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

3-44 API RECOMMENDED PRACTICE 581
Outage
cmd is the probability weighted (on release hole size) numbers of days of downtime required to repair
the specific piece of equipment that is being evaluated, days
Outage
mult is the equipment outage multiplier that can be used to increase the default outage days for an
equipment item, unitless
Outage
n
is the number of downtime days to repair damage associated with the n th release hole size, days
popdens is the population density of personnel or employees in the unit, personnel/m 2 (personnel/ft 2 )
P
atm is the atmospheric pressure, kPa (psia)
P
s
is the storage or normal operating pressure, kPa (psia)
P
trans is the transition back pressure, kPa (psia). Higher back pressures will result in subsonic vapor
flow through the release hole, lower back pressures will cause choked or sonic flow across the
release hole
prodcost
R
Re
n
rate
n
is the cost of lost production due to downtime to repair equipment, $/day
is the universal gas constant = 8.314 J/(kg-mol-K) [1545 ft-lbf/(lb-mol-°R)]
is the Reynolds Number for flow through the release, associated with the n th release hole size,
unitless
is the adjusted release rate for detection and isolation systems associated with the n th release
hole size, kg/s (lb/s)
AIL− CONT
rate n
is the adjusted or mitigated discharge rate used in the AIL continuous consequence calculation
associated with the n th release hole size, kg/s (lb/s)
AINL− CONT
rate n
is the adjusted or mitigated discharge rate used in the AINL continuous consequence
calculation associated with the n th release hole size, kg/s (lb/s)
tox
rate is the release mass rate of toxic component used in the consequence calculation, associated
n
with the n th release hole size, kg/s (lb/s)
t
n
T
s
is the time to release 10,000 lb of fluid mass, calculated for each of the n release hole sizes
selected, seconds
is the storage or normal operating temperature, K (°R)
env
n
vol is the spill volume to be cleaned up, used to determine environmental cleanup costs, calculated
for each of the n release hole sizes selected, barrels