12 psi pitot through 4.5" Pumper Outlet

[SprinklerDesigner2]

68 static
44 residual
12 psi pitot
4 1/2" orifice

Using this Link

Does 1,569 look right to you because it doesn't to me.

 

[skdesigner]

It would appear that the website is applying a discharge co-efficient of 0.75. NFPA 291 table 4.8.2 calls for a discharge co-efficient of 0.83 for a pumper connection with a pitot pressure above 7 psig.

I come up with 1,737 usgpm.

 

[SprinklerDesigner2]

skdesigner,

I came up with the same thing and was curious as to why they differed so.

 

[TravisMack]

29.83*.9*4.5*4.5*12^.5 = 1883 GPM

Apply pumper modifier: 1883*0.83 = 1563 GPM.

It seems they are right on. Probably just rounding differences.

Don't forget that per 291, you have to do the pumper modifier to the flow test data you get.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[chicopee]

Is it really 4-1/2" and not 2-1/2"?

 

[SprinklerDesigner2]

Yes, it's a pumper outlet and I measured it to be sure it was 4 1/2" and not 4".