Crude Oil Tank Arrangement and Protection (AST)

[Red42]

I am currently trying to squeeze 6 million barrels of various Class flammable/combustibles onto an existing undeveloped rural site. I see in the NFPA 30 that for floating roof tanks whose diameter is larger than 150ft, and that contain Class IIIa liquids, then the spacing must be 1/4 X (sum of 2 adjacent tanks). However, going by the codicil concerning partial remote impoundment, it appears that I can reduce this spacing to 1/6 X (sum of 2 adjacent tank diameters). My question is, is there anything else int he NFPA that would allow me to reduce this shell to shell spacing even further? I read something in an old thread that perhaps some type of cooling sprinklers would allow the tanks to be closer together? But I can't seem to confirm that in NFPA 15 or 30. I would appreciate any comments that anyone has on the subject . . . thread184-121239

 

[stookeyfpe]

I'm out of the office on business and I don't have NFPA 30 in front of me. However, NFPA 30 does allow reductions in shell-to-shell tank spacing when tanks are insulated, protected by water spray systems, and other methods. I don't recall that intermediate diking allows a reduction in tank spacing but again, I am without NFPA 30 at the moment.

I've also found problems with a group of tanks within the same dike of different flammable & combustible liquid classifications.

My first question is: if the site is undeveloped, what's limiting your tank spacing? I am assuimg its site dimensions.

 

[cdafd]

Here you go Scott when you need some light reading

http://www.nfpa.org/aboutthecodes/list_of_codes_and_standards.asp?cookie_test=1

 

[Red42]

Yes, the site is undeveloped. I have been told by several sources that NFPA allows the shell to shell tank spacing to be reduced when the tanks are protected by water spray or insulated, etc. But I can't find this anywhere in NFPA 15. I had been told that NFPA 30 references NFPA 15 for that rule. Have I been told wrong? Because obviously, it is not in the nfpa 15, i've read the entire thing twice. I can't find anything about tank spacing mentioned at all in it. I'm also trying to consider making two diked areas, one for the flammable and one for the non-flammable (Carbon Black). The only problem is that the owner of the tank farm doesn't know exactly what products are going in (it is still very preliminary) yet. So maybe seperate containment will be an option, but it doesn't look like the client will go for it. Does anyone know where in the nfpa I can find the statement that would allow me to reduce shell to shell spacing with insulated tanks or water sprinklers?

 

[cdafd]

under 2003 nfpa 30 do not see reduction for water spray or insulation

4.3.2.2 and table 4.3.2.2.1

how about 4.3.2.3.3 (# 6) and 4.3.2.3.2 (F,3)

 

[cdafd]

" thread184-121239: Genset Belly Tank installation " refers to baby tanks

both tanks are greater than 660 gal and less than 3,000 gal

 

[stookeyfpe]

Oh, I think I remember now. The reductions are for emergency vent flow rates rather than tank spacing. I'll check NFPA 30 when I get back in the office tomorrow.

 

[cdafd]

you got stook venting only

 

[cdafd]

meant, you got it right stook, allowance for venting only


Oh, I think I remember now. The reductions are for emergency vent flow rates rather than tank spacing

 

[Red42]

great. thank you!

 

[stookeyfpe]

Red,

The only exception I can find in the 2003 edition of NFPA 30, is exception 1 in Section 4.3.2.2.1. However, given the stated tank diameters, the exception would not be applicable given the volume of liquid that would be stored.

In such a case you would need to perform an alternative means and method to further reduce your spacing or comply with the 1/6 the sum of the adjacent tank diameters.