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API 579-1 Fitness-For Service Assessment Plant ID Equipment Number: Equipment Type:

ABC-1234 Vessel

Opolo Equipment: Date:

Separator 29th August 2014

Introduction

The following Level 1 and Level 2, Fitness-For-Service assessments were carried out on Grid Refe 01, in accordance with API 579-1, Part 4, for Type 'A' pressurized components subject to general resulting from internal corrosion, using the methods outlined in API 579-2, 4.2. The assessement are based on a thickness averaging approach. As per API 579-2, 4.2, the longitudinal weld seam area of assessed corrosion is not considered to be a major structural discontinuity, though the we efficiency of 0.85 has been taken into account. Summary

The Level 1 assessment criteria are not satisfied due to the average measured thickness in the lo The Level 2 assessment criteria are not satisfied. Nomenclature CTP D FCA L LOSS Q

Critical Thickness Profile. inside diameter of the shell corrected for LOSS and FCA as applicable. Future Corrosion Allowance (see API 579-1, Annex A, paragraph A.2.7). length for thickness averaging along the shell. amount of uniform metal loss away from the local metal loss location at the time of the as actor used to determine the length for thickness averaging based on an allowable Remain (see API 579-1, Part 2) and the remaining thickness ratio, Rt (see API 579-1, Table 4.5).

Rt RSFa

remaining thickness ratio. allowable remaining strength factor (see API 579-1, Part 2).

tcam

average measured wall thickness of the component based on the circumferential CTP dete of the inspection.

tsam

average measured wall thickness of the component based on the longitudinal CTP determ the inspection. corroded wall thickness. limiting thickness. minimum required wall thickness of the component (see API 579-1, Annex A, paragraph A.

tc tlim tmin tCmin

minimum required thickness of a conical or cylindrical shell based on the stresses in the ci hoop direction (see API 579-1, Annex A, paragraph A.2).

tLmin

minimum required thickness of a conical or cylindrical shell based on the stresses in the lo (see API 579-1, Annex A, paragraph A.2). minimum measured thickness determined at the time of the inspection. nominal or furnished thickness of the component adjusted for mill undertollerance as appl uniform thickness away from the local metal loss location established by thickness measu of the assessment.

tmm tnom trd

API 579-1 Fitness-For Service Assessment Plant ID Equipment Number: Equipment Type:

Opolo Equipment: Date:

ABC-1234 Vessel

Separator 29th August 2014 Note s

Vessel Data Material Maximum Allowable Stress (S) Design Conditions (P) Inside Diameter (ID) Inside Diameter (D) Inside Radius (IR) Inside Radius (R) Nominal Thickness (tnom) Corrosion Allowance (FCA) Weld Joint Efficiency (E)

SA-516, Grade 70, year 1999 20000 psi 300 psig @ 350 F 48.000 in 48.200 in 24.000 in 24.100 in 0.750 in 0.100 in 0.85

including FCA excluding FCA including FCA excluding FCA

Inspection Data

The grid used for the inspection and the thickness readings are shown below. The grid spacing se Equipment Inspector in the circumferential and longitudinal directions is 1.5 inches based on the Figure 1 Inspection Grid

C 1

C 2

C 3

C 4

C 5

C 6

C 7

Grid Refer CML-01

C 8

M1 M2 M3 Vessel Shell

M4 M5

Weld Seam

M6 M7

Table 1 - Inspection Data (in) Longitudinal Inspection Planes M1 M2 M3 M4 M5 M6 M7 Longitudinal CTP

Circrcumferential Inspection Planes C1 0.75 0.75 0.75 0.75 0.75 0.75 0.75

C2 0.75 0.48 0.57 0.61 0.62 0.57 0.75

C3 0.75 0.52 0.59 0.47 0.59 0.59 0.75

C4 0.75 0.57 0.55 0.58 0.58 0.61 0.75

C5 0.75 0.56 0.59 0.36 0.57 0.57 0.75

C6 0.75 0.58 0.60 0.58 0.48 0.56 0.75

C7 0.75 0.60 0.66 0.64 0.62 0.49 0.75

C8 0.75 0.75 0.75 0.75 0.75 0.75 0.75

0.75

0.48

0.47

0.55

0.36

0.48

0.49

0.75

Circumferential CTP 0.75 0.48 0.55 0.36 0.48 0.49 0.75

Longitudinal 0.75 CTP Grid Spacing 0

0.48

0.47

0.55

0.36

0.48

0.49

0.75

1.5

3

4.5

6

7.5

9

10.5

API 579-1 Fitness-For Service Assessment Plant ID Equipment Number: Equipment Type:

Opolo Equipment: Date:

ABC-1234 Vessel

Separator 29th August 2014

Perform a Level 1 assessment for internal pressure as per API 579-1, paragraph 4.4.2 (a) STEP 1 - Calculate the minimum required thickness.

C tmin 

PR  (SE  0.6P)

0.430 in

L tmin 

PR  (SE  0.4P)

0.212 in

C L tmin  max[tmin , tmin ]

API 579 referenc

0.430 in

(b) STEP 2 - Thickness profiles are provided, the data for thickness readings is in Table 1, above. 0.360 in

tmm 

(c) STEP 3 - Determine wall thickness to be used in the assessment.

tc  trd  FCA 

0.650 in

(d) STEP 4 - Compute the remaining thickness ratio, Rt

Rt 

tmm  FCA  (tc )

0.400 in

(e) STEP 5 - Compute the length for thickness averaging from API 579-1, Table 4.5, with Rt = 0.400 in RSFa = 0.9 Table 2.3 The equation for Q is: 2    1 R t Q  1.123   1   (1 Rt / RSFa )  

Q=

0.4581

0.5

for Rt < RSFa

Q=

50

for Rt ≥ RSFa

for Rt < RSFa

Q=

50

for Rt ≥ RSFa

Is Rt < RSFa YES Q=

Is Rt ≥ RSFa NO

0.4581

Table 4.5

API 579-1 Fitness-For Service Assessment Plant ID Equipment Number: Equipment Type:

Opolo Equipment: Date:

ABC-1234 Vessel

with LOSS =

Separator 29th August 2014

0.000 in

D  ID 2(LOSS FCA) 

48.200 in 2.564 in

L  Q Dtc 

(f) STEP 6 - Establish the Critical Thickness Profiles (CTP's) from the thickness profile data. Deter measured thickness tsam based on the longitudinal CTP and the average measured thickness circumferential CTP. Longitudinal CTP Figure 2: Longitudinal Critical Thickness Profile (in)

0.75

tleft 0.55 0.48

0.47

tright t1

tmm

t2

0.48

0.49

0.36

L = 2.564 in

Grid spacing = tmm = tleft = tright = L=

1.5 in 0.360 in 0.550 in 0.480 in 2.564 in



 (L / 2)   (grid spacing) 

t1  tmm  (tleft  tmm) t1 =

0.522 in

t2 =

0.463 in



 (L / 2)   (grid spacing) 

t2  tmm  (tright  tmm)

0.75

API 579-1 Fitness-For Service Assessment Plant ID Equipment Number: Equipment Type:

Opolo Equipment: Date:

ABC-1234 Vessel

Separator 29th August 2014

The area method is used to determine the average thickness.

 (t1  tmm)   (L / 2) 2  

 (tmm  t2 )   (L / 2) 2  

A1  

A2  

A1 =

0.566 in2

A2 =

0.527 in2

A1 + A2 =

1.093 in2

s tam 

(A1  A2 ) L 0.426 in

s tam 

Circumferential CTP Figure 3: Circumferential Critical Thickness Profile (in)

0.75

tleft 0.55 t3

0.48

tmm 0.36

L = 2.564 in

Grid spacing = tmm = tleft = tright = L=

1.5 in 0.360 in 0.550 in 0.480 in 2.564 in

tright t4

0.48

0.49

0.75



 (L / 2)   (grid spacing) 



 (L / 2)   (grid spacing) 

t3  tmm  (tleft  tmm)

t4  tmm  (tright  tmm)

t3 =

0.522 in

t4=

0.463 in

API 579-1 Fitness-For Service Assessment Plant ID Equipment Number: Equipment Type:

Opolo Equipment: Date:

ABC-1234 Vessel

Separator 29th August 2014

The area method is used to determine the average thickness.

 (t3  tmm)   (L / 2) 2  

A3  

 (tmm  t4 )   (L / 2) 2  

A4  

A3 =

0.566 in2

A4 =

0.527 in2

A3 + A4 =

1.093 in2

c tam 

(A3  A4 ) L

c tam 

0.426 in

(g) STEP 7 - Determine the acceptability for continued operation using Level 1 criteria in API 579 The average measured thickness acceptance is used in this example. s tam  FCA 

0.326 in

c tmin 

0.430 in

s c tam  FCA  tmin 

NO

c tam  FCA 

0.326 in

L tmin 

0.212 in

c L tam  FCA  tmin 

from STEP 1

from STEP 1

YES

The Level 1 assessment criteria are not satisfied due to the average measured thickn

API 579-1 Fitness-For Service Assessment Plant ID Equipment Number: Equipment Type:

Opolo Equipment: Date:

ABC-1234 Vessel

Separator 29th August 2014

Check the minimum thickness criteria in API 579-1, Table 4.4

tlim  max[0.2tnom, 0.10 inches] tlim 

0.150 in

tmm  FCA 

0.260 in

max[0.5tmin , tlim ]=

0.215 in

tmm  FCA  max[0.5tmin , tlim ] 

YES

The minimum thickness criteria are satisfied

Level 1 Assessment Summary The Level 1 criteria are not satisfied, perform a Level 2 Assessment using API 579-1, Table 4.4

Level 2 Assessment s (tam  FCA) 

0.326 in

RSFa  tmin 

0.387 in

s (tam  FCA)  (RSFa  tmin ) 

NO

The Level 2 criteria are not satisfied

Page 1 Opolo

ervice assessments were carried out on Grid Reference: CMLpe 'A' pressurized components subject to general metal loss hods outlined in API 579-2, 4.2. The assessement procedures As per API 579-2, 4.2, the longitudinal weld seam within the be a major structural discontinuity, though the weld joint

d due to the average measured thickness in the longitudinal CTP

the local metal loss location at the time of the assessment. hickness averaging based on an allowable Remaining Strength Factor g thickness ratio, Rt (see API 579-1, Table 4.5).

component based on the circumferential CTP determined at the time

component based on the longitudinal CTP determined at the time of

component (see API 579-1, Annex A, paragraph A.2). or cylindrical shell based on the stresses in the circumferential or or cylindrical shell based on the stresses in the longitudinal direction

mponent adjusted for mill undertollerance as applicable. etal loss location established by thickness measurements at the time

Page 2 Opolo

including FCA excluding FCA including FCA excluding FCA

ess readings are shown below. The grid spacing set by the Fixed longitudinal directions is 1.5 inches based on the corrosion profile. Grid Reference CML-01

Grid Spacing 0 1.5 3 4.5 6 7.5 9

Page 3 Opolo

API 579 reference

e data for thickness readings is in Table 1, above.

Page 4 Opolo

files (CTP's) from the thickness profile data. Determine the average nal CTP and the average measured thickness tcam based on the

Page 5 Opolo

Page 6 Opolo

ntinued operation using Level 1 criteria in API 579-1, Table 4.4.

atisfied due to the average measured thickness in the longitudinal CTP

Page 7 Opolo

Level 2 Assessment using API 579-1, Table 4.4