Subject on GPM ratings higher than 5000 and beyond in NFPA20 2

[annoynimous]

Dear all,

Has anyone had experience designing for water spray systems that go beyond 5000 GPM in capacity? e.g 9000 GPM

We need to know how we should size the pipes, as according to the minimum pize sizing table in NFPA20, it only shows up to 5000 GPM rating...

However, let's say we have a parallel pump design of 4500 GPM + 4500 GPM to get a total of 9000 GPM, how do we determine the main discharge pipe size to cater for the total 9000 GPM?

Thank you

 

[UFT12]

Have you checked NFPA 20/19, A.4.17.6? It might be prudent to check whether one large discharge pipe works for you or not but this is something you will have to evaluate depending other factors as well.

 

[MGXFP]

Check NFPA 20 Table 4.28(a), the intent of the pipe sizes is to limit the water velocity in the discharge pipe to 15 fps at 150% of rated fire pump flow.

 

[TravisMack]

Assuming you are using pumps in parallel, you size the suction / discharge of each pump per the table in NFPA 20. Then, for the common suction/discharge piping, you should size it based on the limits noted above of 15fps. However, NFPA 20 stops governing after the pump discharge control valve. So, you could make the discharge manifold whatever would pass to deliver the required water to your system. We run into some of these very large demands in foam/deluge systems for aircraft hangars.

Travis Mack, SET, CWBSP, RME-G, CFPS
MFP Design, a Ferguson Enterprise

http://www.mfpdesign.com

 

[annoynimous]

thanks for the info all!