O2 clean for mixed gas?

[cdennyb]

OK, would someone please settle this disagreement between myself and a fellow diver buddy.
He says the tanks, reg, etc. need to be O2 cleaned when we run mixed gas like He/Ox/N2 even if the O2 is down below 21%. I said the only tank & reg, etc. that needs to be cleaned is the 100% O2 tank for deco coming up.
We never mix the regulators 'cause the O2 reg will only fit the O2 bottle. Am I just an accident waiting to happen or what?

I agree that it probably wouldn't hurt to clean everything but sometimes we switch between mixed gas and plain air on casual dives. If we cleaned the main gas stuff wouldn't it just become contaminated again when we run air through them that was filled at a dive shop?

thanks

:) :confused:

[OneBrightGator]

IMO, any tank you plan on using for anything other than air should be clean, even if your LDS doesn't use PP blending. Most shops do use PP, so if you ever plan on traveling with your tanks or even using another shop they would need to be clean.

If you're using your tanks with just air then tell the dive shop your tanks are clean and you need hyper-filtered air.

Ben

[padiscubapro]

cdennyb once bubbled...
OK, would someone please settle this disagreement between myself and a fellow diver buddy.
He says the tanks, reg, etc. need to be O2 cleaned when we run mixed gas like He/Ox/N2 even if the O2 is down below 21%. I said the only tank & reg, etc. that needs to be cleaned is the 100% O2 tank for deco coming up.
We never mix the regulators 'cause the O2 reg will only fit the O2 bottle. Am I just an accident waiting to happen or what?

I agree that it probably wouldn't hurt to clean everything but sometimes we switch between mixed gas and plain air on casual dives. If we cleaned the main gas stuff wouldn't it just become contaminated again when we run air through them that was filled at a dive shop?

thanks

:) :confused:

Your friend is right..

most places mix trimix by partial pressure blending although continuous blending is becoming more common..

If you are not diving Heliar (trimix made from strictly blending air and helium) the blender must put oxygen into the tank to raise the oxygen content... for example if you wanted a mix like 18/50 or even 16/50 oxygen has to be added, if you use 50% helium and top with air you get approximately a 10/50 mix...

yes only use oxygen compatible gas..

[pt40fathoms]

Tanks and valve MUST be O2 clean if you are partial pressure blending the gas. In the vast majority of the times, this is the case. End of story, no further discussion needed. If you are not partial blending the gas, I would still O2 clean them. It's cheap and good insurance.

Now for your reg.

Only if you are planning to use gas blends that contain 40% or more O2. If not, than O2 cleaning of the reg is not required. That is not to say that you can pick up any old dirty seldom serviced piece of Ebay bargin special and use it. It should be clean and serviced, but O2 clean is not a requirment. BEWARE of some regs that have "exotic" metals. Titanium WILL react in an O2 enriched environment, causing it to start on fire. This would make for a very short dive,,,and life.

[100days-a-year]

Guess we bettter ground all those fighter planes with titanium components in them as they operate in an enriched 02 environment in the cockpit.Yes aluminium,magnesium and titanium will combust and burn so hot they will self-generate 02 from water.Aluminum in fact is an ingredient in napalm.But spontaneous combustion is a myth.Fire requires fuel,oxygen and a source of ignition and the abdiatic heat generated in a reg seems hardly sufficient to provide the spark.Product liability lawyers have got everyone sceaming "the sky is falling".02 cleaning is better than not but viton and halocarbon lubes are combustible.There's no harm in it, so I 02 clean every piece of equipment I own that may come into contact with enriched air.

[padiscubapro]

100days-a-year once bubbled...
Guess we bettter ground all those fighter planes with titanium components in them as they operate in an enriched 02 environment in the cockpit.Yes aluminium,magnesium and titanium will combust and burn so hot they will self-generate 02 from water.Aluminum in fact is an ingredient in napalm.But spontaneous combustion is a myth.Fire requires fuel,oxygen and a source of ignition and the abdiatic heat generated in a reg seems hardly sufficient to provide the spark.Product liability lawyers have got everyone sceaming "the sky is falling".02 cleaning is better than not but viton and halocarbon lubes are combustible.There's no harm in it, so I 02 clean every piece of equipment I own that may come into contact with enriched air.

I know of at least 1 incident that a titaium reg spontaneously combusted.. it happened in california a few years back. The reg ignited when the gas was turned on (the person was severly injured).. his mix was just over 70%, in fact the diver used an 80% mix more than once with the same reg...

in fact, going from ambient to 3500 psi 100% oxygen can generate temperatures over 2000f at the compression point!!! This definately meets the requirements for an ignition source!

Viton definate can burn but the flash point is very high, EPDM (used in APeks regs sold in the US) has even a higher flash point but is not as durable.. cristolube is extremely inert.. try this.. get a spoon, put a dab of cristolube on the spoon now heat it with a torch, the cristolube protects the covered portion while the unprotected turns color...

[jviehe]

The basic rule is that anything that will touch more than 40% oxygen, whether when filling or breathing, needs to be 02 clean. So, if they are PP filling -any- tank, it needs to be 02 clean. If you are breathign pure 02, the tank, reg needs to be clean.

[100days-a-year]

Where does 02 go from ambient to 3500 psi? Why don't Al tanks blow up when PP filling where it is possible to see the pressure actually go from 3500 to ambient?In a reg the air is at no time ever greater than 150~ more or less over ambient as the 1st stage steps down the pressue .The 1st stage orifice allows only a small volume of air by at lo pressures.Also what does a reg do when it freeflows.....? it gets cold or freezes up due to the expansion of whatever gas is coming out.I beleive there's a lot of legal hype and internet folklore here.Magnesium,Aluminum and to some extent titanium are used in inlet plenums for a variety of engines as well in a hot environment lots of fuel and in many cases increased PP02 due to turbo or superchargers.In a supposedly 02 clean environment,with deltaPs of less than 200 psi limiting abdiatic heat generation I'd have to see it happen in a lab repeatedly to believe it could happen.

[padiscubapro]

100days-a-year once bubbled...
Where does 02 go from ambient to 3500 psi? Why don't Al tanks blow up when PP filling where it is possible to see the pressure actually go from 3500 to ambient?In a reg the air is at no time ever greater than 150~ more or less over ambient as the 1st stage steps down the pressue .The 1st stage orifice allows only a small volume of air by at lo pressures.Also what does a reg do when it freeflows.....? it gets cold or freezes up due to the expansion of whatever gas is coming out.I beleive there's a lot of legal hype and internet folklore here.Magnesium,Aluminum and to some extent titanium are used in inlet plenums for a variety of engines as well in a hot environment lots of fuel and in many cases increased PP02 due to turbo or superchargers.In a supposedly 02 clean environment,with deltaPs of less than 200 psi limiting abdiatic heat generation I'd have to see it happen in a lab repeatedly to believe it could happen.

AMBIENT TO 3500- try the spg and the initial pressurization of a regulator first stage or did you forget it is connected to the tank... an oxygen fill at 3000 is more likely but the temp is still around that point.. I have a picture of an SPG that the boot melted from an oxygen ignition, it happened underwater so there was no catastrophic fire but lots of heat was generated. Even with the "restricted" orifice of the HP hose the gas gets heated quite rapidly, a free flow is a different issue you are getting cooling because there is a pressure drop (and expansion)not a rise... raising pressure of any gas generates heat, dropping the pressure loses heat... once the reg is pressurized the risk due to a small delta p is minimal (cant say zero), all problems are on the initial pressurization, there is very little retriction on the HP side, another source of ignition on initial pressurization is particle impingement, that is small rust particles hitting the screen on the first stage..

Al tanks don't burn for 2 reasons first the alloy is a combination of metals not just al, secondary the tank is a HUGH heat sink.. rapid heat buld up is only going to occur in a place where there is not sufficient material to sink the heat away.. in Russia they used to use TITANIUM cylinders with oxygen and they don't get ignition, why same reason - its one big heat sink....

there are plenty of studies about adiabatic compression with regards to oxygen and more patents to help solve the issue..

[cdennyb]

Well, I just lost a large pepperoni pizza and a pitcher of beer, thank you very much!;-0

But, since the majority of you out there agree, I will have to concede 'defeat' and admit I will now have ALL of my gear O2 cleaned.

I am contemplating having a couple of Al80's allocated to strictly Comp Air and maybe use a backup set of regs for them only. The good stuff will no doubt be kept seperate and now I feel better.

(I certainly appreciate all the accurate and informative opinions out there. Thank you all)

dennisb

[100days-a-year]

So the fire starts in the 1st stage?And what material was that SPG made of?I accede that any contaminants throw out any chance of remaining safe ,but a glass reg would catch on fire with right contaminants.I maintain that Titanium does not spontaneously combust,esp in an 02 clean environment,there must be fuel(in this case we add contaminants)an ignition source(by your admission occuring only in the 1st stage and SPG by way of abdiatic compression)and of course we have the 02.BTW not trying to be a PITA,it just sounds like 2+2=5.cdennyb,sorry about the pizza&beer.This board is wealth of experience&knowledge with very few knuckleheads.

[padiscubapro]

100days-a-year once bubbled...
So the fire starts in the 1st stage?And what material was that SPG made of?I accede that any contaminants throw out any chance of remaining safe ,but a glass reg would catch on fire with right contaminants.I maintain that Titanium does not spontaneously combust,esp in an 02 clean environment,there must be fuel(in this case we add contaminants)an ignition source(by your admission occuring only in the 1st stage and SPG by way of abdiatic compression)and of course we have the 02.BTW not trying to be a PITA,it just sounds like 2+2=5.cdennyb,sorry about the pizza&beer.This board is wealth of experience&knowledge with very few knuckleheads.

if memory serves the spg was a brass guage (very oxygen compat) with a rubber boot, the metal had to get damn hot.., since it didn't completely fail the ignition was probably in the swivel..
the 2nd stages should not be a problem because the greatest the delta p will be is around 10bar/145psi or so and particulate matter should be stopped at the filter...

with an ignition source titanium will burn no extra fuels necessary but there must be some source for ignition.. NASA did test on various metals several years back.. with no contaminates and just a spark they were able to get the titanium to combust at something like 15 psi...

they did the test in a chamber that was pressurized with oxygen to various pressures, the metal under test was several cm long (dont remember the exact length) by 1mm in diameter, this way there was little heat sinking, they generated a spartk and kept repeating as pressure was raised until the metal burned.. copper required a very high pressure, while magnesium burned around ambient and titanium slightly higher...

I'll see if I can dig up copies of the report....

[BOATS313]

I seem to remember in high school we took pure sodium which is a metal and placed a very small piece into a beaker full of room temp water. The result was a fire on the surface as the metal burned. No heat source was needed. We repeated the experiment with magnisium and aluminum with the same results. Pure metals, not alloys, in certian forms will combust without anything more than a little moisture. Tanks and other equipment are made from alloys not pure metals so there should be no problems.

[100days-a-year]

PSP,with a little searching the 02 psi for Aluminium was 35.Metals that end in"ium"are very combustible and are mentioned in MSDS for many 02 handling products.Cadmium,aluminium,titanium,sodium,magnesi um and even chromium.A little chemistry research will tell you why they are susceptible to oxidation reduction reactions.I found a lot of info that suggested the practical ignition source was as you mentioned impingement.I still haven't found any titanium cases that did not have other contributing factors.I found dozens of cases where aluminum 02 regs have burnt up firefighters and medical personel.I will have to accede thier unsuitability based on my biggest find and that was believe it or not ..galling, which could lead to particles, which becoming sonic, striking the titanium and providing the missing factor.. ignition.As an aside in a 145 psi reg there is still a possibility of any chrome,titanium or aluminum particles flashing as the psi has the effect of raising theapparent PO2.I did find cases of aluninum and chrome dive components flashing.I suspect the SPG had organic oils or a rubber o-ring.

[nyresq]

Metals that end in"ium"are very combustible and are mentioned in MSDS for many 02 handling products.Cadmium,aluminium,titanium,sodium,magnesi um and even chromium.

you are talking about pure elemental metals, you don't find any of these metals in pure form in todays manufactured parts, they are combined with other metals and silicates to form alloys.
Titanum by it self is very brittle with aluminum and magnesium being very soft. Pure magnesium and titanium once ignighted makes a hellacious white hot fire that will actually break water into O2 and H and increase the fire.
But look at a dodge viper, the cylinder heads are made of a "magnesium alloy". The temp in a combustion chamber will reach several thousand degrees with an open flame. Titanium is used in firearms now where you also have several thousand degree flames that are shooting against the titanium parts with no explosions and bursting into flames.
I think in the rare circumstances where combustion has occured in regs and valves it could be traced to non O2 compatible seals and lubricants as the source of the fuel, not the exotic metals that are being used.

[100days-a-year]

No...I was not talking about pure elements.I argued your points somewhat previously.My family has a history in aerospace and aviation technology and my experience was in lower pressures and lower PO2s.Upon Googling there is ample evidence than alloys too are susceptible to thier parent metals frailties.AL tanks of various alloys have flashed,as have al 02 regs,chrome valves and other iums.In a raised PO2 the metal is the fuel.My only real beef was the ignition source.BTW I forgot to mention beryllium spheres:)And once the flame is lit it matters not whether the cause was buna-n,body oils,non-oxygen compatable lubes or even bad karma.

[padiscubapro]

nyresq once bubbled...
Metals that end in"ium"are very combustible and are mentioned in MSDS for many 02 handling products.Cadmium,aluminium,titanium,sodium,magnesi um and even chromium.

you are talking about pure elemental metals, you don't find any of these metals in pure form in todays manufactured parts, they are combined with other metals and silicates to form alloys.
Titanum by it self is very brittle with aluminum and magnesium being very soft. Pure magnesium and titanium once ignighted makes a hellacious white hot fire that will actually break water into O2 and H and increase the fire.
But look at a dodge viper, the cylinder heads are made of a "magnesium alloy". The temp in a combustion chamber will reach several thousand degrees with an open flame. Titanium is used in firearms now where you also have several thousand degree flames that are shooting against the titanium parts with no explosions and bursting into flames.
I think in the rare circumstances where combustion has occured in regs and valves it could be traced to non O2 compatible seals and lubricants as the source of the fuel, not the exotic metals that are being used.

I have to agree with 100 days a year... The alloys of the base metals are also suseptible to burning.. many are mixed with more compatible metals but they still burn.. most titanium alloys burn at very low pressures IN THE PRESENCE OF OXYGEN..
Also have you ever tried welding titanium, if you aren't careful the metal burns quite easily under a torch..

Heat is a good ignition source(in scuba, its probably coupled with particle impingement from the cylinders), but it also requires a raised pressure and oxygen as the catalist..
I'm no mechanic but I do know the normal pressure within cylinders of an engine is not very high..
The things you are talking about are NOT a high oxygen enviroment. That is the KEY

[nyresq]

the pressure in a firearm made out of titanium can reach 30-40,000 psi when a cartrige is fired, and I havent seen any problems with titanium guns being fired and burning the frames.
lets look at an engine, normal compression for a high performance motor is roughly 13:1... thats 13 times the normal ambient pressure or 14 ATAs. and thats prior to the explosion, which in turn creates more pressure, and while the burning uses some of the O2 it also creates focused heat on the alloy parts and an ignition source. the temps in a high performance motor is much higher than anything that will occur inside a tank or regulator.

and if your saying titanium alloy will burn when welding (never tried to weld titanium)which is being done at ambient pressure, then the pressure has no bearing on the burning process, just the O2 rich enviorment is enough to ignighte it with some heat applied.

[padiscubapro]

nyresq once bubbled...
the pressure in a firearm made out of titanium can reach 30-40,000 psi when a cartrige is fired, and I havent seen any problems with titanium guns being fired and burning the frames.
lets look at an engine, normal compression for a high performance motor is roughly 13:1... thats 13 times the normal ambient pressure or 14 ATAs. and thats prior to the explosion, which in turn creates more pressure, and while the burning uses some of the O2 it also creates focused heat on the alloy parts and an ignition source. the temps in a high performance motor is much higher than anything that will occur inside a tank or regulator.

and if your saying titanium alloy will burn when welding (never tried to weld titanium)which is being done at ambient pressure, then the pressure has no bearing on the burning process, just the O2 rich enviorment is enough to ignighte it with some heat applied.

14 ATAs you are still under 200 PSI in an engine... in the gun almost all oxygen will be instantaneously consumed and the flash inside the engine also consumes are large quantity of oxygen. in the cylinder of an engine the pressure rapidly drops (forcing cooling) and so does the pressure inside the barell of a gun.. Pressures inside a cylinder head are not as great as you would expect and is not necessary... the required force to move a piston is directly related to the area of the piston.. Thats why where the force is concentrated is a very small area as opposed to the chamber that is being filled.. lets use a simple example we will assume our source gas is 10 psi, if we fill a chamber that has a disk of say 6 inches in diameter and the output side has a diameter of only 1 inch (ratio of areas) the the pressure exerted on the opposite side is about 1440 psi (I did this in my head so dont shoot me if its not totally accurate, but you should get the point) this also doesn;t take into account friction loss and a few other factors but its close enough..

No you don't understand... you need FUEL (the metal), elevated pressure, AND OXYGEN, the last being the strongest factor..

Pressure is a factor that AIDS the combustion by raising the partial pressure of oxygen.. Its not necessary its just an adder.... Remove the extra oxygen things become much more difficult... when welding titanium you don;t get a flash or runaway burn since there is not enough oxygen available.. BTW most flash fires are over before you realized they ever happened.. A flash fire from oxygen usually consumes all the oxygen almost instaneously and the fire is extinguished since there is no more oxygen.. obviously if its connected to an oxygen cylinder like the medical regs that have burned up thiis is a different story..

Oxygen heated through Adiabatic compression can easily reach temps of 2000 degree f at the compression point. The heat rise of air is no where near as high..

[100days-a-year]

Not too many weapons are fired in a pressurized 02 atmosphere.Nitrous oxide is used in gasoline motors as an oxidizer instead of cheaper,more effective 02 for what reason.Another good source of the history of hi pressure oxygen and "iums" can be found by studying the early history of liquid fuel rocketry and jet engines.Something I neglected earlier.

[padiscubapro]

Here is an interesting paper from NASA on Oxygen

http://ston.jsc.nasa.gov/collections/TRS/_techrep/TM104823.pdf

here is a link of a company defending their product of an aluminum oxygen regulator saying its safe and blaming everything else as the problem..

http://www.floteco2.com/htm/Technical%20Bulletins/TB-Aluminum%20Regulator.html