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

3-110 API RECOMMENDED PRACTICE 581
ii) Calculate the Hopkinson-scaled distance, R
HS
function of the distance from the physical explosion chosen above,
, using Equation (3.171). This parameter is a
pexp
xs
cmd
.
iii)
iv)
Calculate the side-on overpressure, P SO
, at the Hopkinson-scaled distance, R
HS
, using
Equation (3.170).
Adjust the distance,
overpressure, P
SO
pexp
xs
cmd
, accordingly, and repeat the above steps until the side-on
, is equal to 34.5 kPa (5.0 psi).
pexp
4) Calculate the component damage consequence area, CA , using Equation (3.193).
f , cmd
5) A probit equation based on building collapse is used for personnel injury consequence area and
detailed in Section 5.8.5.5. This probit equation is used to determine the safe distance, xs , from
the VCE using the following five-step iterative procedure.
i) Guess at an acceptable personnel injury distance from the VCE,
ii) Calculate the Hopkinson-scaled distance, R
HS
function of the distance from the VCE chosen above,
pexp
xs .
inj
pexp
inj
, using Equation (3.171). This parameter is a
pexp
xs .
inj
iii)
Calculate the side-on overpressure, P
SO
, at the Hopkinson-scaled distance, R
HS
, Equation
(3.170).
iv) Calculate the probit value, Pr , using Equation (3.172).
v) Adjust the distance,
equal to 5.0.
pexp
xs , accordingly, and repeat the above steps until the probit value is
inj
pexp
6) Calculate the personal injury consequence area, CA , using Equation (3.174).
f , inj
c) STEP 10.3—For the rupture case, calculate the component damage consequence area, CA
,
the personnel injury consequence area, CA
,
bleve
f inj
, of a BLEVE.
bleve
f cmd
, and
1) Calculate the number of moles of stored liquid that flash to vapor upon release to atmosphere, n
v
.
2) Determine the amount of potential energy in the flashed liquid expressed as an equivalent amount of
TNT, W , using Equation (3.195).
TNT
3) For two-phase cases, add to this value the equivalent amount of TNT for the stored vapor energy using
Equation (3.192).
4) For the component damage consequence area, an overpressure limit of 5.0 psig. This overpressure
limit is used to determine the safe distance, xs , from the BLEVE using the following four-step
iterative procedure.
bleve
cmd
i) Guess at an acceptable component damage distance from the BLEVE,
bleve
xs .
cmd