FWIW - Years ago with an older backflow, we did a forward flow test and measured pressure drop across the device. 6" backflow, 500 gpm flowing and a 38 psig loss. Investigation showed this backflow had issues. Once cleaned and repaired, all was normal.
I always thought the intent of the 25 requirement was to check the pressure loss across the device and compare to manufacture's data. But I was quickly corrected in discussions with 25 committee members. All they were looking for was to "exercise" the device. No pressure loss measurements were required. John -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Todd - Work Sent: Tuesday, June 23, 2015 6:21 AM To: [email protected] Subject: Re: BFP_Compare_Roland John, That sort of is my point. I have heard of BFP issues with ITC flows as well. My question is what new problems are we going to learn about at full flow that would not show up at ITC or 2" drain flows? Todd G Williams, PE Fire Protection Design/Consulting Stonington, CT www.fpdc.com 860-535-2080 (ofc) 860-608-4559 (cell) Sent using CloudMagic [https://cloudmagic.com/k/d/mailapp?ct=ti&cv=6.0.64&pv=8.2] On Tue, Jun 23, 2015 at 5:59 AM, [email protected] <[email protected]> wrote: Todd, I can add cite two instances where the first check of a BFP was too tight at single head flow (low flow) causing the waterflow switch to cycle therein never reaching the retard and never tripping the alarm panel. This was found by conducting a proper waterflow test thru the ITC with the smallest K head in it. The BFP manufacturer was contacted and as happens often enough, the by the way answer comes out about using a special first check for low pressure water systems. Once swapped out worked like a charm. The moral to this story, never ever test a waterflow switch by simply removing the cover and moving the vane arm by hand. We do forward flow BFPs per 25 and have yet to see one hang. But I'm sure that day is coming. John Drucker - Mobile Email Assistant Construction Official Fire Protection Subcode Official [email protected]<mailto:[email protected]> Cell/Text 732-904-6823 Todd - Work <[email protected]> wrote: I wouldn't mind hearing this as well. I would think that between inspector's test flows, 2" drain flows and annual backflow preventer tests (required by states), that the health of the BFP would be sufficiently determined. Of course in Light/Ordinary Hazard situations, the 2" drain could discharge system demand, so the requirement would be met. Perhaps a full flow as part of an acceptance I could understand. Have there been any instances where there has been a backflow preventer failure at full flow and not at a lower flow? Todd G Williams, PE Fire Protection Design/Consulting Stonington, CT www.fpdc.com<http://www.fpdc.com> 860-535-2080 (ofc) 860-608-4559 (cell) Sent using CloudMagic [https://cloudmagic.com/k/d/mailapp?ct=ti&cv=6.0.64&pv=8.2] On Tue, Jun 23, 2015 at 1:55 AM, [email protected] <[email protected]> wrote: Something I have failed to understand, and would appreciate if someone can enlighten me. The forward flow test is required at the full system demand, presumably to check the operation of the BFP. If the test shows that the BFP will open at system demand, what guarantee is there that it will open at a lower flow. I would think higher the flow, greater the force and easier to open the check valves. Or am I missing something? Tony ----- Original Message ----- From: "Brad Casterline" <[email protected]> To: [email protected] Sent: Monday, June 22, 2015 10:42:17 AM Subject: RE: BFP_Compare_Roland Hello Forum, Two weeks ago I said: "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 :)." Here is a summary of the more exhaustive comparisons for the 2" and 2 1/2" Main Drain scenarios: https://www.dropbox.com/s/1tqp42gqdpxum04/BFP_Compare_Roland.pdf?dl=0 and here is the link to the issue of Roland's article: http://digital.turn-page.com/i/127056-may-2013 I added (5) quantities to each calc: 1) velocity 2) HW pf/ft 3) DW pf/ft 4) HW va eq len 5) DW va eq len Looking at 4) and 5) you might see why I said, "My concept of K-Value and Pf and equivalent length being proportional to v^2 was exactly backwards." I hope a Forumite or two finds this kind of thing as interesting as I do!!! Thanks, Brad Casterline AFSA Designer Member and SET _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
