We are working on a new (750 gpm) standpipe system.
When testing and setting the field adjustable 2-1/2" PRV hose valves, do you set each one flowing 250 gpm while also flowing 500 gpm elsewhere, to account for the hydraulically calculated design (i.e. lower inlet pressure per NFPA 14-22.214.171.124)?
Or do you just set each one only flowing 250 GPM by itself?
Thanks in advance.
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1/9/2023 08:02:11 am
Our testing/Cx went as follows:
1/9/2023 08:11:59 am
I like Dan's method. Very comprehensive. We typically just set ours based on 250 gpm of flow. I think the conversation that Dan had with the fire department becomes even more important when you are outside of the responding departments pumping capacity/elevation. Great question.
1/9/2023 08:31:30 am
it needs to be set by the flow expected downstream of the device
1/9/2023 09:00:15 am
I second Dan's approach.
1/11/2023 01:15:51 pm
NFPA 14 requires automatic class 1 standpipes to provide 100 psi during the full system demand flow not just 250gpm. It clearly states that the hose valve manufactures friction loss should be used in determining the loss through the valve. The PRV manufacturer selection spreadsheet should use the highest anticipated static pressure (static pressure during pump churn) and the lowest anticipated residual pressure ( full NFPA 14 system flow plus friction loss) . In other words the PRV setting should be chosen based on that valve being the last 250gpm of the total system flow. If you dont choose your PRV setting using a similar method you will create a lower floor with a hydraulically more remote demand. Ken Isman's Standpipe Handbook explains this dilemma well.
1/12/2023 03:48:02 pm
Bobby, In practice to account for the NFPA 14 lowest anticipated residual pressure, do you flow the extra 500gpm when setting the PRV for acceptance testing to drop inlet pressure on the tested PRV? Or do you set the PRV based on the manufacturer curve using the hydraulic calc info, and then just flow test the PRV at 250gpm for acceptance testing?
1/19/2023 10:35:16 am
Brian we require the calculation and valve selection proving that the valve works during full system flow and then we do the acceptance test at 250gpm unless that PRV is one of the hydraulically most remote valves in the portion of the building where the standpipe acceptance flow test will occur. In which case the PRV is flowed as part of the full 750/1000 . For example a few days ago we were acceptance testing a high rise building that has only 2 risers in the upper floors but 3 risers in the lower floors. The lower floors with 3 stairwells have PRVs so those floors flowed their highest PRVs at 4 valves at 1000 gpm and then the roof without PRVs flowed 750 through standard valves.
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