The API 579 Fitness-for-Service
Standard – The Current State of
Technology and a Ten Year Look
Ahead
10th Annual IPEIA (formerly NPEC) Conference
Banff Centre in Banff Alberta, Canada
February 1 – 3, 2006
Robert Brown, P.E.
Presentation Outline
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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
2
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
3
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
4
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
5
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
6
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
7
Overview of API 579
General
• 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
8
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
9
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
Step
Step
Step
Step
Step
Step
Step
1
2
3
4
5
6
7
8
-
Flaw & damage mechanism identification
Applicability & limitations of FFS procedures
Data requirements
Assessment techniques & acceptance criteria
Remaining life evaluation
Remediation
In-service monitoring
Documentation
• Some of the steps shown above may not be necessary
depending on the application and damage mechanism
10
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
11
Overview of API 579
Contents
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
12
Overview of API 579
Contents
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
13
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 Jintegral, 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)
14
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
15
New Joint API and ASME FFS Standard
• 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
16
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
17
New Developments for API/ASME 579
• 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
18
New Developments for API/ASME 579
• 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
19
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
20
Overview of API/ASME 579-2006
• 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
21
Overview of API/ASME 579-2006
• 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
22
Overview of API/ASME 579-2006
• Part 4: General Metal Loss - Changes
– Minimal changes to existing API 579 methodology
– Change from tmin to trd
S
Existing
t
tmin
tmm
s
New
trd
tmm
23
Overview of API/ASME 579-2006
• 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
24
Overview of API/ASME 579-2006
• 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
25
Overview of API/ASME 579-2006
• Part 5: Local Metal
Loss - Changes
Stiffening Rings
– 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:
n
MAWPr 
L
i 1
n
Actual Cylindrical Shell
LT
Idealized Cylindrical Shell
t1
t2
t3
t4
L1
L2
L3
L4
i
Li

e
P
i 1 i
26
Overview of API/ASME 579-2006
• 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
27
Overview of API/ASME 579-2006
• 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
28
Overview of API/ASME 579-2006
• 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
29
Overview of API/ASME 579-2006
• 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
Rwt 
trd  wmax
tc
where,
trd
 thickness away from pitted region
wmax
 max pit depth
tc
 future corroded thickness
30
Overview of API/ASME 579-2006
• 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
31
Overview of API/ASME 579-2006
• 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”
32
Overview of API/ASME 579-2006
• Part 7: Hydrogen Blisters and HIC/SOHIC (New)
– 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.)
33
Overview of API/ASME 579-2006
• Part 7: Hydrogen Blisters and HIC/SOHIC (New)
– 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
34
Overview of API/ASME 579-2006
• 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
35
Overview of API/ASME 579-2006
• 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
36
Overview of API/ASME 579-2006
• 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
37
Overview of API/ASME 579-2006
• 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
Appendix
Appendix
Appendix
C - Stress Intensity Factor Solutions
D - Reference Stress Solutions
E - Residual Stress Solutions
F - Material Properties
38
Overview of API/ASME 579-2006
• 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
39
Overview of API/ASME 579-2006
• 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 cracklike 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
40
Overview of API/ASME 579-2006
• 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
41
Overview of API/ASME 579-2006
• Part 10: Creep (New)
– Level 1 Assessment – Calculations: single operating
condition
STRESS, KSI
100
250,000 HRS
25,000 HRS
2,500 HRS
250 HRS
25 HRS
10
1
600
700
800
900
1000
1100
1200
TEMPERATURE, F
42
Overview of API/ASME 579-2006
• Part 10: Creep (New)
– Level 1 Assessment – Calculations: multiple operating
condition
DAMAGE ISOTHERMS
STRESS, KSI
10.00
1.00
1E-08
1E-07
1E-06
1E-05
1E-04
1E-03
750,F
775,F
800,F
825,F
850,F
875,F
900,F
925,F
950,F
975,F
1000,F
1025,F
1050,F
1075,F
Dcj  Rcj  t sej
J
Dctotal   Dcj  0.25
j 1
DAMAGE RATE, FRACTIONAL DAMAGE/HR
43
Overview of API/ASME 579-2006
• 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
44
Overview of API/ASME 579-2006
• 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
45
Overview of API/ASME 579-2006
• 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
46
Overview of API/ASME 579-2006
• 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
47
Overview of API/ASME 579-2006
• 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
48
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 stressstrain 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
49
Future Enhancements After the 2006
Publication of API/ASME 579
• 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)
50
Future Enhancements After the 2006
Publication of API/ASME 579
• 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 JIntegral 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)
51
Future Enhancements After the 2006
Publication of API/ASME 579
• 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 dentgouge 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)
52
Future Enhancements After the 2006
Publication of API/ASME 579
• 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
53
Future Enhancements After the 2006
Publication of API/ASME 579
• 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
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Technical Basis and Validation of
API/ASME 579 FFS Assessment
Methods
• 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-ForService Assessments (WRC 476)
– Master S-N Curve Method for Fatigue Evaluation of Welded
Components (WRC 474)
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Technical Basis and Validation of
API/ASME 579 FFS Assessment
Methods
• 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)
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Technical Basis and Validation of
API/ASME 579 FFS Assessment
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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Technical Basis and Validation of
API/ASME 579 FFS Assessment
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 Codes
and Fitness-For-Service
• Jurisdictional acceptance provided by reference from inservice 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 Codes
and 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
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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
216-283-6015
[email protected]
20600 Chagrin Blvd. • Suite 1200
Shaker Heights, OH 44122 USA
Phone: 216-283-9519 • Fax: 216-283-6022
www.equityeng.com
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