Fire Suppresion System, Bottle Pressure for certain discharge rate...help

[ChasGen61]

I've been assigned the task of designing a fire suppression system. The biggest problem I have is knowing what my bottle pressure should be when I have multiple lines branching off from the main line. There will be a nozzle at the end of each line that has a maximum specified flow rate. I have been told that the contents should be discharged totally over a 15 - 20 sec time span. Is there software out there that is available in the public domain that will enable me to calculate this?

 

[Dougt115]

You will need more information.

Size of tank, flow rate of nozzles, pressure and pressure source are just some.

Also define discharged. 100% of content or 100% of pressure. All nozzles open or just some.

Essentially you want a system where the flow rate out of your tank meets the time requirement and the nozzles should be capable of the same rate. Provided that the line resistance is low enough you should be able to size the system.

 

[kacarrol]

I looked at a similar system, and calculation for this (it was a Halon 1301 system) a couple of years ago. In the 1970's there was a calculation outlined in the codes...now you are required to use some kind of calculation software as the Halon is under a complicated two phase flow. I would start by looking at which code you are designing to. Most NFPA codes require an experienced engineer to at least check the calculation. The code may give you some guidance as to what to do.

But for information this document:

http://www.uscg.mil/hq/cg5/nvic/pdf/1970s/n6-72.pdf

has a very similar calculation to the one I had seen in the file.