air tank help

[bokraham]

Hi I recently ordered a 68 45 centerflag screw in with a 750 output pressure for my minimag. I have a series of quesios that I would like to have the ansewers to so that i do not seem like a noob at the field, with my tank.

1- I see people fill up their tanks with their guns still attached. Do they do that because it does not make a difference and has no detremental efffects on their guns when they fill up, or because they have a on/off? My tank does not have a on off and neither does my drop soo...........

2- Would I need to take my tank off every time I get it filled.

3- When I do take my tank off, and it still has some pressure will it do the same thing a co2 tank does and spill air? (rememver it is a screw in)

4- What happens when the pressure in the bottle drops below 750? will the pressure inside the bottle be in my gun. ie pressure on gauge in bottle 450psi, pressure in gun 450 psi. Or will the output pressure stay at 750 untill it gets to a much lower level?

The last question has to do with mathamatics.

5- How many feet does it take for the pressure to rise 1 pound? I ask this because i live high up in the mountains, and cannot get compressed air or n2. So after a day of playing at a lower level it would be nice to bleed the tank down to a certain level, so that by the time I get to my home at 7500 feet my tank would be full, and I could play a day with it.


thanks alot for your answers

[i_baked_cookies]

1) nitrogen tanks have an fill nipple on it which leads directly to the actual tank. it wont hurt your gun because the regulator on the tank will keep your pressure to what its set at.

2) you can get your tank filled with it on or off, doesnt matter

3) depends on what gun and if you have an on/off. if you have an on/off, a little air will exit from your minimag and a very minimal spit of air will come from the tank. if there is no on/off, youll have to do the old shoot and screw... unscrewing the tank while shooting to get rid of air.

4) when the pressure of your tank gets below the regulated output pressure, that output pressure will also drop. minimag valves run on 400 if i remember right.

5) no idea- but i do know that things decompress at a higher level. so there would be less air inside your tank at a higher level. but since its pressurized in its own container... i dont know. im not a math guy.

[trains are bad]

1. it doesn't matter.

2. no

3. yes


4.What happens when the pressure in the bottle drops below 750? The output pressure drops as well. tanks are not air compressors. They can only reduce pressure.

5. altitude has NO significant effect on tank pressure.

[bokraham]

thanks alot for your answers. However I do know that pressure in a closed system will build as it goes higher in altitude.

As the altitude goes higher the air becomes thinner, because gravity draws air closer twords the earth. The differece in pressure in the bottle is much more than that of outside. As the altitude gets higher the difference in pressures get bigger. The pressure will want to be even, so it will try harder to get out, creating more psi.

Well that is what I think happens, it is probably wrong. However, I do know that if I buy a decompresed bag of chips in denver, and drive back to my house at 7500 feet the bag, by the time it gets to my house will be full of air, and some times pop.

[FallNAngel]

The air doesn't compress the higher you go. Basically, at ground level, you have 4500psi in the tank pushing out.. you also have x amount of atmospheric pressure pushing in on the tank as well. As you rise in elevation, the pressure on the outside of the tank drops, so there's more pressure pushing on the inside of the tank (to get out).

The same thing happens with the bag of chips. As you raise in elevation, the amount of pressure pushing on the outside of the bag decreases and the pressure inside is greater than the pressure outside the bag.

It's more of a ratio than anything. At ground level, the ratio is more of a 1:1. As you rise in elevation, the pressure changes to say... .5:1 (just numbers off the top of my head). Now the pressure pushing out is twice the pressure pushing in.

[bokraham]

so then will pressure in the tank compress, or just put more pressure on the tank?

[FallNAngel]

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1901/es1901page01.cfm?chapter_no=19

That might help explain... as the altitude rises, the pressure drops, but volume increases.

[bokraham]

hey thanks

[trains are bad]

True, but it's not SIGNIFICANT, you will notice no difference.