Pipe Schedule System - Amount of Sprinklers

[EricP2005]

Hello,

I am currently making a modification to an existing wet pipe sprinkler system that utilizes the pipe schedule layout. I am very experienced in the design and layout of fire sprinklers, and have been employed in the industry for over 10 years. I am, however, currently blanking on the subject. The light hazard system chart in NFPA 13 23.5.2.2.1 specifies the number of sprinklers allowed per pipe schedule standards; in this chart, 1½" pipe is shown to allow 5 sprinklers. The system I am currently working with is supplied with a 4" wet standpipe and each floor utilizes a 2½" crossmain to supply the branchlines.

My question; in a branchline run, starting with an 1½" pipe size,can that entire branchline only allow 5 sprinklers total, with the reduction of pipe down the line, or are 5 sprinklers allowed on the 1½" section and as the pipe size reduces, those sections can supply the number of sprinklers specified in the table? The reason I ask to clarify, is the existing system has many instances where the 1½" pipe starts the line and there is 6 or more sprinklers on the line; and the two final sprinklers are supplied by 1" piping.

Thank you in advance.

 

[TravisMack]

1½" pipe can only have a max of 5 sprinklers downstream. If there are 6 or more, it has been re-worked and the pipe schedule was broken, or it was hydraulically calculated.

Many people fail to realize that you can't just add a sprinkler to a pipe schedule system without check everything upstream and downstream.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[EricP2005]

TravisMack,

That was my thought as well, I just wanted to verify with some others as well. I appreciate the response.

Thank You!

 

[EricP2005]

Is there something that allows more sprinklers to be placed downstream when they are separated by fire rated walls?

 

[TravisMack]

No. A pipe schedule is just that. Start from the end sprinkler and go back. If you overload at any point, then you have broken the pipe schedule and you must calculate it. It could be Pandora's box.

Rated walls only come in to play when you use the room design method for calculations. But with a pipe schedule system, you don't get that.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

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

 

[MatthewJWillis]

On the flipside...

How much would you spend to calculate the system using today's technology?
Depending on system size, it could save you $$$ overall. Not to mention the added benefit of providing the owner the calcs which would be of benefit later..

R/
Matt

 

[MGXFP]

Not all pipe schedule systems will work using hydraulic design criteria. Also many are old or very old and deciding the C factor for the pipe is a hurdle to overcome.