Well, the 60 second rule pre-dates the software by a LONG time, so I there's no TFP#13 where a code change triggered or mandated sales. And nothing in #13 requires the use of the software. We look at it as working smarter and managing the risk of having to add a DPV during acceptance tests or being able to reduce # of dry valves as much as being able to escape some last day acid test you pass of fail.
I'm not aware of any significant failures of dry systems beyond the usual # of fires that come to my attention from casually coming across them, I don't scan the web for fire news in my free time because I really don't have much of it. I think of FDT more like back when you had the option of pipe schedule vrs calc'd- say late 70's to early 80's- when if you saw a new system with 8" riser you knew the water pressure was bad or they's have calc'd it. If they didn't have calc software, they saved money on software/pc/operators and installed 8" risers (hmm, I see a parallel). Data? This industry doesn't need no stinkin data. Only in the last couple years (AT CONVENTION, AT 2AM) did I learn the basis of the area-density tables in 13 were simply "let's run a test, plot the results that worked, and then draw a line either side at +37% and -37% (exact values escape me now) and that got carved in stone and we've all trusted it for years as if it were based on a significant amount of testing or modeling. And the fact that the systems have performed pretty darn well for decades means they got it right- even if it was by accident or good guessing. Seriously, we do have Data. We seem to either rigorously apply something so old we don't know where it came from (52,000 SF per system) or we have calc programs taking accuracy to .0001 but nobody took the 15 PSI tank gradient drop into consideration. Fires don't start in 1.2xMRA rectangles, commodities change over time, ITM gets missed, cut, or results aren't compared with the past, and some of the badge-heavy think this is a perfect science when all we can possibly do is provide a reasonable level of protection and hope it works when and if needed. Many of us need to take a step back and look at the big picture. Pipe scheduled systems saved a lot of buildings back when we didn't know what we know now, and anyone who's tried a reinforcement no longer even tries to keep the 1' when piecing together a grid from adjacent trees, and if it isn't LH, toss the 1.25" also. But the application of perfect to an imperfect and fluid world is silly. Had a spec on a job we bid today require we pitch the piping downstream of the main drain valve at 1/16" per foot, I forget what the rest of the system was to do but there were criteria. What were we to measure from? If we're trapped below grade in a basement, did it really matter, it goes in a bucket. Funniest part of this LONG spec was how good it must have sounded in the polished ivory tower when written; but the application is hilarious- THEY ARE DEMO'ING AN OLD BOWLING ALLEY IN AN OLD BUTLER BUILDING AND INSERTING A SURGERY CENTER IN THE SHELL!!! So how could 1/16" pitch be something in the relevant range of accuracy when the floor slope, steel sag, etc are all 100x off compared to 1/16" for anything in our world? -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Ron Greenman Sent: Wednesday, June 17, 2009 6:44 PM To: [email protected] Subject: Re: Slow responding dry pipe valves-FDT So what drove the change from the old way of working trip times (under 500 gal. all was good, 500-750 gals. and either 60 seconds or QOD, over 750 gals. QOD and all is good)? was it due to systems failing due to too long trip times or was it a way to sell an expensive computer program? If due to failures did it happen in a cross section of buildings or in certain types of buildings and if the latter is it necessary to treat all systems equally? Certainly requirements to trip test everything to 60 seconds in years past was based on local requirements arrived at collectively by AHJs because they wanted it and it was complied with enough to become the usual thing to do until it became codified--first locally and then in 13. Where's the data that supported this costly change at point in this migration from what 13 said to what it says now? Enquiring minds want to know. On Wed, Jun 17, 2009 at 1:08 PM, George Church<[email protected]> wrote: > To address Mike's concern about trip time, the QRS switch is pretty > dependable- it samples the air pressure every .1 seconds and after enough > degradation is detected 3x in a row, it trips. We input 3.5 second trip time > _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
