Those statistics were given to me by Factory Mutual when I worked for their Pittsburgh office. I have never heard the one about no multi-death fires in sprinkered buildings, so I can't help you there.
Paul J. Pinigis, P.E. Chief Life Safety Engineer -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Joe Hankins Sent: Friday, March 16, 2007 11:56 AM To: [email protected] Subject: Re: Minimum Supply Pressure Paul, Could you pleas provide the source of your statistics? I've heard them quoted many, many times, but never found anyone who could point to the actual data behind them. There is another one going around for years that says there has never been a multiple-death fire in a sprinklered building. That one is definitely not true. Before we start talking about "overkill" in sprinkler designs we need to recognize that some current standards have large safety factors, some have none, and most have unknown safety factors. The idea that there is a huge difference between a 5-sprinkler fire and a 15- or 30-sprinkler fire seems logical on the surface, but if you know how sprinklers operate, you know they operate in rings. The heat that operates sprinklers spreads in a circle from the fire origin. For symetrically-spaced sprinkler system where the fire starts centered among 4 sprinklers, there are 4 sprinklers in the first ring around ignition, so there is virtually no difference between a 1-sprinkler fire and a 4-sprinkler fire. If those sprinklers don't control the fire, then any (and all) of the 12 sprinklers in the next ring can operate, meaning that there is very little difference betwen a 5-sprinkler fire and a 16 sprinkler fire. If you get into the next ring, then the number is 36 sprinklers. So, the 1-ring "safety factor" between 4 and 16 sprinklers is the same as the 1-ring safety factor between 16 and 36 sprinklers. A 1-ring "safety factor" is not overkill in my book! Finally, the "cushion" sometimes applied to a water supply is not a safety factor. In addition to accounting for seasonal, weekly, daily, and hourly fluctuations, it is a recognition that water supplies invariably deteriorate and an attempt to avoid the large cost of upgrading the system or water supply when it does. I'll agree that adding a cushion to a fire pump supply dedicated solely to a fire protection system is not necessary, because the pump supply stays the same unless there is a problem with the pump, which must be fixed immediately. Joe Paul Pinigis wrote: >My point is that there are already so many factors of safety built into >the design of a system that one more is overkill upon overkill. 95% of >fires are controlled with one sprinkler operating, 98% of fires are >controlled with five or less operating, yet we calculate 1,500 square >feet (or 3,000 square feet for military projects), them we overestimate >the friction loss in pipe and fittings, underestimate the water supply, >them worry about adding an additional cushion. > >Please, no "what about the other 2%" comments. > >Paul J. Pinigis, P.E. >Chief Life Safety Engineer > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of George >Church >Sent: Friday, March 16, 2007 9:56 AM >To: [email protected] >Subject: RE: Minimum Supply Pressure > >Well, there ARE a few more considerations. >Was the supply adjusted for lowest tank gradient? >What confidence level do you have in the accuracy of the test data ? >What confidence level do you have that NO additional 90's will be added? >What is the Owner's tolerance for risk? > >NFPA #13 does NOT require a cushion. Good trade practice, flexibility of >installation changes, common sense, and protection of your boss's >retirement >assets require a cushion of some sort. So may the various AHJs you face- >water co, fire and code officials, insurance carrier, etc. > >So you could be right and fine with .0001 cushion- but in so doing, you >may >find yourself in a box scratching for 2.7 PSi in a .0001 margin when a >duct >doesn't go in as planned, some cable bracing is discovered, ANYTHING. > >We deal with a water company that applies a .8 coefficient to all >hydrant >test. If your test was from a .7 hydrant, the supply is overstated and >your >system, upon correction, would be 5 or 6 PSI shy. Or if the tank level >was >3' above lowest tank gradient, your system won't work in August. > >Or 4 heads could control the fire and everyone smiles. We just don't >know >EVERYTHING and we can't look into the future. I have trouble sleeping >when >we don't have 10%, and prefer 15 PSI+ on prelims on bid day. We just >analyzed a new site for a customer wanting to use K25s without a pump- >would >you tell him, based on 3.6 PSI cushion and ignorant of bar joist >spacing, >that it would? We're proceeding with a pump, and if things turn out >better >we can omit it, give him a credit for the pump, take some back with the >$^ >of k25's, but at least the money's in the job to start with. > >When I was assetless and worked for others, I'd consider installing what >you >have. Now, not without everyone involved knowing it, and not if I was on >the >hook for the pump or larger piping replacement, or dual feed mains, or >whatever was needed to fix whatever changed and bumped us up. Imagine >going >to an owner with a $50,000 adder and explaining it with "we had to add a >6" >90 at the top of the riser." Not a situation I'd look forward to ! > >glc > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of Paul >Pinigis >Sent: Friday, March 16, 2007 9:31 AM >To: [email protected] >Subject: RE: Minimum Supply Pressure > >If you can achieve 10% without spending your client's money (or your >own) great, but it is not necessary. > >Paul J. Pinigis, P.E. >Chief Life Safety Engineer > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of Brian >Harris >Sent: Friday, March 16, 2007 9:29 AM >To: [email protected] >Subject: RE: Minimum Supply Pressure > >10% is what we go by, based on your numbers your only at around 2% :( > > Regards, > Brian Harris >First Defense Fire Protection > Design Engineer > [EMAIL PROTECTED] > 704.948.3506 phone > 704.948.3507 fax > > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of Charles >Thurston >Sent: Friday, March 16, 2007 10:19 AM >To: [email protected] >Subject: Mininum Supply Pressure > >Hello All, > >Let me be the one to start things today. > >What is the minimum safety pressure allowed ? I have looked in 13 and >did not find it.... I have a situation where the safety pressure is >0.913 psi. > >Basis is: > Hose 250 > Static 67.00 > Residual 38.00 @ 920.00 > Available 40.128 @ demand of 882.87 > Requires 39.215 psi > Leaving a safety of 0.913 psi > > > > _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
