Fuel Oil Properties

I may not understand what you’re doing but I don’t think you need to go to this level of detail. API-2000 covers venting requirements of flat bottom, cone roof, vertical, storage tanks. It covers venting requirements for thermal expansion, product movement, and emergency venting. The thermal venting requirements are given in a table based on the product flash point and tank capacity. If the tanks are relatively small, say 30,000-gal or less, then UL-142 covers venting requirements to and is simpler to apply. Varec (makers of vapor recovery products) has a good summary of API-2000 and you may be able to get it on line.

Note, that the emergency venting can be handled by a weak shell to roof seam depending on the construction details and the diameter of the tank. You should have a qualified engineer check this.

Ken Hardy
Tampa Tank Inc

dockthedog,
Thanks for the quick reply. Actually, these are three large (40,000 gal. UL tanks, horizontal). So, the weak shell to roof seam is out. What I didn't really explain well regarding the equation I am using is that the 'V' stated, is found in a table based on wetted area of the tank. It is the required cfh based upon that wetted area. But, this table is based on hexane. That is why the *(1337/L*sqrtMW) is added, to correct the requried flow for different fluids. So, I really can't get away with not knowing the properties of the fuel oil, because obviously, it could potentially require a larger flow than what is listed in the table.

thanks,
Kayla

Kryanl,

Back from the holidays.

The equation you are referring to is in section 2.2.5.2.5 of NFPA 30 which is referenced as the source for the required venting given in UL-142. While UL-142 references NFPA-30 I don’t think UL-142 allows you to reduce the UL-142 venting requirement based on a formula in NFPA-30. So, if you have to comply with UL-142 then you must meet its provisions regardless.

But if you don’t have to meet UL-142 and you want to use NFPA, then you could use the formula. The way I read NFPA, the formula “shall be permitted” to be used in lieu of the tables preceding it. I think there intent is to allow a reduction in the venting capacities if the designer is willing to take a more rigorous approach. In other words, I think all you have to do is meet either of NFPA 2.2.5.2.3 or 2.2.5.2.4 but if you wanted to do the additional work, you can reduce the requirement using the formula.

Personally, I would not use the formula. First off, it isn’t worth it. Say your tank is 12’ x 48’ long. Then I get an area of roughly 2,033-sqft. So the venting requirement is about 600,500-CFH and UL-142 would require a 10” vent. If you apply the formula for diesel fuel (see below for properties) then you get 40,143-CFH and UL-142 would require a 3” vent. By the time you add in the cost of labor, the hot work permits, the equipment, consumables, etc.. I don’t’ think the difference in cost between installing a 10” nozzle is that much more than installing a 3” nozzle. The second reason I wouldn’t do it is because NFPA allows the formula reduction for a “specific” product. If you ever changed the service of the tank then you would have to re-evaluate the vent.

But to answer you question, I only found information for Diesel. I found it on a web site for Ethanol which had a table of properties of fuels. It gave the molecular weight of 200 and a latent heat of vaporization of about 100-btu/hr. Of course the reason it’s so hard to find this information is because fuels vary widely in their properties. I could take a gallon of diesel here in Tampa and a gallon from say New York, and get different numbers for both.

Hope this helps.

Ken Hardy
Tampa Tank