Another thing to consider with safety margins is that too much pressure can be a bad thing too. We frequently deal with jurisdictions in the Phoenix Metro Area that have a “maximum flow test” that you can use. For example, there is one that limits us to 80 psi static. If our water supply is, say, 100 psi static (somewhat common in these areas) we have to reduce the static and residual pressure by 20 psi for our calcs. But we have to account for the real pressure available when looking at maximum pressures allowed. That “safety margin” of 20 psi or more can lead to a lot of “unused” pressure and/or pressure reducing valves that would not normally be required.
But, then again, we have some pretty large seasonal fluctuations in available pressure in some areas as well. It’s probably best to just leave it up to the local AHJ to determine what they think is best based on what they know about the water supply. Although I would support a code-mandated minimum safety margin of 10%, knowing the local AHJs would require larger margins if they deemed necessary. Of course, knowing how some of them think, they might be perfectly happy with 10% now, but if that were in NFPA 13, they would probably want another 10% on top of that. -Kyle M From: Sprinklerforum [mailto:[email protected]] On Behalf Of Bruce Verhei Sent: Friday, June 15, 2018 12:26 PM To: [email protected] Subject: [EXTERNAL] Re: Safety Margin As plan reviewer any authority I applied was adopted codes, including standards adopted by ordinance through codes. Also I was expected to pass on local conditions that a designer working in a much bigger regional area would not have at fingertips. Calculation to the right of the curve is code complying. Rare exception might apply if it is known or reasonable to expect pressure/flow curve to degrade at a given point. I only remember this applying at one isolated area. (See recent talk about tank sizes). This would have been supplied to project team at first meeting, with near complete surety that information would not be passed onto sprinkler bidders. Hydraulically calculated systems all have safety factors built in. Somewhere I had to take a test that I had to list five or seven. Two that immediately come to mind are: Test setups at FM’s test building, and later UL’s, are designed to maintain as much as they can a constant pressure at the heads as more heads open. In our world the first couple heads flow more at higher pressure than the minimum design flow when all heads in the calculated area are flowing. Another is that the every part of the system outside the worst (selected, calculated) part of the system has better flow/pressure, although with grids delta is often not much. We did not include by ordinance a safety margin. So I can’t understand authority to require one. Again above example where we knew an area was going to lose one end of a loop, and become a long dead end (~3,000’) during major road construction. Best. Bruce Verhei On Jun 15, 2018, at 11:59, Parsley Consulting <[email protected]<mailto:[email protected]>> wrote: 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<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.parsleyconsulting.com_&d=DwMFaQ&c=wn3mZQLIuInh2ClcJ0_DIA&r=Z_2A85VL7AQzoqudh6uOyS3bn8etxB7nLN8OBJwQd9A&m=1ijig43TftozXhrOSGBx_6O4wV3KFggwpSfaG0bngN8&s=TRW4ZQ5yhOmJnYpqetg0JT55DXLYuw3KOBFaVssPgCE&e=> 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 <image001.jpg> <image002.png> 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<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.parsleyconsulting.com_&d=DwMFaQ&c=wn3mZQLIuInh2ClcJ0_DIA&r=Z_2A85VL7AQzoqudh6uOyS3bn8etxB7nLN8OBJwQd9A&m=1ijig43TftozXhrOSGBx_6O4wV3KFggwpSfaG0bngN8&s=TRW4ZQ5yhOmJnYpqetg0JT55DXLYuw3KOBFaVssPgCE&e=> 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<https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.firesprinkler.org_listinfo.cgi_sprinklerforum-2Dfiresprinkler.org&d=DwMFaQ&c=wn3mZQLIuInh2ClcJ0_DIA&r=Z_2A85VL7AQzoqudh6uOyS3bn8etxB7nLN8OBJwQd9A&m=1ijig43TftozXhrOSGBx_6O4wV3KFggwpSfaG0bngN8&s=7hoxXWo6cVgn00pCF5w9IVnnoW669lTJNuBVhrhvhw4&e=> _______________________________________________ Sprinklerforum mailing list [email protected]<mailto:[email protected]> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org<https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.firesprinkler.org_listinfo.cgi_sprinklerforum-2Dfiresprinkler.org&d=DwMFaQ&c=wn3mZQLIuInh2ClcJ0_DIA&r=Z_2A85VL7AQzoqudh6uOyS3bn8etxB7nLN8OBJwQd9A&m=1ijig43TftozXhrOSGBx_6O4wV3KFggwpSfaG0bngN8&s=7hoxXWo6cVgn00pCF5w9IVnnoW669lTJNuBVhrhvhw4&e=> _______________________________________________ Sprinklerforum mailing list [email protected]<mailto:[email protected]> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org<https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.firesprinkler.org_listinfo.cgi_sprinklerforum-2Dfiresprinkler.org&d=DwMFaQ&c=wn3mZQLIuInh2ClcJ0_DIA&r=Z_2A85VL7AQzoqudh6uOyS3bn8etxB7nLN8OBJwQd9A&m=1ijig43TftozXhrOSGBx_6O4wV3KFggwpSfaG0bngN8&s=7hoxXWo6cVgn00pCF5w9IVnnoW669lTJNuBVhrhvhw4&e=> _______________________________________________ Sprinklerforum mailing list [email protected]<mailto:[email protected]> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org<https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.firesprinkler.org_listinfo.cgi_sprinklerforum-2Dfiresprinkler.org&d=DwMFaQ&c=wn3mZQLIuInh2ClcJ0_DIA&r=Z_2A85VL7AQzoqudh6uOyS3bn8etxB7nLN8OBJwQd9A&m=1ijig43TftozXhrOSGBx_6O4wV3KFggwpSfaG0bngN8&s=7hoxXWo6cVgn00pCF5w9IVnnoW669lTJNuBVhrhvhw4&e=>
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