Why helium, and not some other, less expensive gas?

thanks

gary

Because helium permeates leaks very well and is easy to separate from
abundant background ions in a cheap mass spectrometer.

--
Regards,
Carl Ijames carl dott ijames aat verizon dott net
(remove nospm or make the obvious changes before replying)

wrote in message
...
Why helium, and not some other, less expensive gas?

thanks

gary

Helium is the only gas that is monatomic and therefore smaller
than the diatomic, or molecular, form of all other gases such
as H2, O2, N2, etc; and it will find leaks nothing else will.
Art

wrote in message
...
Why helium, and not some other, less expensive gas?

thanks

gary

wrote:
Why helium, and not some other, less expensive gas?
If you've never used a helium leak detector, you don't NEED much
of it. Some pros who go around large labs finding leaks use
tanks just the next size up from a lecture bottle, and that
lasts them months. A 5' tall tank (120 CF? 160 CF?) lasted us
about 8-10 years in our lab. You let the helium trickle out of
an un-sharpened hypodermic needle just fast enough to make
bubbles in water.

Jon

On Sun, 11 Nov 2007 22:37:54 -0600, Jon Elson
wrote:

wrote:
Why helium, and not some other, less expensive gas?
If you've never used a helium leak detector, you don't NEED much
of it. Some pros who go around large labs finding leaks use
tanks just the next size up from a lecture bottle, and that
lasts them months. A 5' tall tank (120 CF? 160 CF?) lasted us
about 8-10 years in our lab. You let the helium trickle out of
an un-sharpened hypodermic needle just fast enough to make
bubbles in water.

Jon

Jon they are called "drawing up" needles. used to load a syringe with
a dose of medication delivered through a very fine needle.
they are made with a squared off tubular end.
Stealth Pilot

In article ,
"Artemus" wrote:

Helium is the only gas that is monatomic and therefore smaller
than the diatomic, or molecular, form of all other gases such
as H2, O2, N2, etc; and it will find leaks nothing else will.
Art

Hydrogen also works, but is explosive and harder (more expensive) to
detect.

Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/

Stealth Pilot wrote:
On Sun, 11 Nov 2007 22:37:54 -0600, Jon Elson
wrote:


wrote:

Why helium, and not some other, less expensive gas?

If you've never used a helium leak detector, you don't NEED much
of it. Some pros who go around large labs finding leaks use
tanks just the next size up from a lecture bottle, and that
lasts them months. A 5' tall tank (120 CF? 160 CF?) lasted us
about 8-10 years in our lab. You let the helium trickle out of
an un-sharpened hypodermic needle just fast enough to make
bubbles in water.

Jon


Jon they are called "drawing up" needles. used to load a syringe with
a dose of medication delivered through a very fine needle.
they are made with a squared off tubular end.
Stealth Pilot

Yes, but our stockroom doesn't have them, so we just grind down
a standard sharp needle. It is pretty quick to do.

Jon

On Nov 12, 1:55 am, "Artemus" wrote:
Helium is the only gas that is monatomic and therefore smaller
than the diatomic, or molecular, form of all other gases such
as H2, O2, N2, etc; and it will find leaks nothing else will.
Art
Argon is also monatomic, but way too big to use for leak detection.

I can't find the reference now, but as I remember the diffusion rate
is 1/AT^.5( inversely proportional to the square root of the atomic
weight.)

Dan

"Artemus" wrote in message
. ..
Helium is the only gas that is monatomic and therefore smaller
than the diatomic, or molecular, form of all other gases such
as H2, O2, N2, etc; and it will find leaks nothing else will.
Art

Everyone always says that, but ISTR some experiments which showed that the
permeability wasn't all that different. OTOH
the rarity of He other than from the leak site is a very good reason.

newshound wrote:
"Artemus" wrote in message
. ..

Helium is the only gas that is monatomic and therefore smaller
than the diatomic, or molecular, form of all other gases such
as H2, O2, N2, etc; and it will find leaks nothing else will.
Art


Everyone always says that, but ISTR some experiments which showed that the
permeability wasn't all that different. OTOH
the rarity of He other than from the leak site is a very good reason.



I think hydrogen will diffuse through insanely small holes very
well, too, making it hard to keep it in sealed systems. But, it
has this other property, related to hydrogen embrittlement, and
adsorption on and in a number of metals, such as Ti, W, Mg, etc.
Once you get H2 adsorbed onto metals, it can take years to go
away if you don't cook the metal. So, allowing H2 to get into a
vacuum chanber will result in a LONG time decay of the tracer
gas. He has that inertness that means it won't stick to
ANYTHING, and will just diffuse away as fast as it diffused in,
thus making it a GREAT tracer gas.

Jon

On Nov 12, 4:51 pm, "newshound" wrote:

Everyone always says that, but ISTR some experiments which showed that the
permeability wasn't all that different. OTOH
the rarity of He other than from the leak site is a very good reason.

I did a temp job at a place that made sealed opto-electro-mechanical
instruments which were leak-tested with hydrogen. The H2 background
level in the room was significant despite a rollup truck door that was
opened several times a day.

Hydrogen doesn't use 2 atoms for a gas it uses 1. When forming the oxide
of oxygen - H2O it uses two. Without the oxygen atom one would have two
atoms of Hydrogen gas.

One would not want to put Hydrogen in steel pipe as stated embrittlement.
So it would be He or Ne(on). are the best. Putting a tracer on one or the
other would be best. Easier to trace the tracer (radio-active) than that of
a atom or a bunch...

Martin
Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Life; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
http://lufkinced.com/


Jon Elson wrote:
newshound wrote:
"Artemus" wrote in message
. ..

Helium is the only gas that is monatomic and therefore smaller
than the diatomic, or molecular, form of all other gases such
as H2, O2, N2, etc; and it will find leaks nothing else will.
Art


Everyone always says that, but ISTR some experiments which showed that
the permeability wasn't all that different. OTOH
the rarity of He other than from the leak site is a very good reason.



I think hydrogen will diffuse through insanely small holes very well,
too, making it hard to keep it in sealed systems. But, it has this
other property, related to hydrogen embrittlement, and adsorption on and
in a number of metals, such as Ti, W, Mg, etc.
Once you get H2 adsorbed onto metals, it can take years to go away if
you don't cook the metal. So, allowing H2 to get into a vacuum chanber
will result in a LONG time decay of the tracer gas. He has that
inertness that means it won't stick to ANYTHING, and will just diffuse
away as fast as it diffused in,
thus making it a GREAT tracer gas.

Jon

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Martin H. Eastburn wrote:

Hydrogen doesn't use 2 atoms for a gas it uses 1. When forming the oxide
of oxygen - H2O it uses two. Without the oxygen atom one would have two
atoms of Hydrogen gas.

Well, no, hydrogen gas is composed of H2 molecules. Two atoms.

I do think that Artemus was incorrect in saying that helium is the
only monatomic gas. There's neon, argon, krypton, xenon and radon.

Slater

On Nov 14, 10:14 pm, wrote:
Martin H. Eastburn wrote:

Hydrogen doesn't use 2 atoms for a gas it uses 1. When forming the oxide
of oxygen - H2O it uses two. Without the oxygen atom one would have two
atoms of Hydrogen gas.

Well, no, hydrogen gas is composed of H2 molecules. Two atoms.

Electrolysis of water does produce about twice the volume of hydrogen
gas (H2) as the volume of oxygen gas (o2). Exactly twice the number of
molecules. Maybe that's what you were thinking of?

Slater

On Wed, 14 Nov 2007 19:14:20 -0800 (PST), with neither quill nor
qualm, quickly quoth:

Martin H. Eastburn wrote:

Hydrogen doesn't use 2 atoms for a gas it uses 1. When forming the oxide
of oxygen - H2O it uses two. Without the oxygen atom one would have two
atoms of Hydrogen gas.

Well, no, hydrogen gas is composed of H2 molecules. Two atoms.

True, but when encruptured by the Retro Encabulator, an additional
atom of oxygen is introduced and di-hydrogen monoxide results. The
toxic result has to be removed, at great cost, mind you, by the burly
and spacesuited men from deep in the bowels of the EPA's Superfund.

--
Real freedom lies in wildness, not in civilization.
-- Charles Lindbergh

Larry Jaques wrote:

True, but when encruptured by the Retro Encabulator, an additional
atom of oxygen is introduced and di-hydrogen monoxide results. The
toxic result has to be removed, at great cost, mind you, by the burly
and spacesuited men from deep in the bowels of the EPA's Superfund.

I'll be darned.

http://en.wikipedia.org/wiki/Turboencabulator

Slater

You are right - hum - so much work in the old days with H. 1h1 2h1 3h1.
But that was 40 some odd years ago.

Martin
Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Life; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
http://lufkinced.com/


wrote:
Martin H. Eastburn wrote:

Hydrogen doesn't use 2 atoms for a gas it uses 1. When forming the oxide
of oxygen - H2O it uses two. Without the oxygen atom one would have two
atoms of Hydrogen gas.

Well, no, hydrogen gas is composed of H2 molecules. Two atoms.

I do think that Artemus was incorrect in saying that helium is the
only monatomic gas. There's neon, argon, krypton, xenon and radon.

Slater

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Hey - that isn't funny -

Just moved out of a 100 site super fund area. That map was freaky.
Shown once and then hidden for all eyes but the EPA and those who did it.

Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Life; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
http://lufkinced.com/


Larry Jaques wrote:
On Wed, 14 Nov 2007 19:14:20 -0800 (PST), with neither quill nor
qualm, quickly quoth:

Martin H. Eastburn wrote:

Hydrogen doesn't use 2 atoms for a gas it uses 1. When forming the oxide
of oxygen - H2O it uses two. Without the oxygen atom one would have two
atoms of Hydrogen gas.
Well, no, hydrogen gas is composed of H2 molecules. Two atoms.

True, but when encruptured by the Retro Encabulator, an additional
atom of oxygen is introduced and di-hydrogen monoxide results. The
toxic result has to be removed, at great cost, mind you, by the burly
and spacesuited men from deep in the bowels of the EPA's Superfund.

--
Real freedom lies in wildness, not in civilization.
-- Charles Lindbergh

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

On Wed, 14 Nov 2007 19:32:13 -0800 (PST), wrote:

On Nov 14, 10:14 pm, wrote:
Martin H. Eastburn wrote:

Hydrogen doesn't use 2 atoms for a gas it uses 1. When forming the oxide
of oxygen - H2O it uses two. Without the oxygen atom one would have two
atoms of Hydrogen gas.

Well, no, hydrogen gas is composed of H2 molecules. Two atoms.

Electrolysis of water does produce about twice the volume of hydrogen
gas (H2) as the volume of oxygen gas (o2). Exactly twice the number of
molecules. Maybe that's what you were thinking of?

Slater


Not in the least. Both Hydrogen and Oxygen have two atoms per molecule.


Mark Rand
RTFM

Mark Rand wrote:
wrote:
[...]
Electrolysis of water does produce about twice the volume of hydrogen
gas (H2) as the volume of oxygen gas (o2). Exactly twice the number of
molecules. Maybe that's what you were thinking of?

Not in the least. Both Hydrogen and Oxygen have two atoms per molecule.

I'm not sure what you're disagreeing with.

Yes, gaseous hydrogen and oxygen each have two atoms per molecule,
as I indicated by saying "H2" and "O2". Water, however, has two
hydrogen atoms and one oxygen atom, so decomposition releases twice as
many molecules of H2 as O2:

Two H2O - two H2 + one O2

The volume of the hydrogen gas will be about twice that of the
oxygen gas at STP.

Slater

On Fri, 16 Nov 2007 18:07:30 -0800 (PST), wrote:

Mark Rand wrote:
wrote:
[...]
Electrolysis of water does produce about twice the volume of hydrogen
gas (H2) as the volume of oxygen gas (o2). Exactly twice the number of
molecules. Maybe that's what you were thinking of?

Not in the least. Both Hydrogen and Oxygen have two atoms per molecule.

I'm not sure what you're disagreeing with.

Yes, gaseous hydrogen and oxygen each have two atoms per molecule,
as I indicated by saying "H2" and "O2". Water, however, has two
hydrogen atoms and one oxygen atom, so decomposition releases twice as
many molecules of H2 as O2:

Two H2O - two H2 + one O2

The volume of the hydrogen gas will be about twice that of the
oxygen gas at STP.

Slater


I think I was agreeing with you and disagreeing with Martin. Must have been a
bad day at the orifice :-)


Mark Rand
RTFM