API RP 581 - 3rd Ed.2016 - Add.2-2020 - Risk-Based Inspection Methodology

2-102 API RECOMMENDED PRACTICE 581
extcorr
Po p 3
extcorr
Pr p 1
extcorr
Pr p 2
is the posterior probability for damage state 3
is the prior probability of corrosion rate data reliability for damage state 1
is the prior probability of corrosion rate data reliability for damage state 2
extcorr
Pr p 3
S
extcorr
SR P
t
t c
t min
t rde
TS
YS
α
is the prior probability of corrosion rate data reliability for damage state 3
is the allowable stress, MPa (psi)
is the strength ratio parameter defined as the ratio of hoop stress to flow stress
is the furnished thickness of the component calculated as the sum of the base material and
cladding/weld overlay thickness, as applicable, mm (inch)
is the minimum structural thickness of the component base material, mm (inch)
is the minimum required thickness, mm (inch)
is the measured thickness reading from previous inspection with respect to wall loss
associated with external corrosion, mm (inch)
is the tensile strength, MPa (psi)
is the yield strength, MPa (psi)
is the component geometry shape factor
β 1 Thin is the β reliability indices for damage state 1
β 2 Thin is the β reliability indices for damage state 2
β 3 Thin is the β reliability indices for damage state 3
Φ
is the standard normal cumulative distribution function