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8/19/2019 API 579 - A Comprehensive Fitness-For-service Guide-A
1/11
API 579: a comprehensi
ve
fi tness-for-service guide
Ted
L
Anderson•·*, David A. Osageb
S
mt
cluml Reliabilil •
Teclmolg
y, 1898 S Flmirort Cotm. Sui1e 235, Boulde
r
CO 80301. USA
M
M
Engineering, Sltaker
fl
eiglm.
OH.
USA
Received 4
Augus
12000; revised II Decemher 2000; accep1ed 13 Decemher 2000
bs
tract
This an iclc presents an overv iew of the rcccmly published Amc1i can Pctroleumlnstitutc (API) Recommend ed Pwctice 579, which covers
fitness-for-service assessmem of pressure equipmem in petrochemical and other industries. Although API 579 covers a wide range of flaws
isms, including local metal loss, pitting coiTosion, blisters, weld misal ignmem. and fi re damage, the emphasis of the
resent arr
icl
e is on the assessment of crack-like llaws. The API 579 p rocerlure for evaluating c.-acks
in
corporates a
fai
l
m·e
assessment
ram (FAD) methodology very similar to that in other documents. such as the British Energy R approach and the BS 7910 method. The
PI document contains m extensive compendium of K solu tions, including a number of new cases generated specifically for AP1579. In the
initi
al
release of the document. API bas adopterl ex isting reference stress solutions
fo.r
the calcul.a
ti
on of
L
in the FAD procerlure.
In
a future
elease, however, API plans to rep lace these solutions with values based on a more ra
ti
onal definition of reference stress. These revised
reference stress solutions will incorporate the effect of we
ld mi
smatch.
In
addition to the Appendices of
K
and reference stress so
lu
tions, API
579 i
nc
ludes
awen
dices that provide guidance on es
ti
mating fracture toughness and
we
ld residual stress
di
stributions. Over the next few
ears these appemUces will be enhanced with advances in technology. Recently, API has entered into discussions with the American Society
Mechanical Engineers (ASME) to convert API 579 into a
jo
int APIIASME fitness-for-service guide. © 2001 PubJishcd by Elsevier
ywo
rds: American Petroleum Institute; Pai lu
n::
assessment diagram; f:o Jaw assessment: J}itness for service; Fracture toughness; Rcfcn::m:c Slress; Residual
Stress imcosity fac1or
1. Backgrou
nd
Existing US design codes
and
smndards for pressurized
nt
provi de ru.les for the design, fabrica tion, inspec
i
on
and testing of new pressure vessels. piping systems.
and
torage tanks. These code-s do not address the fact that
u
ip
ment
degrades whi le in -service
and
deficiencies due
o degra
dation or from original fabrication may be found
subsequent inspections. Fitness-for-service FFS)
n
tS are quantitativ
e engi n
ee r
ing eva.luations,
hich are
performed to demon
strate
the str
uctural integrity
f an in-service componen t
conta
ining a flaw or damage.
American Perro.leum Institute APT) R
ecom
mended
ractice
579 [
l
has
b
een developed
to provide
guidance
co ndu cting FFS assessments
of
flaws
commonly
encoun
ered in the refining and petrochemica l industry which occur
in pressure
vesse
ls, piping, and ta nkage. However, the
can
also be
app
lied
to
flaws
encoun
ered in other industries such as the pulp and
paper
industry,
Com
:s
p
ondingaulho
r. Tel.: +1 -303-415-1475; fa.: +J-303-415-1847.
E-mail address: [email protected] (T.L. Anderson).
-0 161/001$ - see f
ron1
mauer © 2001 Published
by
Elsevier Science Lrd.
ll :
S0308-0161 01l000
1
8-7
fossil fuel util ity industry, and nuclear industry .
Th
e guide
lines provided in
API
579
can be
used
to
make run-repair
replace decisions to ens
ur
e that pressurized
equipment
contain.ing flaws that has been ident ified
during
an inspec
tion can continue to be operated safe.ly .
API
579 is intended
to supp
lement
and augment
the
requireme
nt
s in
AP
T 510 [2], APT 570 [3], and API 653
[4
): to ens
ur
e safe
ty
of plant
perso
nnel
and
the publ ic
whi le older equipment continues to
op
erate; 10 provide tech
nica
lly
sou
nd
FFS
asse
ss
me
nt procedur
es :
to
e nsure that
di:fferent serv ice
providers
furnish consistent remaining
life predictions; and to help optimize maintenance
and
operation of e) iS iing facilities to maintain avai ability of
ol
der
pl
ants and enha
n
ce lo
ng-te
nn
economic viabi
li
ty
.
In
addition. API 579 will also
be
used in conjunction with API
580
Recommended
Practice For
Risk
-Based Inspection [5]
that is
being
developed
to
provide guidel ines for
risk
asse-ss
ment,
and
prioritization f
or
inspection
and
m ai ntenance
plann ing for pressure-conta ining
equ
ip
me
nt.
The initi al impetus to
develop
an FFS standard that
cou
ld
be referen
ced
from the API inspection codes
wa
s
prov
ided
by a Joint I
ndu
stry Project
(JlP)
administ ered by the
8/19/2019 API 579 - A Comprehensive Fitness-For-service Guide-A
2/11
954
T.L Anderso
n D A
Osag /lntenuuiOiwl Journal
o
Presmre Vessels and Piping 77 (2000) 953- 963
Material Properties Council MPC). The driving force
behind this development was p lant safety.
The
methodology
provided for
in
this document, together with the appropriate
API
inspection code, had to ensure that equipment integrity
cou ld be safely maintained when operating equipment with
flaws or damage, and could also be u
se
d to demonstrate
compUaoce with
US
Occupational Safery and
Hea
l
th
Administmtion OSHA) 19 10 Process Safety Management
PSM) Legislation.
mented in a
MPC
FFS TIP Consul tant
s
Report [6), and this
document was subsequently turned over to the
AP
I Commit
tee
on
Refinery Equipment CRE) FFS
Ta
sk Force charged
with development
of
the FFS standard.
In terms adopted
by
the API CRE FFS Task Group devel
oping APT 579, an FFS assessment is an engineering analy
sis
of
equipment to determine whether
it
fit for continued
se
rvice.
The
equipment may contain flaws, may not meet
current design standards, or may
be
subjected to more
severe operating condi tions than the original or current
design.
The
product
of
a FFS assessment is a decision to
operate the equipment as is , alter , repa ir , monitor,
or
replace; guidance on an inspection interval is al
so
provided.
FFS assessments consist of analytical methods to assess
flaws and damage and usually require an interdisciplinary
approach consisting
of
the following:
A review
of
the existing international FFS standards by
the members
of
the MPC
JlP
was undertaken in 199 1 as the
starting point for the development
of
a new FFS standard.
Based
on
the results of this review,
it wa
s detennined that a
comprehensive FFS standard covering many of the typical
ftaw types and damage mechanis
ms
found
in
the
re
fining
and petrochemical industry did not ex ist. In addition, the
existence of many company-based FFS methods, the
complexi ty of the technology that no single company c;m
solve on its own, and the need to gain acceptance by local
jurisdictions in the US further indicated the need for a new
standard. Therefore, the JJP decided to start the develop
ment
of
the required FFS technology that would be needed
to
write a comprehensive FFS standard for the refining and
petrochemical indus
oy
.
The
results
of
this
work
were docu-
• Knowledge of damage mechanisms/material behavior.
• Knowledge
of
past and future operating conditions and
interaction with operations personnel.
• NDE flaw loca
ti
on and sizing).
• Material properties environmenta l
effe
8/19/2019 API 579 - A Comprehensive Fitness-For-service Guide-A
3/11
1:1-.
Amlcrson, D.A.
Os< ge
I
rern l iona/ Journal
o Pressure
v,ssels
tmd
Piping 77
2000) 953-963
955
ased on this definition, the APT CRE FFS Task Group
odified and greatly enhanced the initial efforts of the
MPC Jfp to produce the first edition
of
API 579.
The
PC JTP conti.nued tO prov ide valuable technical contribu
ions throughout this development effort and essentia lJy
ecame the technic
al
development
an
n of the API Task
Th
e MPC FFS JfP is s
ti
ll
in
existence and continues
o provide FFS technology development while working
ly with the needs of the API CRE FFS Task Group.
consrructed to the following codes:
• ASME
B
and PV code, Section
Vlll,
Division
1
• ASME
B
and PV
co
de, Section VJIT, Divis ion
2
• ASME B and PV code, Section I
• ASME B31.3 Piping code
• ASME B31.1 Piping code
• API 650
• APT 620.
The
overall organi zat ion and assessment procedures
in API 579 are reviewed below. This is followed by a
ore detailed discussion
of
the API 579 assessmem of
Guidelines are also provided for applying APL579 to pres
sure-containing equipmeot constructed to other recognized
codes and standards, inc
lu
ding international and internal
corporate standards.
. Overview of API 579
2.2. Organization
.1. Applicable codes
API 579 provides guidelines for perfonning FFS assess
ments that can be
useJ
in
conjun
ct
ion with the APT Inspec
ion codes (APT
510
, API 570 and API 653) to determine the
itability for continued operation. The assessmem proce
ures in t
hi
s recommended practice could be used for FFS
rerating of components designed and
APT 579 is a highly srructured document designed to
facilitate use by practitioners and to
fa
cilitate future
enhancements and modifications by the API CRE FFS
Task Group. Section I
of
the document covers: introduction
and scope; responsibil ities
of
the owner-user,
in
spector, and
eng
ineer; qualification requirements for the inspector and
engineer; and references to other codes and standards. An
outline of the overall FFS assessment methodology that is
ab le 2
erview o f flaw an
ct
dmnage assessment procedures
tion in
PI 579
3
4
5
6
7
8
9
10
I I
Fl
aw
or damage
mechanism
Brittle fractw·c
General
me
ta l loss
Loca
l
me
tal l
oss
Pitdng corrosion
Blisters and
lamina1ions
\ Veld misaJignmenL a nd
shell d i ~ t o n o n s
Crack-like f1aws
High
p ~ r a l u r e oper..ttion
and creep
Fi
re damage
Overview
Asscssmcn1 pr
oce
du r
es
an: provided to evaluate t.hc r
es
istance to briulc rr Ctun:
of
n-ser
vice
l arbon and low aJI()y steel prcssw·c vessels, piping. and storage tanks. C ri teria arc pruvided to
evaluaLe nonnaJ op-cra1ing, swn-up. upset, and shutdown condi1ions
Assessme nt procedur
es
are provided to eval uate general
8/19/2019 API 579 - A Comprehensive Fitness-For-service Guide-A
4/11
956 T.L Anderson.
D A
Osag / lntenuuiOiwl Journal
o
Presmre Vessels and Piping 77 (2000) 953- 963
common to all assessment procedures included in API 579 lS
provided in Section 2 of the documcm. The organization of
Section 2 is shown in ab le I. This same organization is
utilized in
aU
subsequent sections that contain FFS assess
ment procedures.
Starting with Section 3, a catalogue of FFS assessment
procedur
es
organized by damage mechanism
is
provided
in
API 579. A complete listing
of
the flaw and damage assess
ment procedures currently covered
is
shown in able 2.
These damage mechanisms can be grouped at a higher
level to foT111 a degradation class (see Fig. I). This higher
level
of
organization is usef
ul
in that it provides insight into
how the assessmem procedures
of different sections may be
combined to address complex flaws in a componen1. As
shown in Fig. I , several flaw types and d;unage mechanisms
may need to be evaluated 10 detem1ine the FFS of a compo
nent. Each section in API 579 referenced within a degrada·
tion class includes guidance on how to perform an
assessment when multiple damage mechanisms are present.
When assessment procedures are developed for a new
damage mechanism, they wi
II
be added
a.s
a
self
-contained
section to maintain the strucmre
of
API 579. Currently, new
sections are being developed to address hydrogen induced
cracking (HIC) and stress-oriented hydrogen induced crack
ing (SOHlC) damage. local hot spots, assessment proce
dures for riveted components, and creep c rack growth.
A
series
of
append.ices are provided which contam tech
nical information that can be use with all sections of API
Flaw Dimensions
Stress Analysis
I
Stress Intensity Factor
Material Toughness,
Solution, K
1
~
:
K =
Kl
r
K ~ T
Failure Assessment
Diagram Envelope
Brittle Fracture
Unacceptable
Region
I
Mixed
Mode·
Brittle
"-
..
-
..
·
-
· · · ·.
0
Assessment/ l
Fracture And Plastic
~
Collapse
Point
f)
f)
l1J
Acceptable
z
:I:
Region
( )
:::>
0
t
Plastic Collapse
l
LOAD RATIO
.
L = ,.
r
I
rys
Reference Stre
ss
Material Yield Stress,
Y
Solution, ret
l
I
Flaw Dimensions Stress Analysis
F'ig. I. Schemal ic overview of the FAD prn
8/19/2019 API 579 - A Comprehensive Fitness-For-service Guide-A
5/11
1
:1 .
Amlcrson,
D A
.
Os
ge I lnrern(l(iona/ Journal
o
Pressure ssels tmd Pipi
n
77 2000)
95
-
96
3
957
able J
PI 579 appendice
s
pp
endix
Tio
le
I
Thickness.
MAWP
and membrane
srress
equati
ons r
or
a FFS as
sessment
Su·
es
s analys is overview for a FFS
assessme
nt
Compendimu of SLTess intensity factor
so
lut.
o
ns
Compendium o reference
stress
solutions
Re
sidual s
tre
sses in FFS evaluation
Material
pro
pc11
ies
for a FFS assessment
Deter
ioo·aolon and failuo·e modes
Va liclaoion
Gl ossary of 1em1.s and d e f i n i t
Technica l inqu i(ies
Overview
Equations for the
thi
cklless. MAWP . a
nd
mem
brane
stress
are
given foo
ono
s1of
lhe common
press
urized components. These e q u ~ t i o n s are
provided to
ass ist intenlational practitioners who
may no1
ha
ve access
1
ohe ASfVlE c
ode and
who
need
10 deoennine if ohe local d
es
ign
code
is
si
mi
ao
10 ohe
ASME code for w
hich oh
e
FFS as,;essoneno procedure
s
were
prim
arily
d
es
i
gned
for
Recomonendaoions for ana lysis oechoiques thai can
he
used
10
peri ol m
an FFS assessmeno
are
provided including guide
lin
es for
fi
nite element analysis
A ornpendium of snes.s
int
ensity f ~ t c t o r .soJutions for
co
mmon
press
ur:ized components (i.e.
cyl_nders. spheres. nozzle. etc.) are given. These solu1ions are used fo r 1he-assess
me
.nt of crack
like
na
ws . The solutions presented represent
Lh
e l
atest
technology and have been d e r i v e d using
the finile e.lement method in conjunction w
il
·h weigh t func tions
A com pendium o refe.rencc
stress
solutions for common pr
es
surized componen ts (i.e. cylinders,
spheres no.u.lc, e tc.) arc given. These
so
lutions
are
used fo r the ass
es
sment
of l i k e
llaws
Procedur
es
to estimate the re sidual stress fidel for dilfercnt weld
ge
mc tries are
provided; this infonnation is requ ired ror the assessment of crack like Haws
Material
proper
ies required for all FFS assessments arc provided including:
Sutngoh par.nnerers (yield and
ten
sile su·css)
Phys ical
pr
operties (i.
e.
Yo
ung
s Modulu
s,
e1
c.
f'ra.clw·e (Ough ness
Dma
for
fariguc
crack.
growth ca
kulaLons
Pao i
gue
cur
l es
(lnioiao i
on)
Mareria l
data
for coee1> analysis includ ing remaining li fe and creep cr•ck
growo
h
An
overview o
tl
le types o naws and damage
mec
hanisms
thai
can occur is pl ovide
d.
concem
rat
ing on
service-indu
ced
degl
adation
mechan
isms. T
hi
sap
pe
ndix only prov
id
es an
abridge-d
Q\
erv
iew on dama
ge
mechanisms;
API
57 1
is
cun·e
nt
ly be iog d
eve
l
oped
to provide a
definitive
refe
rence for
damage
m
ec
han isms ohm can
be
used wioh AP I
579 and
A
PI
580
n overview
of
the smdies use.d to valjdate the gene.ral and local l l o s s and the cr
ack
-like
llaw
a.c;sess
menL pro
ce
dur
es
are
pro
vided
DeH
ni
lions for common terms used throughout the sect ionsand of
AP
I 579 are given
Guide
lines
for .subm
iuing a l
e e
hni
ca
l in
qu
iry tn AP
·r
are provided. Techn i
cal
inquires will be
for
ward
ed 10 1he AP I
CRE
FFS
tas
k
grour
for
resoluoio
o
79, wh
ic
h cover
FF
S assessment procedures. The majority
f the information in the appendices covers stress analysis
echniques, material property data, and other
pe11ine111
infor
ation that is required when performing a
FFS
assessmen
t.
n overview of the appendices is provided n Ta
bl
e 3.
each flaw and damage type. A logic diagram is included in
each section tO illustrate how these assessment levels arc
interrelated. As an example, the logic diagram for evaluat
ing crack-
li
ke flaws is shown in Fig. 2. In general, each
assessment level
pr
ov ides a balance between conservatism,
the amount of information required for the evalu
at
ion. the
skill of the practitioner perform ing the assessment, and
th
e
complexity
of
analysis being performed. Level I is the most
conservative, but is easiest to use. Practi tioners usually
proceed sequentially from a Level l to a Level 3 assessment
unless otherwise directed by the assessment techniques)
if
the current assessment level does not provide an acceptable
result or a clear course of action cannot be determined.
3. Assessmem me hodology
The
API 579 FFS assessment methodology used for aU
ge y p e _ ~ is provided in Table 4.
The
organization of
h section of APT
579
that covers an assessment procedure
s consistent
wi
th this methodology. This consistent
to the treatment of damage and the associated
FS assessment procedures
fa
cilitates use of
th
e document
in
thai, if a pm ctitioner is fami liar with one section
of
the
, it is not difficult ro utilize another section
ecause of the commoo structure. This assessment metho
logy has proven to be robust for all flaw and damage types
hat have been incorporated into API 579.
Be
cause of this
ccess, when new sections
ar
e added to APT 579, the
emplate used for the development will be based on this
nt me
th
odology.
.4. Assessmem levels
Three levels of assessment are provided in API 579 for
A general overview of each assessment level and its
intended use are described below.
• Level 1 -
The
assessment procedures included in this
level are imended to prov
id
e conservative screening
criteria that
c;m
be utilized with a minimum amount
of
inspection or component information. The Level I
assessment procedures may be used by ei
th
er pl ant
inspection or engineering personnel.
•
Level
2 - The assessment procedures included in th is
level are intended to provide a more detai led evaluation
that produces results that are less conservative than those
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958 T.L Anderson. D.A. Osag / lntenuuiOiwl Journal
o
Presmre Vessels and Piping 77 (2000) 953- 963
Tab
le 4
API 579 FFS asse
s;men1 melho
ctology for al l damage 1
ypes
Srep l.kscriplion
Flaw t
m
tltunage mechw1ism ldentijicmion - The first step in a FFS a s s e s . ~ m e n t is to identify the tlaw type and cause of damage. FFS assessments
should
no
t be pcrfonned unless the c ~ u s e of the damage can be identified. The o riginal design and fab 1cation practices. materials of construction.
servi
ce
his tory, and environmental
cond
itions can
be
used to
a . ~ > C e r a i n Lh
e likely
cause
of the damage. Once the naw ty
pe
is idcntilicd, the appropriate
section
of
Lh is document t:an be se len
1
and a de
n whether
10 proceed
with
an
assessment
can be made
3
Data requin•mems -
The d
ata
required for
FF·s a
ss
essmen ts
depend
on
Lhe
naw t)'pc or
damage mechanism being
c \•aluated.
Dma
requirements may
include: original
equipment design
in formation
pcnaining to maintenance an
d op
era
tional hi
sto
ry
; expected
fu1Urc
s e r v i c e ~ an
d
data
specific
to
the
FFS
as.sessmem
such
as llaw
size.
s1
a
1e
of s
tr
ess
in
lhe com ponem
ar lh
e l
oca1
i
on of
1be Oaw.
and material
properties.
Da1a
re
qu
iremen1s common 10 all
FFS assessm_nt procedures are covet'ed in Sectio1 J. Data reqWrements specific lO;;. damage
mechanism
or flaw type.are covered
in
lhe seclion
comai
.ning
the con·esponding assessmem
p.1
·ocedU1'
es
4
m e . n t
teclmiques and acceptance trittria
-
Assessment techniqu-es and acceptance criteria
al'e
prov ided in each $ection. I f multiple damage
mechanisms al'e p1
esem. more than
one L i o n
may
have to he used for
the
evalua1.ion
5 Remainillg life evaluurioll -
An es1ima1e of 1he 1emaining life or limi1ing Oaw size should be made. The remain
in
g life is eslabl ished using he PFS
assessmem
procedures with
an eslima1e of
urore
damage
nne
(i.e.
con·osion all
owance
.
The
remaining l
i f
e
can be used in
conjunction with
nn
inspec tion code to establish
an inspec1io
n interval
6
Remedimion - Remedi
ation
1nerhods
are provided in
each sec1ion based
on
the
damage
mechanjsm
or
naw type..
_n so
me cases.
remediation
techniques may be used 10 control fu ture damage associated with naw growth and/or material degradat ion
7 In service
monitoring -
M.e
Lhoct
s
fo
r in-servi
ce
monitoring Hre prov ided in each
sec
ti
c.
)n based
on the
damage
mechanism or
tl
aw
type. hH;ervi
ce
monitoring may
be
U.""-d for
Lhosc
case5 where, a remaining life and inspeclion interval cannot be adequately established because of the complexi lies
associated
damage
mechanism and
serv
ice environment
8 Dnrwnenration
- The
documentation
of
an FFS asse5Stnenl s
hou
ld incl ude a record of all data and decisions made in each of the
prev
ious steps to
qualify lbe component for continued operation . Documcnlat ion r e q u i r c m e n L t•ommon to all FFS assessment procedures arc given in Section 2 of AP I
579. Spcdfk
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Andersu, , D.A. O.wge I
lnrern lfiOn l/
Journ l
of
Pressure
V
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96
T Anderson. D.A. O s a . . ~ • I lnttrmuiontll Journal
of
Pr .ssure Vns< am/ Piping 77 (2000)
953 963
available options for a Level 3 assessment include:
• Method A - Level 2 assessment with user-generated
partial safety factors or a probabilistic analysis.
• Method B - Material-specific FAD. similar to R6
Option 2.
• Method C - J -based
FA
D
ob
tained from clastic - pl;t
st
ic
finite element analysis, similar
to
R6 Option 3.
• Method D - Duct
il
e teari
11g
assessment.
• Method
E -
Use
a
recognized assessment procedure.
such as R6
orBS
7910.
The
Level I as
e ~ s m e n t
is very simple screening evaluation
that can be perfonned by a qualified inspector. Level I
consists
of
a series
of
allowable flaw size curves. These
curves were gcner.ucd using the Level 2 assessment with
conservative input assumptions.
l ote
that the
APT
579
Level I asscssmcm of cracks is completely diffcrcnr than
the BS 7910 Level I iiSSessment. The Iauer is u pseudo FAD
ana lysis that is intended to maintain
ba
ckward compatibil ity
wi
th the 1980
vc1
·sion
of
the
BS PD
6493 procedure. Unlike
Level I of BS
79
10 , the APT 579 Level I assessment
requires almost no calculations.
4.
New K solu tions in AP
I 579
Appendix C contains an extensive library of stress imen
sity solutio ns for cracked bodies. Many
of
these solutions
were obtained from the published literature as well as other
assessment procedures, including
BS
7910. New
K
solutions
were also generated for inclusion in APl579. Tn particular, a
comprehensive
set of
so lutions for c racks in cy
li
ndrical and
spherical shells was recently developed [14]. Th is study
involved over 2400 finite clemem runs. Of course. there
were a number
or
existing
so
lutions for cylinders and
spheres. bm these tended to cover a limited mnge of
radius/thickness and flaw aspect ratios.
ln a study commissioned by the MPC FFS project [14),
the follow ing geometries and Haw orientations were
considered:
• Internal axial surface flaws in a cylinder.
• External axial surface flaws in a cy linder.
• Internal circumferential
sUJ:face
flaws in a cylinder.
• External c ircumferential surface flaws in a cyl inder.
• Int
er
nal meridiana surface flaws in
a
sphere.
• External meridiana surface flaws
in
a sphere.
Three load cases were analyzed:
• Uniform crack f01ce pressure.
• Linearly varying crack face pressure.
• Global bending moment (circwnfcrcntial
c r . t c k . ~
in
cyl inders).
The
first 2 load cases
ca
n be used to derive a weight func-
tion. which can be used to infer K for an arbitrary through
wall
stress
field. The procedure for generating weight func
tions from the uniform and linear crack face pressures is
outlined in Appendix C of APT 579.
The range of dimensional paramerers for the cylinder 01nd
s
ph
ere analyses is as follows:
• R;lt =
3, 5, 10. 20. 60, 100, oo.
• all = 0.2, 0.4, 0.6. 0.8.
• cia=
0.5, I. 2, 4. 8, 16. 32.
where
R
is the inside hell radius.
1
is the wa
ll
thickness.
a
is
the depth of the surface flaw. and 2c is the surface flaw
length.
Fi
g.
3
is a plot o f typical resultS from the recent analyses.
Uniform crack face pressure was applied. giving a stress
intensity solution of the following form:
5)
where p is the crack face pressure, G
0
is a dimension less
geometry fuctor , and
Q
is the flaw shape parameter:
(
a 1.
6
Q= I
1.464
6)
Note that there is a significant R 1 efl'ect on the nondimcn
sional stress intensity factor, G
0
• Consequently. using a
K
solution for a s u r t < ~ c e cmck in a flat plate when assessing a
curved shell could lead to significam errors.
The
K
solurion libmry in APT 579 will be expanded as
new cases become avai
I
able. Currently. solutions for cy lin
ders
wi
th R 1 = I arc being computed.
ln
the ncar future. K
so lutions for cracks at structural discontinuities such s
noz2eles
and stif
fe
ning rings
wi ll be
generated.
5. Fractu
re
tough
ne
ss estimation
Appendix F of API 579 eo mains information
on
material
properties. including 10ughness. This appeodix does not
contain a database of toughness values, however. Rather.
it provides correlations and estimation methods. For ferritic
steels, there are lower-bound co
rre
lations of toughness to
Charpy transition temperature. These correlations were
adapted from Sections lTl and Xl of the ASME boiler und
pressure vessel code. For static loading in the
~ b s e n c e of
dissolved hydrogen. the lower-bound toughness corre
la
tion
is as follows:
K
1
c
= 36.5 3.084 exp[0.036(T-
T cr +
56))
(
MP-a../iii.
oq.
K
1
c
= 33.2 2.806
cxpt0.02(T- T .r
100)]
(7a)
(7b)
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Amlcrson,
D A
.
Os
lalion for hydrogen charged steels is as follows: If dissoh•ed hydrogen is
resent it may degrade the ma terial s ahility to resisl brittle frac ture
io
n.
Once
mpid
crac
k
pr
op
agat
i
on
b
egins
h
owever
l
hc
hydrogen
can no
l
onge
r inlluencc the 111atcrial
beha
vio r.
Th
erefore, the cr•ck
a r r e ~
tough
ss should e a reasonab le lower bound estitnate of the mate1iaPs ability
o
re
sist un
able crack propagation .
bution with two of the three parameters specified:
[
B
K - 20)
4
]
F = I - exp - - -- ~ c (lllJll, MPaJffi), (9a)
2;,.4 20
[ (
K)c
-
18.2 )
4
] . .
F
=
I - exp
-8
Ko
_
18
_2 (m., k
s1v111
.),
(9b)
where F
is
the cumulative probability. 8 the specimen thick
ness (crack front length), and K
0
is the Weibullmean tough
ness, wh i ch corresponds to the 63rd perceotile value. The
temperature dependence
of
the median (50th percentile)
toughness is given by
KJ
c{median) =
30 + 70 exp[
O.OI90(T-
To)] (MPaJffi, C),
( lOa)
KJc
{
rn
cdiun
1
= 27 + 64 exp[0.0106(T -
To)]
(ksi.Jin., "F
,
(
lOb
)
where To is the index transition temperature material for the
material
of
interest.
It
corresponds to the temperature at
which the median tOughness for a 25 mm ( l in.) th ick speci
men is I00 MPaJiil (9 1 ks i.Jin.). The median and Weibull
mean are related as follows:
Ko=
KJc(mcdi.m) - 20
+20 (MPaJiU),
(
Ia
)
[ln(2)]0
25
Ko=
Kk(median) - 18.2
+ L8.2 (ksiJin.). {II b)
[I
n (2)
025
By combining Eqs. (9a), (9b), (lOa), ( lOb) and (
II
a), (
lib),
we see that once T
0
is known, the toughness in the transition
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962
T Anderson. D.A. O s a . . I
lnttrmu
iontll Journal
of
Pr.ssure Vns< am/ Piping 77 (2000)
953-963
region is completely described. ASTM E 1921 -98 outlines
the procedure
for
determining To from fmcrure 10ughness
test ing in the transition region.
When fracture 10ughness testing is not feasible.
To
can
be
esti
ma
ted from the 27
J
(20 ft-lb) rransition temperature:
T
o=
T
2
J -
18°C. (12a)
To
=
T
o
- 32.4o
F.
( 1
2b
Th
e above correlation has a standard deviation of approxi
mate y I5°C (2'PF).
6. Refer ence
c s . ~
and we ld mis
match
Appendix D
of
API 579
co
ntains reference stress
so
lu
ti
ons for a variety ofcracked bodies. Fo r the most part , these
solutions were adopted directly from
R6
and BS 79 10 and
are bascu on limit loau so lutions.
Th
e authors believe that the current uefinition of refe r
e nce stress based o n li mit load is inappropriate and should
be
replaced in the long run. When rigorous c lastic- plastic J
l u t i o n ~ f
or
cr;1cked bodi
es
are plolted in terms
of
FADs.
the resulting curves exhibit a strong geometry dependence
when 4 is compute
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Arukmm
V.A. Osu qe l lfl lenwtionfll
Jounwl
ofPressure Vessels und f>ipi11g 77 2000) 9SJ - 96J
963
rojec t will ;tddress the following issues:
• Confirmation of some of the parametric distributions in
Appendix
E.
• A c l
ea
r criterion for electing
'be
ndin
g'
and 'self-
equ
ili
brating' type· of residual stress distributions in pi
pe/
vessel welds.
• Development o f improved residual stress distributions
for fillet welds at comer joints. nozzle welds. and repair
welds.
• Tncorpomti on of local post-weld heat treatment e lfects.
Appendix
E
will continually be expanded and revised as
new results become available.
8. API and ASME FFS ac t
ivities
T
he
American Society of M
ec
hanical Engineers (ASME)
has formed a new main
comm
ittee, the Post ConsmJC tion
Mai.n Committee. with
a
chart
er to
develop codes and stan
dards for in-service pre
ss
ure
co
ntaining equipment
cover
i
ng
all industries. Curre ntly. standards development activity is
underway in the areas
of Ri
sk-
Base
d Inspection (RBI) and
repair methods (e.g. le
ak
seal ing. boxes, patches. etc.).
Tn the area of FFS. A
PI
and ASME are working to create a
new standards comminee that will jointly produce a s ingle
FFS standard in the US thai c;m be used for pressure
containing equipment.
It
is envisioned
that
once the nego
tiations and opemting procedures for the new committee
srrucrure
arc
complete. API
579
will form the basis
of
the
joint APIJASME stand;trd that will be produced by this
committee. The
inili