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

3-116 API RECOMMENDED PRACTICE 581
HC
TNT
is the heat of combustion of TNT ≈ 2000, J/kg (Btu/lb)
HC
v
is the heat of combustion of the vapor fuel for the jet fire calculations, J/kg (Btu/lb)
fball
Ith is the radiant heat flux received at a distant receiver location from a fireball associated with the
rupture case, W/m 2 (Btu/hr-ft 2 )
jet
Ith
n
is the radiant heat flux received at a distant receiver location from a jet fire associated with the
n th release hole size, W/m 2 (Btu/hr-ft 2 )
pool
Ith
n
is the radiant heat flux received at a distant receiver location from a pool fire associated with the
n th release hole size, W/m 2 (Btu/hr-ft 2 )
k
is the release fluid ideal gas specific heat capacity ratio, unitless
k is the thermal conductivity of the surface for liquid pools, W/m-K (Btu/hr-ft- o R)
surf
ld
max,n
is the maximum leak duration associated with the n th release hole size, minutes
ld
n
is the actual leak duration of the flammable release based on the available mass and the
calculated release rate, associated with the n th release hole size, seconds
tox
ld
n
is the actual leak duration of the toxic release based on the available mass and the calculated
release rate, associated with the n th release hole size, seconds
L is the pool fire flame length, associated with the n th release hole size, m (ft)
pf , n
LFL
m
b
is the lower flammability limit for the fluid
is the burning flux rate of a pool fire, kg/m 2 -s (lb/ft 2 -s)
m is the burning flux rate of a pool fire for the i th component in the fluid mixture in the pool fire,
bi ,
kg/m 2 -s (lb/ft 2 -s)
mass is the available mass for release for each of the release hole sizes selected, associated with the
avail,
n
n th release hole size, kg (lb)
mass is the flammable mass of the stored liquid used in the fireball calculation, kg (lb)
fb
mass
vce
is the mass of flammable material in the vapor cloud used in the VCE calculation, kg (lb)
flam
mfrac is the flammable mass fraction of the released fluid mixture
tox
mfrac is the toxic mass fraction of the released fluid mixture
tox
molfrac is the toxic mole fraction of the released fluid mixture