I don't think we can predict that Brad, but pipe sizes were much bigger in those days, weren't they? If I had to guess, I think the safety factor would be "more" if the available pressure was higher and "less" if it was fair-to-poor.
Regards, Steve Leyton -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of [email protected] Sent: Monday, June 18, 2018 3:59 PM To: [email protected] Subject: Re: Safety Margin My last two cents (i guess i started it and Roland is nudging toward an end): A calculated system is simply a reconfigured pipe scheduled system, i.e., make the second piece 1-1/4 and get rid of the 8". Before calcs,5 heads on 1-1/2" was 'right on the curve'. If that was changed to 4, how much safety margin is that? Brad Quoting Ben Young <[email protected]>: > Most of our work in done in Delaware where the 10 PSI safety margin has > been in place since before I started. I guess I take it for granted > anymore, and we have what I would consider not-great water. You're not > likely to get anything above 50 PSI static anywhere in the state. Maybe 60 > if you're lucky. > Flows are in the 1000s. But I seriously don't even notice it anymore. I try > and shoot for 15-17 PSI to give our fitters some cushion for minor field > variations, but sometimes you can't do that and you have to live with 11 or > even 10.1. That 10 PSI isn't for field changes either, its specifically for > water supply degradation and fluctuation. > > Its interesting to hear about the water level being lower in the winter > too, winter flow tests here are always 3-4 PSI higher and have better flow > vs the summer. I have been seeing a lot of single hydrant flow tests > lately which is troubling. > > I mean at the end of the day, 13 will get modified or overwritten by the > building code adopted or some other ordinance or legislative change, so why > is this any different? States and towns have been deleting adding and > modifying sections of code forever, so if your local jurisdiction doesn't > like the 10 PSI, just change it when its adopted. > > > Benjamin Young > > On Mon, Jun 18, 2018 at 1:20 PM, Daniel Arnold <[email protected]> > wrote: > >> But Horror stories have been the basis for ‘safety margins’ in our codes >> and standards since their inception... including NFPA 13. >> >> There have been amazing strides made in understanding and quantifying >> the dynamics of sprinkler performance, limitations, etc. over the past 30 >> years and incorporating that knowledge into NFPA 13. A defined safety >> factor in hydraulic calculations is but one logical step in the continuing >> maturation of 13 and will eventually be in the standard. The more useful >> discussion is how it should be quantified and Incorporated. I agree with >> Scott and share his experiences....NFIRS stats are not helpful in >> justifying technical stagnation. >> >> I absolutely understand and agree with the position that a safety factor >> is already baked in the standard but what is it? Saying it’s “enough” >> without being able to eventually define it doesn’t help further progress. >> >> ... 2 cents from a lurker (usually 😉) >> >> Daniel Arnold, PE, FSFPE >> Seneca Fire Engineering, LLC >> Atlanta, Georgia >> >> Daniel L. Arnold, PE, FSFPE >> Sent from my iPhone >> >> On Jun 18, 2018, at 11:34 AM, Mark Sornsin [FAR] <[email protected]> >> wrote: >> >> All of the horror stories in the world do not change the fact that >> requiring a specific safety margin for calculations is difficult to justify >> in an internationally recognized standard. I could see Annex language >> offering pros for a margin and maybe giving examples of when one might be >> considered. >> >> >> >> In my view it’s the responsibility of the person engineering the system to >> make this call. In this industry 99% of the time that is the designer >> working for the low-bid contractor. The designer who may or may not be >> NICET certified, depending on the rules of the jurisdiction in which they >> are working. The point is the person with the most knowledge of the local >> conditions should be making this call. In an ideal world, when you have >> someone specifying the design parameters for a bid project, it would be the >> specifying engineer. I also realize that this is fantasy 98% of the time, >> which is a stain on the engineering profession, but that’s a different >> rant. We can’t expect to codify a requirement like this in a standard that >> needs to apply throughout the world. It would require specific numbers and >> these will vary on local conditions. Instead it is the engineer/designers >> responsibility to become familiar with local conditions and adjust >> accordingly. The example of reduced water levels in municipal water towers >> is a great one. Not all cities engage in this practice, but where they do >> the designer needs to know what the minimum static pressures can be. Or >> the local reviewing authority needs to adopt specific requirements to match >> their local conditions. >> >> >> >> But the real problem comes when a contractor is bidding on a job with no >> real engineering guidance and no local amendments to account for special >> local conditions. The low-bid contractor or will be the one who assumes >> their water test is valid despite having taken it at the highest possible >> pressure of the day/season. And a specific safety margin requirement in >> NFPA 13 cannot guarantee proper correction for this error. >> >> >> >> <image1fad98.JPG> <http://www.SummitCoUS.com> Mark Sornsin >> Sr. Fire Protection Engineer >> Direct: 701-499-1391 >> Cell: 701-526-8585 >> >> *From:* Sprinklerforum [mailto:[email protected]. >> org <[email protected]>] *On Behalf Of *Scott >> Futrell >> *Sent:* Saturday, June 16, 2018 9:51 AM >> *To:* [email protected] >> *Subject:* RE: Safety Margin >> >> >> >> As a plan specifier, plan reviewer and an investigator I see designs right >> to the supply and then as-built conditions far worse (read more demanding) >> than the design submitted with the calcs. This is not a regional >> observation. >> >> >> >> Additionally, I am aware of communities that lower elevated tank levels >> 20’ in winter to lower heating costs. Contractors in those areas do NOT >> adjust flow tests for this seasonal variation. >> >> >> >> No safety margin what-so-ever in NFPA 13 is unreasonable for a design >> standard. >> >> >> >> Arguments on the floor including ‘requiring all systems to have back-up >> power’ were ridiculous. >> >> >> >> Scott >> >> >> >> Office: (763) 425-1001 x2 >> >> Cell: (612) 759-5556 >> >> >> >> *From:* Sprinklerforum [mailto:[email protected]. >> org <[email protected]>] *On Behalf Of *Steve >> Leyton >> *Sent:* Friday, June 15, 2018 2:16 PM >> *To:* [email protected] >> *Subject:* RE: Safety Margin >> >> >> >> That was the conversation on the floor of the code hearing. The concerns >> underscored by the CAM were not about whether safety factor is a good >> practice, it was that a fixed minimum value as high as 10 PSI could trigger >> all sorts of cost-impact consequences, particularly in areas where >> pressures are middling to poor – in Rhode Island, 10 PSI could be 25-30% of >> the available pressure. >> >> >> >> In the West, due primarily to the politics of drought, water districts are >> using models in lieu of physical flow tests. Prudent and conservative >> programming makes it possible for them to issue safeguarded values from >> which it’s not necessary to reduce the available pressure. For ex., City >> of San Diego uses a three-level safety factor in their (highly accurate) >> models: starting with legacy drought water levels in the reservoirs, then >> factor the highest seasonal demand, then the highest peak day demand of >> that season. The values we’re getting are usually significantly lower >> than what can be measured on the hydrant, and this practice isn’t without >> controversy because there are obvious complications that can and do occur, >> particularly with existing systems based on 20-year old (and older) >> pressures that were physically measured (with crappy equipment) when first >> designed and built. >> >> >> >> But if modeling becomes the new normal, prudent water district engineering >> departments and fire departments they serve can coordinate manipulating >> data to include reasonable safety factors. The range of variation in >> pressures, accuracy of flow test equipment, the use of modeling in many >> areas … there are too many variables to set a fixed minimum safety factor >> based on PSI, IMHO. >> >> >> >> SML >> >> >> >> *From:* Sprinklerforum [mailto:[email protected]. >> org <[email protected]>] *On Behalf Of *Parsley >> Consulting >> *Sent:* Friday, June 15, 2018 12:00 PM >> *To:* [email protected] >> *Subject:* Re: Safety Margin >> >> >> >> Richard, >> >> If my memory is accurate of the issues raised in the discussion that >> ambiguity was a part of the differing viewpoints. >> >> Some argued that 10 psi was not workable in their locale as their >> pressures were so limited that an imposition of 10 psi was simply to >> drastic and would result in much larger pipe sizes as a result. >> >> Others argued that 10 psi was not enough, and in their area 10 psi didn't >> equal 10%, and there was some reluctance to base their designs on a >> pressure greater than 90% of the available. >> >> It was quite a discussion. >> >> >> *Ken Wagoner, SET * >> >> >> *Parsley Consulting 350 West 9th Avenue, Suite 206 Escondido, California >> 92025 * >> *Phone 760-745-6181 Visit the website <http://www.parsleyconsulting.com/> * >> >> On 06/15/2018 10:23 AM, Richard Carr wrote: >> >> Even though it is not in NFPA most AHJ’s require some sort of safety >> margin, 10%, 10 psi which we have had to provide for a long time so most >> designers know to leave safety margin in the calc’s. it would be nice if >> they all used the same amount. >> >> >> >> Richard M. Carr, SET >> >> Project Manager/Design >> >> Diboco Fire Sprinklers, Inc. >> >> 325 Jackson Loop Road >> >> Flat Rock, NC 28731 >> >> >> >> [email protected] >> >> 828-696-3400 >> >> 828-696-2288 Fax >> >> 828-708-9118 Mobile >> >> >> >> <image001.jpg> >> >> >> >> <image002.png> >> >> >> >> >> >> *From:* Sprinklerforum <[email protected]> >> <[email protected]> *On Behalf Of *Parsley >> Consulting >> *Sent:* Friday, June 15, 2018 1:22 PM >> *To:* [email protected] >> *Subject:* Safety Margin >> >> >> >> Scott, >> >> Based on the material which was presented to the -24 and -291 committee >> meetings I believed the proposed safety margin and the means to calculate >> that margin there was some merit in the proposal. >> >> For reasons I don't quite remember the PI was voted down at the 2nd draft >> meeting. I listened to some of the discussion, and there were some good >> points made. I'm not terribly surprised it failed at the convention >> level. Perhaps the attendees were following the lead of the technical >> committees, and declining to overrule their decision. >> >> sincerely, >> >> >> *Ken Wagoner, SET **Parsley Consulting* >> >> >> * 350 West 9th Avenue, Suite 206 Escondido, California 92025 * >> *Phone 760-745-6181 Visit the website <http://www.parsleyconsulting.com/> * >> >> On 06/15/2018 8:09 AM, Scott Futrell wrote: >> >> Only that the 'safety margin' inclusion in the 2019 edition of NFPA >> 13 failed, so it won't be included or required. >> >> >> >> I consider this unfortunate, but I'd guess that not everyone on the >> forum would agree. >> >> >> >> Scott >> >> >> >> Office: (763) 425-1001 x2 >> >> Cell: (612) 759-5556 >> >> >> >> -----Original Message----- >> >> From: Sprinklerforum >> [mailto:[email protected] >> <[email protected]>] On Behalf Of >> [email protected] >> >> Sent: Thursday, June 14, 2018 5:46 PM >> >> To: [email protected] >> >> Subject: NFPA Vegas Convention >> >> >> >> I didn't make it again this year. >> >> "Caputo" is the only speaker name I recognized. >> >> Anybody have any earthshaking epiphanies? >> >> >> >> >> >> _______________________________________________ >> >> 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 >> >> >> >> >> ______________________________________________________________________ >> This email has been scanned by the Symantec Email Security.cloud service. >> For more information please visit http://www.symanteccloud.com >> ______________________________________________________________________ >> >> _______________________________________________ >> 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
