Sprinklers and Fire hose served by same piping 1

[PeterStahl]

Hello,

maybe its a strange question, but a colleague told me that in general here the fire suppression plumbing is one piping serving both sprinklers and fire hoses.
Now we saw a project where we have two pipings, one for the sprinkler and one for the Fire hose.

I was asked if this procedure is correct regarding NFPA.

As its a predesign its not sure which NFPAS will be demanded.

From what I know (from Germany) there is always a separate sprinkler and fire hose line, and I guess it would be against DIN/VDI regulations to run both by one piping.
F.e. in the case of a fire:

- sprinklers would take away the pressure of the fire hose
- turning of sprinklers would end in turning of the fire hose
- the calculated and needed pressures would have to fit for both sprinklers and the fire hoses.

What is your opinion on this topic? Does the NFPA standards say anything regarding this topic?

Thanks in advance

 

[TravisMack]

It is very common to run combination standpipes. They are calculated independently. Look in NFPA 14 for descriptions of and how to design combination standpipes.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[Artisi]

Guess reading the standard would have answered your question.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[rfp2015]

500 gpm stand pipe @ 100 psi....250 additional gpm @ same 100psi for every additional standpipe... 4 in pipe minimum...

if combination system, 500 gpm @ 100psi...plus above additional if additional stand pipe is needed, then add hydraulic calc for sprinklers.... pipe riser is minimum 6in FOR COMBINATION SYSTEM ...do code analysis

 

[TravisMack]

The above is not fully correct. 4" pipe is permitted for standpipes if calculated for such when the building is protected with a fire sprinkler system.

7.6 Minimum Sizes for Standpipes and Branch Lines, Class I and Class III Standpipes.
7.6.1 Standpipes shall be at least 4 in. (100 mm) in size.
7.6.2 Standpipes that are part of a combined system in a building that is partially sprinklered shall be at least 6 in. (150 mm) in size.
7.6.2.1 Where the building is protected throughout by an approved automatic sprinkler system in accordance with NFPA 13 or NFPA 13R, the minimum standpipe size shall be 4 in. (100 mm) for systems hydraulically designed in accordance with 7.8.1.

Note that 7.6.2.1 is a clarification or addition to 7.6.2. In the older versions, 7.6.2.1 was called an exception to 7.6.2. But, with the new writing style for the standard, the exceptions have been removed.

Also, you don't add standpipe and sprinkler demand. They are independent calculations, unless you have a partially sprinklered building. You should refer to 7.10.1.3 Combined Systems for clarification of that issue.

The true calc is 250 gpm at the top two hose valves on the remote standpipe..If you figure the flow at the outlet on the standpipe, then you will not be accounting for about a 7 psi loss between the valve, nipple and tee outlet.



Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

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