Diesel Storage Tank: Vaporisation rate and Fire Relief 1

You have several choices. If you have a process simulation of the stream, you can heat it up and vaporize a small portion of the stream, say 5%, and calculate use that MW and effective latent heat for your simulations. Or, you can use the MW and the latent heat chart in API 520 or 521 (can't remember which one).

Alternatively, you could use the following arguement. Diesel is composed mostly of C10 to C22 hydrocarbons (I think I got this from the Chevron fuel webpages). You could use the lighter of those and use the chart I mentioned above to estimate the latent heat.

Then just make sure you put in a hatch or something with lots of extra capacity to account for the inaccuries in the above approach.

25362 or Art might have some better ideas also.

API-2000 has the entire procedure for determining the flow rates for No. 2 Diesel. You don't need the specific properties. The rules are based on heptane (or was it hexane?). This is a far more volital (sp) product that diesel, so its conservative. In the overall scheme of things, don't skimp on a vent by performing more detailed calcs. Besides, the local juridiction probably mandates use of API-2000 anyway by reference to NFPA 30.

Steve Braune
Tank Industry Consultants

thank you: I had seen the API hexane-based approach, but initially rejected it since the substances appeared to be totally dissimilar.

I shall proceed with the API approach. It is a new tank andd therefore a little but of conservative fat won't cause any harm.

I absolutely do agree with SteveBraun, as hexane is one of the most volatile product and thus calculations given by API method are really conservative. No real needs to go further into detailled calculations as the ank is a new tank and nozzle can be manufactured accordingly.