Be careful, is it really a "requirement" when the FMDS says "should" and not "shall"?
Craig L. Prahl, CET Fire Protection CH2MHILL Lockwood Greene 1500 International Drive Spartanburg, SC 29304-0491 Direct - 864.599.4102 Fax - 864.599.8439 CH2MHILL Extension 74102 [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Chappell, Carl Sent: Wednesday, December 29, 2010 10:24 AM To: [email protected] Subject: RE: USACE Velocity FM Global does have requirements on the friction loss equations that are to be used when the velocity exceeds a certain criteria. For FM systems, the use of Darcy-Weisbach is required if the velocity exceeds 30 ft/s; otherwise Hazen-Williams is the acceptable method for anything below 30 ft/s. This is in FM Data Sheet 2-0. The Hazen Williams method is not invalid at the higher velocities, from what I understand it somewhat loses it becomes less conservative in the estimates of friction loss. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Brad Casterline Sent: Wednesday, December 29, 2010 9:12 AM To: [email protected] Subject: RE: USACE Velocity Velocity restrictions are bad for dry systems-- huge capacities at the same time as demand is way under the curve. I was wondering why GSA would pay big money for something they want to last 100 years, but then not maintain it very well? -----Original Message----- From: Mark Sornsin [mailto:[email protected]] Sent: Wednesday, December 29, 2010 8:58 AM To: [email protected] Subject: RE: USACE Velocity One last thing to note about the velocity restrictions: their use helps to continue the myth throughout engineering circles that they are a necessity. I am certain most engineers who see a GSA spec with the velocity restrictions aren't thinking it is there merely to give a larger safety factor. Instead they are thinking things like :'high velocity is bad for pipes'; 'it is too noisy'; 'the H-W equation is invalid at high velocities', etc. So they continue to keep it within THEIR specs, which are seen by other engineers and AHJs - and the myths of velocity restrictions continue. And if there is a desire to keep the restrictions in place strictly for the more robust design, then please explain it in the specs, so the myths aren't promulgated. 'As an additional safety factor, all pipe velocities shall be limited...' At least then if the design goes awry the designer/engineer can come back and explain why the restriction should be lifted for their particular case. Mark A. Sornsin, PE | Fire Protection Engineer Ulteig Engineers, Inc. |Fargo, ND Direct: 701. 280.8591 | www.ulteig.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Ron Greenman Sent: Tuesday, December 28, 2010 5:40 PM To: [email protected] Subject: Re: USACE Velocity Given your argument maybe the oversized main/velocity restriction is just a simpler way to get desired results in most cases but your example points to the less than most cases and is valid. And maybe a simple way to beat the devil isn't any more warranted than designing to the extreme least costly. Comes back to the fact that some projects are less critical than others and lend themselves to the low bid at any cost philosophy, some have higher goals that can be dealt with by using rule of thumb requirements, and some are so high value that neither approach works, but since each project is unique until defined. Each has to be analyzed and assessed, the cost of that assessment being commensurate with the benefit of paying for it.Mark's example requires a lot of value engineering to avoid very high unnecessary costs, a strip mall or the latest Meth Lab Manor apartment complex needs to be low-balled, while most projects may be somewhere in between. _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.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) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.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) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.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) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.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)
