dents being relocated to Part 12

– Part 10 – Assessment of Equipment Operating in the Creep Range, assessment procedures for remaining life calculations for components with or without crack-like flaws are provided

– Part 12 – Assessment of Dents, Gouges, and Dent-Gouge Combinations, new Part

– Part 13 – Assessment of Laminations, new Part

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• New Enhancements – Existing and New Appendices– Appendix B – Stress Analysis Overview for a FFS Assessment,

complete rewrite to incorporate new elastic-plastic analysis methods and fatigue evaluation technology developed for the ASME Div 2 Re-write Project

– Appendix C – Compendium of Stress Intensity Factor Solutions, new stress intensity factor solutions for thick wall cylinders, through wall cracks in cylinders and spheres, holes in plates

– Appendix E - Compendium of Residual Stress Solutions, complete rewrite to incorporate new solutions developed by PVRC Joint Industry Project

– Appendix F – Material Properties for a FFS Assessment, new fracture toughness estimation methods and stress-strain curve model incorporated

– Appendix H – Technical Basis and Validation of FFS Procedures

– Appendix K – Crack Opening Areas, new appendix covering crack opening areas for through-wall flaws in cylinders and spheres


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• New Enhancements – Example Problems

– All example problems will be removed and placed in a separate example problems manual

– Additional example problems with more background information will be provided

• Future Enhancements (after 2006) - New Parts

– Assessment of Hot-Spots

– Assessment of HTHA (High Temperature Hydrogen Attack) Damage

– Assessment of Fatigue Damage


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Overview of API/ASME 579-2006

• Part 3: Brittle Fracture– Provides guidelines for evaluating the resistance to brittle

fracture of existing carbon and low alloy steel pressure vessels, piping, and storage tanks+ Screening of equipment for susceptibility (Level 1 & 2)+ Detailed assessment using fracture mechanics (Level 3 per

Part 9) + Assessment typically performed on a weld-joint by weld joint

basis

– The purpose of this assessment is to avoid a catastrophic brittle fracture failure consistent with ASME Code, Section VIII design philosophy; however, it does not ensure against service-induced cracks resulting in leakage or arrest of a running brittle fracture

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• Part 3: Brittle Fracture - Changes– Minimal changes to existing

API 579 methodology in Section 3; Changes in structure to improve user friendliness

– Minimum Allowable Temperature (MAT) -Single temperature or envelope of temperature as function of pressure

– Critical Exposure Temperature (CET) -Lowest metal temperature at primary stress > 8 ksi


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• Part 4: General Metal Loss

– Covers FFS for pressurized components subject to general metal loss resulting from corrosion and/or erosion+ Procedures can be applied to both uniform and local metal

loss+ Procedures provide an MAWP or MAT

– Assessment procedures in this section are based on a thickness averaging approach+ Suitable result is obtained when applied to uniform metal loss+ For local or non-uniform metal loss, the Part 4 thickness

averaging approach may produce overly conservative results; the assessment procedures of Part 5 (FFS rules covering local metal loss) can be utilized to reduce the conservatism in the analysis

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• Part 4: General Metal Loss - Changes– Minimal changes to existing API 579 methodology

– Change from tmin to trd

New

Existing

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• Part 5: Local Metal Loss– The assessment procedures of Part 5 are for the analysis

of local metal loss or Local Thin Areas (LTA)– The procedures of Part 4 are for general (uniform and

non-uniform) metal loss

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• Part 5: Local Metal Loss - Changes

– Level 1 Assessment

+ Longitudinal plane - screening curve changed to family of curves f(RSFa, E); groundwork for adapting to different Codes

+ Circumferential plane - screening curve changed to family of curves f(RSFa, E); Includes 20% of allowable as bending stress; more conservative

– Level 2 Assessment

+ Longitudinal plane - New Folias factor; no limitation on length of LTA (was lambda<5)

+ Circumferential plane - Added “circumferential” Folias factor to analysis; changed acceptability criteria from yield basis to allowable stress basis

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• Part 5: Local Metal Loss - Changes – New Level 2 Assessment

procedure is provided for evaluating cylindrical shells with LTAs subject to external pressure

– New method based on idealized cylindrical shell

– Basic equation is:

L1 L2 L3 L4

LT

t1 t2 t3 t4

Actual Cylindrical Shell

Idealized Cylindrical Shell

Stiffening Rings

1

1

n

ii

r nie

i i

LMAWP

LP

=

=

=∑

∑

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• Part 6: Pitting

– The assessment procedures in Part 6 were developed to evaluate metal loss from pitting corrosion

– Pitting is defined as localized regions of metal loss which can be characterized by a pit diameter on the order of the plate thickness or less, and a pit depth that is less than the plate thickness

– Assessment procedures are provided to evaluate both widespread and localized pitting in a component with or without a region of metal loss

– The procedures can be used to assess a damaged array of blisters as described in Part 7

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• Part 6: Pitting - Changes

– Level 1 Screening+ Pitting Charts

* Visual FFS Assessment (similar to ASME Code porosity charts),* Current Level 1 and existing Level 2 merged into new Level 2

+ Data for Assessment* Include a photograph with reference scale and/or rubbing of the

surface* Maximum pit depth* Cross section of UT thickness scan can also be used

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• Part 6: Pitting - Changes– Pitting Charts

+ FFS by visually comparing pit chart to actual damage plus estimate of maximum pit depth

+ Pit charts provided for a different pitting damages measured as a percentage of the affected area in a 6 inch by 6 inch

+ RSF provided for each pit density and four w/t ratios (0.2, 0.4, 0.6, 0.8)

Pitting Chart – API 579 Grade 4 Pitting

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• Part 6: Pitting - Changes

– Level 1 Screening+ Determine ratio of remaining wall thickness to the future

wall thickness in pitted region:+ Find pitting chart that matches damage and determine RSF

,

max

rd maxwt

c

rd

max

c

t wR

t

where

t thickness away from pitted region

w pit depth

t future corroded thickness

−=

=

=

=

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• Part 7: Hydrogen Blisters and HIC/SOHIC (New)

– Provides assessment procedures for low strength ferritic steel pressurized components with hydrogen induced cracking (HIC) and blisters, and stress oriented HIC (SOHIC) damage

– Excludes:+ Sulfide stress cracking (SSC)+ Hydrogen embrittlement of high strength steels (Brinnell

>232)+ Excludes methane blistering+ HTHA

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• Part 7: Hydrogen Blisters and HIC/SOHIC (New)– Various forms of damage all related to hydrogen being

charged into the steel from a surface corrosion reaction in an aqueous H2S containing environment.

– Hydrogen Blistering+ Hydrogen blisters form bulges on the ID, the OD or within

the wall thickness of a pipe or pressure vessel. + Atomic H collects at a discontinuity (inclusion or lamination)

in the steel + H atoms form molecular hydrogen which is too large to

diffuse out; pressure builds to excess of YS and local deformation occurs, forming a blister

– Hydrogen Induced Cracking (HIC)+ Hydrogen blisters can form at different depths from the

surface. And may develop cracks that link them together. + Interconnecting cracks between the blisters often are

referred to as “stepwise cracking”

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– Stress Oriented Hydrogen Induced Cracking (SOHIC)+ Similar to HIC, but more damaging+ Arrays of cracks stacked on top of each other, resulting in

through-thickness crack+ Seen mostly in HAZ, due to residual stresses


Zero degree scan overlaid with 45 degree shearwave results (provided by Westech Inspection, Inc.)

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– Level 2 HIC Assessment


Strength check - Determine RSF by considering region as LTA with reduced strength (20%)

Fracture check - Evaluate HIC as a crack-like flaw per Part 9

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• Part 8: Weld misalignment And Shell Distortions– The procedures in this part can be used to assess weld

misalignments and shell distortions in components made up of flat plates; cylindrical, conical, and spherical shells; and formed heads.

– Weld Misalignment – centerline offset, angular misalignment (peaking), and a combination of centerline offset and angular misalignment

– Shell Distortion – Categories include:+ General Shell Distortion+ Out-of-roundness+ Bulge

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• Part 8: Weld misalignment And Shell Distortions - Changes– Pseudo code provided for computation of Fourier Series

coefficients for analysis of out-of-roundness radius data – Assessment procedure rules for bulges deleted, new rules

currently being developed by MPC FFS JIP, will not be included in the 2006 edition

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• Part 9: Crack-Like Flaws

– Crack-like flaws are planar flaws which are predominantly characterized by a length and depth, with a sharp root radius, the types of crack-like flaws are+ Surface breaking+ Embedded+ Through-wall

– In some cases, it is conservative and advisable to treat volumetric flaws such as aligned porosity or inclusions, deep undercuts, root undercuts, and overlaps as planar flaws, particularly when such volumetric flaws may contain microcracks at the root

– Grooves and gouges with a sharp root radius are evaluated using Section 9, criteria for the root radius is in Section 5

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• Part 9: Crack-Like Flaws

– The assessment procedures in Part 9 are based on a fracture mechanics approach considering the entire range of material behavior+ Brittle fracture+ Elastic/plastic fracture+ Plastic collapse

– Information required to perform an assessment is provided in Part 9 and the following Appendices+ Appendix C - Stress Intensity Factor Solutions+ Appendix D - Reference Stress Solutions+ Appendix E - Residual Stress Solutions+ Appendix F - Material Properties

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• Part 9: Crack-Like Flaws - Changes

– Appendix C - Stress Intensity Factor (K) Solutions + Improved K solutions over larger range of geometries (Small

R/t)+ K solutions for shallow cracks a/t<0.2 improved

– Appendix E – New Residual Stress Solutions based on PVRC Residual Stress JIP research

– Appendix F - Material Properties, new methods to estimate fracture toughness based on MPC FFS JIP research co-funded by API

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• Part 10: Creep (New)

– API 579, Part 10 provides assessment procedures for pressurized components operating in the creep range

– The temperature above which creep needs to be evaluated can be established using a Level 1 Assessment

– Assessment procedures for determining a remaining life are provided for components with and without a crack-like flaw subject to steady state and/or cyclic operating conditions

– The procedures in this Part can be used to qualify a component for continued operation or for re-rating

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• Part 10: Creep (New)– Level 1 Assessment - Limitations

+ Component has been constructed to a recognized code or standard

+ A history of the component can be provided covering both past and future operating conditions

+ The component has been subject to less than 50 cycles of operation including startup and shutdown conditions

+ The component does not contain a flaw such as an LTA, pitting or crack-like flaw

+ Component has not been subject to fire damage or another overheating event that has resulted in a significant change in shape such as sagging or bulging, or excessive metal loss from scaling

+ The material meets or exceeds minimum hardness and carbon content limitations

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Overview of API/ASME 579-2006• Part 10: Creep (New)

– Level 1 Assessment – Calculations: single operating condition

1

10

100

600 700 800 900 1000 1100 1200

TEMPERATURE, F

ST

RE

SS

, K

SI 250,000 HRS

25,000 HRS2,500 HRS250 HRS25 HRS

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Overview of API/ASME 579-2006• Part 10: Creep (New)

– Level 1 Assessment – Calculations: multiple operating condition

DAMAGE ISOTHERMS

1.00

10.00

1E-08 1E-07 1E-06 1E-05 1E-04 1E-03

DAMAGE RATE, FRACTIONAL DAMAGE/HR

ST

RE

SS

, K

SI

750,F775,F800,F825,F850,F875,F900,F925,F950,F975,F

1000,F1025,F1050,F1075,F

j j jc c seD R t= ×

1

0.25J

total jc c

j

D D=

= ≤∑

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• Part 10: Creep (New)– Level 2 Assessment - Limitations

+ Component has been constructed to a recognized code or standard

+ A history of the component can be provided covering both past and future operating conditions

+ The component has been subject to less than 50 cycles of operation including startup and shutdown conditions

+ The component does not contain a flaw such as an LTA, pitting or crack-like flaw

– Level 2 Assessment - Calculations+ Analysis (i.e. FEA) used to determine temperature and stress

as a function of time

+ Material data and damage rule used to determine acceptability for continued operation

+ Method based on MPC Project Omega JIP

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• Part 11: Fire Damage– Covers assessment procedures for evaluating pressure

vessels, piping and tanks subjected to flame impingement and the radiant heat of a fire

– Assessment procedures address the visually observable structural degradation of components and the less apparent degradation of mechanical properties, such as strength, ductility, and toughness

– Assessment procedures may also be used to evaluate process upsets due to a chemical reaction within process vessels

• Part 11: Fire Damage - Changes– Reference provided to new Part 10 to evaluate creep

damage resulting from a fire

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• Part 12: Dents, Gouges, and Dent-Gouge Combinations (New)– Assessment procedures for pressurized components

containing dents, gouges, or dent-gouge combinations resulting from mechanical damage

– Dent – An inward or outward deviation of a cross-section of a shell member from an ideal shell geometry that is characterized by a small local radius or notch

– Gouge – An elongated local removal and/or relocation of material from the surface of a component caused by mechanical means that results in a reduction in wall thickness; the material may have been cold worked in the formation of the flaw

– Dent-Gouge Combination – A dent with a gouge present in the deformed region

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• Part 12: Dents, Gouges, and Dent-Gouge Combinations (New)– Assessment procedures permit calculation of MAWP or

MFH– Level 1 Assessment Procedures based on simple

screening criteria– Level 2 Assessment Procedures require some stress

analysis, fatigue calculation method included for dent and dent-gouge combinations

48


• Part 13: Laminations (New)– Covers assessment procedures for pressurized

components with laminations, excluding HIC or SOHIC damage

– Laminations are defined as a plane of non-fusion in the interior of a steel plate that results during the steel manufacturing process

– Existing assessment procedures in Part 7 will be significantly updated

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Overview of API/ASME 579-2006• Appendices – updates previously discussed have been

completed– Appendix B – Stress Analysis Overview for a FFS Assessment -

Change, complete rewrite to incorporate new elastic-plastic analysis methods and fatigue evaluation technology developed for the ASME Div 2 Re-write Project

– Appendix C – Compendium of Stress Intensity Factor Solutions - Change, new stress intensity factor solutions for thick wall cylinders, through wall cracks in cylinders and spheres, holes in plates

– Appendix E - Compendium of Residual Stress Solutions - Change, complete rewrite to incorporate new solutions developed by PVRC Joint Industry Project

– Appendix F – Material Properties for a FFS Assessment - Change, new fracture toughness estimation methods and stress-strain curve model incorporated

– Appendix H – Technical Basis and Validation of FFS Procedures – NEW, technical basis document that provides an overview of the technical background and validation with essential references

– Appendix K – Crack Opening Areas - NEW, appendix covering crack opening areas for through-wall flaws in cylinders and spheres

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• Technology Development Efforts Currently Underway– Documentation of validation of new assessment procedures

for HIC/SOHIC damage (2006)– Allowable Remaining Strength Factor (RSFa) calibration

based on original construction code (2006)– Assessment of local thin areas (2007)

+ Development of a new method for computing the RSF factor for both Level 1 and Level 2 Assessments

+ Development of new LTA-to-LTA spacing criteria+ Development of new LTA-to-structural discontinuities spacing

criteria + Development of new rules for assessment of local thin areas at

nozzles and other shell discontinuities

– Completion of Example Problems Manual (2007)

Future Enhancements After the 2006 Publication of API/ASME 579

51


• Technology Development Efforts Currently Underway– Assessment Procedures for bulges (2007)– Assessment of crack-like flaws (2007)

+ New PSF (Partial Safety Factors) for crack-like flaws, introduction of PSF’s for LTA’s

+ Development of new reference stress solutions based on J-Integral Technique

+ Evaluation of weld mismatch effects

– Assessment procedures for HTHA (2007)– Assessment procedures for hot-spots (2008)– Assessment of damage in cast iron components (paper

mill dryers) (2008)

52


• Future Technology Needs– Improved fracture toughness evaluation for in-service

materials+ Carbon steel and low alloys+ Environmental effects (e.g. hydrogen)+ Temperature dependency+ Statistical evaluation

– Improved assessment procedures for dents and dent-gouge combinations+ Removal of geometry restrictions+ Coverage of more materials+ Coverage of more loading types

– Evaluation of material toughness effects on the burst pressure of components with non-crack-like flaws (i.e. LTAs, pitting)

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• Future Technology Needs– Assessment Procedures for Crack-Like Flaws

+ FAD dependency on stress-strain curve+ Evaluation of pressure test and warm pre-stress effects+ Improved crack growth models, including data, considering

environmental efforts

– Assessment Procedures for Fatigue+ Multiaxial fatigue+ Cycle counting+ Environmental effects

– Assessment Procedures for Creep Damage+ Include primary creep in MPC Project Omega Creep Model+ Creep damage from triaxial stress states+ Development of new procedures to evaluate creep-fatigue

damage+ New procedures to evaluate creep-buckling


54


• Future Technology Needs– Improved Stress-Strain Models

+ Temperature Effects+ Loading Rate Effects+ Cyclic Stress-Strain Curves

– Introduction of partial safety factors for other types of damage (i.e. LTA, pitting)

– Additional stress intensity factor solutions for common pressurized component geometries (e.g. cracks at nozzles)

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Technical Basis and Validation of API/ASME 579 FFS Assessment

Methods

• The API CRE FFS and Joint API/ASME Committees are committed to publishing the technical basis to all FFS assessment procedures utilized in API 579 in the public domain

• It is hoped that other FFS standards writing committees adopt the same policy as it is crucial that FFS knowledge remains at the forefront of technology on an international basis to facilitate adoption by jurisdictional authorities

• The new API 579 Appendix H of API 579 provides an overview of technical basis and validation with related references organized by damage type, the references are published in a series of WRC Bulletins and technical papers

56

• WRC Bulletins Published– Review of Existing Fitness-For-Service Criteria for Crack-Like Flaws

(WRC 430)– Technologies for the Evaluation of Non-Crack-Like Flaws in

Pressurized Components - Erosion/Corrosion, Pitting, Blisters, Shell Out-of-Roundness, Weld Misalignment, Bulges, and Dents in Pressurized Components (WRC 465)

– Development of Stress Intensity Factor Solutions for Surface and Embedded Cracks in API 579 (WRC 471)

– Stress Intensity and Crack Growth Opening Area Solutions for Through-wall Cracks in Cylinders and Spheres (WRC 478)

– Recent Progress in Analysis of Welding Residual Stresses (WRC 455)– Recommendations for Determining Residual Stresses in Fitness-For-

Service Assessments (WRC 476)– Master S-N Curve Method for Fatigue Evaluation of Welded

Components (WRC 474)


Methods

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• WRC Bulletins Pending– Compendium of Temperature-Dependent Physical Properties for

Pressure Vessel Materials (WRC 503)

– An Overview and Validation of The Fitness-For-Service Assessment Procedures for Locally Thin Areas in API 579 (WRC 505)


Methods

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Methods

• WRC Bulletins In Preparation– An Overview of The Fitness-For-Service Assessment Procedures

for Pitting Damage in API 579

– An Overview of the Fitness-For-Service Assessment Procedures for Weld Misalignment and Shell Distortions in API 579

– An Overview and Validation of the Fitness-For-Service Assessment Procedures for Crack-Like Flaws in API 579

– An Overview and Validation of Residual Stress Distributions for Use in the Assessment Procedures of Crack-Like Flaws in API 579

– An Overview and validation of the Fitness-For-Service Rules for the Assessment of HIC/SOHIC Damage in API 579

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Methods

• WRC Bulletins In Preparation– MPC Project Omega and Procedures for Assessment of Creep

Damage in API 579

– Development of a Local Strain Criteria Based on the MPC Universal Stress-Strain Equation

– Update on the Master S-N Curve Method for Fatigue Evaluation of Welded Components

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Understanding of Damage Mechanisms

• The first step in a Fitness-For-Service assessment performed in accordance with API 579 is to identify the flaw type and associated damage mechanism

• Appendix G in API 579 provides basic information to assist the practitioner in this step

• The following WRC Bulletins have been produced to provide the practitioner with in-depth information

– Damage Mechanisms Affecting Fixed Equipment in the Pulp and Paper Industry (WRC 488)

– Damage Mechanisms Affecting Fixed Equipment in the Refining Industry (WRC 489 & API RP 571)

– Damage Mechanisms Affecting Fixed Equipment in the Fossil Electric Power Industry (WRC 490)

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In-Service Inspection Codesand Fitness-For-Service

• Jurisdictional acceptance provided by reference from in-service inspection codes in the US– API 510 – Vessels– API 570 – Piping– API 653 – Tankage– ANSI/NB-23 – Vessels & Boilers

• Status of reference from US inspection codes is as follows:– API 510 – Reference in 8th Edition, 2nd Addendum– API 570 – Reference in 2nd Edition, 2nd Addendum– API 653 – Reference to appear in 3rd Edition, 1st Addendum– ANSI/NB-23 – Reference in Introduction of 2001 Addendum

• Working to achieve recognition by other international in-service inspections codes

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In-Service Inspection Codesand Fitness-For-Service

• Reactive FFS can be used to assess damage found during an inspection; provides basis for run, repair, or replace decision

• Proactive FFS can be used prior to shut-downs to help develop inspection plans (e.g. determine maximum permissible flaws sizes)

• The remaining life is determined as part of an FFS assessment:

– Used to establish an inspection interval

– Half-life or similar concepts can be used

– “Snap-Shot” approach to FFS is not adequate, an evaluation of the time dependency of damage is required

63

Fitness-For-Service and RBI - Complimentary Technologies

• Assessment of damage in many of the RBI methods currently being used is needs updating; is not consistent with FFS assessment procedures

• Documented and validated FFS methods for flaw and damage assessment may be used to establish a probability of failure as a function of time by considering uncertainties in the damage model and independent variables

• The resulting probably of failure can be combined with a consequence model to produce an estimate of risk as a function of time

• Time dependency of risk permits development of an inspection plan

• Work is underway to integrate API 579 with API 581

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Harmonizing Pressure Vessel Design and Fitness-For-Service

• To remain technically competitive, and to facilitate incorporation of new technology and future updates, ASME is developing a new pressure Vessel Code; this code will replace the existing Section VIII, Division 2 Code

• The new code is being developed primarily to address design and fabrication “of engineered” pressure vessels (as typically used in the refining and petrochemical industry); will result in significant cost savings

• The new code is consistent with developments in Europe • Objective to develop a new organization and introduce a clear

and consistent writing style to facilitate use; consistent with API-579 philosophy

• Shared technology between API-579 and new design Code.

• Draft version of new Code is complete; work is underway to ballot the Div 2 Rewrite in 2006

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Summary• Fitness-For-Service (FFS) assessments are quantitative

engineering evaluations that are performed to demonstrate the structural integrity of an in-service component containing a flaw or damage

• API and ASME have agreed to form a joint committee to produce a single FFS Standard, API/ASME 579, that can be used for pressure-containing equipment– Permits focusing of resources in the US to develop a single

document that can be used by all industries– Helps avoid jurisdictional conflicts and promotes uniform

acceptance of FFS technology• The 2006 edition of API/ASME 579 represents a significant

update in assessment procedures• The technical basis and validation of the API/ASME 579 FFS

assessment procedures will be published in the public domain• API/ASME 579 FFS assessment methods have been integrated

with API & NBIC inspection codes and will be integrated into API RBI technologies

• Significant technical development work remains and a work plan is being formulated

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Robert Brown, P.E.FFS Team Leader

[email protected]

20600 Chagrin Blvd. • Suite 1200Shaker Heights, OH 44122 USA

Phone: 216-283-9519 • Fax: 216-283-6022www.equityeng.com