How to choose fire pump 1

[waterzoot]

Hi ! does somebody can help me ?
I want to know in witch NFPA Code I can find how to choose a fire pump and
water tank after having result of hydraulic calculation for sprinkler system
and hose demand.
Thanks

 

[TravisMack]

One question leads to several:

NFPA 13 gives water supply durations based on NFPA hazard classifications. Do you know that?
NFPA 20 is the standard on installation of fire pumps.
NFPA 22 is standard on tanks.

You mention hose demand. Is your hydrant upstream or downstream of your pump?

You really need to get someone that is competent to review everything you have. This is a life safety device. Do you really want to risk lives by stepping into an area where you are not fully experienced?

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[waterzoot]

In fact I've made a calculation and I want to size my pump.
My results are 522 m3/h (8700 lpm - 2300 usgpm) at 8,10 b (117 psi)
I decide to choose a pump 2500 usgpm at 125 psi.
Does it correct to do that saying that sprinkler demand (2300 usgpm) + hose demand(250 gpm for ESFR system) is less than 150 % of my pump rating (1,5 x 2500 = 3750)?
So if it's corect I decide to choose my tank like this :
1 hour for (sprinkler + hose demand) --> 1 x (2300+250) = 2550 us gallon = 580 m3

 

[TravisMack]

Do you have inside hose stations, or a hydrant downstream of your fire pump? That is one issue.

Why not a 2000 gpm pump at a pressure rating that will provide for your requirements.

How do you get 2300 gpm on an ESFR system? Is this a very high storage??

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[waterzoot]

Thanks for your help Travis.
Values I give are just for an example.
I've only inside hose station downstream of my pump.
I've choosen a rating pump of 2500 gpm because I thought that the flow of my
calculation point must be under the 100% rating flow of my pump.
It is not true ?
I don't find the explanation in NFPA 13 and NFPA 20

 

[TravisMack]

I was taught to size a pump at 90-120% of rated capacity. So, your 2300 gpm could be met by a 2000 gpm pump.

Then, just make sure you choose a pump with a curve that provides adequate pressure at your flow rate. You also want to make sure that your pump doesn't churn over the max working pressure of your components. ESFR sprinklers only rated for 175 psi, so you can't have a churn pressure of 175 psi at the lowest ESFR sprinkler. If you have pendent sprinklers in office ceilings, you need to watch for that as well.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[SprinklerDesigner2]

In the commentary found on page 140 of the 2013 NFPA #20 handbook:

Maximum system demand flow should be between 90% and 140% of pump’s rated capacity, but, in no case, greater than 150% of the pump’s rated capacity.

 

[LCREP]

If this is a FM job they like/want 100%, check with the insurance carrier if one is involved.

 

[waterzoot]

Thanks a lot for your answers my friends.
When NFPA speaks about maximum system demand, does it mean all systems downstream of the pump ? in my case Sprinkler (2300 gpm) + inside hoses stations (250 gpm) = 2550 gpm
so If it's rignt I can choose à fire pump of 2000 gpm (2000 x 1,4)=2800 > 2550
My thank capacity must be (for ESFR - 1 h)= (2300 + 250) x 1 h = 2550 gallons
Regards

 

[SprinklerDesigner2]

Waterzoot,

Yes, appears to be 2,550 gpm and 153,000 gallon tank minimum.

A 2,000 gpm pump would be near perfect unless perhaps it is an FM job but if so FM would have told you already.

 

[TravisMack]

I have a feeling that this is just an academic exercise based on your descriptions. But, you never answered if the pump supplies hydrants or not. If not, the most you need to figure for inside hose is 100 gpm. So, your demand is your ESFR + inside hose (100 gpm max). If your system demand is 2300 gpm and you have 100 gpm, then you have 2400 gpm demand on your pump. This would then let you get a 2000 gpm pump even at FM criteria of 120% max for pump capacity.

Yes, the details really do matter in these situations.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692