Sprinkler K Factor & Flow Through Sprinkler Head

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Prepared by S M Afreen Ali ( BS / MSc in Engineering)

Sprinkler K Factor & Flow Through Sprinkler Head

Generally the NFPA 13 "K factor" for Sprinkler is K=5.6 (Ordinary Hazard )

Generally sprinklers are 1/2"  connection size.   

You can't use less than 5.6 k for Ordinary hazard. 

 In light hazard, you can go down to 2.8 k before you need to put a strainer on the line.

Many sprinklers are rated with a K factor that describes their performance. This is defined as:

Q = K √(P) 

Where:

Q – flow in gpm

K – nozzle discharge coefficient of K-factor for head in gpm/psi

P – pressure in psi


P- 40 psi ( 2.76 Bar)

K- 5.6

Q = K √(P) 

Q = 5.6 √(40)                    note *  5.6 X  6.32

Q = 35.41 gpm