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

RISK-BASED INSPECTION METHODOLOGY, PART 2—PROBABILITY OF FAILURE METHODOLOGY 2-113
CUIF
N C is the number of C level inspections
CUIF
N D is the number of D level inspections
P
CUIF
Po p 1
CUIF
Po p 2
CUIF
Po p 3
CUIF
Pr p 1
CUIF
Pr p 2
CUIF
Pr p 3
S
CUIF
SR P
t
t c
t min
t rde
TS
YS
α
is the pressure (operating, design, PRD overpressure, etc.) used to calculate the limit state
function for POF
is the posterior probability posterior for damage state 1
is the posterior probability posterior for damage state 2
is the posterior probability posterior 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
is the prior probability of corrosion rate data reliability for damage state 3
is the allowable stress
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
is the minimum structural thickness of the component base material
is the minimum required thickness based on the applicable construction code
is the measured thickness reading from previous inspection with respect to wall loss
associated with CUI
is the tensile strength
is the yield strength
is the component geometry shape factor
β 1 CUIF is the β reliability indices for damage state 1
β 2 CUIF is the β reliability indices for damage state 2
β 3 CUIF is the β reliability indices for damage state 3
Φ
is the standard normal cumulative distribution function
16.8 References
See Reference [83] in Section 2.2.