Preaction System with Nitrogen supervision instead of a compressor 1

[joecianfarra]

I am designing a very small Pre-action System application where the plan is for a single interlocked valve group with electric release and pneumatic pipe supervision. Traditionally I have used a compressor or shop air on rare occasions, however since the piping volume is only 11 gallons I was thinking about Nitrogen gas supervision instead of a 1/6 HP compressor. I figure that this option should be considerable cheaper and shouldn't be too difficult for the fitters to assemble. Is there anything I should be concerned about regarding equipment pricing or installation costs that would surprise me? Thanks Joe C.

 

[cdafd]

Which edition of NFPA 13 are you under?


Problems might be from 2010 edition

7.3.2.4.4, how is someon going to know that the nitorgen tank is empty?

7.2.6.2.2 appears you still have to meet thirty minute fill time?

 

[joecianfarra]

Thanks cdafd,

NFPA_13 2007 edition

7.3.2.4.4 Since the nitrogen is for supervision of the piping, I assume LPS supervises for release of gas as well as when it is empty. Plus there are gauges throughout the system.

7.2.6.2.2 Filling the system (~11 gallons) would be the biggest demand on the cylinder opposed to pressure maintenance. I haven't researched the size cylinder needed. However with the high pressures of compressed nitrogen, (similarly to Inergen hardware I assume) the high pressure tank and valve hardware could get pricy rather quickly.

Of course the biggest obstacle was one I anticipated. The superintendent didn't want to introduce difference technology than what the fitters are used to.

 

[peshadows]

I am late to respond to this but I wanted to issue a caution for you (based on past design experience). Nitrogen is an oxygen-displacing gas that is nearly the same density as oxygen. Any leak could give you a hazardous area for working. If it is an area that is rarely entered and closed off (aka no air circulation) I would strongly suggest that control measures be put in place. In the projects I have worked on there were oxygen monitors, confined spaces training (for areas with nitrogen and no active circulation system).

 

[Sdpaddler50]

Are you saying the N2 in a sprinkler system and a few bottles that feed it will cause life safety issues?

some of the largest corporations In the US use this method.

you may want to re think this. for a typical, large volume building, the emission of nitrogen should not be a problem.

 

[EEEliminator]

It can be and should be calculated....

The high pressure water mist systems utilize nitrogen for reducing oxygen levels and are supposed to be safe for breathing.