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

5-40 API RECOMMENDED PRACTICE 581
Tables
Bundle Remaining Life Methodology
Specified MTTF
Specified Weibull η
Specified Weibull β
Bundle Life
Consequences of Bundle Failure
Financial Risk Target
Table 5.1—Basic Data for Exchanger Bundle Risk Analysis
User specified MTTF for bundle, years to be used in
calculation
User specified Weibull characteristic life (years) to be used in
calculations ( β must also be provided)
User specified Weibull slope parameter to be used in
calculations (η must also be provided)
The life of the bundle under evaluation, years (required for
inactive bundles)
User risk target, $/year
Tube Wall Failure Fraction
Wall thickness fraction that constitutes bundle failure (0 and
1.0)
Production Cost
Unit production costs, $/day (should be equal to the
production rate, bbls/day x margin ($/bbl)
Production Impact
Production impact, e.g. none, bypass, bypass with rate
reduction, shutdown
Rate Reduction
Rate Reduction, % (required if Production Impact is Bypass
with Rate Reduction”)
Planned Shutdown Days
Number of days required to repair or replace failed
exchanger bundle when the shutdown is planned, days
Number of days required to repair or replace failed
exchanger bundle when the shutdown is unplanned, days
Unplanned Shutdown Days
(should be a longer duration than a planned shutdown to
allow for lead time to mobilize or to purchase a replacement
bundle)
Environmental Impact
Environmental costs associated with bundle failure that
includes damage to cooling water system and towers
Lost Opportunity Cost
Additional cost beyond production losses or environmental
costs as a result of bundle failure, $
Bundle Cost Cost of replacement bundle, $
Bundle Installation Cost
Cost of maintenance required to remove, clean, and re-install
exchanger bundle, $
Hurdle Cost
Additional cost above the economic breakeven point at which
a decision to inspect or replace a bundle is made, $
Turnaround Date 1
The date for the next scheduled turnaround from the RBI
date (used as Plan Date for calculating risk)
The date for the second scheduled turnaround from the RBI
Turnaround Date 2
date (used in the cost benefit analysis to make inspection or
replacement decisions)