What did you calculate for an outlet? Just the manifold (5-10'), tee (5-15'), nipple(?) and valve (5-25')? At what flow per 2.5" outlet? 250 per? What happens when you put 50-75-100' of hose, playpipe, monster or meter on it? I'm sure the upsize rule is to minimize friction loss. If it's in the standard, it must be done.
Interesting thing I just noticed this afternoon. I just got home from an acceptance test just now. I used 4 digital flowmeters on a derby cap for a 1500 GPM diesel. They have pressure gauges on them for FDV testing. We had a gauge on the 8" to the derby with (6) 2.5" angle valves just inside the wall at the butterfly header valve. At 2250, we had a 16 PSI drop from the gauge on the 8" to the gauges on the meters. I thought that was substantial. We pretty much balanced the flow between the four meters but a drop that great was surprising to me. 3' of 8" to a derby (this is like a bullhead tee hydraulically I would imagine) and a 2.5x5 nipple and angle valve. 16 PSI at roughly 550 GPM. I thought this to be substantial and they all read the same and are almost new. Tom Duross Living Water Fire Protection, LLC 1160 McKenzie Road Cantonment, FL 32533 850-937-1850 Fax: 850-937-1852 This is from the 2007 edition of NFPA #20. 5.19.3.4 Pipe Size. The pipe size shall be in accordance with one of the following two methods: (1) Where the pipe between the hose valve header and connection to the pump discharge pipe is over 15 ft (4.5 m) in length, the next larger pipe size than required by 5.19.3.1.3 shall be used. (2)* This pipe is permitted to be sized by hydraulic calculations based on a total flow of 150 percent of rated pump capacity, including the following: (a) This calculation shall include friction loss for the total length of pipe plus equivalent lengths of fittings, control valve, and hose valves, plus elevation loss, from the pump discharge flange to the hose valve outlets. (b) The installation shall be proven by a test flowing the maximum water available. I just calculated a test header located approx. 65' from a 750 gpm pump and it seems to work easily with 6" pipe flowing 1,125 gpm in lieu of increasing the pipe to 8". Has anyone got experience using this method? Space is the issue and 6" works much better then 8" in this situation. Thanks, Greg McGahan _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
