Why nitrogen?

Nomen Nescio wrote in
:

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From: "Viperdoc"

The thread on brakes raised a question from the past- why nitrogen in
the tires of big jets and heavies? Air is around 78% nitrogen anyway,
and the coefficient of expansion of the remaining 20% that's oxygen
can't make that much difference in volume.

Why not just use dry air?

1) It's AVIATION
2) Nitrogen is more expensive


Asked a grease monkey friend there a few minutes ago.
He says that O2 under pressure is considerably more reactive than it is at
normal atmospheric pressures. So the main reason is to prevent oxidation of
tires and seals. A secondary consideation is detonation in oleos.

Bertie

Bertie:

I find this hard to swallow, and I doubt that oxygen (at 20% of air),
regardless of pressure, is going to cause a detonation in an oleo. Just like
in a tire, the percentage of oxygen remains the same, so its ability to
support combustion also remains the same. Now, the increased oxygen pressure
might slightly increase the risk of corrosion, but we are not talking orders
of magnitude higher compared to ambient. At least this is my understanding
as I recall from being a chemistry undergrad and grad student.

The more I hear about this, the more I think it's an old wive's tale.

Anway, what did you think of Anthony's claim"it's not me?" What a moron.

"Viperdoc" wrote in
:

Bertie:

I find this hard to swallow, and I doubt that oxygen (at 20% of air),
regardless of pressure, is going to cause a detonation in an oleo.

Our oleos are a little more, eh, enthusiastic shall we say, than the
oleo on a cherokee! Thumping a hypothetical airplane that weighs, say
500,000 lbs onto an oleo strut of about a foot in dia at, maybe over
1,000 fpm rate of descent is going to get things pretty exciting inside
the strut.I have no idea what the compression ratio is in there, but
it's got to be reasonably high.
I do come across one grease monkey who has answers galore. Anything he
doesn't know he finds out for me the next time I'm through. He's just
one of these guys with an insatiable curiosity about all things
mechanical..

Just like in a tire, the percentage of oxygen remains the same, so its
ability to support combustion also remains the same.


Now, the
increased oxygen pressure might slightly increase the risk of
corrosion, but we are not talking orders of magnitude higher compared
to ambient. At least this is my understanding as I recall from being a
chemistry undergrad and grad student.

Apparenlty, the increased prsssure makes O2 much more aggresive so the
effect is not slight, but in any case, I'm only telling you what my bud
said and he's quality control for a big airline.

The more I hear about this, the more I think it's an old wive's tale.

Anway, what did you think of Anthony's claim"it's not me?" What a
moron.

Oh yeh. Couldn't care less if it's him or not, to be honest!


Bertie

"Viperdoc" wrote in message
...
Bertie:

I find this hard to swallow, and I doubt that oxygen (at 20% of air),
regardless of pressure, is going to cause a detonation in an oleo. Just
like in a tire, the percentage of oxygen remains the same, so its ability
to support combustion also remains the same. Now, the increased oxygen
pressure might slightly increase the risk of corrosion, but we are not
talking orders of magnitude higher compared to ambient. At least this is
my understanding as I recall from being a chemistry undergrad and grad
student.

The more I hear about this, the more I think it's an old wive's tale.

Anway, what did you think of Anthony's claim"it's not me?" What a moron.

About all that I know on the reactivity subject is by inferance from the
assertion that our own need for suplemental oxygen at altitude is based on
partial pressure. On that basis, it seems to make a sort of sense, even
though it would require a *lot* of pressure and might also require the oil
in the strut to be partially vaporized--possibly during the early stages of
the rebound after the struts were vigorously compressed.

In the case of light plane tires, I agree with you that really dry air
should work well enough to make the issue trivial. But, if you need
nitrogen for any other reason, it is the cheapest thing that I know of in an
L bottle or larger and using it in the tires may be essentially
free--because you may have to pay rental on the tanks if they are not
refilled at a prescribed interval.

Peter

"Peter Dohm" wrote in
:

In the case of light plane tires, I agree with you that really dry
air should work well enough to make the issue trivial. But, if
you need nitrogen for any other reason, it is the cheapest thing
that I know of in an L bottle or larger and using it in the tires
may be essentially free--because you may have to pay rental on the
tanks if they are not refilled at a prescribed interval.

My daughter is a Crew Chief on a C-130 Herc and said that Nitrogen is
used in the struts.

--

"John Godwin" wrote in message
...
"Peter Dohm" wrote in
:

In the case of light plane tires, I agree with you that really dry
air should work well enough to make the issue trivial. But, if
you need nitrogen for any other reason, it is the cheapest thing
that I know of in an L bottle or larger and using it in the tires
may be essentially free--because you may have to pay rental on the
tanks if they are not refilled at a prescribed interval.

My daughter is a Crew Chief on a C-130 Herc and said that Nitrogen is
used in the struts.

--

I'm sure that they use nitrogen in the tires as well--even though they run
at less than half of the pressure of a lot of the heavy jets--it just makes
sense to use it when you have it available.

Getting back to the original subject of whether nitrogen behaves in a manner
more like an "ideal gas" than air, aside from the issue of reactivity, the
answer is yes--especially as pressure is increased and/or temperature is
decreased. Basically, it is relatively easy to have nitrogen that is
extremely dry because it it normally dispensed from the top of a very high
pressure storage bottle--with the result that nearly all of any water vapor
and/or CO2 that is in the bottle will be left in a condensed form at the
bottom of the bottle.

John Godwin wrote in news:Xns9B1BD7A3321FBAvSvcs@
208.49.82.60:

"Peter Dohm" wrote in
:

In the case of light plane tires, I agree with you that really dry
air should work well enough to make the issue trivial. But, if
you need nitrogen for any other reason, it is the cheapest thing
that I know of in an L bottle or larger and using it in the tires
may be essentially free--because you may have to pay rental on the
tanks if they are not refilled at a prescribed interval.

My daughter is a Crew Chief on a C-130 Herc and said that Nitrogen is
used in the struts.


Your daughter smokes cigars?



Bertie

"Bertie the Bunyip" wrote in message
...
John Godwin wrote in news:Xns9B1BD7A3321FBAvSvcs@
208.49.82.60:

"Peter Dohm" wrote in
:

In the case of light plane tires, I agree with you that really dry
air should work well enough to make the issue trivial. But, if
you need nitrogen for any other reason, it is the cheapest thing
that I know of in an L bottle or larger and using it in the tires
may be essentially free--because you may have to pay rental on the
tanks if they are not refilled at a prescribed interval.

My daughter is a Crew Chief on a C-130 Herc and said that Nitrogen is
used in the struts.


Your daughter smokes cigars?



Bertie

You're a dumb ass.