Cave Fills on LP tanks

[Diver-Drex]

Law and legality are two separate issues.
When a law only applies to certain situations, it’s regulation.

Punching someone in the face and then breaking their arm is assault in most situations...thus it is illegal.....unless you are engaged in an mma match.



Can you at least openly concede that the above statement is only true under certain caveats? And only in the USA?

Yes. I was not at all clear in specifying that the CFRs apply to only those situations that they apply to.

In the US, while engaged in commerce, one is required to comply with the CFRs and other appropriate regulations which are enforceable in the same way laws are. If you are not engaged in commerce, you can fill your own cylinders, etc. you can do as you please.

Taking a cylinder to a shop in the US and paying the shop to overfill it is asking the shop to do something illegal.

A shop in the US renting, sellling or transporting overfilled cylinders or overfilling cylinders with the intent to rent, sell or transport them or overfilling a privately owned cylinder for a fee is illegal.

No one on this board should be advising people to do any of these things IMO.

And as all of the discussions I have seen on the board have all involved some variation of “find a shop that will give you good fills” and never “buy your own compressor so you can fill as you would like” I don’t think it is a stretch at all to discuss this solely in the context of commerce being conducted.

 

[BRT]

The CFR absolutely applies to SCUBA cylinders in the US. The DOT has jurisdiction over them as clearly evidenced by the DOT stamping on cylinders. The permit and specification under which all SCUBA cylinders are produced is issued by the DOT.

I listed 39 CFR 183.115 and 29 CFR 1910.1200 as each defines compressed gas over 40psi as hazardous. That was I believe the specific question I was addressing, that compressed air isn’t a hazardous material. Not surprisingly 49 CFR Chapter 1 Subpart G has the same exact definition.

The requirements for overfilling a 3AA cylinder are indeed in 173.302. 173.302a to be more specific.

I assume these CFR's are "laws" that you have to pay to read?

 

[PfcAJ]

Lock me up and take me away.

#criminal

 

[victorzamora]

I have also read posts regarding this that said overseas tanks use a a slightly different alloy in the steel tanks and that it was not simply a regulation problem or safety factor of 3 or 2.5 compared toe the us of 4.

I haven't seen anything definitive on the alloys, metallurgy, specs, wall thicknesses, safety factor, etc regarding the US tanks vs Euro tanks.

My point was specifically that the situation is different here and there. Fully valid opinions about tanks in Europe/Russia may not apply to US tanks as they're different tanks.

 

[kelemvor]

Or I was being sarcastic...



Isn’t that exactly what normalization of deviance is? It’s wrong but accepted because it hasn’t gone wrong yet that we know of.

It's not wrong. Think about it like this. If you deviate by violating your NDL, the evidence suggests that you might get bent. Heck, even if you don't violate your NDL apparently some people get undeserved hits. If you overfill an LP tank, the evidence suggests there is no problem. We're talking about decades and decades of thousands of divers doing it over a period of 30 or more years. If it was a real concern don't you think there would be at least a single incident to point at?

Let's reverse this for a moment. If you don't overfill that tank and you decide to bring less breathing gas... there is a LOT of evidence that divers die when they bring too little gas for the dive. I mean, OOA is cited in many many diving fatalities as either a primary or contributing factor. One way to deal with that is to bring more gas. Yes, you can buy/bring more tanks and regulators on your dive. You can also fill your tanks up a little more if you had the foresight to buy LP tanks.

Also, as I understand it, most of the risk here falls upon the guy operating the fill station. I don't fill my own tanks, so if those professionals are willing to take the risk, I'm willing to thank them profusely for it and dive a little longer or just have more of a buffer. What's the risk to me? I might have to buy burst discs sooner. I might have to skip a dive if it's in the winter and the water actually heats my tank when I submerge causing a disc to blow. I might have to scrap a tank sooner (although, again, history shows that to be unlikely).

I'm not trying to talk you into doing it. I think it's a personal decision and you can see which way I went. If you're not comfortable with it then by all means, skip the overfill.

 

[J-Vo]

I have another reason to buy LP tanks. In my area we are lucky to get a 2500 psi fill in an AL80. I'm not sure what it is, that's just what the shops do. An LP 85 with this fill is a full 80 cuft of gas. So for sport diving LP85s actually get me a full fill.

 

[Charles2]

How much overfill are you comfortable with for HP tanks? Why?

 

[2airishuman]

It's not wrong. Think about it like this. If you deviate by violating your NDL, the evidence suggests that you might get bent. Heck, even if you don't violate your NDL apparently some people get undeserved hits. If you overfill an LP tank, the evidence suggests there is no problem. We're talking about decades and decades of thousands of divers doing it over a period of 30 or more years. If it was a real concern don't you think there would be at least a single incident to point at?

That's not entirely true because the early "cave fills" were much less ambitious than today's "cave fills." The evidence for the safety of filling an LP steel to 3600 hot and letting it cool to 3200 or whatever does not go back 30 years, because that wasn't routinely done 30 years ago.

Let's reverse this for a moment. If you don't overfill that tank and you decide to bring less breathing gas... there is a LOT of evidence that divers die when they bring too little gas for the dive. I mean, OOA is cited in many many diving fatalities as either a primary or contributing factor. One way to deal with that is to bring more gas. Yes, you can buy/bring more tanks and regulators on your dive. You can also fill your tanks up a little more if you had the foresight to buy LP tanks.

I'm a big fan of bringing more gas. I do it by using cylinders with a higher rated capacity.

Also, as I understand it, most of the risk here falls upon the guy operating the fill station.

The available data on cylinder ruptures is very thin because such events are rare. But it is not true that most of the risk is during fill, either in terms of the number of ruptures or the number of fatalities. Piecing together what anecdotal reports I can find, I conclude that about 25% of the risk is during the fill, and most of the balance of the risk is while handling the tank between the conclusion of filling and the beginning of the dive.

 

[Diving Dubai]

Lets look at cylinders:

They're made from commercial grade material. The difference between commercial grade and say aerospace, it the level of allowable defects allowed in the raw material, which is established by the level of inspection carried out.

The slugs from which cylinders are manufactured may carry such material defects such as voids, inclusions piping and lapping or lamina defects.

These defects can reside in the cylinder and lay dormant for the life of the cylinder or they can get a trigger which will cause a defect to grow.

Hydro's and Vis inspections wont' show up such defects, nor will the Eddy Current test currently employed

I've investigated a few hundred failures of components that failed within their design life and loads because of a material defect. How ever rare it might be, it was no consolation to the family of the deceased on a few of those cases.

As a postscript; last year I was involved with developing a technique for inspecting carbon wrapped tanks. Anyhow as a control we used some steel and ali cylinders that were in test.

We found internal material defects on a couple of them that wouldn't' have shown up on hydro or vis....

 

[2airishuman]

How much overfill are you comfortable with for HP tanks? Why?

I fill HP cylinders so that they reach 3500 PSI at 72 degress, which is the design fill capacity of the cylinders. They are derated to 3442 PSI for technical compliance with the 200 bar DIN connector standard, which I find irrelevant to safety in my situation.