converting air tanks to EAN

[Scared Silly]

This is incorrect. If you read CFR 49 171.7 it incorporates CGA G4.1 only as it applies to CFR 49 178.338-15. 178.338-15 relates to the required cleaning for a cargo tank which is defined in the CFRs as:

Actually it is correct, one needs to fully read the text including the precursor text.

Read page 93 here:


http://www.gpo.gov/fdsys/pkg/CFR-2011-title49-vol2/pdf/CFR-2011-title49-vol2-sec171-7.pdf


And in particular this paragraph.


(3) Table of material incorporated by reference. The following table sets forth material incorporated by reference. The first column lists the name and ad- dress of the organization from which the material is available and the name of the material. The second column lists the section(s) of this subchapter, other than §171.7, in which the matter is referenced. The second column is presented for information only and may not be all inclusive.


The key here is the last sentence which states that the second column (i.e. the reference to CFR 49 178.338-15) is for information only (i.e. a case where the particular material is specifically referenced with in a chapter but is not all inclusive). Thus all of CGA 4.1 pertains and is applicable to portable cylinders.

 

[DivemasterDennis]

My only comment is when you fill a tank with something other than air, it should be clearly marked, whether by an ugly yellow or green sticker, or some other way. I also strongly suggest that if you are going to use a tank for nitrox you dedicate to that use, and not switch back and forth from air to EAN. Finally, it's hard to argue with the wisdom of following the protocols of the place that is going to sell you your gas and put it in your tank. The rest of the debate in this thread is interesting, but exhausting.
DivemasterDennis

 

[DogDiver]

In North Florida 99% of facilities use banked nitrox & trimix.
Oh, I always thought that the "2400" stamped on my tanks was the "turn" pressure.

 

[Kitty_Kat]

So...
I'm still confused... Here's what I have so far:

- If partial blend => Clean the tanks
- If NOT => Use the tanks as they are?

Other than the explosion issue, is it there other risk? or everything goes back to that?

Sorry for the dumbness, I need to decide on my used (10 dives) tanks' destiny.

Thanks!

Everything goes back to O2's strength as an oxidizer. Some of the most common oxidation reactions happen to result in fire, explosions, or corrosion. Depending on what types of gunk the inside of your tank/o rings/lube have accumulated, these reactions become possible in the presence of enough O2. Pure O2 is not the problem, but rather what it comes into contact with. O2 cleaning just tries to make sure that the O2 doesn't have anything to oxidize.

As quite a few others have said, see what the shops you use require. It isn't usually an expensive deal bit of maintenance though...

 

[halocline]

It would not surprise me to learn that the "40%" practice evolved in the dive industry as did the use of recreational nitrox, also limited to 40% O2. It's a matter of convenience.

Bottom line, the shop owns the compressor, they make the rules.

To the OP in Argentina, you should check with the shop you're going to get fills from. That said, it never hurts to learn something yourself, like exactly what O2 cleaning is. It's not difficult. Rebuilding a tank valve with oxygen-compatible grease and o-rings is likewise not difficult.

One problem with the whole "O2 clean" concept is that one bad fill, or even one fill with air not filtered to O2 standards, means.....guess what, your tank is no longer O2 clean. You could spend hours cleaning and rebuilding the valve under impeccable conditions, making sure not a speck of dust is in the tank, take it to the shop, one quick burst from a compressor with less-than-perfect filter conditions, and you might as well never have cleaned the damn tank.

 

[DevonDiver]

Debating the requirements in the USA may not be relevant to the OP (in Argentina), as those requirements do vary considerably across international borders. In that respect, it may be better for the OP to seek that specific information locally, from the Argentinian dive community/industry.

As to what needs to be done to convert a tank for nitrox (oxygen clean), here are some useful references:

CONVERTING DIVE TANKS FOR OXYGEN SERVICE


Cylinder Oxygen Cleaning

[PDF] LUXFER'S SCUBA CYLINDER VISUAL INSPECTION GUIDE



Also, do check out ANDI's "Oxygen Handling & Gas Blending Procedures" manual. It's very comprehensive - a useful knowledge addition for a divemaster.

 

[NAM001]

Yes and i have seen when 2400 being turn presure meant yuou got a short fill.

 

[nitroxfox]

Gentlemen,

Directly from the DOT, please read:

PHMSA - Interpretations by Regulation - Interpretation #11-0175

PHMSA - Interpretations - Interpretation #11-0238

PHMSA - Interpretations by Regulation - Interpretation #06-0064

PHMSA - Interpretations by Regulation - Interpretation #05-0060

Cylinders do need to be cleaned at 23.5% in the USA. International standards are 25% as is the US Navy's. Cylinders used in transportation in commerce are subject to regulations. 49CFR173.6 gives business owners a furtherance of trade exemption with a maximum weight of cylinders at 440lbs. Private individuals are limited to 490lbs. If you own a boat and are doing charters, that is commerce and you must comply. Again, read the above links but here are some excerpts:

Q1. Do the HMR apply to a cylinder that is transported to and from a dive shop by a private individual for personal use? Do the HMR apply to a cylinder that is filled by a dive shop and rented to a customer who then transports if off the premises?

Al. The HMR generally apply to the transportation of hazardous materials in commerce. Transportation of hazardous materials by a private individual in a private motor vehicle for personal use is riot commercial transportation. Note, however, that a cylinder that is marked to certify that it conforms to HMR requirements must he maintained in accordance with applicable specification requirements whether or not it is in transportation in commerce at any particular time.
​

Q2. Do the HMR apply to a cylinder that is shipped to a customer by UPS, FedEx, or other commercial carrier?

A2. Yes. A person, such as a dive shop, who offers a hazardous material for transportation in commerce or a person, such as a commercial carrier, who transports a hazardous material in commerce is subject to all applicable HMR requirements.
​

Q3. Do the HMR apply to a cylinder that is transported by a private individual in a private motor vehicle for personal use when transported on a public road or a Federal highway?

A3. See response Al above.
​

Q4. Do the HMR apply to a cylinder that is carried by a private individual on a commercial bus or boat licensed to carry passengers?

A4. Yes. Passengers and crew members traveling on a commercial bus or vessel are “in commerce” and are fully subject to the HMR.
​

Q5. Do the HMR apply to a cylinder owned by a private individual who takes it on a vessel licensed to carry passengers and has the cylinder filled while on the vessel?

Also from the above referenced OFFICIAL INTERPRETATIONS, which have the effect of law:


This responds to your letter regarding the requirements for compressed gas cylinders containing breathing enriched air (Nitrox) under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). Specifically, you state in your incoming letter that Department of Transportation (DOT) Specification 3AL (Aluminum) and 3AA (Steel) cylinders are commonly used for containment of Nitrox and the air in these cylinders will have elevated levels of Oxygen ranging from 21% to 100% depending on the application. Your questions are paraphrased and answered as follows:
Q1: If a cylinder is to be used to transport Nitrox, at what Oxygen percentage must a cylinder used for Oxygen service be cleaned and must the cylinder cleaning conform to the cleanliness standards specified in 173.302?
A1: Gas mixtures with Oxygen concentrations greater than 23.5% by volume should be considered to cause or contribute to combustion of other material to a greater extent than air. These gas mixtures must be described as "Compressed gas, oxidizing, n.o.s." and must be classified and labeled with a Division 2.2 (nonflammable gas) primary hazard and a Division 5.1 (oxidizer) subsidiary hazard. If the Oxygen concentration is greater than 23.5%, the conditions specified in § 173.302(b) must be met. Each DOT Aluminum cylinder, including a 3AL cylinder, must be cleaned in accordance with the requirements of General Services Administration (GSA) Federal Specification RR¿C¿901D, paragraphs 3.3.1 and 3.3.2 (IBR, see §171.7 of this subchapter). Cleaning agents equivalent to those specified in Federal Specification RR¿C¿901D may be used provided they do not react with Oxygen. One cylinder selected at random from a group of 200 or fewer and cleaned at the same time must be tested for oil contamination in accordance with Federal Specification RR¿C¿901D, paragraph 4.3.2, and meet the specified standard of cleanliness. The HMR does not indicate specific cleaning standards for 3AA steel cylinders used for Oxygen service.
Q2. What is the maximum pressure to which a cylinder can be filled, when charging the cylinder with enriched air containing elevated levels of Oxygen? Additionally, is this pressure the same for both aluminum and steel cylinders?
A2: For aluminum cylinders used for Oxygen service, including 3AL cylinders, the pressure in each cylinder may not exceed 3000 psig at 21 °C (70 °F) as specified in § 173.302(b). The HMR does not indicate a specific operating pressure for steel cylinders, including 3AA cylinders, used for Oxygen service, thus, the cylinder must not exceed the marked service pressure.


The DOT is adamant about cleaning at 23.5%. I attended DOT Multi-Modal training in Atlanta last June and they were quite clear. I was the only individual there from the dive industry, sadly as the training was free. I also attended the inaugural CGA Cylinder Requalification Seminar in Raleigh and the same message was hammered upon. My suggestion is to avail yourselves of the training and to ask questions of the DOT for clarification. You may be surprised at what you hear. There have been many misinterpretations by many well meaning people and this misinformation has been taken as fact by a host of people. Please check for yourselves.

 

[TMHeimer]

A lot of technical info. Our shop in Canada fills my tanks with Nitrox with no 02 cleaning because the shop has the "membrane". No stickers. However in Florida one shop would not without O2 cleaning (partial blending I guess), need the sticker-- cost $40. I went with Air there--O2 cleaning & $14 for Nitrox = $54 for each tank to do the charter. Yet another shop close by would just fill them with Nitrox, no sticker.

 

[waterpirate]

This entire discussion is exausting, and has been since padi said nitrox would kill you. Scuba is an unregulated industry so far. That means that you get interpretation from many different agencies outside of the scuba parameter, trying to apply rules for transport, and filling, and storage. A hodge podge of selective implementation at best.

Like everything else, do your own research and determine what makes sense to you and the people in your hood. This entire debate and the poor quality of the fill stations in my hood is what prompted me to bite the bullet and by my own compressor. In the USA it is really hard to seperate marketing, revenue generation, urban scuba myth, and reality. It is why you have had so many responses from differing angles.
Eric