Fire Pump flow rate

[Alireza01]

Hi, I think two methods are mentioned in NFPA codes to determine fire pump capacity and ground-level water tank volume in an industrial site with some sprinklered and unsprinklered buildings and some hydrants in the yard.
the first method is based on chapter 18 NFPA 1, "Minimum Required Fire Flow and Flow Duration for Buildings" Table (for highest hazard classification and biggest building) also a comparison with the aggregate of hydrants fire flow.
And the second method is based on NFPA 13 and NFPA 14, the sum of sprinkler demand and combination of inside and outside hoses.
I think the first method is sometimes more reasonable since the second method flow rate calculation has less flow rate most often and the first method pump flow rate calculation usually covers the other one.
do you think what calculation procedure is more applicable?

 

[UFT12]

Unless you are designing a municipal water supply system, you may want to check 18.4.5.4 of NFPA 1/18.

 

[Alireza01]

Thank you!
But I think paragraph 18.3.1 of NFPA 1 (2018) expands this subject because we don't have any municipal water supply system and we use a pre-filled water tank, So I think we can consider NFPA 1 method for Pump and tank sizing. as a result, it meets the NFPA 13 requirement also ( I assume NFPA 13 Specifies the minimum system size).

 

[MGXFP]

Both. The water supply should meet both fire sprinkler and fire flow demands but not simultaneously. The fire sprinkler demand is generally a lower flow and higher pressure and the fire flow is the available flow at 20 psi. If fire flow is met but not enough pressure for the fire sprinkler systems or standpipes is available, then additional fire pumps must be added in the applicable buildings.

 

[Alireza01]

Thank you!
I quite agree with that.
The water supply (tank and fire pump set) should be such that to supply sprinkler and standpipe water demand at the required pressure and also fire flow at residual 20 psi pressure.
Is there any difference between the outside hose definition and the hydrants located in the yard adjacent to the building definition according to the NFPA13? Because for ordinary hazard construction, the total hoses water demand is 250 GPM even if we have some hydrants outside of the building for use in case of fire.

 

[MGXFP]

Outside hose demand or inside/outside hose demands are simply added to the fire sprinkler discharge criteria.