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

3-100 API RECOMMENDED PRACTICE 581
ii) Calculate the atmospheric transmissivity, τ , and the view factor, Fcyl
atm,
n
n
, using Equation
(3.140) and Equation (3.142). Both of these parameters are functions of the distance from the
pool fire chosen above,
xs .
pool
n
iii)
iv)
pool
Calculate the received thermal heat flux, Ith
n
, at the distance chosen using Equation (3.139)
and compare it to the acceptable radiation limit [37.8 kW/m 2 (12,000 Btu/hr-ft 2 ) for component
damage and 12.6 kW/m 2 (4,000 Btu/hr-ft 2 ) for personnel injury].
Adjust the distance, xs
pool
n
thermal heat flux equals the allowable limit.
, accordingly, and repeat the above steps until the calculated received
pool
8) Calculate the component damage consequence area, CA , and the personnel injury
f , cmd , n
pool
consequence area, CA , using Equation (3.150) and Equation (3.151).
f , inj,
n
l) STEP 8.12—For each hole size, calculate the component damage consequence area of a jet fire,
jet
jet
CA , and the personnel injury consequence area,
l, cmd , n
CA , of a jet fire.
l, inj,
n
1) Calculate the amount of heat radiated from the jet fire, Qrad
release rate, W , established in STEP 7.5.
jet
n
jet
n
, using Equation (3.164). Use the jet
2) A radiation limit of 37.8 kW/m 2 (12,000 Btu/hr-ft 2 ) is used for component damage consequence area.
For personnel injury, 12.6 kW/m 2 (4,000 Btu/hr-ft 2 ) is used. These radiation limits are used to determine
the safe distances, jet
jet
xs and
cmd , n
xs , from the jet fire using the following four-step iterative
inj,
n
procedure.
jet
i) Guess at an acceptable distance from the jet fire, xs
n
.
ii) Calculate the atmospheric transmissivity τ , and the view factor, Fp
atm,
n
n
, using Equation
(3.140) and Equation (3.154). Both of these parameters are functions of the distance from the
jet fire chosen above, xs .
jet
n
iii)
iv)
Calculate the received thermal heat flux, Ith , at the distance chosen using Equation (3.153)
jet
n
and compare it to the acceptable radiation limit [37.8 kW/m 2 (12,000 Btu/hr-ft 2 ) for component
damage and 12.6 kW/m 2 (4,000 Btu/hr-ft 2 ) for personnel injury].
Adjust the distance, xs
jet
n
thermal heat flux equals the allowable limit.
, accordingly, and repeat the above steps until the calculated received
jet
3) Calculate the component damage consequence area, CA , and the personnel injury
f , cmd , n
jet
consequence area, CA using Equation (3.155) and Equation (3.156).
f , inj,
n
fball
m) STEP 8.13—For the rupture case, calculate the component damage consequence area, CA , and
f , cmd , n
fball
the personnel injury consequence area, CA , of a fireball.
f , inj,
n