Risk with 1972-1988 AL80 Tanks ?

[JahJahwarrior]

Look, the DOT and CGA both mandate that a cylinder passing a thorough inspection is good for service. Of course, I am assuming the cylinder has met other legal conditions such as renewing its permit if necessary and being a DOT approved cylinder. That being said, so long as a 6351 alloy AL passes a thorough inspection, its cool. The shops that will not fill them are both overreacting and probably ill trained. Call PSI like I did about a week ago and they will give you details on the last few cylinder explosions, which by the way were not even AL. The 6351 alloy is more susceptible to sustained load cracking which is caught by a thorough inspection. Investigations into cylinder explosions relating to the 6351 alloy have revealed that a thorough inspection would have taken the cylinder out of service. I would probably take that cylinder to a TRAINED facility.

Now, every fill station operator has the right to refuse to fill if they have any doubt as to the integrity of the cylinder. If they see a VIP/VCI sticker from a known slap the sticker on the tank facility (ie homemade), then I understand refusing to fill it pending a thorough inspection.

The DOT and CGA both permit cylinders that have passed requisite tests to be filled, but none of their rules say a cylinder is legally required to be filled by a shop, or suggest that passage of tests is a 100% gaurantee that a cylinder is fine.

6351 alloy tanks that pass inspections are supposed to be ok, but that is no gaurantee. How many shops are out there that will take a 45 second look in a tank with a dental mirror and a small flashlight, and call it safe?

The shops who will not fill them are protecting themselves. DOT would not have special rules for testing those tanks if they weren't slightly more dangerous than other cylinders. It is possible to miss SLC cracks. Another way to miss them is to skimp on VIPS and only do one before the cylinder goes to hydro. It comes back you slap a sticker on it without looking inside again, yet a crack has formed. My 6351 alloy tank was condemned because of a barely visible crack that only appeared after hydro. I got lucky that my vip guy has young, good eyes, or else I might have filled an unsafe tank.

Investigations into whether or not a good inspection would have caught cracks can make guesses, but can never say for certain. Needless to say, it is possible to miss cracks in a 6351 alloy cylinder. 6351 alloy cylinders crack more often than 6061. 6351 alloy cylinders are old, 20 years or more. Assuming $150 for the tank, that is $7.50 per year depreciation. Why is it so difficult to get rid of the tank and buy a new one?

Look around, read the other threads. Come to whatever conclusion you want to but do not make the mistake of blindly assuming your tank is safe just because it recently passed hydro and has a vip sticker on it. And if you ever come to a shop where I am filling tanks, do not throw a fit when I refuse to fill your 6351 alloy tank.

Also, Dalec, I never said diving only has one attribute. It is expensive and fun. If it weren't fun, no way would I have dumped so much money into it. It is my opinion that a safe tank is a necessary object, and that a fill person and the fill station should not be put at risk just because you want to save some money. I mean, think about it. Here we all argue until we are blue in the face that people should shop in the LDS instead of online because we don't want the LDS to go out of business. If their shop is partly destroyed by an exploding cylinder, that won't help them stay in business. Lastly, I pay for everything dive related in cash, if at all possible. Untrackable, no one can know what I actually paid for things so I never get in trouble with the significant other for spending so much on dive gear

 

[PhilEllis]

The shops that will not fill them are both overreacting and probably ill trained.

While easy to say, this statement may well not be the truth. Decisions about the policy of filling these cylinders are made on much more data than a DOT decision.

Phil Ellis
www.divesports.com

 

[cbrich]

I would say your risk of buying a 6351 tank is very small, as long your LDS knows how to do a visual on them, ie perform an Eddie Current on the threads. My LDS does an Eddie Current on all tanks whether they are 6351, 6061, or steel. I have several 6351 tanks and the SLC is always on mind, but it was put easy when my LDS hit one of them with 3,200 psi. The tank was getting a visual, so the tank had no pressure in it. All of the storage bank valves were open, to bring the pressure in the whip to 3,200, and then he open the quarter turn ball valve on the whip. I know my heart skip a beat or two.

The tanks I have do not show signs of SLC. Since the requirement of an Eddie Current inspection on the threads, how many tanks have exploded. The last case I heard about was in the 1990s before the Eddie Current Requirement, but I could be wrong.

 

[Davidstealey3]

jahjah

i know shops will do whatever they want. we own a shop and my father will not fill them. this is his decision not mine.

all i can do is state the info i have learned from taking inspection classes. you take a risk filling all kinds of tanks everyday. granted the 6061 do not suffer the SLC but who knows how the tank has been treated. if you dont want to fill these tanks that is fine. i will not say you are wrong. it is your choice.

like i said, i am just stating what i have learned. if they have passed hydro, the VE testing and a through VIP the tank should be fine. inspectors are getting to comfortable doing fast inspections and not throughly checking everything they should. it was drilled in to us that the threads need to be CLEAN in order to look for cracks. just cause the new 6061 are a better ALM dosent meen i dont look for cracks.

just my opinion on this subject. as the saying goes " to each his own " do as you will.

 

[WD8CDH]

Shops can and will do whatever they want. Time has shown us that aluminum scuba tanks made from alloys other than 6061 explode more often than any other type of scuba tank. Shops have realized that they are safer and put less people at risk by not filling these riskier tanks.

To add to this, if your 6351 alloy tank explodes, and someone sues (there will be a lawsuit...lawsuits abound nowadays), everyone is over a barrel. The shop will be run out of business when the lawyers for the other side find out that other shops refuse to fill these tanks due to perceived risk. You will be in trouble when the family of the shop employee who got killed/hurt and their lawyers read your post in this thread about how you know your tank is safe even though you've read that 6351 alloys tend to be riskier. Everyone loses. Is it worth putting a tank monkey's life in danger? Why would you do that? Aluminum tanks can be had for $150 or less used, in great shape, in a safe alloy. Are you willing to put someone at higher risk of injury to save $150?

I will never fill a 6351 alloy tank. No one can make me. I will never ask anyone else to fill a 6351 alloy tank. In my opinion, they are riskier than 6061 alloy aluminum and steel alloys, and I am not willing to subject myself or others to that higher risk.


Will yours blow up? Are you willing to bet so much on the answer, when there is even a slight probability that you might be wrong? Scuba tanks are different than regulators. If a regulator breaks, it rarely destroys entire rooms, or rips off limbs. The stakes are high in tank explosions, so even a slight increase of probability of explosion scares me and scares me good!

Then you shouldn't dive steel tanks either because records show far more steel tanks have exploded than 6351 tanks.:shocked2:

I usually don't fill 6351 tanks because of the hassle and perceived risk rather than the actual almost imperceptibly small real risk. I absolutely will not go out of my way to get a 6351 tank but in using one, I know that the risk to me and others is far less even driving to the dive site or any one of the 10 or 20 other hazards in our sport.

 

[Scared Silly]

While easy to say, this statement may well not be the truth. Decisions about the policy of filling these cylinders are made on much more data than a DOT decision.

A while back a little shop down in Bama that I have a lot of respect for was filling a 6351 cylinder. They were doing everything right and still had one slip by them. When they decided to no longer fill 6351 cylinders I had to nod my head in agreement as I did not blame them. Glad that shop the folks that run it are still around.

Conversely, when I walk into a shop that has a sign that says we do not fill cylinders over 20 years old I just laugh at them. Same with the shops that do eddy current tests on steel and 6061 cylinders.

BTW I do own a 6351 cylinder but it is LP and for CO2 (which has very different pressure properties). I still had it VE tested with hydro. The tragedy for that cylinder is that when it goes empty I can't get any beer out of my kegs and have to do an OOB ascent from the basement.

 

[zaberman1]

I wonder how many people refuse to fill 6351 alloys and proceed to overfill, fill at high rates, and double up burst disks...

 

[PhilEllis]

A while back a little shop down in Bama that I have a lot of respect for was filling a 6351 cylinder. They were doing everything right and still had one slip by them. When they decided to no longer fill 6351 cylinders I had to nod my head in agreement as I did not blame them. Glad that shop the folks that run it are still around.

I still have an uncontrollable momentary shudder when I recall that.

Phil Ellis
www.divesports.com

 

[JahJahwarrior]

Then you shouldn't dive steel tanks either because records show far more steel tanks have exploded than 6351 tanks.:shocked2:

I'm from Cave Country, where LP steels routinely get "overfilled" and I have never heard of one exploding. Infact, I've never heard of or seen pictures of any steel tank that exploded, save for one bank bottle explosion due to heavy rust.

Anecdotal evidence isn't everything, but a search for "steel tank explosion" gave 3 pages of results, and no thread in there was about a reported steel tank explosion. If steel tanks really do explode so much more often, why aren't there any threads where someone says "OMG A STEEL TANK JUST EXPLODED!" ? I found several posts by people on the first page of tank explosion threads saying that they had been in a store or near a store when an aluminum tank blew up...

 

[cbrich]

Conversely, when I walk into a shop that has a sign that says we do not fill cylinders over 20 years old I just laugh at them. Same with the shops that do eddy current tests on steel and 6061 cylinders.

I agree with you on not filling tanks 20+ years old, but what is wrong with doing an eddy current test on 6061 and steel tanks? My LDS does it, and they don't charge for it, they need to keep prices the same as the other dive shops. A visual for a 6351, 6061, and steel tank cost the same at my LDS. Do I care if they do an eddy current test on 6061 or steel, NO. However with that said if my LDS charges more for a visual with eddy current, than a visual without eddy current; I would be finding another LDS very quickly.

I have yet to find a dive shop in Texas that will not fill a 6351 tank. Some LDS still use 6351 tanks as rentals.

If someone is considering buying a used aluminum tank, they need to make sure their LDS will service and fill them, if they can not fill or service them, look for another tank.