oxygen cleaning for nitrox (partial pressure) fills

[bnelson]

oxygen clean simply means "will not explode is 02 is run through this equipment"

clean inert particulates will not render something "unclean" for 02 use, just dirty

most common oils and lubricants will react with 02 under pressure and explode

 

[JeffG]

most common oils and lubricants will react with 02 under pressure and explode

You sure about that?

 

[espenskogen]

You sure about that?

I share your scepticism regarding this, Jeff.

I suspect most common lubricants and oils, when exposed to heat (Which can be generated in the fill process) and oxygen, will burn rather merrily. (Which is why we use an oxygen compatible, water based lubricant in oxygen valves). It will not however react to oxygen as such. Remember the fire triangle - combustible material, oxygen and heat makes fire.
Take one out, and you have no fire.
An explosion is just a particularly fast and furious fire.

 

[oxyhacker]

Wow if anything could guarantee something will not explode if O2 is run through it we would all be happier people.

A more accurate definition might be "probably won't combust due to issues related to the presence of the more easily removed contaminants". Oxygen cleaning does nothing about design shortcomings and little about material incompatibilities so it cannot be said to make anything safe. Just, hopefully, safer.

oxygen clean simply means "will not explode is 02 is run through this equipment"

clean inert particulates will not render something "unclean" for 02 use, just dirty

most common oils and lubricants will react with 02 under pressure and explode

 

[dflipp]

I just found this in the FAQ section of the Luxfer website:

"8. Question: Are Luxfer scuba cylinders ready for oxygen service when they leave the Luxfer factory?

Answer: New Luxfer scuba cylinders manufactured from January 1, 2000 , until December 31, 2004 , will have been cleaned for oxygen service at the factory and sealed with an oxygen-compatible cap before being shipped. However, starting on January 1, 2005 , Luxfer will provide oxygen-clean scuba cylinders only by special order. Unless specifically ordered “oxygen clean,” all new Luxfer scuba cylinders will be cleaned for gas mixtures containing only up to 23.5% oxygen. (Of course, it will still be possible to have these cylinders cleaned for use with higher concentrations of oxygen by following the DOT-specified procedures cited above.) "

So perhaps it is true that the cylinder my LDS has for sale has not been cleaned for O2 service. It is an XS branded cylinder so I guess the question would be does XS special order all of their cylinders from Luxfer? I didn't see the green bordered decal on it.

 

[bnelson]

not heat

oxygen is not a fuel, it's an oxidizer

any presence of fuel (including oils, petrolium products, organics, etc will cause a reaction, in presence of an oxidizer.

oxygen is such a good oxidizer that nothing will oxidize oxygen, not even itself, and under pressure, it's an even better oxidizer

oh, and when i say "reaction" i mean "big explosion" in regards to the unclean 02 regulator

I share your scepticism regarding this, Jeff.

I suspect most common lubricants and oils, when exposed to heat (Which can be generated in the fill process) and oxygen, will burn rather merrily. (Which is why we use an oxygen compatible, water based lubricant in oxygen valves). It will not however react to oxygen as such. Remember the fire triangle - combustible material, oxygen and heat makes fire.
Take one out, and you have no fire.
An explosion is just a particularly fast and furious fire.

 

[DA Aquamaster]

not heat

oxygen is not a fuel, it's an oxidizer

any presence of fuel (including oils, petrolium products, organics, etc will cause a reaction, in presence of an oxidizer.

oxygen is such a good oxidizer that nothing will oxidize oxygen, not even itself, and under pressure, it's an even better oxidizer

oh, and when i say "reaction" i mean "big explosion" in regards to the unclean 02 regulator

"Oxidizer"??? Think about the root word for awhile, then reconsider what you just said.

Of course "oxygen" is a good "oxidizer" - it's the only "oxidizing" element on the periodic chart and any "oxidizing" compound has to contain O2 that is available to react with whatever it is opxydizing. There are other elements and compounds however that are catalysts that cause reations to occur faster.

You are not going to have a fire with just oxygen and a fuel source present, you also need an ignition source. This could be due to adibatic heating due to a sudden increase in pressure (such as turning a valve on very fast, suddenly pressurizing your first stage), gas flow around a sharp corner, or from a spark.

As far as O2 clean goes, it's a relative term. Even if you atarted out with a perfectly clean O2 tank assembled in a NASA clean room, as soon as you fill it with an Air/02 mix you are going to begin adding impurities to the tank and these impurities are going to build up with each and every fill. Consequently those impurities will eventually add up to a sizeable fuel source and recleaning will be needed.

But getting really anal about 02 cleaning makes little sense as at best you are minimizing the risk not eliminating it.

Local dive shops are of course concerned about O2 cleaning as they are the ones who get hurt if somethihng blows up. Personally, however I think LDS's are much safer if they offer affordable O2 cleaning and have their customers get their tanks cleaned more often. I don't understand the logic behind over priced O2 cleaning - other than of course just trying to gouge technically oriented divers (who would spend more money with them if they treated them fairly).

Perfectly O2 clean or not, any diver is well served to follow safe procedures when using high percentage O2 tanks, such as opening valves slowly and with the purge button depressed slightly to reduce any heating from compression that may occur inside the regulator. Far more fires and explosions occur on that end than on the fill end of things.

 

[JeffG]

You are not going to have a fire with just oxygen and a fuel source present, you also need an ignition source. This could be due to adibatic heating due to a sudden increase in pressure (such as turning a valve on very fast, suddenly pressurizing your first stage), gas flow around a sharp corner, or from a spark.

Yeppers, but pressure by itself isn't going to cause it to go "boom"

as per

most common oils and lubricants will react with 02 under pressure and explode

 

[Mark Vlahos]

Yeppers, but pressure by itself isn't going to cause it to go "boom"

as per

I was taught in my welding class that high pressure can change the temperature needed for some materials to burn. A diesel engine is a pretty good example of how this works.

Mark Vlahos

 

[WarmWaterDiver]

Oxygen can so oxidize itself - the compound is known as ozone (O3). Just the facts. You're doing some of this each time you drive a vehicle with a catalytic converter BTW. Fuel formulation can help reduce this. You can generate this around electrical equipment too. Some is present in the upper layers of the Earth atmosphere.

We are a bit more conservative than the average poster here about O2 cleaning of our equipment, but that's based on our industrial experience (I've worked with liquid O2 systems, converting to vapor and then injection for combustion enhancement).

Everyone is free to make their own choices.

It's the change in pressure that generates the heat needed for self-ignition in a diesel engine, along with some residual heat from the previous cycle - it still needs glow plugs to get started.