Hello, Use bottled nitrogen for the 30 minute refill time and the nitrogen generator for the pressure maintenance of the system.
Friday, October 5, 2012, 10:55:28 AM, you wrote: > 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 >> -- Best regards, Charles mailto:[email protected] Confidentiality Notice: This e-mail message, including any attachments, is for the sole purpose of the intended recipients and may contain confidential and privileged information. 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