Oxygen refilling hazards

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Another thread mentioned hazards while refilling O2 systems, and I think the subject is serious enough to warrant its own independent thread.

A few years ago, a visiting pilot came into my shop, saying his Oxygen transfill line was leaking. (He carries his own cylinder for refills.) I inspected the fittings, as they are the usual source of leaks, but he said, "No, it is leaking in the middle." Since it was a braided stainless steel line, I was skeptical. But on closer examination, I found two "burn spots" in the braid. They were about two inches apart, and I realized that they had been caused by the line shorting across his battery terminals. (The batteries were behind the cockpit on the shelf and the O2 cylinder was mounted farther back in the fuselage.)

I told the pilot to go buy a lottery ticket, as he is one of the luckiest people alive. If the line had been pressurized when the arc happened, I am pretty sure the combination of high-pressure oxygen, a lead-acid battery with a plastic case, aviation fuel present (it was a motorglider) and a lot of petroleum based epoxy in the aircraft structure would have brought a quick end to his charmed life.

Then we insulated his battery terminals with a few layers of heat shrink tubing and a shield that prevents unwanted contact across the terminals.

Something to watch for. Be careful. High pressure oxygen and the refilling process can be very dangerous. Make sure you KNOW what you are doing, and look out for subtle "gotchas" that are not readily apparent.

[Richard Pfiffner[_2_]]

On Monday, June 4, 2018 at 5:55:13 AM UTC-7, wrote:
> Another thread mentioned hazards while refilling O2 systems, and I think the subject is serious enough to warrant its own independent thread.
>
> A few years ago, a visiting pilot came into my shop, saying his Oxygen transfill line was leaking. (He carries his own cylinder for refills.) I inspected the fittings, as they are the usual source of leaks, but he said, "No, it is leaking in the middle." Since it was a braided stainless steel line, I was skeptical. But on closer examination, I found two "burn spots" in the braid. They were about two inches apart, and I realized that they had been caused by the line shorting across his battery terminals. (The batteries were behind the cockpit on the shelf and the O2 cylinder was mounted farther back in the fuselage.)
>
> I told the pilot to go buy a lottery ticket, as he is one of the luckiest people alive. If the line had been pressurized when the arc happened, I am pretty sure the combination of high-pressure oxygen, a lead-acid battery with a plastic case, aviation fuel present (it was a motorglider) and a lot of petroleum based epoxy in the aircraft structure would have brought a quick end to his charmed life.
>
> Then we insulated his battery terminals with a few layers of heat shrink tubing and a shield that prevents unwanted contact across the terminals.
>
> Something to watch for. Be careful. High pressure oxygen and the refilling process can be very dangerous. Make sure you KNOW what you are doing, and look out for subtle "gotchas" that are not readily apparent.

Great battery story. I always recommend soldering the wires to the battery and then using hot glue to cover the terminals.

Also never lubricate or get oil near the O2 fittings.

Richard

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Too right, pure Oxygen will cause greases, along with other things to spontaneous ignite on contact!
I luckily have a very large cylinder, which gives me about 50 hours on EDS.

[Charlie M. (UH & 002 owner/pilot)]

In reference to high pressure O2, be careful on petroleum contamination.
Body oil can be an issue as well as almost any grease/oil.
This goes for breathing O2 or for mixed gas welding/heating (Oxy Acetelyne).
I have read mixed results with silicone grease used sparingly on fitting threads and O-rings.

Better is......
Krytox (industrial supply house like McMaster-Carr) ...http://www2.dupont.com/Lubricants/en_US/assets/downloads/new/H-93907,-Oxygen-challenges-.pdf

Other options..... http://www.ikvlubricants.com/grease-oxygen-greases-pastes

[Dan Marotta]

I have a large bottle and a trans fill hose.Â* I remove the cylinder from
the Stemme and carry it to the big bottle for filling.

On 6/4/2018 10:43 AM, Charlie M. (UH & 002 owner/pilot) wrote:
> In reference to high pressure O2, be careful on petroleum contamination.
> Body oil can be an issue as well as almost any grease/oil.
> This goes for breathing O2 or for mixed gas welding/heating (Oxy Acetelyne).
> I have read mixed results with silicone grease used sparingly on fitting threads and O-rings.
>
> Better is......
> Krytox (industrial supply house like McMaster-Carr) ...http://www2.dupont.com/Lubricants/en_US/assets/downloads/new/H-93907,-Oxygen-challenges-.pdf
>
> Other options..... http://www.ikvlubricants.com/grease-oxygen-greases-pastes
>

--
Dan, 5J

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"pure Oxygen will cause greases, along with other things to spontaneous ignite on contact!"

OK, we have heard this from every "authority" going back to the fifties, but it is NOT necessarily true. If you take a small puddle of oil, grease, acetone or other petroleum lubricant and flow a gentle stream (<20 psi) over it, you will not get a fireball unless there is a source of ignition.

As Charlie M. posted, it is HIGH PRESSURE O2 that provides the mechanism for disaster. The speed at which the oxygen molecules exit the container cause friction. Friction causes heat. Pure oxygen dramatically lowers the flash or ignition point of any material with which it comes in contact. Oils, greases and other petroleum products already have a lower flash point than say, wood, although both are fuels and will burn. If the friction caused by rapidly moving oxygen molecules combines with the fuel and reaches that magic ignition point, then combustion will occur. Try to be somewhere else when this happens.

This is NOT "spontaneous combustion" where the combination of chemicals in contact with each other produce a reaction that produces enough heat to reach the flash or ignition point of one chemical or another, causing the aforesaid disaster. Of course, in any combustion scenario, pure oxygen is the life of the party.

So is tequila, and we all have memories of how that works.