Titanium vs EAN

[MSilvia]

I found the 50 year old testing to be tremendously interesting...with the understanding it was for LOX and not 40% Nitrox.

Gaseous mixtures containing various concentrations of O2 were a part of the study also, and are what was being discussed in the excerpt of "G. Reactions in Gaseous and Oxygen Containing Mixtures" I posted.

The Titanium used on LOX Tanks, aircraft, bicycles, glasses, etc are Titanium Alloys. The production of Titanium Alloys and post production treatments following component manufacturing have certainly changed in the past 50 years.

No argument there, but it has little bearing on the study I posted, which was evaluating the suitability of pure elemental titanium, not it's alloys. The material that was finally selected for use in LOX tanks after reviewing the results of this, and numerous other studies, is irrelevant.

 

[Downing]

you think they'd do the engraving at an extra cost...

I'm glad I got my brand new spankin' T2x ! but honestly, who cares about the engraving... most people would overlook it anyways!

True. I was just being silly. My guess is they'd do the engraving for an extra $1549 and throw in the other bits for free.

 

[martzak]

Ahhh - A 47 year old paper. If references are going to be quoted, this would be a more appropriate source: Amazon.com: Materials Properties Handbook: Titanium Alloys (06005G): E. W. Collings, Gerhard Welsch: Books

the chemical properties of metals do not change with time.
Specifically, which part of that $335 book are you referring to?

 

[martzak]

This is from the UK "DIVER" mag, aug 09.

"The presents of some small titanium components inside the second stage of certain regulators does not in any way affect their use with nitrox.
Some incompatibility between oxygen and titanium has been found, but it occurs only at very high pressure, at high temperatures (over 80 deg Cel) and with a very high oxygen percentage in the mixture (90-100 percent).
So it could be a problem only with a titanium first stage that used pure oxygen in water too hot for a human to endure!"

This is on page 70 in the Kit Q&A.

Really???...then how do you explain this?:
http://www.undercurrent.org/UCnow/issues/y2003/UC0103/Nitrox200301.pdf

 

[DwayneJ]

Really???...then how do you explain this?:
http://www.undercurrent.org/UCnow/issues/y2003/UC0103/Nitrox200301.pdf

80% oxygen on a regulator designed for 40% and we have no idea if the regulator was O2 cleaned. What's the surprise?

 

[MSilvia]

What's the surprise?

The surprise is that anyone would think it was okay to dive a hot (>EAN40) mix with a titanium reg (against manufacturer recommendations) knowing that the titanium could ignite, and that the possibility of ignition could be increased if hydrocarbons were present. What's even more surprising to me is that some folks seem eager to pay extra for that possibility.

 

[fnfalman]

What's even more surprising to me is that some folks seem eager to pay extra for that possibility.

Many fancy themselves to be better experts/engineers/scientists than the original manufacturer, and this applies to a lot of things and not just scuba gears alone.

 

[Sadamune]

No argument there, but it has little bearing on the study I posted, which was evaluating the suitability of pure elemental titanium, not it's alloys. The material that was finally selected for use in LOX tanks after reviewing the results of this, and numerous other studies, is irrelevant.

After perusing the NASA study, (very interesting BTW) I learned that the principal concern of NASA that spurred the study was the reactivity of thin walled (.01 to .063 of an inch) titanium pressure vessels to gaseous and liquid oxygen after impacts (sparking events). The samples they tested of titanium and several of it's alloys, such as 6Al-4V, were of the thicknesses mentioned above. The components of a titanium regulator's 1st stage are unlikely to be so thin I think. The high surface area to volume ratio of such a thin piece of metal makes it especially vulnerable to combustion. Larger (thicker) pieces of titanium, with corresponding greater thermal inertia, would be less prone to combustion as they can absorb more heat. Considering the components of a titanium first stage have greater masses, and thus different vulnerabilities to combustion, I find the narrow focus of the NASA study to be of questionable relevance to the issue titanium regulators.

Another issue is that the specific type of titanium used to manufacture a Ti regulator will affect its oxygen reactivity characteristics. I am aware of at least one Ti regulator that is made from commercially pure titanium (Modulo M's 'Oxygen') I don't know what type of titanium Atomic Aquatics/Scuba Pro/Mares use for their regulators, but it would be interesting to know as it affects the oxygen sensitivity their respective products, albeit to a slight degree. Does anyone happen to know what they use?

Post script - A suggestion for regulator manufacturers: Check out Wah Chang's Ti-45 Nb (55% titanium 45% Niobium) alloy.

Sadamune

 

[MSilvia]

Many fancy themselves to be better experts/engineers/scientists than the original manufacturer, and this applies to a lot of things and not just scuba gears alone.

Sometimes, they are. Manufacturing something doesn't make a person infallible, or even an expert. I've made a bunch of stuff that works great, but I'd be fooling myself if I thought it was above improvement. Working in product development only reinforces this.

 

[Downing]

I don't know what type of titanium Atomic Aquatics/Scuba Pro/Mares use for their regulators, but it would be interesting to know as it affects the oxygen sensitivity their respective products, albeit to a slight degree. Does anyone happen to know what they use?

I think I remember reading the type somewhere in Atomic's literature but don't remember for sure. If Darcy ever comes back from vacation and drops by this thread, I'm sure she could tell you. Or you could just call them, I suppose.

As a post-script to one of my earlier posts, I did the T2 to T2x upgrade earlier this week. The kit contained one metal part, stamped "MONEL", that replaced a titanium part on top of the reg (sorry, I'm unfamiliar with the name of the part), an o-ring and a "T2x" purge cover to replace the "T2" purge cover. Tah-da! I have a T2x, sans the engraving on the first stage, and can switch back and forth between air and nitrox without fear of flames and/or lawyers. :cool2: