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]] 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]<mailto:[email protected]> 828-696-3400 828-696-2288 Fax 828-708-9118 Mobile [cid:[email protected]] [cid:[email protected]] From: Sprinklerforum <[email protected]><mailto:[email protected]> On Behalf Of Parsley Consulting Sent: Friday, June 15, 2018 1:22 PM To: [email protected]<mailto:[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]] On Behalf Of [email protected]<mailto:[email protected]> Sent: Thursday, June 14, 2018 5:46 PM To: [email protected]<mailto:[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]<mailto:[email protected]> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected]<mailto:[email protected]> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected]<mailto:[email protected]> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
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