4 replies to this topic

[somayehn]

Dear all
Please consider this section of API standard:

API-2030-2005:
7.3.17:
"When reviewing an atmospheric storage tank’s protection
from an external fire the design personnel should
recognize that cooling water is of potential benefit only for
the exposed portions of the roof and for those portions of the
shell that are not in contact with the liquid contents. Those
portions of the tank most likely not to be in contact with liquid
include the roof of cone roofed and covered floating roof
tanks and the upper portion of the shell on all tanks. If spray
is used, typically only the upper 12 to 24 ft (3.7 to 7.4 m) of
shell is sprayed; up to 12 ft (3.7 m) of rundown is allowed on
inclined and vertical surfaces. If there are wind girders at the
top of the tank, spray nozzles should be placed below each
girder ring."

because of this note: what is the best number for water spray nozzle ring of a storage tank?
thanks for your guidance

somayeh

[kkala]

We had designed a group of API 650 atmospheric tanks for a local refinery (2007), height about 14 m. Each of them had one ring of fire water spray nozzles, located close to upper end of the shell, say ~ 1 m below this end (floating roof tanks could additionally "sprayed" with foam onto the roof). Existing tanks had also this single fire water ring (also called cooling ring), so this is widely applied here, where local regulations commply with NFPA in general. See also some posts in http://www.cheresour...n-storage-tank/.
API-2030 is applicable for refineries. Some of its points is not clear to me, e.g. difference between sprays and sprinklers (http://engineers.ihs...DXJIBAAAAAAAAAA). Concerning "sprayable" area, upper limit of 24 ft reminds height affected by ground fire per API, but low limit of 12 ft is not understood, since tank liquid level can happen to be less than this. Besides wall area below 12 ft will be externally wetted (though not sprayed) by falling water. I am not aware to give an explanation.
Despite that, design case of the group of API 650 tanks may have some usefulness as an example.

Edited by kkala, 02 October 2011 - 03:19 PM.

[breizh]

http://minhbao.com.v...le/A_NFPA15.pdf

Consider this resource it may help you .

Breizh

Edited by breizh, 02 October 2011 - 06:30 PM.

[sureshl]

As per NFPA 15, first ring shall be placed in ~1m from the roof. second ring shall be placed at a distance of 3.7m from first ring (same as API 2030), 3.7m run down is allowed. Based on the height of the tank, no of ring will be calculated. Max of 3 rings are sufficient for spray coolings, since tank height will not exceed 20 m max.
Top half of the tank is sprayed with water, bottom half of the tank will have a run down (if water demand is calculated properly).
Eg: Assume, Tank Ht is 14m. First ring will be placed in 13m ht, 2nd ring will be placed in 9.3m ht. bottom portion will have run down.

[kkala]

Explanation by sureshl makes sense and helps (me) understand the meaning of "rundown". Is there an explanation of having placed only one ring of sprays on mentioned API 650 tanks (height ~ 14 m), about 1 m below roof? Or these were sprinklers?
Indeed, what is the difference between spray and springler?

Edited by kkala, 06 October 2011 - 01:24 PM.