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

RISK-BASED INSPECTION METHODOLOGY, PART 5—SPECIAL EQUIPMENT 5-91
Figures
Select type of device
• Spring loaded PRV
• Balanced bellows PRV
• Pilot-operated PRV
• Rupture disc
• Other
Select fluid severity
Fail to Open
• Mild
• Moderate
• Severe
Leakage
• Mild
• Moderate
• Severe
Select overpressure
demand case(s)
• Fire, Power failure
• Blocked discharge
• Loss of cooling water, etc.
Select equipment
item(s) protected by
device
RBI or equipment database
Enter PRD inspection
history
• Date
• Duration
• Inspection
Effectiveness
• Result
Default Weibull POF curves in the
absence of test data
Calculate current Weibull
Parameters for device
leakage
Calculate current
Weibull Parameters for
device failure to open
Fluid type,
phase,
temperature
pressure &
inventory
Determine overpressure
scenarios from demand
cases
Correction of
overpressure for
multiple valve
installation
Calculate consequence of
leakage
Calculate consequence
of failure to open
Calculate current risk and
future risk as function of time
Calculate current risk and
future risk as function of
time
Fluid type,
phase,
temperature,
pressure &
inventory
Determine next inspection
date based on risk criteria
Figure 5.2—PRD RBI Methodology