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

RISK-BASED INSPECTION METHODOLOGY, PART 5—SPECIAL EQUIPMENT 5-73
D f
D mild
D sd
D so
DR j
DR total
DRRF j
EF j
F MS
F a
F c
F env
F op
F op,j
F r
F s
F set
F(t)
gff n
gff total
lrate mild
lrate so
MAWP
MTTF
ndc
P f,j
is the damage factor as a function of time for equipment components protected by the PRD
is the duration that a minor or moderate PRD leak will go undiscovered, days
is the number of days required to shut a unit down to repair a leaking or stuck open PRD,
days
is the duration of a stuck open PRD, days
is the demand rate associated with the j th overpressure demand case, demands/year
is the total demand rate on a PRD, demands/year
is the demand rate reduction factor associated with the j th overpressure demand case
is the initiating event frequency associated with the j th overpressure demand case,
demands/year
is the management systems factor
is the multiple device installation adjustment factor
is the adjustment factor for conventional valves
is the adjustment factor for environmental factors
is the adjustment factor for overpressure
is the adjustment factor for the overpressure for the j th overpressure demand case
is the recovery factor applied to lost inventory
is the adjustment factor for the presence of soft seats
is the adjustment factor for the ratio of operating pressure to set pressure
is the cumulative failure density function or unreliability
is the GFF for the protected equipment associated with the n th hole size, failures/year
is the total GFF for the protected equipment, years
is the leakage rate of a mild or moderate leaking PRD, kg/hr (lb/hr)
is the leakage rate for a stuck open PRD, kg/hr (lb/hr)
is the maximum allowable working pressure of the protected equipment, kPa (psig)
is the mean time to failure
is the number of demand cases
is the POF (loss of containment) of the protected equipment associated with the j th
overpressure demand case, failures/year