6 replies to this topic

[chemproc]

Anybody know of any article or thread that can help explain how to draw fire circles for a given plot plan when trying to determine flow during a fire sizing case? Thanks.

[Bobby Strain]

Nowhere is a circle mentioned in the recommended practices. Maybe this will help.

 

Bobby

[Sharma Varun]

For a new design, wetted area for equipments falling in 300 m2 (3200 ft2), is the area to be considered to calculate relief load for a system. If there are no physical barriers (say walls) present, fire zone shape is considerd as circular.

 

This is based on SHELL guidelines, hope this helps.

 

regards,

Varun

[NAP]

Most of the proects, I have used a 25ft radius horizontally and 25ft height from grade. Some clients go conservative with 50ft radius...

 

I believe API 520/521 also recommends something about fire circule radius/height. Its been a while I did relief design...

[NAP]

Most of the proects, I have used a 25ft radius horizontally and 25ft height from grade. Some clients go conservative with 50ft radius...

 

I believe API 520/521 also recommends something about fire circule radius/height. Its been a while I did relief design...

 

Usually the source of ignition are regarded as rotating machines which are spark prone...

 

So say, from a pump, 25 ft radius and 25ft height. Whatever comes in this zone, has to be accounted for wetted area to be exposed to fire...

[shekhar dhuri]

Hi,

 

If I understood the query correctly, it is reagrding the extent of ground area covered during Fire (and not height of Pool Fire i.e = 25 ft). As per API 521 (5th Edition, Year 2007), 'Ground area of 230 - 460 m2 is recommeded as the extent of Fire'. API does not mention it as a circle. However, We generally consider it to be circular & hecne term them as 'Fire Circle'.

 

I have not worked extensively on this activity but what I heard from my collegues is,  'We take Piping Plot Plan, Draw circles of 460 m2 area & then add the Relief / Blowdon Load of the PSVs. The Circle which gives the Relief / Blowdon quanity is considered as the maximum load for the given Zone. Flare is then sized for Zone giving highest load.  

 

Hope it helps.

 

Regards,

Shekhar Dhuri

[chemproc]

Thanks everyone