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

RISK-BASED INSPECTION METHODOLOGY, PART 3—CONSEQUENCE OF FAILURE METHODOLOGY 3-99
2) Probability of a jet fire given a release (continuous releases only):
pjet = poi ⋅ poii
(3.181)
vn , vn , vn ,
3) Probability of a VCE given a release:
( 1 ) ( 1 )
pvce = poi ⋅ − poii ⋅ − pvcedi
(3.182)
vn , vn , vn , vn ,
4) Probability of a flash fire given a release (instantaneous releases only):
pflash = poi ⋅ poii
(3.183)
vn , vn , vn ,
5) Probability of a fireball:
pfball
vn ,
= 0.0
(3.184)
6) Probability of safe dispersion given a release:
psafe
= 1− poi
(3.185)
vn , vn ,
k) STEP 8.11—For each hole size, calculate the component damage consequence area of a pool fire,
pool
pool
CA , and the personnel injury consequence area,
f , cmd , n
CA , of a pool fire.
f , inj,
n
1) Determine the pool type, i.e. non-boiling or boiling per the procedure described in Section 5.8.2.2.
2) Calculate the burning rate off the pool surface, m
b
, using Equation (3.128), (3.129), or (3.130), based
on whether the pool is a non-boiling or a boiling pool.
3) Calculate the burning pool fire size, Aburn , using Equation (3.131). Use the pool release rate,
pf , n
pool
W
n
, established in STEP 7.4.
4) Determine the pool fire size to be used in the consequence analysis, A , using Equation (3.133).
pf , n
Note that the pool size will in general be equal to the burning pool fire size, Aburn , calculated using
pf , n
Equation (3.143) but cannot exceed the maximum value calculated using Equation (3.132).
5) Calculate the radius of the pool fire, R , using Equation (3.134) and the length of the pool fire,
pf , n
L pf , n
, using Equation (3.135). Also, calculate the pool flame tilt, θ , using Equation (3.137).
pf , n
6) Calculate the amount of heat radiated from the pool fire,
pool
Qrad
n
, using Equation (3.138).
7) 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, pool
pool
xs and
cmd , n
xs , from the pool fire using the following four-step iterative
inj,
n
procedure.
i) Guess at an acceptable distance from the pool fire,
pool
xs
n
.