Fire pump flow

[mabed]

Good day,
I am checking the fire drawings of a project, The fire pump is sized to be 1500 gpm, but as per NFPA 14 section 7.10.1.1.5 "The maximum flow rate shall be 1000 gpm (3785 L/min) for buildings that are sprinklered throughout, in accordance with NFPA13, Standard for the Installation of Sprinkler Systems, and 1250 gpm (4731 L/min) for buildings that are not sprinklered throughout, in accordance with NFPA 13." my project is fully sprinklered so I proposed to change the pump to 1000 gpm. But he designer claims that additional 500 gpm is needed for external fire hydrants.
My question is there anything in NFPA that say I need to consider for internal and external fire at the same time and if possible to point which sections talk about this issue?

 

[stookeyfpe]

Is the building protected or not protected by sprinklers? How can you expect for us to answer a question when you don't give us preliminary background. Is this building in the US? What is the building code? You recently asked about sprinkler systems in Light and Ordinary Hazard occupances? Do you understand fire protection systems or are you seeking free engineering assistance from certified or licensed fire protection professionals?

 

[mabed]

four times mentioning NFPA in my post and still not clear which code I am using.
and still not clear if it is sprinklered or not

 

[TravisMack]

NFPA 13 is a standard, not a code. So, there may be specific code requirements above and beyond NFPA 13/14.

To my knowledge, you do not add outside hose allowances to an NFPA 14 standpipe calculation. Maybe he is supplying outside hydrants from the pump and needs the 1500 gpm to meet the site fire flow requirements. For example, if the site fire flow requirements from IBC are 2000 gpm, then the 1000 gpm pump would not cut it, but a 1500 gpm would.

So, as stated above, more information is needed to determine the pump options.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[chicopee]

Water supply of 1000gpm plus two hose streams (H.S.) (@ 250 gpm/H.S.) if hydrants are to be part of the fire pump supply makes very good sense and you will see that this thinking would be backed up by fire specialist from insurance carriers.

 

[mabed]

I have both fire hydrants and building landing valves and sprinklers supplied form same pump.
Is it a good argument to rise that at 150% of rated capacity, the pump will provide the 1500 gpm, while maintaining 65% of rated head? The pump head is calculated assuming 100 PSI at the most demanding landing valve, at 65% of rated head the pressure at landing valve will drop to about 65PSI which is still in range as per NFPA 14. But if this is applicable do I need to size the pipes and pump head at 1000 gpm or 1500 gpm.
Thanks for your help.

 

[DavidCR]

If not in USA maybe there is no a specific building code or AHJ requirement and you are just following NFPA. Consider NFPA 13 sprinkler demand plus NFPA 13 hose demand as a case. 500gpm for external hydrants as a different case. Consider NFPA 14 cases for internal hoses if it has as other case. Take the worst case. Generally for common buildings you are not obligated to add the sprinkler plus the external hydrants or the internal hose coonections simultaneously (???).
Following NFPA 20, work with the pump curves maybe not to 150% capacity but for a little less like 140% for flow and some psi of pressure as safety margins, to see if the pump suits.
About the pipe diameters, follow hydrualic calcs. do a good hyd. calc. for design scenarios or ask an expert for this.

 

[FIRESPRINK]

FYI-I just completed a project where the public water supply entered a 400K SF building, went through a booster pump, then exited to supply a fire loop with exterior fire hydrant protection, the loop also supplied the interior fire sprinkler systems. There was no enforceable building and/or fire code as this was in a rural area of MO. We (1) determined the required outside fire flow demand per the IFC, there are allowable reductions for various items. BTW-outside fire flows are usually at a residual 20-psi. (2) The booster pump rating was checked against the interior sprinkler system demand through calculations. (3) Our occupancy did not require interior fire hose stations, I recall that we accounted for hose allowance per the NFPA standard, combined with the inside fire sprinkler system demand. Per NFPA 13 unless the occupancy requires inside fire hose demand I believe that NFPA 13 contains verbiage to add the fire hose allowance at the connection to the water source. I do not recall that the standard requires outside fire flow to be combined with the interior fire sprinkler system demand.

Another comment was right on the mark about terminology. Before I hired him away from public service, my company's design professional was a PRO (plan review officer), he always said "The building and fire codes tell you what has to be sprinklered, the standards tell you how to do it."