51 replies to this topic

[WreckWench]

Anyone ever get a so called 'cave fill'? Anyone want one? Anyone know what one is?

Is it the greatest thing to happen to diving or just pure stupidity. What do you think?

[BlckShadow]

Anyone ever get a so called 'cave fill'? Anyone want one? Anyone know what one is?

Is it the greatest thing to happen to diving or just pure stupidity. What do you think?

Do you mean filling your LP tanks to around 3900 psi? I wish all shops would do that. It wears the tanks down a little faster but most of the steel tanks coming from Europe are designed to be filled to 300 bar anyways. (4400 psi) If you change out the burst disc with a 5000 psi one worst case is it will fail hydro at some point still very far down the road. Most shops here outside of cave country usually don't do it because DOT regulations won't allow it.

[captsteve]

Anyone ever get a so called 'cave fill'? Anyone want one? Anyone know what one is?

Is it the greatest thing to happen to diving or just pure stupidity. What do you think?

Do you mean filling your LP tanks to around 3900 psi? I wish all shops would do that. It wears the tanks down a little faster but most of the steel tanks coming from Europe are designed to be filled to 300 bar anyways. (4400 psi) If you change out the burst disc with a 5000 psi one worst case is it will fail hydro at some point still very far down the road. Most shops here outside of cave country usually don't do it because DOT regulations won't allow it.

That is the way i understand it.....

[Diverbrian]

I refuse to do it. I run 3500 psi tanks for a reason. That reason would be that it is difficult to damage them with a "cave fill". The DOT puts a rated pressure on a tank for a reason. I don't assume that I know more than them. Oh, and I like the fact that I can count on my tanks to pass hydro for the next couple of cycles .

If I need enough gas to warrant a "cave fill", then I should be using a CCR anyways. Ask the people teaching the PSI Inspectors course and you may get that same answer.

BTW, that high pressure has been known to beat the ever living you-know-what out of regulators as well.

[ScubaDadMiami]

I have overfilled low pressure (2640 psi) steels on occasion. However, even when doing so, I did not do the extreme overfills that some do on a regular basis. I am talking more about taking a tank rated to 2640 up to about 3000 psi or so. I also regularly "overfilled" my tanks once they were past the "+" rating period by continuing to fill them to the original "+" rated fill pressure. I did not overfill my high pressure (3442 psi) steels other than to compensate for cooling after the fill (filled to about 3700 psi, and then I would let them cool to 3400-3500 psi).

DO NOT OVERFILL ALUMINUM TANKS. They are based on the strength of the wall thickness to provide their ability to retain gas. Aluminum does not have the ability to flex as does steel. Overfilling aluminum tanks is downright dangerous.

[PerroneFord]

Well, ummm...

Half the guys I know around here ARE PSI instructors and they ALL cave fill. The only shops around here that don't are the ones who only cater to recreational divers.

To my knowledge, there has not been a single instance of a steel tank exploding from a "cave fill". There are tanks in use from the 70s that see regular cave fills and they still pass hydro.

So, you guys are welcome to do as you like.

As far as the comment about using CCR instead of cave fills, well, I don't know. There's a whole lot of cave line laid in Florida, Mexico, and elsewhere that wasn't done by the CCR guys.

[Walter]

It's dangerous. It's illegal and it shortens the life of your tanks. If you do it, I don't even want to be near your tanks.

[Lubold8431]

I have two sets of LP 112's that rountinely get overfilled, however, usually only to 3300. They have had two hydro's and passed. Instead of 112 cu ft of gas per cylinder, I have 140 cu ft at 3300. Thats 56 cu ft more without the added weight of larger cylinders.

[TekDiveGirl]

Walter -- do you have some statistics on what you say to back them up?

Dangerous? Look at what tanks go through during hydro -- overfilling steel tanks (only steel - not al) a bit (I am not talking 5000psi here) is not statistically a dangerour prospect.

Illegal? Cite please.

Shortening the life -- what are we talking a few fills -- months -- years -- again cite please.

I don't go to the extremes like I have seen/heard some people do -- but I have no problems overfilling my lp tanks to the 3200/3500ish range depending on the diving to be done.

[drbill]

Not something I'd even consider, although I have heard that the Fabers are rated at much higher pressures in Europe than the DOT allows here. My PST steel 120HP tank failed after 10 years due most likely to hot fills at Casino Point, and those were to its rated pressure.

Of course the only cave I "penetrate" with any frequency is the one at Sea Fan Grotto here on Catalina, and that is fairly shallow both in terms of depth and "depth."

Kimber... isn't it illegal to violate the DOT's recommended maximum pressure? I'd always thought that was the case but I may be wrong.

Edited by drbill, 02 June 2006 - 08:59 AM.

[TekDiveGirl]

Kimber... isn't it illegal to violate the DOT's recommended maximum pressure? I'd always thought that was the case but I may be wrong.

I have yet to see actual regulations stating that the tank police are out there and going to take you to jail for overfilling.

[Diverbrian]

Actually, I believe that one of the major reasons for cave fills that the only way that they can get so far into the back of a cave on rule of 1/3's is to overfill existing tanks. The other reason is the use of scooters. Otherwise, after a while, a cave diver would "hit the wall" at the 1/3 mark of air supply as they would.

I will correct myself and define what I won't do. I have no problem with the LP tanks to 3000ish. But, I do have an issue with LP tanks being filled to 4000 or above. I have heard of fills in cave country where the regs were bleeding air through their second stage until the tanks bled down a bit. Even then, if you want to do that I don't have a problem. You just may be turning the dive before you want if you are diving with me because I will have 3500 psi in my HP tanks. What you do with your tanks is your business. The worst risks that I see are failure of a tank at hydro time and damage to one's regs and both of these would be in extreme cases. But, those extreme cases are more prone to happen if you keep pushing it.

The CCR comment came from a PSI Inspector who took his renewal this year. That was the response that instructor of that program gave the class about extreme overfills.

And no, the tank police won't arrest you. By rights, the DOT could ticket me for every time that I go on an extended trip for not having a commercial drivers license and the not placarding a vehicle carrying so much High Pressure gas. Even customs at Port Huron seems to ignore that rule .

[TekDiveGirl]

And no, the tank police won't arrest you. By rights, the DOT could ticket me for every time that I go on an extended trip for not having a commercial drivers license and the not placarding a vehicle carrying so much High Pressure gas. Even customs at Port Huron seems to ignore that rule .

Not to sound like a broken record here -- but please cite your DOT reference.

From all I could find -- you do not need a placard unless you are transporting in excess of 1000# combined total weight of cylinders/gas. And I don't see where a CDL comes into play.

This all may be tedious -- but it is really one area where rumour/stories seem to win out over truth/laws.

People should be educated on the ins/outs/whys of what they are doing and not running on "I was told by ..."

[Diverbrian]

And no, the tank police won't arrest you. By rights, the DOT could ticket me for every time that I go on an extended trip for not having a commercial drivers license and the not placarding a vehicle carrying so much High Pressure gas. Even customs at Port Huron seems to ignore that rule .

Not to sound like a broken record here -- but please cite your DOT reference.

From all I could find -- you do not need a placard unless you are transporting in excess of 1000# combined total weight of cylinders/gas. And I don't see where a CDL comes into play.

This all may be tedious -- but it is really one area where rumour/stories seem to win out over truth/laws.

People should be educated on the ins/outs/whys of what they are doing and not running on "I was told by ..."

Good point on that. I just know that the when that guy turned out in front of me last December, the officer was not pleased to hear that I had a tank of O2 in the vehicle that had just been involved with a collison . He wrote the ticket for the accident to the other guy, but wasn't very thrilled with me either. I work at a chemical plant, so most of the vehicles that we get deliveries from have some kind of hazmat warnings.

Good call again. I stand corrected.

[ScubaDadMiami]

At a previous PSI update, I don't recall them talking about a weight limit. I recall them mentioning carrying more than about 15 cylinders or so. I really can't recall the number exactly since I knew that it would be beyond what I would potentially carry in my car/truck at any time.