Hydraulically Calculated Pipe Diameters for Fire Fighting Networks 4

[solidspaces]

I am searching for the software to calculate hydraulically the pipe diameters of the firefighting network for extra hazard classification of the sprinkler system as per NFPA.
The sizing is to be calculated hydraulically and not by the Pipe Schedule System of NFPA.
In Chapter 13 of NFPA there is an example of the Hydraulic Calculations, but I believe that is only to size the Pump Capacity for the remotest area of sprinkler activation and that procedure does not give the pipe sizes for the rest of the network.
Some of the Software Companies that I have consulted contend that they have the software for the entire network but the pipe sizes must be entered from the Pipe Schedule System. This is puzzling given that the very purpose of going to the software is to calculate the diameters hydraulically without any reference to the pipe schedule system.
Please shed some light on this subject and recommend some software that could do the needful. Thanks.

 

[BigInch]

That's not the way hydraulics works. There aren't any magic silver bullets.

To make pipe design practical you must make some initial assumptions, as follows

Spacial position of each sprinkler
Location of the source(s) of water
Location of pump(s)
Topological configuration of the piping system (network)
Determine the length of each pipe
Material of each pipe (roughness)
Inlet pressure at your sources and/or outlet pressures at all sprinklers
Assume a Diameter of each pipe.
Required flows out of each sprinkler.

With the above information, you will determine the pressure losses and find out the flows possible at each sprinkler. You will change the pipe diameters and inlet and/or outlet pressures and the pump, and/or change the piping configuration as necessary to ensure that you have the correct flows issued by each sprinkler.

Maybe what you really want is to hire an engineer that understands all of that. Otherwise get some training in it yourself, which is better done before you start trying to buy magic silver bullets.

 

[solidspaces]

Thanks a lot for the methodology involved.
The pipe schedule system of pipe sizing is fairly straightforward, and there is no need to use any software for that.If the hydraulically calculated pipe network requires input of the pipe diameters that are taken from the pipe schedule system table developed by NFPA, then one could simply size the system without the software.
I appreciate your response but I am still waiting to hear someone say:
YES WE NEED TO ASSUME THE SAME PIPE DIAMETERS AS IN THE PIPE SCHEDULE TABLES OF NFPA,
OR
WE CAN PLUG IN PIPE DIAMETERS AS ZERO, BUT THE PROGRAM WILL OUTPUT THE REQUIRED DIAMETERS…..

 

[BigInch]

Commonly available programs do not iterate past the first pass, what I told you already. There are some experimental programs that will do everything, but they run forever and rarely result in a practical solution.

Just use the canned scheduled pipe diameters in the programs and be happy you don't have to deal with impractical computer generated results. That would require more work then a skilled designer could do in pass #1.

 

[solidspaces]

Thank you BigInch and please do recommend any particular software that you found to be good.

 

[solidspaces]

One more piece of information. The branches closer to the pump would require smaller pipe diameters from those that are listed in the Pipe Schedule System due to higher pressures near the pump. It therefore appears a waste to use pipe sizes that just depend on the count of sprinklers without regards to available pressures.

 

[BigInch]

Can't recommend software for fire protection; I don't use it. I just know the methods that most all other hydraulic design software choose to operate.

 

[Artisi]

I second BigInch's comment re engage a competent engineer who understands sprinkler systems. You also need to bear in mind that pipes come in standard sizes, therefore there is always a compromise in size selections.

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.)

 

[BigInch]

Solidspaces,
Segments near the pump discharge normally have higher flows, thereby requiring largest diameters, as full source flow has usually just been pressured up and flow has yet to be split amongst any laterals running to the sprinklers.

 

[solidspaces]

Thanks to all respondents. I wrote earlier that the software has been acquired and it is functioning well without the need to borrow values of pipe diameters from the Pipe Schedule System. This thread can now be considered to be complete and closed.
Thanks again to BigInch, Artisi.......and all.