Ron, I requested a technical interpretation from NFPA for that exact question.
My question was: NFPA 13, 2010, 7.2.6.2.2 states; The air supply shall have a capacity capable of restoring normal air pressure in the system within 30 minutes. It does not state that the system shall be restored to normal system pressure in 30 minutes. It states that the air supply shall be capable of restoring the system to normal pressure in 30 minutes. My question is, If you can prove through calculations that the air supply is capable of restoring normal pressure in 30 minutes, would it be acceptable to actually take longer than 30 minutes to restore normal pressure? The purpose for the delayed fill time would be to use a nitrogen generator as a pressure source instead of an air compressor. If an empty system was initially pressurized with nitrogen, that would eliminate the purging process that would be necessary if the system was first pressurized with air and then the air slowly replaced by nitrogen over time. This would help to slow any oxygen corrosion that might be initiated if the system was filled with air. Membrane type oxygen generators work by forcing air into a membrane that separates the nitrogen from the oxygen. The CFM output of a nitrogen generator is about 50% less than the CFM of the air compressor supplying the nitrogen generator. The nitrogen generator has a bypass loop so the system could be filled directly from the compressor if desired. This is similar to the fill and maintain modes of an Air Maintenance Device. Their response was: The intent of NFPA 13, 2010 edition ยง7.2.6.2.2 is to provide a guideline which will protect the owner of the system from someone installing an undersized compressor which would render systems out of service for elongated periods of time while increasing service costs. The compressor is not required to be listed, in fact - a compressor is not required. The compressed gas supply may be from a reliable plant air source or nitrogen tanks with a regulator. The committee intent is to have the system returned to service within the 30 minute timeframe - regardless of the source for compressed air or nitrogen. It is assumed that a nitrogen generator (or other approved compressed gas) will provide nitrogen over the subsequent hours of operation and replace the air used for initial charging. Regards, mike Mike Henke CET Sprinkler Product Manager 314-595-6740 direct [email protected] www.pottersignal.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Ron Greenman Sent: Friday, October 05, 2012 9:19 AM To: [email protected] Subject: Re: Air Supply I'm curious where the 30 minute fill came from. Convenience to FDs? I'd certainly not want my highly paid and trained engine company hanging around for a couple of extra hours to watch the system fill. But if I'm likely have the service guy from the sprinkler company, or even my owned trained maintenance, hanging around, and I'm willing to pay for him to watch the paint dry, and I'm so concerned with my system as to have bought a nitrogen generator instead of using that nasty moisture holding air, why not ignore that code section? Or is the 30 minute rule there just because we needed a definitive time frame and 30 minutes sounded reasonable at the time? Or is there another, more compelling reason? Curious minds want to know. On Fri, Oct 5, 2012 at 6:07 AM, Tom Duross <[email protected]> wrote: > Most generators, if not all, have a nitrogen storage tank. The one I used > put out 70 PSI requiring an AMD and we still had a riser mount air > compressor because the generator could not fill in 30 minutes. They're > interconnected and valved. > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Roland > Huggins > Sent: Thursday, October 04, 2012 5:44 PM > To: [email protected] > Subject: Re: Air Supply > > If you use nitrogen (7.6.2.7) it now kicks you over to 7.2.6.5 (Automatic > Air Maintenance). Must admit, I see no reason to use an air tank and > plenty > not to (as George already said). I'd say an air cylinder would be not > different than a nitrogen cylinder when it comes to requiring an AMD. If > you do not have a low pressure alarm, the pressure gauge has to be checked > weekly instead of monthly. Now that dry pipe system have to have an air > leakage test performed every 3 years, there shouldn't be any systems (or at > least as many) needing a compressor running full time to keep it from > tripping. > > Roland > > On Oct 4, 2012, at 12:54 PM, Cahill, Christopher wrote: > > > Looking over a job where the EOR wants to use cylinders to supply the > > air for a dry system. There is plenty of power to the building so > > that's not the issue. They are showing lab air cylinders from both > > air (NC) and nitrogen (NO) into an AMD into the system. I get > > automatic air is not required. But I'm seeing NFPA 13 '12-7.2.6.5.1 > > limiting air supply when AUTOMATIC to dependable shop system or a > > compressor. I don't see bottles being allowed. Or that is to say I > > don't see bottles as being a dependable shop system. > > > > I assume some of you have done bottles for the air to a dry system? > > As I read you can have them if someone manually opens a valve and > > refills the system when needed? Of course this is even confusing. > > Is there something on a manual fill system that requires daily > > checking? Or are they relying on the low pressure alarm to note when > > time to refill? Actually, the low pressure alarm isn't even required, > > right, so are they waiting for a system trip to know when to add air? > > > > If manual is allowed isn't an AMD off a bottle a little better but not > > quite the full blown compressor? Why would they restrict the middle > > on the order of worst to best? > > > > Who wants to straighten me out 'cuz none of us here have ever seen > > bottles used on a system? > > > > Chris Cahill, PE* > > Senior Fire Protection Engineer, Aviation & Facilities Group Burns & > > McDonnell > > > > http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum > -- Ron Greenman Instructor Fire Protection Engineering Technology Bates Technical College 1101 So. Yakima Ave. Tacoma, WA 98405 [email protected] http://www.bates.ctc.edu/fireprotection/ 253.680.7346 253.576.9700 (cell) Member: ASEE, SFPE, ASCET, NFPA, AFSA, NFSA, AFAA, NIBS, WSAFM, WFC, WFSC They are happy men whose natures sort with their vocations. -Francis Bacon, essayist, philosopher, and statesman (1561-1626) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://fireball.firesprinkler.org/mailman/private/sprinklerforum/attachments/20121005/6c848fa4/attachment.html> _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum
