Fire Pump Size and external hose stream allownce 1

[farid2176]

The project i am working on has fire protection storage tank and wall hydrant from tank directly. the firepump will provide water to sprinkler system and fire hose cabinet inside the builidng. i am not sure that if i need to add external hose alownce flow to my pump size. can sombody explain how this external fire hose work
Thanks

 

[MGXFP]

Is there a fire hydrant fed by the fire pump?

 

[LCREP]

If all you have is inside hose stations add 100 gpm to the pump discharge if 1.5" and 250 gpm if 2.5". You did not say what pressure you have but you may need to reduce the pressure at the hose station if it is more then I think 100 psi at the hose station. I do not have NFPA 13 handy to check on the 100 psi.

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Fire Sprinklers Save Firefighters’ Lives Too!

 

[stookeyfpe]

LCREP,

He mentioned sprinklers but he never gave the hazard classification. Grasping for straws....

 

[farid2176]

In my building i have 25% of the area odinary hazard 2
and rest of the building light hazard
can sombody explain how external hose stream works
my understanding is tha the fire truck will hook up to fire hydrant and use their hose using the fire truck pumper
is that right

 

[Oremus]

See nfpa #13 11.2.3.1.2 ('07 ed).

In your case lets say you're going with the 250 hose stream allowance. That is a combined allowance meaning a combination of inside hose and outside hose. If you have more than one hose station inside your building the max used would be 100 gpm and the difference would be required to be flowing at the source node or hydrant if it's located in the fire line piping.

So you would have 100 gpm inside hose and 150 outside hose (250 total for ord. group 2).

However, you said this is hooked up to a storage tank. If the storage tank is dedicated entirely to sprinklers you would just have to worry about the inside hose demand since a fireman's draw off the line wouldn't affect your dedicated water supply unless the pump is feeding a hydrant downstream.

Your understanding on outside hose is correct. The required GPM differs with hazard classification. The presence of hose stations or connections changes the rules a little since some of the hose allowance will be inside and some outside - accounting for someone using a hose station inside the building as well as the fire dept' outside using their hoses.

 

[farid2176]

Thank Oreamus

 

[PEDARRIN2]

Watch your tank size also.

I had a tank I sized for 3 hoses in the building so I sized my tank at 30,000 gallons (1000 gallons per minute for the 3 hoses and 30 minutes for a building that is mainly light hazard).

The sprinkler contractor came back with an ordinary hazard zone with a hydraulic calc that indicates 700+ gpm which is required to be calculated for 60 minutes - thus they want a 42,000 gallon tank.

We are having to go through extra effort to show that the fill for the tank will keep the fire pump running to provide teh 42,000 gallons for the zone.