Storage Tank Fire Hazard Analysis 1

[TMEldridge]

A local jurisdiction fire marshall has asked us to, as a portion of permitting, submit a Fire Hazard Analysis on the proposed installation of two ASTs - heat output, risk to adjacent tanks, fire probabilty, overfill probability, etc. We designed to NFPA and API, but I have no background on a FHA of this nature. Help?

 

[stookeyfpe]

My first question is What section of what fire code is the basis for this requirement? What it sounds like he wants is a pool fire analysis in the event that either the floating roof sinks (assuming these are field erected tanks) or if a ground spill and ignition occurs, a pool fire analysis of this.

As it relates to fire probability, look at API RP 2021, Guideline for the Management of Large Atmospheric Storage Tank Fires. API surveyed storage tank fires for a 40 year period. The survey revealed 109 field erected storage tank fires over this period. It also revealed that 78% of these fires were rim seal fires. In my own opinion this reflects well on the proper and safe operation and maintenance of field erected aboveground storage tanks.

I think overfill probability is going to be more difficult. First, if one follows API RP 2350 then the hazard of this event are being managed. However, based on what we're learning from the Buncefield Terminal explosion and fire, this is an area that may be revisted.

Give us some more information and we'll try to give you more guidance.

 

[TMEldridge]

stookeyfpe, thanks for your very clear and informative response.
The request was for hazard analysis done based on a fuel release and the thermal impact on the secondary tank and surrounding properties. These are field-erected tanks with IFRs, with worst-case product of gasoline.
I have contacted his office to get more detailed information on what he is interested in, but this is what I have for now.
On a deliverables standpoint, how is this generally presented - a full-blown report, PE stamped letter, sketch and calculations, etc?

 

[stookeyfpe]

Eldridge:

Generally such a report would be presented as a full report sealed by a PE. An approach I would take is

1) Hazard analysis of the fuel e.g., heat release and burning rates, miscible or nonmiscible, vapor pressure, boiling and flash point temperatures

2) Safety features of a field erected IFR tank and dike system

3) Tank controls: motorized or manual valves, overfill protection systems, fire protection, hazardous location electrical equipment etc.

4) Your selected fire scenarios: rim seal, roof collapse, tank overflow resulting in a dike spill fire.

5)Pool fire calculations demonstrating the thermal flux imposed on the tank. Because the tank is an IFR the dike fire scenario is probably the most applicable scenario. I would also look at a wind directed fire plume because this can really impact your thermal flux on exposure tanks.

6) I would include in the analysis why the risk of such an event is relatively low e.g., US fire loss history, spill history, etc. One very useful source of information on spill data is the US Coast Guard. The link to the data is attached:

http://www.uscg.mil/hq/g-m/nmc/response/stats/Summary.htm