Assessment of General and Local Metal Loss in Cylindrical Shells
according to API 579 Fitness-For-Service Part 4
Attention!
This calculation is only a simplified estimation, and does not replace a detailed design calculation.
Input data
Outside diameter of the shell
D
o
mm
Nominal thickness of the component adjusted for mill undertolerance
t
nom
mm
Minimum required shell thickness based on the stresses in the circumferential direction
t
C
min
mm
Minimum required shell thickness based on the stresses in the longitudinal direction
t
L
min
mm
Future corrosion allowance
FCA
mm
Maximum length of thickness averaging in longitudinal direchtion
L
s
mm
Maximum length of thickness averaging in circumferential direchtion
L
c
mm
Longitudinal spacing of thickness readings
L
sL
mm
Circumferential spacing of thickness readings
L
sC
mm
Uniform thickness away from the local metal loss location established by thickness measurements at the time of the assessment
t
rd
mm
Thickness readings data table with rows in longitudinal direchtion
mm
Calculate
Results
Minimum measured thickness
t
mm
mm
Coefficient of variation
COV
%
Average measured wall thickness
t
am
mm
Length of thickness averaging in longitudinal direchtion
L
s
mm
Length of thickness averaging in circumferential direchtion
L
c
mm
Average measured wall thickness based on the longitudinal critical profile
t
s
am
mm
Average measured wall thickness based on the circumferential critical profile
t
c
am
mm
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