Fire relief heat input equation in API 521
Fire relief heat input equation in API 521
(OP)
I have a vessel with lots of large bore liquid pipework within a fire area.
I want to confirm the correct option for gire heat input as per the API 521 equation. Is it
Option 1: calculate total wetted surface area then do A^0.82
Or
Option 2: calculate A^0.82 for all pipes and vessels individual and sum them.
Option 2 results in significantly larger fire heat inputs but im worried it is overly conservative or even wrong.
Thanks.
I want to confirm the correct option for gire heat input as per the API 521 equation. Is it
Option 1: calculate total wetted surface area then do A^0.82
Or
Option 2: calculate A^0.82 for all pipes and vessels individual and sum them.
Option 2 results in significantly larger fire heat inputs but im worried it is overly conservative or even wrong.
Thanks.





RE: Fire relief heat input equation in API 521
Option #2 can be considered, IMHO, only if these piping/vessel areas belong to different fire zones or if there are multiple relief valves for fire relief, and the fire scenario evaluation has confirmed a sequential nature of depressurization.
Dejan IVANOVIC
Process Engineer, MSChE