nitrogen or Air???
I have a source of nitrogen at my work that I can fill my tank to 4500. is there anything special I need to use or do to the tank/gun to use nitrogen?
what are the pros and cons of using nitrogen in a cricket .25?
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Saltwater,
I once saw a post from Ted (ted’s holdover) where he said he had problems with his Edgun in extreme cold. Obviously we have seen Ed hunt in weather that would make non-Russians cry. I wondered at the time if his fill had too much water in it and the extreme outside temperature caused water to freeze in the regulator.
Thank you sir! Sort of gives me a good perspective. Our intensifiers are air operated, but at -40F dew point, they’ll run continuously and not freeze up. The pressure dew point is likely quite a bit higher, but still good enough for our application, plus, we’re only operating at 145 psig or less…
Dew point of -65ºF at one atmosphere pressure, the water content will be 24ppmv, and the air is considered dry. If you then charge a SCUBA tank to 3100psig with that same air, the moisture content will still be 24 ppmv, but because the water and air molecules are now compressed together, it is easier for the water molecules to “stick” together and condense onto the cylinder walls. If you measure the dew point of the air in that cylinder at the 3100 psi pressure, you would discover that the dew point inside the cylinder is now +28 ºF (that dew point is called the Pressure Dew Point). That means that if the outside temperature becomes colder than +28ºF, the compressed air in the cylinder will condense onto the SCUBA flasks interior walls. If the Dew point gets to -50º the filter needs to be changed. The moister content is too high and it can cause malfunctions if the weather is cold.
The paragraph below is a direct quote from CGA G-7.1 – 2011.
The water content of compressed air required for any particular QVL can vary with the intended use from saturated to very dry. For breathing air used in conjunction with a self-contained breathing apparatus in extreme cold where moisture can condense and freeze causing the breathing apparatus to malfunction, a dew point not to exceed -65 ºF (24ppm v/v) or 10 ºF lower than the coldest temperature expected in the area is required. If a specific water limit is required, it should be specified as a limiting concentration in ppm (v/v) or dew point. Dew point is expressed in ºF at 1 atm abs (101 kPa, abs).
Dry air is terrible to breathe, we run humidifiers to keep the air to have moisture in it.
Do you have any info on dew point of the humidified air for breathing? And is that the air compressed in the bottles or is that a separate addition to the bottles? I know zippo about breathing air… do all sorts of stuff with industrial air and all manner of gasses, but not breathing air.
Thx,
Fire departments generally follow the moisture requirements of the NFPA specifications which require that the breathing air in SCBA flasks have a dew point be no warmer than -65 ºF. For Divers, the rules are more vague because there are more gas possibilities (normal air, Nitrox, and Tri-mix), and there are more associations that have their own ideas (AAUS, ANDI, IANTD, and the CGA). The most common specification in use is CGA Grade E for diving, but this specification does not require routine moisture determinations; it only suggests them.
The paragraph below is a direct quote from CGA G-7.1 – 2011.
The water content of compressed air required for any particular QVL can vary with the intended use from saturated to very dry. For breathing air used in conjunction with a self-contained breathing apparatus in extreme cold where moisture can condense and freeze causing the breathing apparatus to malfunction, a dew point not to exceed -65 ºF (24ppm v/v) or 10 ºF lower than the coldest temperature expected in the area is required. If a specific water limit is required, it should be specified as a limiting concentration in ppm (v/v) or dew point. Dew point is expressed in ºF at 1 atm abs (101 kPa, abs).
Dry air is terrible to breathe, we run humidifiers to keep the air to have moisture in it.
Those systems probably have driers on them. Here on the Gulf Coast, we must use driers for critical air applications. We specify air with a dew point of -40F. I’m sure the firehouses will have something similar. If so, there’ll be no moisture issues from tanks filled from those systems.
I never hand pumped but my buddy did ONCE. He then bought a tank and now I fill his tank for him.
I always wondered how much moisture was in the firehouse air I always used for free. I even left a tank for them to fill and then I would just switch tanks. Since they breath that air in a fire situation they may need some moisture in it. 😕 They have a large 6000 psi system at each of the three firehouses I went to (Bauer I think). The tank is even in a steel-walled box when they fill it. It fills a wall.
Yea, last year when I got my first PCP a Condor SS and a pump, I found out right quick that either I was gonna go the bottle route or this was going to be a short-lived hobby! That pumping is for the birds!
That must be nice to have that available to you. I know nitrogen is very dry air as we used it to buffer our lead phone cables when we had a leak. I also used it to run my airgun when taking cases apart.
I sure did Coda. I almost went nitrogen but the cost was to high to fill and refill, plus tank rental.
availability of gas is why I started this stuff in the first place… I build gas systems, so always have a source to top off a tank… Filled my 6K bottle last week, so I won’t need pellet fuel for quite a while… got about 614 cubic feets in that little baby… Set my regulator on 4500 psi and it takes about 1 minute or less to top off my CF tank… drops my pressure in the big tank about 80 psi…
I sure did Coda. I almost went nitrogen but the cost was to high to fill and refill, plus tank rental.
No sir. air is about 80% nitrogen to start with… over time your tank will become all nitrogen. Only thing that is in air that is detrimental to your gun is moisture. If you aren’t having moisture issues now, the switch will not be noticeable.
The cost effective source seems to be the trick. I know a lot of folks that explored it.
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That could have something to do with it. If there’s any leak or seepage at all, in cold temps, I guarantee you it will freeze if there’s ANY moisture in real cold temps… I know it gets cooooold in Ted country too. Generally gasses get hotter when pressure increases and less when pressure reduces… That’s how an air conditioner works… Heat of compression vs. heat of vaporization…. What goes up must come down. So a leaky regulator in cold weather very likely will freeze. Even wetter air in a regulator or unregulated gun when fired I suppose could form ice crystals… be interesting to find out.