https://www.dropbox.com/s/dca8ixazzjo4jr2/BFP_Forward_Flow_fix.xlsx?dl=0
Dear Brad, You wanted feedback so here it is: Your spread sheet is WRONG! What you call "angle valve (ft)" is actually the friction loss in PSI. sincerely yours, you... Ha! I am so sorry Forum. My concept of K-Value and Pf and equivalent length being proportional to v^2 was exactly backwards. I fixed it and compared the results for a wide range of flows to the results in Roland's article and I will never bad-mouth Hazen, Williams, or Roland again :). I made diameter, length and fitting input easier (column K) and made a table of values for 1 1/4" through 2 1/2". I also added what I think is the most interesting thing (bottom middle)-- comparing HW to DW Pf/ft and C-Factor to Absolute Roughness. So as you vary Q GPM at B-10 and look at the velocity at D-10 you can see where DW exceeds HW. You can vary either the C-Factor or E (abs. roughness) at B22 until the Pf/ft is equal also. I think it is common hearsay that HW is based on 50 year old pipe. Well, the data I looked at shows abs. roughness = .004 inch at the high end of 'New Pipe' and at the low end of 'Lightly Corroded', if that means 50 years old then fine!! Now I feel really very good about it, and would welcome any data someone has. I think with enough pitot'd flows we could get a good C of D for a 2" 45!!! thanks, Brad _____ From: Brad Casterline [mailto:[email protected]] Sent: Tuesday, June 02, 2015 8:45 AM To: '[email protected]' Subject: BFP_Forward_Flow https://www.dropbox.com/s/atozznb9rc6bjor/BFP_Forward_Flow_.xlsx?dl=0 Dear Forum, Several recent posts prompted me to finally clean up a spread sheet I have been working on. I started it a couple of years ago with the intention of estimating the flow based on the main drain gauge drop. I apologize to those I have exposed it to in its various stages of 'half-bakedness', but I really feel good about it now, not for the original intent as much as for using it to estimate the flow through a BFP, along the lines of Roland's May 2013 Sprinkler Age article. I have come to appreciate more and more what Roland has said about the velocity being "self limiting"; most normal water supplies cannot handle consistently high velocities! But this is different because we "give her all she's got". So I used Darcy-Weisbach instead of Hazen-Williams, and for the angle valve I used the K-Value, which means the Pf (equivalent length) is ALSO proportional to v^2. This morning I thought about the recent post where the static at the riser is going to be about 72 PSI. I thought "Uhoh, Colin better use a 2.5" main drain to allow for forward flowing the system demand through the BFP because he has OHII, Dry, so .2*1950=390, *1.2 (overage)= 468 GPM. Figuring 2x5' + 1T, + 1E, + 1EE = 22', I stated adjusting the flow until I got 72 Pt (static at riser), and I think the best he could get from a 2" is 390 GPM. (to get 468 he would need about 125 PSI). Anyway, take it or leave it as you will and as always, any and all feedback on or off Forum is always appreciated. To continue to the original intent I would need half a dozen sets of data that included the gauge static and residual, the pitot'd flow, size, lengths, fittings, elevations, and riser size. (thanks again Jeremy!). wbr, Brad Casterline AFSA Designer Member and SET _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
