Purpose: Draft Committeeballots.api.org/cre/sci/ballots/docs/APIRP581AI2008-026Coatinglifer4.pdf ·...

AMERICAN PETROLEUM INSTITUTE API RP 581 – RISK BASED INSPECTION BASE RESOURCE DOCUMENT

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Document Rev 0 – 6/11/2012 of 27

Ballot ID:

Title: External coating life

Purpose: This ballot is intended to address 2 action items. The first was to have a method to give additional coating life when inspection found that a coating was still fully intact. (Action item 2008-026, ID #31) The second was to give the user more flexibility in selecting expected coating life considering the wide variety of coatings, services and application conditions. (Action item 2013-003, ID #125) The current methodology only allows coating life to be 0, 5 or 15 years depending on the classification of the coating quality Low, Medium High, respectively. Coatings clearly may have different useful life.

Impact: None

Rationale: Create a new variable called the Coating life. This would be selected when the coating is applied and then may be adjusted based on inspection of the coating. No guidance is given on how to adjust the coating life based on inspection. That would be left to the End-User and their coating specialists. The intent is to acknowledge this is an acceptable approach and to give a methodology to handle the approach. A high quality external inspection is required to apply a coating life greater than 0 on existing coatings to ensure a sufficient representative sample of the coating is reviewed when establishing the coating remaining life. Ideally, the initial coating application QA/QC inspections are used for newly installed coatings. The current methodology only allows coating life to be 0, 5 or 15 years depending on the classification of the coating quality Low, Medium High, respectively. Coatings clearly may have different useful life.

Technical Reference(s):

Primary Sponsor:

Name: John Scott Company: LyondellBasell

Phone: 563-244-2306 E-mail: [email protected]

Cosponsors: Name/Company: Allison Hardy / LyondellBasell Name/Company:

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Tracking Status

Submitted to Task Group Submitted to SCI Submitted to Master Editor

Date Resolution Date Resolution Date Added

Proposed Changes and/or Wording {attach additional documentation after this point} Example Comparisons: In the time lines shown below, the red bar indicates the time frame in which the coating is no longer protecting the equipment and the external corrosion rate is being applied.

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1) New drum installed June 1, 1985 with a high-quality coating and Clife estimated to be 15 yrs at the

time it is installed. RBI evaluation date is June 1, 2018. You can see no change from current analysis if Clife is estimated at 15 years.

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

2000 - 2018Time frame external DM is active

1985Equipment installed

with new coating2018

RBI Evaluation Date

1985 - 2000Clife = 15 yrs

high quality coating

2000 - 2018age = 18

2000 - 2018Time frame external DM is active


with new coating2018

RBI Evaluation Date

2000 - 2018age = 18

1985 - 2000Coatadj = 15 yrs


Basic DataDate thickness is established (agetk) 06/01/1985Coating Installation Date 06/01/1985Coating Evaluation Inspection Date 06/01/1985Calculation Date 06/01/2018

Method to estimate C life

Coating age at evaluation date 0.00Estimated remaining life on evaluation date 15Suggested Clife 15.00

EQ 2.35 thru 2.42 calcs Current Ballotagecoat 33.0 33.0

agetk 33.0 33.0

Clife (agecoat + Estimated remaining life at time of evaluation during inspection) 15.0Coating Quality? High Coating QualityCoatadj 15.0 15.0Has coating failed? No

Age 18.0 18.0

Sample calcs for 15.6.3 Age evaluation based on coating adjustmentSteps 5 through 7

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2) Same drum is inspected in June 1, 2014. During the A-level External inspection the thickness is established, and the coating is evaluated to have an estimated remaining life of 10 more years from 2014. RBI evaluation date is June 2018.

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018


with new coating

2018RBI

Evaluation Date

2018RBI

Evaluation Date


with new coating

1985 - 2000 high quality coating 2014

tk insp

2014 - 2018age = 4

2014tk inspCoating

Ealuated

1985 - 2018Clife = 39 yrs






agetk 4.0 4.0


Age 4.0 0.0


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3) Same drum is inspected in June 1, 2014. During the A-level External inspection the thickness is

established and the coating is evaluated to have an estimated remaining life of 10 more years from 2014. RBI evaluation date is June 2038





agetk 24.0 24.0


Age 24.0 14.0


1985 2038

1985 2038

1985 - 2024Clife = 39 yrs


2014 - 2038age = 24

2038RBI

Evaluation Date

2014tk insp

1985 - 2000 high

quality coating

2024 - 2038age = 14


with new coating

2014tk inspCoating

Ealuated

2038RBI

Evaluation Date


with new coating

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4) A drum is grit blasted, inspected and coated on June 1, 2014. An A-level inspection is performed and

the thickness is established based on the inspection. A high-quality coating is applied. On June 1, 2014 the drum is inspected and the coating is found to have failed. The RBI evaluation date is June 1, 2024.

2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024

2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024

2024RBI

Evaluation date

2010 - 2024age = 14

2014External insp,

Coating Evaluated,Coating failed

2024RBI

evaluation date

2010Thickness insp

New coating applied

2010 - 2024High Quality coating

Coat adj = 142014External insp

2010Thickness insp

New coating applied





agetk 14.0 14.0

Clife (agecoat + Estimated remaining life at time of evaluation during inspection) 0.0Coating Quality? High Coating QualityCoatadj 14.0 0.0Has coating failed? Yes

Age 0.0 14.0


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15.1.115.6.3 Calculation of the Damage Factor

The following procedure may be used to determine the DF for external corrosion, see Figure 15.1.

a) STEP 1 – Determine the furnished thickness, t , and age, age , for the component from the installation date.

b) STEP 2 – Determine the base corrosion rate, rBC , based on the driver and operating temperature using Table 15.2.

a)c) STEP 3 – Calculate the final corrosion rate, rC , using Equation (2.32).

max , r rB EQ IFC C F F = ⋅ (2.32)

The adjustment factors are determined as follows. 1) Adjustment for Equipment Design or Fabrication,

EQF – If the equipment has a design which allows water to pool and increase metal loss rates, such as piping supported directly on beams, vessel stiffening rings or insulation supports or other such configuration that does not allow water egress and/or does not allow for proper coating maintenance, then 2EQF = ; otherwise, 1EQF = .

2) Adjustment for Interface, IFF – If the piping has an interface where it enters either soil or water, then

2IFF = ; otherwise, 1IFF = .

b)d) STEP 4 – Determine the time in-service, agetk since the last known inspection thickness, rdet (see

Section 4.5.5. The rdet is the starting thickness with respect to wall loss associated with external

corrosion. If no measured thickness is available, set rdet t= and agetk = age. The measured wall

loss due to external corrosion, eL , may be used to calculate rdet using Equation (2.33).

rde et t L= − (2.33)

Note: When using Equation (2.33), agetk, is the time in service since eL was measured.

c)e) STEP 5 – Determine the in-service time, coatage , since the coating has been installed using Equation (2.34).

coatage Calculation Date Coating Installation Date= − (2.34)

f) STEP 6 – Determine the expected coating age, lifeC , based on coating type, quality of application and

service conditions. lifeC should be 0 years for no coating or poorly applied coating. Lower quality

coatings will typically have a lifeC of 5 years or less. High quality coatings or coatings in less harsh

external environments may have a lifeC of 15 or more years. lifeC may be adjusted based on an

evaluation of the coating condition during a high-quality inspection.

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d)g) STEP 76 – Determine coating adjustment, adjCoat , using Equations (2.35) and through (2.3640).

If tk coatage age≥ :

( )min ,adj life coatCoat C age=

0 adjCoat No Coating or Poor Coating Quality= (2.35)

[ ]min 5, adj coatCoat age Medium Coating Quality= (2.36)

[ ]min 15, adj coatCoat age High Coating Quality= (2.37)

If :tk coatage age<

1. If the coating has failed at the time of inspection when tkage was established, then

0adjCoat = .

2. If the coating has not failed at the time of inspection when tkage was established, use

Equation (2.36) to calculate adjCoat .

( ) ( ), ,adj life coat life coat tkeCoat min C Age min C Age Age= − −

Coatadj = min(Clife, agecoat)-min(Clife, agecoat-agetk) (2.3636)


[ ] [ ]min 5, min 5, adj coat coat tkeCoat age age age Medium Coating Quality= − − (2.39)

[ ] [ ]min 15, min 15, adj coat coat tkeCoat age age age High Coating Quality= − − (2.40)

e)h) STEP 87 – Determine the in-service time, age , over which external corrosion may have occurred using Equation (2.3741).

age = agetk - Coatadj (2.4137)

f)i) STEP 98 – Determine the allowable stress, S , weld joint efficiency, E , and minimum required

thickness, mint , per the original construction code or API 579-1/ASME FFS-1 [10]. In cases where components are constructed of uncommon shapes or where the component's minimum structural

thickness, ct , may govern, the user may use the ct in lieu of mint where pressure does not govern the minimum required thickness criteria.

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g)j) STEP 109 - Determine the rtA parameter using Equation (2.4238) based on the age and rdet from

STEP 4, rC from STEP 3.

rrt

rde

C ageAt⋅

= (2.4238)

h)k) STEP 101 – Calculate the Flow Stress, extcorrFS , using S from STEP 89 and Equation (2.4339).

( ) 1.12

extcorr YS TSFS E

+= ⋅ ⋅ (2.4339)

Note: Use Flow Stress (ThinFS ) at design temperature for conservative results, using the

appropriate Equation (2.44) or Equation (2.45).

i)l) STEP 112 – Calculate the strength ratio parameter, ThinPSR , using Equation (2.4440) or (2.4541).

1) Use Equation (2.4440) with rdet from STEP 3, mint or ct , S and E from STEP 89, and extcorrFS

from STEP 1011.

min( , )extcorr cP extcorr

rde

S E Max t tSRFS t

⋅= ⋅ (2.4440)

Note: The mint is based on a design calculation that includes evaluation for internal pressure hoop stress, external pressure and/or structural considerations, as appropriate. The minimum

required thickness calculation is the design code mint . Consideration for internal pressure hoop

stress alone may not be sufficient. ct as defined in STEP 5 may be used when appropriate.

2) Using Equation (2.4415) with rdet from STEP 4 and extcorrFS from STEP 101.

extcorrP extcorr

rde

P DSRFS tα

⋅=

⋅ ⋅ (2.4541)

Where α is the shape factor for the component type

2 ,4 ,1.13 for a cylinder for a sphere for a headα =.

Note: This strength ratio parameter is based on internal pressure hoop stress only. It is not

appropriate where external pressure and/or structural considerations dominate. . When ctdominates or if the mint is calculated using another method, Equation (2.4440) should be used.

j)m) STEP 123 – Determine the number of inspections, , , ,extcorr extcorr extcorr extcorrA B C DN N N N , and the

corresponding inspection effectiveness category using Section 15.6.2 for past inspections performed during the in-service time (see Section 4.5.5).





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k)n) STEP 134 – Determine the inspection effectiveness factors, 1 2 3, ,extcorr extcorr extcorrI I I , using Equation

(2.426), Prior Probabilities, 1extcorrpPr , 2

extcorrpPr and 3

extcorrpPr , from Table 4.5, Conditional Probabilities (for

each inspection effectiveness level), 1extcorrpCo , 2

extcorrpCo and 3

extcorrpCo , from Table 4.6, and the number of

inspections inspections, , , ,extcorr extcorr extcorr extcorrA B C DN N N N , in each effectiveness level obtained

from STEP 123.

( ) ( ) ( ) ( )( ) ( ) ( )

1 1 1 1 1 1

2 2 2 2 2 2

extcorr extcorr extcorr extcorrA B C D

extcorr extcorr extcorrA B C

N N N Nextcorr extcorr extcorrA extcorrB extcorrC extcorrDp p p p p

N N Nextcorr extcorr extcorrA extcorrB extcorrC extcorrp p p p p

I Pr Co Co Co Co

I Pr Co Co Co Co

=

= ( )( ) ( ) ( ) ( )3 3 3 3 3 3

extcorrD

extcorr extcorr extcorr extcorrA B C D

ND

N N N Nextcorr extcorr extcorrA extcorrB extcorrC extcorrDp p p p pI Pr Co Co Co Co=

(2.462)

a)o) STEP 145 – Calculate the Posterior Probabilities, 1extcorrpPo , 2

extcorrpPo and 3

extcorrpPo using Equation

(2.473) with 1 2 3, ,extcorr extcorr extcorrI I I in Step 123.

11

1 2 3

22

1 2 3

33

1 2 3

extcorrextcorrp extcorr extcorr extcorr



IPoI I I

IPoI I I

IPoI I I

=+ +

=+ +

=+ +

(2.473)

b)p) STEP 156 – Calculate the parameters, 1 2 3, ,extcorr extcorr extcorrβ β β using Equation (2.448) and

assigning 0.20tCOV∆ = , 0.20fSCOV = and 0.05PCOV = .

( )

( )

1

1 1

2

2 2

3

1 22 2 2 2 2 2

2 22 2 2 2 2 2

3

1,

1 ( )

1,

1 ( )

1

f

f

extcorrS rt pextcorr

extcorrS rt t S rt S p P


extcorrS rt t S rt S p P


D A SR

D A COV D A COV SR COV

D A SR


D A SR

β

β

β

∆

∆

− ⋅ −=

⋅ ⋅ + − ⋅ ⋅ + ⋅

− ⋅ −=

⋅ ⋅ + − ⋅ ⋅ + ⋅

− ⋅ −=

( )3 3

22 2 2 2 2 2.

1 ( )f

extcorrS rt t S rt S p PD A COV D A COV SR COV∆⋅ ⋅ + − ⋅ ⋅ + ⋅

(2.484)

Where 1 2 31, 2, 4S S SD D D= = = . These are the corrosion rate factors for damage states 1, 2 and 3 as as discussed in 4.5.3 [35]. Note that the DF calculation is very sensitive to the value used for

the coefficient of variance for thickness, tCOV∆ . The tCOV∆ is in the range 0.10 0.20tCOV∆≤ ≤ ,

with a recommended conservative value of 0.20tCOV∆ = .



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c)q) STEP 167 – Calculate extcorrfD using Equation (2.495).

( )( ) ( )( ) ( )( )1 1 2 2 3 3

1.56 04

extcorr extcorr extcorr extcorr extcorr extcorrp p pextcorr

f

Po Po PoD

E

β β β Φ − + Φ − + Φ − =

−

(2.495)

Where Φ is the standard normal cumulative distribution function (NORMSDIST in Excel).


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15.2 15. 7 Nomenclature age is the in-service time that damage is applied

coatage is the in-service time since the coating installation

agetk is the component in-service time since the last inspection thickness measurement with respect to wall loss associated with external corrosion or service start date

rtA is the expected metal loss fraction since last inspection

α is the component geometry shape factor

1Thinβ is the β reliability indices for damage state 1



adjCoat is the coating adjustment

rC is the corrosion rate

rBC is the base value of the corrosion rate

Clife is the total anticipated coating life from the time of its installation

CA is the corrosion allowance

1extcorpCo

is the conditional probability of inspection history inspection effectiveness for damage state 1

2extcorpCo


3extcorpCo


PCOV is the Pressure variance

fSCOV is the Flow Stress variance

tCOV∆ is the Thinning variance

D is the component inside diameter

1SD is the corrosion rate factor for damage state 1

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extcorrfD

is the DF for external corrosion

Date is the coating installation adjusted date extcorr

PDF is the DF parameter defined as the ratio of hoop stress to flow stress

E is the weld joint efficiency or quality code from the original construction code

IFF is the corrosion rate adjustment factor for interface for soil and water

EQF is the adjustment factor for equipment design/fabrication detail extcorrFS is the Flow Stress

1extcorrI is the first order inspection effectiveness factor

2extcorrI is the second order inspection effectiveness factor

3extcorrI is the third order inspection effectiveness factor

S is the measured wall loss from external corrosion extcorrAN is the number of A level inspections extcorrBN is the number of B level inspections extcorrCN is the number of C level inspections extcorrDN is the number of D level inspections

Φ is the standard normal cumulative distribution function

P is the Pressure (operating, design, PRD overpressure, etc.) used to calculate the limit state function for POF

eL measured wall loss due to external corrosion

extcorrPSR is the strength ratio parameter defined as the ratio of hoop stress to flow stress

1extcorrpPo is the posterior probability for damage state 1



1extcorrpPr is the prior probability of corrosion rate data reliability for damage state 1



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t is the furnished thickness of the component calculated as the sum of the base material and cladding/weld overlay thickness, as applicable

ct is the minimum structural thickness of the component base material

mint is the minimum required thickness based on applicable construction code

rdet is the measured thickness reading form prevousprevious inspection with respect to wall loss

associated with external corrosion TS is the the Tensile Strength

YS is the Yield Strength

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15.2.116.6.3 Calculation of the Damage Factor The following procedure may be used to determine the DF for CUI, see Figure 16.1.

a) STEP 1 – Determine the furnished thickness, t , and age, age , for the component from the installation date.

b) STEP 2 – Determine the base corrosion rate, rBC , based on the driver and operating temperature using Table 16.2.

c) STEP 3 – Calculateompute the final corrosion rate using Equation (2.462.50).

max , r rB INS CM IC EQ IFC C F F F F F = ⋅ ⋅ ⋅ ⋅ (2.502.46)

The adjustment factors are determined as follows.

1) Adjustment for insulation type; INSF , based on Table 16.3.

2) Adjustment for Complexity, CMF – Established based on the following criteria.

• If the complexity is below average, then 0.75CMF = .

• If the complexity is average, then 1.0CMF = .

• If the complexity is above average, then 1.25CMF = .

3) Adjustment for Insulation Condition, ICF – Established based on the following criteria.

• If the insulation condition is below average, then 1.25ICF = .

• If the insulation condition is average, then 1.0ICF = .

• If the insulation condition is above average, then 0.75ICF = . 4) Adjustment for Equipment Design or Fabrication,

EQF – If equipment has a design which allows water to pool and increase metal loss rates, such as piping supported directly on beams, vessel external stiffening rings or insulation supports or other such configuration that does not allow water egress and/or does not allow for proper coating maintenance, then 2EQF = ; otherwise, 1EQF = .

5) Adjustment for Interface, IFF – If the piping has an interface where it enters either soil or water, then

2IFF = ; otherwise, 1IFF = .

d) STEP 4 – Determine the time in-service, agetk, since the last known thickness, rdet (see Section

4.5.5). The rdet is the starting thickness with respect to wall loss associated with external corrosion

(see Section 4.5.5). If no measured thickness is available, set rdet t= and .

The measured wall loss from CUI, eL , may be used to calculate rdet using Equation (2.5147).

rde et t L= − (2.487)

Note: When using Equation (2.4751), agetk, is the time in service since eL was measured.





















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e) STEP 5 – Determine the in-service time, coatage , since the coating has been installed using Equation (2.5248).


f) STEP 6 – Determine the expected coating age, lifeC , based on coating type, quality of application and



CUI environments may have a lifeC of 15 or more years. lifeC may be adjusted based on an


f)g) STEP 76 – Determine the coating adjustment, adjCoatadjCoat , using Equations (2.49531) and

(2.50) through (2.58).

:

Coatadj = min [Clife, agecoat] (2.5149)

1. If the coating has failed at the time of inspection when tkeage was established, then

0adjCoat = .

2. If the coating has not failed at the time of inspection when tkeage was established, use


Coatadj = min[Clife ,agecoat] – min[Clife, agecoat - agetk] (2.5250)

If :tke coatage age≥




If :tke coatage age<


[ ] [ ]min 5, min 5, adj coat coat tkCoat age age age Medium Coating Quality= − − (2.57)


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[ ] [ ]min 15, min 15, adj coat coat tkCoat age age age High Coating Quality= − − (2.58)

g)h) STEP 87 – Determine the in-service time, age , over which CUI may have occurred using Equation

(2.5951).

age = agetk - Coatadj (2.5351)

h)i) STEP 98 – Determine the allowable stress, S , weld joint efficiency, E , and minimum required

thickness, mint , per the original construction code or API 579-1/ASME FFS-1 [10]. In cases where components are constructed of uncommon shapes or where the component's minimum structural

thickness, ct , may govern, the user may use the ct in lieu of mint where pressure does not govern the minimum required thickness criteria.

i)j) STEP 109 - Determine the rtA parameter using Equation (2.5452) based on the age and rdet from

STEP 4, rC from STEP 3.

rrt

rde

C ageAt⋅

=

(2..5452)

j)k) STEP 101 – Calculate the Flow Stress,

CUIFFS , using E from STEP 98 and Equation (2.5553).

( ) 1.12

CUIF YS TSFS E

+== ⋅ ⋅

(2.5553)

Note: Use Flow Stress ( ThinFS ) at design temperature for conservative results, using the appropriate Equation (2.6254) or Equation (2.6355).

k)l) STEP 112 – Calculate strength ratio parameter, ThinPSR , using Equation (2.6254) or Equation

(2.632.55).

1) Use Equation (2.6254) with rdet from STEP 4 and S , E and mint or ct from STEP 98 and flow

stress CUIFFS from STEP 101.

min( , )CUIF cP CUIF

rde

S E Min t tSRFS t

⋅= ⋅ (2.6254)

Note: The mint is based on a design calculation that includes evaluation for internal pressure hoop stress, external pressure and/or structural considerations, as appropriate. The minimum

required thickness calculation is the design code mint . Consideration for internal pressure hoop

stress alone may not be sufficient. ct as defined in STEP 5 may be used when appropriate.





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2) Use Equation (2.6355) with rdet from STEP 3 and flow stressCUIFFS from STEP 101.

CUIFP CUIF

rde

P DSRFS tα

⋅=

⋅ ⋅ (2.6355)

Where α is the shape factor for the component type

2 ,4 ,1.13 for a cylinder for a sphere for a headα = .

Note: This strength ratio parameter is based on internal pressure hoop stress only. It is not

appropriate where external pressure and/or structural considerations dominate. When ctdominates or if the mint is calculated using another method, Equation (2.6254) should be used.

l)m) STEP 123 – Determine the number of inspections, , , ,CUIF CUIF CUIF CUIFA B C DN N N N , and the

corresponding inspection effectiveness category using Section 16.6.2 for all past inspections.

m)n) STEP 143 – Determine the inspection effectiveness factors, 1 2 3, ,CUIF CUIF CUIFI I I using Equation

(2.586456), Prior Probabilities, 1CUIFpPr , 2

CUIFpPr and 3

CUIFpPr , from Table 5.6, Conditional Probabilities

(for each inspection effectiveness level), 1CUIFpCo , 2

CUIFpCo and 3

CUIFpCo , from Table 5.7, and the

number of inspections, , , ,CUIF CUIF CUIF CUIFA B C DN N N N in each effectiveness level obtained from STEP

123.

( ) ( ) ( ) ( )( ) ( ) ( ) ( )( ) ( )

1 1 1 1 1 1

2 2 2 2 2 2

3 3 3 3 3

CUIF CUIF CUIF CUIFA B C D

CUIF CUIF CUIF CUIFA B C D

CUIF CUIFA B

N N N NCUIF CUIF CUIFA CUIFB CUIFC CUIFDp p p p p

N N N NCUIF CUIF CUIFA CUIFB CUIFC CUIFDp p p p p

N NCUIF CUIF CUIFA CUIFB Cp p p p

I Pr Co Co Co Co

I Pr Co Co Co Co

I Pr Co Co Co

=

=

= ( ) ( )3

CUIF CUIFC DN NUIFC CUIFD

pCo

(2.6456)

d)o) STEP 145 – Calculate the Posterior Probabilities, 1CUIFpPo , 2

CUIFpPo and 3

CUIFpPo using Equation

(2.6557) with 1 2 3, ,CUIF CUIF CUIFI I I in Step 143.

11

1 2 3

22

1 2 3

33

1 2 3

CUIFCUIFp CUIF CUIF CUIF



IPoI I I

IPoI I I

IPoI I I

=+ +

=+ +

=+ +

(2.6557)

e)p) STEP 156 – Calculate the parameters, 1 2 3, ,CUIF CUIF CUIFβ β β using Equation (2.6658) and assigning

0.20tCOV∆ = , 0.20fSCOV = and 0.05PCOV = .





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( )

( )

1

1 1

2

2 2

3

3 3

1 22 2 2 2 2 2

2 22 2 2 2 2 2

32 2 2

1,

1 ( )

1,

1 ( )

1

1

f

f

CUIFS rt pCUIF

CUIFS rt t S rt S p P

CUIFS rt pCUIF

CUIFS rt t S rt S p P

CUIFS rt pCUIF

S rt t S

D A SR


D A SR


D A SR

D A COV D A

β

β

β

∆

∆

∆

− ⋅ −=

⋅ ⋅ + − ⋅ ⋅ + ⋅

− ⋅ −=

⋅ ⋅ + − ⋅ ⋅ + ⋅

− ⋅ −=

⋅ ⋅ + − ⋅( )2 2 2 2.

( )f

CUIFrt S p PCOV SR COV⋅ + ⋅

(2.6658)

Where 1 2 3

1, 2, 4S S SD D D= = = . These are the corrosion rate factors for damage states 1, 2 and 3 as as discussed in 4.5.3 [35]. Note that the DF calculation is very sensitive to the value used for the

coefficient of variance for thickness, tCOV∆ . The tCOV∆ is in the range 0.10 0.20tCOV∆≤ ≤ , with

a recommended conservative value of 0.20tCOV∆ = .

f)q) STEP 167 – Calculate CUIFfD using Equation (2.6759).

( )( ) ( )( ) ( )( )1 1 2 2 3 3

1.56 04

CUIF CUIF CUIF CUIF CUIF CUIFp p pCUIF

f

Po Po PoD

E

β β β Φ − + Φ − + Φ − =

−

(2.6759)

Where Φ is the standard normal cumulative distribution function (NORMSDIST in Excel).

15.316.7 Nomenclature age is the in-service time that damage is applied

is the in-service time since the coating installation

is the component in-service time since the last inspection thickness measurement with respect to wall loss associated with CUI or service start date

rtA is the expected metal loss fraction since last inspection

α is the component geometry shape factor

1CUIFβ is the β reliability indices for damage state 1




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is the corrosion rate

rBC is the base value of the corrosion rate

CA is the corrosion allowance

1CUIFpCo is the conditional probability of inspection history inspection effectiveness for damage state

1


2


3

PCOV is the Pressure variance

fSCOV is the Flow Stress variance

tCOV∆ is the Thinning variance

D is the component inside diameter




CUIFfD is the DF for CUI for ferritic components

Date is the coating installation adjusted date E is the weld joint efficiency or quality code from the original construction code

CMF is the corrosion rate adjustment factor for insulation complexity

ICF is the corrosion rate adjustment factor for insulation condition

INSF the corrosion rate adjustment factor for insulation type

IFF is the corrosion rate adjustment factor for interface for soil and water

EQF is an adjustment factor for equipment design detail

CUIFFS is the Flow Stress




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1CUIFI is the first order inspection effectiveness factor

2CUIFI is the second order inspection effectiveness factor

3CUIFI is the third order inspection effectiveness factor

eL is the measured wall loss due to CUI

CUIFAN is the number of A level inspections

CUIFBN is the number of B level inspections

CUIFCN is the number of C level inspections

CUIFDN is the number of D level inspections

Φ is the standard normal cumulative distribution function P is the Pressure (operating, design, PRD overpressure, etc.) used to calculate the limit state

function for POF

S is the allowable stress CUIFPSR is the strength ratio parameter defined as the ratio of hoop stress to flow stress

1CUIFpPo is the posterior probability posterior for damage state 1



1CUIFpPr is the prior probability of corrosion rate data reliability for damage state 1



t is the furnished thickness of the component calculated as the sum of the base material and cladding/weld overlay thickness, as applicable

ct is the minimum structural thickness of the component base material

mint is the minimum required thickness based on the applicable construction code

rdet is the measured thickness reading from previous inspection with respect to wall loss associated with CUI

TS is the Tensile Strength

YS is the Yield Strength

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15.3.117.6.3 Calculation of the Damage Factor The following procedure may be used to determine the DF for external ClSCC, see Figure 17.1.

a) STEP 1 – Determine the susceptibility using Table 17.2 based on the driver and the operating temperature. Note that a HIGH susceptibility should be used if cracking is confirmed to be present.

b) STEP 2 – Determine the Severity Index, VIS , using Table 17.3 based on the susceptibility from STEP 1.

c) STEP 3 – Determine the in-service time, crackage , since the last Level A, B or C inspection was performed with no cracking detected or cracking was repaired. Cracking detected but not repaired should be evaluated and future inspection recommendations based upon FFS evaluation.

d) STEP 4 – Determine the in-service time, coatage , since the coating has been installed using Equation (2.6860)


e) STEP 5 - Determine the expected coating age, lifeC , based on coating type, quality of application and



external environments may have a lifeC of 15 or more years. lifeC may be adjusted based on an


e)f) STEP 65 – Determine the coating adjustment, adjCoatadjCoat , using Equations (2.6961) andand

Equation through (2.7462).

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If :crack coatage age≥

Coatadj = min [Clife, agecoat]

0 adjCoat No Coating or Poor Coating Quality=

(2.6931)



If :crack coatage age<

If the coating has failed at the time of inspection when agecrack was established, then 0adjCoat = .

1.



Coatadj = min[Clife ,agecoat] – min[Clife, agecoat – agecrack] (2.642)


[ ] [ ]min 5, min 5, adj coat coat crackCoat age age age Medium Coating Quality= − − (2.73)

[ ] [ ]min 15, min 15, adj coat coat crackCoat age age age High Coating Quality= − − (2.74)

f)g) STEP 76 – Determine the in-service time, age , over which external ClSCC may have occurred using Equation (2.75653).

crack adjage age Coat= − (2.7653)

g)h) STEP 87 – Determine the number of inspections performed with no cracking detected or cracking was

repaired, and the corresponding inspection effectiveness category using Section 17.6.2 for past inspections performed during the in-service time. Combine the inspections to the highest effectiveness performed using Section 3.4.3. Cracking detected but not repaired should be evaluated and future inspection recommendations based upon FFS evaluation.

h)i) STEP 98 – Determine the base DF for external ClSCC, ext ClSCCfBD − , using Table 6.3 based on the

number of, and the highest inspection effectiveness determined in STEP 87, and the severity index,

VIS , from STEP 2.












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i)j) STEP 109 – Calculate the escalation in the DF based on the time in-service since the last inspection using the age from STEP 6 and Equation (2.2.7664). In this equation, it is assumed that the probability for cracking will increase with time since the last inspection as a result of increased exposure to upset conditions and other non-normal conditions.

( )( )1.1[ ,1.0] ,5000ext ClSCC ext ClSCCf fBD Min D Max age− −= ⋅ (2.7664)

15.417.7 Nomenclature age is the component in-service time since the last cracking inspection or service start date


crackage is the in-service time since the last ClSCC inspection



ext ClSCCfD − is the DF for external ClSCC

ext ClSCCfBD − is the base value of the DF for external ClSCC

VIS is the severity index



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15.4.118.6.3 Calculation of the Damage Factor The following procedure may be used to determine the DF for CUI ClSCC, see Figure 18.1. Note that a HIGH susceptibility should be used if cracking is known to be present.

a) STEP 1 – Determine the susceptibility using Table 18.2 based on the driver and the operating temperature and the following adjustment factors.

1) Adjustments for Piping Complexity – If the piping complexity is Below Average, then decrease Susceptibility one level (e.g. Medium to Low). If the piping complexity is Above Average, then increase Susceptibility one level (e.g., Medium to High). If the piping complexity is Average, then there is no change in the susceptibility.

2) Adjustments for Insulation Condition – If the insulation condition is Above Average, then decrease Susceptibility one level (e.g., Medium to Low). If the insulation condition is Below Average, then increase Susceptibility one level (e.g., Medium to High). If the insulation condition is Average, then there is no change in the susceptibility.

3) Adjustments for Chloride Free Insulation – If the insulation contains chlorides, then there is no change in the susceptibility. If the insulation is chloride free, then decrease the Susceptibility one level (e.g., Medium to Low). 1. Note that a High susceptibility should be used if cracking is confirmed to be present.

b) STEP 2 – Determine the Severity Index, VIS , using Table 17.3, based on the susceptibility from STEP 1.

c) STEP 3 – Determine the in-service time, crackage , since the last Level A, B or C inspection was performed with no cracking detected or cracking was repaired. Cracking detected but not repaired should be evaluated and future inspection recommendations based upon FFS evaluation.

d) STEP 4 – Determine the in-service time, coatage , since the coating has been installed using Equation (2.6775).

age Calculation Date Coating Installation Date= − (2.6775)

e) STEP 5 – Determine the expected coating age, lifeC , based on coating type, quality of application and



CUI environments may have a lifeC of 15 or more years. High quality coatings or coatings in less

harsh external environments may have a lifeC of 15 or more years. lifeC may be adjusted based on

an evaluation of the coating condition during a high-quality inspection. e)f) STEP 65 – Determine the coating adjustment, , using Equations (2.7686) andthrough (2.6782).

If :crack coatage age≥

( )min ,adj life coatCoat C age=

0 adjCoat No Coating or Poor Coating Quality=

(2.76866)

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1. If the coating has failed at the time of inspection when tkage

was established, then 0adjCoat = .



( ) ( ), ,adj life coat life coat tkeCoat min C Age min C Age Age= − −

Coatadj = min[Clife ,agecoat] – min[Clife, agecoat – agecrack] (2.6967)


[ ] [ ]min 5, min 5, adj coat coat crackCoat age age age Medium Coating Quality= − − (2.82)

g) STEP 57 – Determine the in-service time, age , over which external CUI ClSCC may have occurred using Equation (2.687083).

crack adjage age Coat= − (2.687083)

f)h) STEP 68 – Determine the number of inspections performed with no cracking detected or cracking was repaired, and the corresponding inspection effectiveness category using Section 18.6.2 for past inspections performed during the in-service time. Combine the inspections to the highest effectiveness performed using Section 3.4.3. Cracking detected but not repaired should be evaluated and future inspection recommendations based upon FFS evaluation

g)i) STEP 98 – Determine the base DF for CUI ClSCC, CUI ClSCCfBD − , using Table 6.3 based on the number

of, and the highest inspection effectiveness determined in STEP 63, and the severity index, VIS , from STEP 2.

h)j) STEP 109 – Calculate the escalation in the DF based on the time in-service since the last inspection using the age from STEP 67 and Equation (2.8469). In this equation, it is assumed that the probability for cracking will increase with time since the last inspection as a result of increased exposure to upset conditions and other non-normal conditions.

[ ] [ ]min 15, min 15, adj coat coat crackCoat age age age High Coating Quality= − −

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( )( )1.1[ ,1.0] ,5000CUI ClSCC CUI ClSCCf fBD Min D Max age− −= ⋅ (2.697184)

15.518.7 Nomenclature age is the component in-service time since the last cracking inspection or service start date


crackage is the in-service time since the last ClSCC inspection



CUI ClSCCfD − is the DF for CUI ClSCC

CUI ClSCCfBD − is the base value of the DF for CUI ClSCC

VIS is the severity index

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