Titanium plates....(silly question?)

[dlarbale]

All Docs,

I know that Titanium is a problem with 100% O2, I pressume that this is just at high pressures and that the dozen odd plates that I have in my face wont cause any issues (even if I'm decoing on O2)?

Just a thought - Dave.

 

[norcaldiver]

Not a doc, but:
It was my understanding that Titanium is an igniter and is dangerous with anything over 40%. But I don't think that this would be a problem with plates "in" you face, only if the metal was actually making contact WITH the O2, like a titanium 1st stage.

 

[agstreet]

The problem with titanium is that it starts burning easier than brass or steel, and once started is almost impossible to stop (for most of us who don't have specific chemicals intended for fighting metallic fires). Titanium is contraindicated for high O2 concentrations in regulators because it's fairly easy to generate high temperatures under conditions of high pressure and a closed system.

In your case, the titanium is protected from direct contact with the breathing gas by your body tissues. And even if you had exposed Ti screws in your mouth, they wouldn't be subjected to the conditions that cause heating inside a regulator.

Alan

 

[Scubaroo]

The problem with titanium is when it is used in a regulator component that is subject to adiabatic heating - usually when the tank valve is first turned on. In laymans's terms, the small amount of air inside of the regulator is at room temperature, and room pressure, and is then subject to a massive increase in pressure from the valve being opened, eg from 14.7psi to 3000psi. It's the existing air in the regulator that is compressed, and this results in the molecules being compressed, and through some fancy physics stuff I forget, results in an increase in thermal energy. In other words it gets real hot real fast. This could result in heat that is sufficient to ignite the titanium, and the higher the O2 content of the incoming gas, the more likely combustion is.

Titanium face plates are absolutely irrelevant, but they might screw your trim up a little

 

[dlarbale]

All,

Thanks for the replies. I suspected there was no cause for concern but thought I'd best check.

Learnt a bit about O2 dangers as well.

Dave.

 

[BigJetDriver]

As has been suggested above, the problem with titanium occurs in those places in a gas system where oxygen molecules moving at high speed strike an object, such as a high pressure seat. Thus we have both molecular friction, and the heat of compression. This may be, and has been, the point at which a substance which is normally fairly inert goes above the required ignition temperature in the presence of an increased amount of oxidizer.

That having been said, the usual culprits are the O-rings and the lubricant in any system. They have the lowest ignition temperatures, and become problematic when the gas in the system gets above the 40% O2 mark, hence the need for Viton rings and Christolube (or suitable equivalents).

Two excellent references are the PSI Inc. text on cylinder inspection by Bill High, and the Oxygen Hacker's Companion.

 

[MercutioATC]

and since, in an emergency situation, you obviously might not be able to tell them about the titanium plates, I'd assume it was OK. I can't see a surgeon placing somebody at risk like that.

 

[Laurence Stein DDS]

Hi dlarbale

It's not a silly question. I'm a dentist rather than an MD or an engineer.

We use titanium all the time for dental implants and I have yet to have a patient catch on fire while diving!

At high temperatures and/or pressures and/or O2 concentrations many metals can ignite. POWDERED aluminum is used for solid rocket fuel--it's mixed with a butyl rubber and ammonium perchlorate oxidizer. It will also ignite in air if dispersed and a source of ignition is added.

Powdered iron dust is used in Thermite and steel wool can be ignited with a candle.

Powdered zinc is damned near explosive when mixed with sulfur and ignited in air.

Magnesium does not need to be powdered...friction can be sufficient to ignite it like the struts on aircraft landing gear---and a flat tire...water won't put it out.

Sodium metal ignites spontaneously in air.

And, yes, titanium can be ignited by oxygen at high pressure and at least momentary high temperature.

The key here is several fold. By powdering the metals, there is a huge amount of increased surface area to react with an oxidizer and then ignited,

Your titanium are solid. They may have been powdered and then compressed/sintered or may be alloyed with nickle, aluminum and vanadium for extra strength. It could have also been cast as solid ingots and machined. No matter, the solid surface is insufficient even in the presence of PPO2 that is a few atmospheres over atmospheric will cause ignition.

Another consideration is that once the hemoglobin in the blood is saturated, the PPO2 won't significantly increase the amount of oxygen carried by the red blood cells. However the increased PP will allow additional oxygen to dissolve in plasma and tissue fluids. The titanium plate is surrounded by fluid rather than gasous oxygen so again ignition is not a factor.

Finally, as an aside, the biologic compatibility of titanium is directly related to the titanium oxide that will coat the outside of plates, screws or implants. Bone will adhere to this layer. Some dental implants are now being fabricated with titanium oxide of variable thickness to facilitate bone adhesion.

Remember DON'T SMOKE!!!ut:

Larry Stein