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
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