Sizing sprinklers cross main
Sizing sprinklers cross main
(OP)
Hi,
I have attached a sprinkler layout from NFPA 13. Can you tell me why the size of cross main after 10 branches has changed from 2-1/2" to 3"?
I think in hydraulic calculation, the criteria in sizing main branch is keeping the velocity and pressure in an appropriate range, so the number sprinklers does not matter. Am I right?
Also, is there any limit for the number of sprinklers on a branch? For example, can a branch consist of say 12 sprinklers?
Thanks
I have attached a sprinkler layout from NFPA 13. Can you tell me why the size of cross main after 10 branches has changed from 2-1/2" to 3"?
I think in hydraulic calculation, the criteria in sizing main branch is keeping the velocity and pressure in an appropriate range, so the number sprinklers does not matter. Am I right?
Also, is there any limit for the number of sprinklers on a branch? For example, can a branch consist of say 12 sprinklers?
Thanks





RE: Sizing sprinklers cross main
The reason for the change in size, because the 3 inch is actualy feeding the 2 1/2 inch
The riser is on the right side of the picture
RE: Sizing sprinklers cross main
I want to know is it still correct to keep the size of cross main 2-1/2 and unchanged entire the cross main?
I also would appreciate it if you shed some light on the rest of the questions I asked
Merci!
RE: Sizing sprinklers cross main
There is nothing in NFPA 13 that limits the length of a branch line. You are only limited to what you can calc.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
RE: Sizing sprinklers cross main
But like stated above most systems are hyrdaulicly . calculated