Liquid hydrocarbon rain out and pool fire formation 1

[dean427]

Hello

I am currently assessing hydrocarbon pool fire formation from leak sources in an NGL/LPG service. My company has an internal quick reference flow chart to decide whether or not hydrocarbons released in the form of an aerosol jet could rain out and form a pool of liquids at grade. This flow chart is simple to use and all one needs is the normal boiling point of the liquid, the adiabatic flash fraction at 1 bar from MOP and the resulting adiabatic flash temperature. The problem is that I cant locate any engineers which understand the origin or the background of the limits on this decision tree. Therefore I feel that this is difficult to defend to health and safety regulators.

To demonstrate ALARP to a regulator we often make use of codes accepted by wider industry e.g. API codes. Does anyone know if there is an industry accepted method/code/best practice guideline to determining if hydrocarbons can rain out and form pools?

Many thanks

Dean

 

[georgeverghese]

Would be reasonable that liquid pools can form from an NGL or LPG stream, if flashpoint temp < ambient, and the adiabatic flash liquid fraction >0 ?

 

[EmmanuelTop]

For accurate assessment you would need to consider computational fluid dynamics (CFD) modeling. The best in class for that is Gexcon FLACS software, because it takes into account the actual plant geometry (obstacles) and characteristics of terrain (slopes, elevation changes etc.) into account. For simpler calculations, any consequence modeling software would do but you need to be careful how you interpret the results in actual environment.

See also section 2.2 from the document

http://www.ogp.org.uk/pubs/434-07.pdf

and also

http://www.hse.gov.uk/research/rrpdf/rr1001.pdf

Dejan IVANOVIC
Process Engineer, MSChE