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

3-120 API RECOMMENDED PRACTICE 581
rate
n
is the adjusted or mitigated discharge rate used in the consequence calculation associated with
the n th release hole size, kg/s (lb/s)
tox
rate
n
is the toxic portion of the adjusted or mitigated discharge rate used in the consequence
calculation associated with the n th release hole size, kg/s (lb/s)
R is the Hopkinson’s scaled distance used in the blast calculations associated with the n th release
HS , n
hole size, m/kg 1/3 (lb/ft 1/3 )
t fb
is the fireball duration, seconds
t is the time it takes for the liquid pool to reach steady state, seconds
pn ,
tox
lim
is the toxic exposure limit for a toxic component in the released stream (e.g. IDLH, AEGL-3,
ERPG), usually expressed in ppm.
mod
tox is the modified toxic exposure limit to account for cloud modeling of mixtures, ppm
lim
T
atm
is the atmospheric temperature, K (°R)
T
b
is the bubble point temperature of released liquid, K (°R)
T
d
is the dew point temperature of released vapor, K (°R)
T
f
is the flash temperature of the released fluid, K (°R)
T
fp
is the flash point of the released fluid, K (°R).
T
g
is the ground temperature, K (°R)
T
s
is the storage or normal operating temperature, K (°R)
u is the non-dimensional wind speed associated with the n th release hole size, unitless
sn ,
u
w
is the wind speed measured at 6 ft off of grade, m/s (ft/s)
UFL
is the upper flammability limit for the fluid
V pn ,
is the volumetric vapor rate leaving the pool surface associated with the n th release hole size,
m 3 /s (ft 3 /s)
V
s
is the equipment stored vapor volume, m 3 (ft 3 )
jet
n
W is the portion of the release rate that forms a jet associated with the n th release hole size,
kg/s (lb/s)