Do you use nitrogen?

[mtrv]

If temp goes up, pressure goes up.

Yes, but the statement is misleading. I'm going to use common refrigerent gasses for A/C units as an example.

R-22, which has been used for many years, will be running approx. 102 psi at 60 F. , while the new replacement freon, R410A will hit approx 170 psi at 60F. This is over 1 1/2 times the pressure, for the same identical temp. Increase the R-410A temp to 120F, and it's now 350psi, versus 260+ for the R-22. Needless to say, using freon, isn't the best for pumping tires that will tend to heat up, with some use.

These same differentials apply to Nitrogen and ordinary compressed air. However, I'm not in the mood to look up the exact differentials, so that I appear to be a walking encyclopedia. In the end, the pressure increase for nitrogen, as the temp. increases, will be less for nitrogen.

At least, I believe so! And no, I'm still not going to look up the exact differences.

 

[The_Russian]

Actually he did rip apart a few other posts, not just yours, however, you are the only one who can't admit that you were wrong.

What's wrong about my first post? Nitrogen does eventually freeze. I failed to state it would turn to liquid first. Am I the only one not taking crazy pills?

Nitrogen freezes at a lower temperature. It also retains a constant pressure over large temperature changes. On top of that it does not contain moisture, unlike the ambient outside air. If outside air is pumped into an aircraft that flies above the freezing level, the moisture within the air will freeze inside the tire. This can cause an imbalance or corrosion.

Also, aircraft tires are designed to resist nitrogen permeation though the carcass.

In its context for pilot information this is correct. If we get into the science of gas laws, the paragraph can be expanded on. If A Squared had the capacity to teach instead of insult, then he would have added constructive statements. Such as, "Russian, nice post. But I would like to add a few tidbits of info".

 

[wrxpilot]

Yes, but the statement is misleading. I'm going to use common refrigerent gasses for A/C units as an example.

R-22, which has been used for many years, will be running approx. 102 psi at 60 F. , while the new replacement freon, R410A will hit approx 170 psi at 60F. This is over 1 1/2 times the pressure, for the same identical temp. Increase the R-410A temp to 120F, and it's now 350psi, versus 260+ for the R-22. Needless to say, using freon, isn't the best for pumping tires that will tend to heat up, with some use.

These same differentials apply to Nitrogen and ordinary compressed air. However, I'm not in the mood to look up the exact differentials, so that I appear to be a walking encyclopedia.

Huh??

You're talking about a refrigerant system at particular operating temperatures and pressures. A very confused analogy to inflated tires. Your initial pressure for the tires will be whatever you set it at, regardless of temp. Here's how the gas laws work:

PV=nRT

Rearranges to P/T = nR/V

We're going to look at two different states of pressure/temperature:

P1/T1 = P2/T2
(n, R, and V cancel out as they are equivalent)

Initial conditions at Jim Bob's garage for the tire filling:
T1 = 20C = 293.1K, P1 = 80 psig

Now the tire is flying around in some airplane up really high:
T2 = -40C = 228.1K, P2 = ?

P2 = P1*T2/T1 = 62 psig

Notice there is nothing whatsoever related to the gas in the ideal gas law equation (Dry air and N2 are very close to being ideal gasses).

This is starting to sound like that stupid treadmill question, except this is even more ridiculous. Read the link I put on here earlier from Ingersoll-Rand.

After some reading, the benefits from Nitrogen are:
1)Reduced loss of pressure over time due to N2 having larger molecules than O2, which is apparently permeated through the rubber.

2)Reduced pressure differentials with temperature due to the lower water vaport content of pure N2.

Here's another link:
http://www.popularmechanics.com/automotive/sub_care_clinic/1272166.html?page=2&c=y

 

[mtrv]

Huh??

You're talking about a refrigerant system at particular operating temperatures and pressures. A very confused analogy to inflated tires. Your initial pressure for the tires will be whatever you set it at, regardless of temp. Here's how the gas laws work:

It's not confusing at all. In the days before high cost refrigerants, and the decision that some could lead to global warming; it wasn't uncommon to see a semi-flat tire pumped up with freon in an emergency; should you just happen to have some around. Just count on a rapid pressure increase, as the tire temp increases in road conditions, even though the initial pressure was at the tire rated pressure of 35 psi, at the particular ambiant temp. of the moment.

Now whip out your forumula's, and find the pressure increase for a racing tire thats been super heated since it's initial inflation. I want to see exact numbers comparing nitrogen & compressed air. Do nitrogen filled tires remain more stable in psi with increased temp ranges?

edit: I need to clarify this question slightly.

Since pressure does increase with temperature, then I can assume that the nitrogen filled racing tire is going to be cooler, than an air filled tire under the same racing conditions; which is the same as saying, that the nitrogen filled tire will have less pressure increase, as the outside ambient temps rise, while the vehicles sit motionless in the noon day sun.

 

[wrxpilot]

It's not confusing at all. In the days before high cost refrigerants, and the decision that some could lead to global warming; it wasn't uncommon to see a semi-flat tire pumped up with freon in an emergency; should you just happen to have some around. Just count on a rapid pressure increase, as the tire temp increases in road conditions, even though the initial pressure was at the tire rated pressure of 35 psi, at the particular ambiant temp. of the moment.

I think what you were seeing was the Freon expanding from a very high pressure tank to the relatively low tire. Expansion requires lots of heat, so the gas was very cold inside the tire. As it was driven around, it heated up such that there was a much bigger temperature difference than if it were air.

Now whip out your forumula's, and find the pressure increase for a racing tire thats been super heated since it's initial inflation. I want to see exact numbers comparing nitrogen & compressed air. Do nitrogen filled tires remain more stable in psi with increased temp ranges?

They do apparently remain more stable than the air ones, but still follow the ideal gas law. If the air was totally dry, they would both be very similar. The benefit you're getting is dryness - though I'd be surprised if there was any more than 5-10% difference. Water vapor is a very small component of the total pressure ratio.

edit: I need to clarify this question slightly.

Since pressure does increase with temperature, then I can assume that the nitrogen filled racing tire is going to be cooler, than an air filled tire under the same racing conditions; which is the same as saying, that the nitrogen filled tire will have less pressure increase, as the outside ambient temps rise, while the vehicles sit motionless in the noon day sun.

Not sure how the nitrogen filled tire is going to be cooler, you've lost me there. The tire heat is generated from friction between the tire and the road, and it is whatever it is.

 

[mtrv]

If A Squared had the capacity to teach instead of insult, then he would have added constructive statements. Such as, "Russian, nice post. But I would like to add a few tidbits of info".

It's just a person's way, of making them feel above the rest. Someone might have a solid background in physics; while another has mastered the art of language, and will forever use words that make little sense to the common man.

Yet, in both instances, these two people can be brought to their knees, should a third person be very learned in a subject these two are faintly familiar with. It can make them feel like asses, if the subject isn't changed.

But that's how it works! Speak with total authority on a subject you know, or can look up; and then remain silent on all those many other wonders of the world that will make you consistently look like a fool.

And P.S. --- I used spell check. Missed one word, but didn't want to look too stupid. Saved by the power of the internet!

 

[A Squared]

These same differentials apply to Nitrogen and ordinary compressed air.

That's just the point, the same differentials do *not* apply. The difference between nitrogen and oxygen is about 2% up to 10 atmospheres 150 psi. The difference between nitrogen and air will be even less.

I want to see exact numbers comparing nitrogen & compressed air

I've already posted fairly exact numbers comparing nitrogen and oxygen. Dry air being a mixture of nitrogen and oxygen (mostly nitrogen) will fall someplace in between.

Do nitrogen filled tires remain more stable in psi with increased temp ranges?

Actually, the numbers I posted showed that a nitrogen filled tire would have a slightly *less* stable pressure than one filled with oxygen. Again, dry air would presumably fall someplace between nitrogen and oxygen.

 

[A Squared]

What's wrong about my first post?

You have already been told, with complete explanations what is wrong. the Thing is, you are absolutely unwilling to consider that you are wrong, so you will not actually read what I have written and attempt to understand it.

Apparently your entire though process goes something like this:

"A Squared says I am wrong, and I won't consider that I am wrong, therefore A Squared is wrong."

WHatever gets you through the night, but it a pretty poor intellectual approach to life.

Nitrogen does eventually freeze. I failed to state it would turn to liquid first. Am I the only one not taking crazy pills?

No, you're the only one not reading and understanding what others have written. I have already explained it to you several times, It's pretty simple, I will explain one more time (anlthough for the life of me I don't know why I'm bothering)

ready?

OK. Of course Nitrogen freezs, *NOBODY* said it doesn't, not me, not anyone else. That wasn't the point. The point was this: the freezing point of the various gasses which make up dry air are so low, that it is ridiculous to mention freezing point of nitrogen in the context of an tire, even a tire on a high altitude aircraft. None of the gasses in dry air will freeze at any temperature that will ever be encountered in our atmosphere.



Also you were wrong that nitrogen "retains a constant pressure over large temperature changes" It doesn't. I've explained this, I've shown you the numbers, and you don't address anything that's been said, Instead, you just repeat that you are right, without offering anything to support your words.

Again, this appears to be because your entire though process is limited to:

"A Squared says I am wrong, and I won't consider that I am wrong, therefore A Squared is wrong."

As syllogism, it is badly flawed.

 

[aucfi]

I once used compressed Nitrogen to start a Yak 52.

Its true

 

[The_Russian]

It's just a person's way, of making them feel above the rest. Someone might have a solid background in physics; while another has mastered the art of language, and will forever use words that make little sense to the common man.

Yet, in both instances, these two people can be brought to their knees, should a third person be very learned in a subject these two are faintly familiar with. It can make them feel like asses, if the subject isn't changed.

But that's how it works! Speak with total authority on a subject you know, or can look up; and then remain silent on all those many other wonders of the world that will make you consistently look like a fool.

And P.S. --- I used spell check. Missed one word, but didn't want to look too stupid. Saved by the power of the internet!

Great post! Now we are just waiting for this third person....

 

[The_Russian]

A Squared,

Well, I typed an entire post of about 50,000 words to respond to you. My cpu glitched and I lost all the info.:smash: All-in-all it was just to say that you basically offended me and that is why I responded as such.

A Squared, you have offended me since your first response to my posts on a thread years ago. In fact, the only time you respond to me is when you feel like putting me down. Does that make you feel good? You have no idea what my education is or my background. You feel that just because my background includes Gulfstream, that my posts are no longer credible. That is why I brought the subject up. You and I know that is the truth that you feel that way. I have to say, it is not right. You should have a better attitude towards your fellow pilots. Your referal to me as "scum" is unjustified.

My post was informative and proper in response to the level of pilot that was asking the question. You were wrong about one thing, and so was I. You broke my entire post down to say it was all wrong and, in its context, it was not completely wrong.

Please, have some respect for me and never respond to my posts again. Unless, of course, you can be civil. In that light, I will return the favor. This is my last only attempt to be civil with you, so please don't waste it.

 

[Gorilla]

Here's what it boils down to guys, physics aside.

Since air is 78% Nitrogen to begin with, making the jump to 100% nitrogen does not create some huge difference in the two compositions inside the tires. Trace gasses aside, the difference between the two is oxygen and water vapor.

Oxygen gas is one of the most reactive free substances on earth. If it wasn't continually replenished, it would very quickly vanish from the atmosphere as it oxidizes (corrodes/rusts) rocks, minerals, rubber, metals, etc.

Anyone who welds knows what oxygen can do. Once you get metal bright red with oxy/acetylene, you can turn OFF the acetylene, and blow cold, pure oxygen on the hot metal. It causes the metal to burn, and the reaction can be used to cut large sections of metal, without a fuel gas.

Water vapor is also problematic in that it can condense (think fog) when the interior of the tire gets very cold. Droplets of moisture can get wicked to sensitive (metallic) areas, causing hidden corrosion.

My point is that both oxygen and water vapor are bad juju for tires that see minus 50C to +200C or whatever they get to with hot brakes. I doubt very much that any significant benefit is tied to permeability. It's all about corrosion and degradation of the rubber.

 

[Sig]

Jesus Harold Christ, for a bunch of physical chemists you sure can fly planes- and pee quite a distance.

A Squared has been the most right the most often in this thread; I'm impressed. Especially when he nailed the binary N2, and how covalence, not weight, makes the binaries their size. 'Swhy an H20 is much less dense than a binary 02; not just weight, but the topography of each molecule itself is of a totally different set of orbits, and the mass is diffused from the polar - out towards each polar + in water. Not to mention water's behavior chemically and physically; just a little bit completely screws gas behavior. So, N2 is a wise choice for predictability, slow leak, and inability to corrode anything or feed a fire.

And no, N2 isn't inert- but the spirit of the word "inert" holds true. Good job, A. I'm truly impressed.

However.... the DUMBEST THING I'VE EVER READ ON THIS WEBSITE was H402, for math reasons?! Holy crap, you're a moron.

Oh, Gorilla- good one. Just read it.

Two true or false questions:

1. Water is a binary acid.
2. Hydrogen is a metal.

/chemical engineer that drives planes

 

[A Squared]

Two true or false questions:

1. Water is a binary acid.
2. Hydrogen is a metal.

/chemical engineer that drives planes

OooooHH OOhhh, I know!

 

[Sig]

Betcha do, actually.

 

[Gorilla]

Two true or false questions:

1. Water is a binary acid.
2. Hydrogen is a metal.

/chemical engineer that drives planes

I'll bite. Water dissociates into H+ and OH- ions in equal quantities, making absolutely pure water a pH 7. There's sure to be some energy associated with it, and at any moment a given % of H2O molecules are in fact dissociated, but it's going to be very, very small.

Hydrogen chemically behaves like a metal due to its position on the periodic table, but its physical attributes are obviously not metallic. It is suposed that under enormous pressure, it would in fact form a nice happy metallic-looking substance that might superconduct, but IIRC the pressures are unbelievably high.

Do I get a dork award? :0

 

[IFollowRoads]

No, but you do earn a "Why wont you guys let this thread die?" award.

 

[UA-RESURRECTED]

Looks like some of you need to go back to grade school. There is no such thing as a "molecule" of Nitrogen, any more than there is a "molecule" of Helium".

 

[A Squared]

Looks like some of you need to go back to grade school. There is no such thing as a "molecule" of Nitrogen, any more than there is a "molecule" of Helium".

Ahhhhh, a little knowledge can be a dangerous thing. In your case, a *very* little knowledge. You knowledge is missing some pretty important parts.

Nitrogen isn't normally found as a single atom. It is however found in abundence as two atoms bonded together by a covalent bond. Do you happen to recall what we call two or more atoms bonded together by a chemical bond? It's a molecule. THat's right, a molecule of N2. The reason you don't normally have Helium molecules is because helium has a complete valence so it doesn't normally form chemical bonds, and it exists as a single atom. It's pretty pathetic that you're getting sarcastic when you don't grasp even the fundamentals of chemistry yourself.

Have you planned your return to grade school yet? You may want to step up that timeline before you embarrass yourself further.

 

[UA-RESURRECTED]

A Squared,

You CANNOT take atomic nitrogen and break it down into molecules.

I stand corrected that nitrogen occurs nearly exclusively in the diatomic form, and that is in fact what is used in aircraft struts and tires.