Regulators and Nitrox

[Lost Yooper]

 

[100days-a-year]

Guess we should recall all those planes the milatary use due to the use of multiple fire hazardous material.In the aviation industry O2 regularly comes in contact with Aluminum,Magnesium and Titanium.Also in the prescence of thermoplastics and PTFE lubricants and more.They seem to have a grasp on the concept of a fire TRIANGLE.BTW stories that begin with "once upon a time"are called fairy tales.When they start with"this really happened"they're called something else.

 

[roakey]

100days/Tony,

I’m trying to be careful here. O2 is not trifled with. I’m guilty of joking too about using O2 compatible mouthwash after eating a greasy pizza, but in actuality I do take the topic seriously. In reality when looking at O2 combustion we’re probably looking at a four-dimensional function, pressure being one axis, O2 concentration being a second axis, temperature a third and component flammability a fourth.

The first two we can’t change. The last two we can control. Both are important, I choose to sweat (no pun intended) the temperature part because it’s totally under my control. I also control the flammability (contamination) part as best I can, but I consider it secondary.

So in some ways I’m backpedaling. I think blacknet thought LY and I were laze-faire about the whole O2 thing. We’re not, though we do have a different emphasis. With this clarification we’ll see where the discussion goes from here.

Roak

 

[sharpenu]

Actually, the fire triangle is an outdated concept. The proper term is "fire tetrahedron" It is a four sided equation. Fuel, heat, oxidizer and an uninhibited chemical reaction. While I agree with Roak that it is a complex process, you need to understand that mechanical heat (that which is generated during compression) is only part of the process. Chemical heat (from O2 and hydrocarbons mixing) and solar heat also play a role. The biggest controlling factor is the mixture and state of the fuel. If the fuel/oxidizer ratio falls within the explosive range, it will burn. Even with 21% O2. This is how a diesel engine works. The pressure change in your first stage is 200:1. The ratio in a diesel engine is between 14 and 25 to 1. So, the only question remains is what the safe level of O2 is. The federal government says that oxygen deficient air is any mixture that (at atmospheric pressure) contains less than 19.5% oxygen and enriched has greater than 23.5%. Any equipment that uses enriched air must meet government standards for enriched oxygen service. So, it isn't up to the manufacturer.

 

[roakey]

Originally posted by sharpenu
The pressure change in your first stage is 200:1. The ratio in a diesel engine is between 14 and 25 to 1.

Ah, no. If a diesel is "between 14 and 25 to 1" then the pressure change in the first stage is 1:200, not 200:1. A diesel compresses gas, your first stage reduces pressure.

Any equipment that uses enriched air must meet government standards for enriched oxygen service. So, it isn't up to the manufacturer.

So you're saying that contrary to blacknet's claim that 2nd stages do not have to be O2 clean, that our 2nd stages, BCs, drysuits and mouthwash has to be O2 clean and O2 compatible by [I assume] federal law? Because that's *exactly* what you're saying with this statement!

Methinks you either don't have the whole story, or you're not telling us the whole story.

Roak

Ps. And folks wonder why I get so upset with all the misinformation, voodoo and FUD that surrounds gas, cylinders and mixing!

PPs. Everyone have fun, I'm going diving for a week.

 

[sharpenu]

no sir, I am saying that when you initially open the tank valve, the air in the 1st stage pressure chamber jumps from 1ata to 200ata as the pressure from the cylinder rushes into the regulator. Perhaps I should have made that more clear.

The current regulations concerning enriched oxygen handling are set forth in the following publications:
ASTM G128 Guide for the control of hazards in Oxygen enriched systems
ASTM G93 Practice for cleaning methods for oxygen service
CGA P-14 Accident prevention in Oxygen rich and Oxygen deficient atmospheres.

As for why you do not have to clean bc's etc, I will check, but I KNOW regulators and cylinders MUST be cleaned for oxygen service, by law. As for misinformation, FUD etc in diving, I would point out that you are in disagreement with the government and the entire industry of compressed gas handling, based on the fact that you have never seen an accident. Well, I have never seen an atom, but I am quite sure they exist. It seems to me that you are so absorbed in your own OPINION that you have become blind to the FACTS. A bad trait in someone who wants to be a safe diver.

 

[chuckrt]

There has been alot of back and forth about the nitrox cleaning. I have a ScubaPro Gs250/MK20 and to keep both in warrenty for life they must be nitrox compatable and have th nitrox colors on the stages. I do dive with air and this reg but I also check with my LDS about where I'm going and if it is alright. My alternate air reg needed no service by the shop(Oceanic BC/air2). Just in case I also have R380/190 for a back up and for my Dght when she is old enough.

 

[omar]

ASTM and CGA standards are just that.. Standards NOT regulations. These standards can be incorporated into law if specificaly referenced, but by themselves they are not law.

Also, I would like you to provide specific reference to these "regulations" that require oxygen cleaning.

omar

 

[roakey]

Originally posted by sharpenu
no sir, I am saying that when you initially open the tank valve, the air in the 1st stage pressure chamber jumps from 1ata to 200ata as the pressure from the cylinder rushes into the regulator. Perhaps I should have made that more clear.

Point taken.

The current regulations concerning enriched oxygen handling are set forth in the following publications:
ASTM G128 Guide for the control of hazards in Oxygen enriched systems
ASTM G93 Practice for cleaning methods for oxygen service
CGA P-14 Accident prevention in Oxygen rich and Oxygen deficient atmospheres.

Neither the Compressed Gas Association nor the American Society for Testing and Materials is a governmental agency. Are their guidelines law? If so, how do their guidelines become law? (this is a test, I know the answer but it’s buried at the moment).

As for why you do not have to clean bc's etc, I will check, but I KNOW regulators and cylinders MUST be cleaned for oxygen service, by law. As for misinformation, FUD etc in diving, I would point out that you are in disagreement with the government and the entire industry of compressed gas handling…

I’m not in disagreement of the government, I’m in disagreement with the folks that think O2 cleaning is the be all and end all to O2 safety. If you dragged a moderately used, 6-months-since-O2-cleaning cylinder that’s banged around in the back of a truck and boat into a lab and told someone sitting around in a white coat that the cylinder was “ready for O2 service”, he’d laugh in your face. The fact that we don’t have cylinders blowing up left and right while O2 filling is not a testament to O2 cleaning, it’s an indication of how overly paranoid some folks are to the risk. You ever walk into a welding shop and amidst the dust, metal particles and grease, see a welder slap a regulator on a bulk O2 bottle and yank the valve open? (173:1 ratio) Yup, many welding shops are reduced to rubble each and every day. Heck, last weekend we lost four shops right here in the ‘springs! Not.

I’m looking for cylinder and regulator fires. We have one that’s been mentioned. 6351-T6’s cato at the average rate of four a year and they’re considered safe, so one reg in the past number of years is statistical noise. The examples I AM being given are compressor fires, hydrogen/oxygen fires and handwarmers in hyperbaric chambers. Interesting, but not applicable unless you’re trying to make the point that “things in an oxygen atmosphere burn.” I’ll concede that point. I’ve been on the technical lists trying to find out anything about the “recent” cylinder fire previously mentioned. No joy. A huge Florida technical diving community up and down both coasts and inland hasn’t heard about it.

… you are in disagreement with the government and the entire industry of compressed gas handling based on the fact that you have never seen an accident. Well, I have never seen an atom, but I am quite sure they exist. It seems to me that you are so absorbed in your own OPINION that you have become blind to the FACTS.

I’m not in disagreement, you need to back and read my previous posts where I do in fact agree with cleaning.

Contrary to your assertion, they’re a lot of things I believe that I’ve never seen. Atoms, as you say, are a good example. There’s lots of evidence out there that atoms exist. I don’t need to see them myself to believe in them. I look at all the evidence out there and draw a logical conclusion. I’ve never seen an accident but I wear a seatbelt religiously.

There’s a very, very large diving community that doesn’t believe that O2 cleaning is necessary. That’s beyond my comfort level, but at least we have some folks that are willing to be the miner’s canary for the rest of us. Guess what? No fires, no explosions. For a single example the WKPP fills hundreds of cylinders for a weekend dive. No O2 cleaning, no problems either. They’re paranoid about the fill rate and therefore the heat, not the cleaning.

Is that my comfort level? No, but it’s one heck of a datapoint, wouldn’t you say? I suggest you go back and read my previous posts where I made it perfectly clear that:

1) I believe in cleaning.
2) I don’t trust it.

Blind to the facts? I’ll need to be presented with a few before you can claim that I’m blind to them. Let’s move beyond handwarmers in hyperbaric chambers and bring on the cylinder explosions that all those non-O2 clean cylinders are causing. I’m waiting. You got a week until I’m back.

Roak

 

[Norm]

Like some have told you, I think this is basically "hype". A couple of manufactures did jump on it "big time", but I feel this was just for financial rea$on$. I have put 50% through several of my old regs many times with no problems at all. I can see no way this should ever be a problem.......EXCEPT with a titanium first stage - THERE is an exception. There have been several documented cases of fires when 'hotter' nitrox mixes were put through titanium regs. Otherwise, personally, I don't worry about it.
JMO