Finding min psi or gpm

[CPleasant]

I am working on a project that requires the hydraulic calculation to have a 0.39/2600 density. I'm using HASS as my calc program and I can not input the density into the program. I need to get the minimum allowable end head condition in either psi or gpm. Heads are space 10x10 and are 5.6 k-factor.

 

[skdesigner]

Q=K(P^.5)

Q= (area) * (Density)

Therefore,

P= [(ad) / k]^2
P= [(100sq.ft * 0.39gpm/sq.ft) / 5.6] ^2

P= 48.5 psig required at the most remote sprinkler.

I don't use HASS, but it should derive Q from this equation. Otherwise, re-arrange and calc it yourself.

 

[skdesigner]

Purely as an aside...

Why not consider using a larger orifice sprinkler? 5.6 is pretty small to be pushing that kind of water through. Consider using an 8.0, 11.2, 14.0 etc. in your calcs. As you can see from the above calc, increasing the K factor (denominator in the pressure equation) will decrease the required end head pressure, while increasing the total flow required in GPM. Could make it possible to decrease pipe sizes, or even delete a fire pump.

 

[CPleasant]

It's an existing system, they want to use it to store tires in without changing the sprinklers in the area

 

[pipesnpumps]

>It's an existing system, they want to use it to store tires in without changing the sprinklers in the area <

Wow, good luck with that. Most of the older abandoned factories have a tank and pump set, is that the case here? The pressure is one thing, the onsite water storage is quite another.

I once tried to "find a home" for a displaced tire manufacturer; the fire protection was just one of the features that factored into the cost, but we looked at many many different existing spaces before finding one that worked for the sprinklers, and even then didn't get near the storage height they would have liked..

 

[KDLLC]

You don't mention the applicable edition of NFPA 13. The 2002 edition (that's the olded I have on my desk) and newer would require a K-factor of 11.2 or greater and be listed for storage applications. Reference section 12.1.13.3 in the 2002 edition. The owner may not want to change out sprinklers, but I don't believe that's an option.

Ed Kramer
Kramer Design, LLC

 

[CPleasant]

I believe that since they are not changing the building or sprinkler system they don't need to upgrade the heads. The company just wants to know what they're ability to store the tires is, if any.

 

[CPleasant]

Oh, and there are 8.0 K-factor heads, which makes the calc better, but still not good enough to work

 

[TravisMack]

You can buy retrofit heads where you have a 1/2" thread with a 11.2k orifice. That may help to salvage the lines. Changing out the heads is typically not near as expensive as changing out the lines when the sizes won't work.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[CPleasant]

They don't want to change anything, but I did get it to work, they just can't store the tires higher then 5'-0 in that area.

 

[stookeyfpe]

I won't touch this mess.

 

[SprinklerDesigner2]

Stookey is right as usual.

When I was young and brash I would go for this sort of work but have since learned the owner will stack to whatever height he wants and when there is a fire they will come after me as the last one who "touched it".

Given it is an older building and pipe schedule nothing you do will work.

I would be happy to install a brand new system. New heads, new pipes, new everything.

 

[MGXFP]

Egads. Moving tire storage in sounds like a powder keg just waiting to take your head off.

Sometimes the customer is wrong.