What is the foam friction loss (in head per 100 ft) and flow velocity for a 4:1 expansion foam flowing 130 gpm in a 2-1/2" schedule 40 pipe (with a c-factor of 100) most nearly?
a. 4.5 ft head/100 ft pipe and 4.75 ft/s
b. 8 ft head/100 ft pipe and 4.75 ft/s
c. 10 ft head/100 ft pipe and 4.5 ft/s
d. 30 ft head/100 ft pipe and 5.5 ft/s"
Solution | Posted 09/13/18
So much for trying to stump you all. As several people point out in the comments, the tables used to write this problem is not in the required reference material, so this problem needs to be scratched. NFPA 11 does address expanded foam velocities (see NFPA 11-2016 Figure A.184.108.40.206(a) on page 11-54).
On a side note, had the foam been a 1:1 expansion and Hazen-Williams been applicable, it could be solved by the Hazen-Williams formula or via the Hazen-Williams nomograph of page 1394 in the 5th Edition of SFPE.
Great discussion and feedback, keep up the great work everyone.
Subscribe and learn something new each day:
Top August '21 Contributors
Get 100 Days of Free Sample Questions right to you!
PE PREP SERIES