Tank explosion kills one - Cozumel

[boulderjohn]

A burst disk will prevent a properly inspected tank from exploding.

And how is one to know a tank has been properly inspected?

When I was getting my initial training through PSI, the instructor said that a tank that fails hydro should have failed a visual inspection several times before. He was not saying the tanks were not inspected--he was saying the inspector missed the cracks. They can be very hard to see. I said this earlier in the thread--a shop employee hurriedly inspecting all the tanks due for inspection that month can easily miss a crack.

There was a ScubaBoard thread a few years ago about annual inspections. A lot of posters who did not like the fact that they were expected to get their tanks inspected every year confidently and defiantly said they solved that problem by getting a stack of stickers they could slap on their tanks each year, thus doing away with that "unnecessary" hassle and expense.

---------- Post added September 4th, 2014 at 09:03 AM ----------

Here is another problem with annual inspection stickers--they can come off through normal use.

I try to place stickers in a location where they are not as likely to rub against something that will tear them loose, but it still happens. I had my steel doubles hydroed last February, and the shop put the new stickers in the place where they were most likely to get rubbed off through transportation, etc., and they didn't last a month, with only a few uses. Was I going to reinspect them? Nope. I have my own stickers, and I put them on in a more secure location.

So what do you do when a sticker is damaged beyond value and you know the tank is still well within its annual range? You put a new sticker on it, and there is a good chance the new sticker will be marked with a new date, not the original date. If you have a large inventory, there is no way you will know the legitimate dates. A tank with a brand new sticker on it might not have been inspected for years.

 

[flots am]

And how is one to know a tank has been properly inspected?

By using a tank service facility with properly trained inspectors and equipment.

When I was getting my initial training through PSI, the instructor said that a tank that fails hydro should have failed a visual inspection several times before. He was not saying the tanks were not inspected--he was saying the inspector missed the cracks. They can be very hard to see. I said this earlier in the thread--a shop employee hurriedly inspecting all the tanks due for inspection that month can easily miss a crack.

AL cylinder neck cracks are best detected with a good Eddy Current Tester, like the Visual Plus 3. Just looking for the cracks using a light and/or a mirror is pretty ineffective. The best use I've seen for the light and mirror is after the eddy current test picks up a crack, you can go to the location of the crack and say "Wow, I'm glad I spent $2K on the EC machine. Someone could have been killed by this thing!"

There was a ScubaBoard thread a few years ago about annual inspections. A lot of posters who did not like the fact that they were expected to get their tanks inspected every year confidently and defiantly said they solved that problem by getting a stack of stickers they could slap on their tanks each year, thus doing away with that "unnecessary" hassle and expense.

That's exactly why many fill stations don't accept DIY inspections.

So what do you do when a sticker is damaged beyond value and you know the tank is still well within its annual range?

You take it back to the shop, they look it up and say "This tank was inspected on xx/xx/xx" and they punch out a replacement sticker and put it on the tank.

You put a new sticker on it, and there is a good chance the new sticker will be marked with a new date, not the original date.

So you're saying that if someone punches the sticker wrong, it will be wrong?

That's a reason for the owner to "educate" the employees about the procedure for replacing a damaged sticker, not a reason to declare inspections useless.

If you have a large inventory, there is no way you will know the legitimate dates. A tank with a brand new sticker on it might not have been inspected for years.

It does seem reasonable that If the employees perform the inspection poorly or stamp the sticker wrong, you can get tanks that aren't properly inspected.

I prefer to have my stuff serviced by people who do it correctly, and when I need a new sticker, they stamp the right date. It's not complicated. I'd feel terrible if one of my tanks killed someone.

flots.

 

[boulderjohn]

Many shops use their own stickers with their own shop names on them. I just bought a pair of tanks that have such stickers on them. As far as I can tell, it was a legitimate inspection--or was it?

I will inspect them myself, probably later today. I will O2 clean them when I do, and when I am done, I will put a PSI O2 clean sticker on them. It will be a legitimate inspection with a legitimate sticker with a legitimate number on it. In the ScubaBoard thread I mentioned, a lot of the posters had acquired similar stickers and were using them. If I am in a shop and two customers come in with very official looking PSI stickers, how do I know which one did a real test and which one did not?

If I go to a die operator in a place like Cozumel and see current visual inspection stickers on the tanks, how do I know that the employee who put those stickers on did a good job with that inspection?

 

[redacted]

Many shops use their own stickers with their own shop names on them. I just bought a pair of tanks that have such stickers on them. As far as I can tell, it was a legitimate inspection--or was it?

I will inspect them myself, probably later today. I will O2 clean them when I do, and when I am done, I will put a PSI O2 clean sticker on them. It will be a legitimate inspection with a legitimate sticker with a legitimate number on it. In the ScubaBoard thread I mentioned, a lot of the posters had acquired similar stickers and were using them. If I am in a shop and two customers come in with very official looking PSI stickers, how do I know which one did a real test and which one did not?

If I go to a die operator in a place like Cozumel and see current visual inspection stickers on the tanks, how do I know that the employee who put those stickers on did a good job with that inspection?

Yet there are ops that will not accept that sticker because it lacks a responsible shop name with assumed insurance coverage.

It is really hard to understand why the current "annual inspection" industry standard (USA) is acceptable.

 

[flots am]

Many shops use their own stickers with their own shop names on them. I just bought a pair of tanks that have such stickers on them. As far as I can tell, it was a legitimate inspection--or was it?

Wheter a shop trusts a particular sticker is up to the shop.

The place I work for only trusts their own sticker because the inspection process and inspector is known.

I will inspect them myself, probably later today. I will O2 clean them when I do, and when I am done, I will put a PSI O2 clean sticker on them. It will be a legitimate inspection with a legitimate sticker with a legitimate number on it. In the ScubaBoard thread I mentioned, a lot of the posters had acquired similar stickers and were using them. If I am in a shop and two customers come in with very official looking PSI stickers, how do I know which one did a real test and which one did not?

You don't, which means that if you want to be safe, you don't accept the sticker, which is how lot of places currently operate.

If I go to a die operator in a place like Cozumel and see current visual inspection stickers on the tanks, how do I know that the employee who put those stickers on did a good job with that inspection

If the tanks in Coz were inspected and certified by a qualified, unbiased, properly trained inspector using the right equipment, you could be pretty certain they were OK.

If they were "maybe inspected" by an employee of the fill station, using no/unknown equipment and an unknown level of training, you don't know anything about the safety of the tanks.

You would be taking a chance.

flots.

 

[grf88]

I will be taking a much closer look at the tanks I am provided while on vacation and I will certainly not be strapping any "bad alloy" tanks on my back and may even be leery of getting on a boat that has any on board.

 

[Mike]

I would assume that the majority of risk of failure and explosion if not 100% of it, is during the filling, and not afterwards while using it. I may be wrong but I suspect the number of tank explosions are statistically non existent when comparing them those exploding while in use compared to exploding while being filled.

 

[boulderjohn]

You don't, which means that if you want to be safe, you don't accept the sticker, which is how lot of places currently operate.

I have never been to a shop that does not accept my current stickers. That does not mean they do not exist--I have just never heard of one until now. There is a current thread on shop tank filling policies, and I don't think this was even mentioned, although I could be wrong. A shop refusing to fill any tanks they have not personally inspected, even with everything current, would really tick a lot of people off. I would not patronize such a shop.

If the tanks in Coz were inspected and certified by a qualified, unbiased, properly trained inspector using the right equipment, you could be pretty certain they were OK.

If they were "maybe inspected" by an employee of the fill station, using no/unknown equipment and an unknown level of training, you don't know anything about the safety of the tanks.

Back to my question--how are you to know? Are you going to say, "Were these tanks certified by a qualified, unbiased, properly trained inspector using the right equipment?" How would you expect them to answer? Would you expect them to say, "No, we have some Bozo with no training do it"?

 

[DjDiverDan]

Just wondering, if anyone can tell me. Metal fatigue in airplanes is highly related to the number of "cycles", i.e., takeoffs and landings, because of the effects of expansion and contraction resulting from repeated pressurization and depressurization of the fuselage. These cycles of expansion and contraction result in metal fatigue in the aluminum skin of the airplane fuselage, resulting in cracks and fractures in the skin. Don't Scuba tanks expand (very slightly) upon being completely filled, then contract upon being emptied down to 200-500 psi? Have there been any studies on the effect of "cycles" on scuba tanks? If repeated cycling of Scuba tanks does increase metal fatigue, it seems that places like Cozumel, where the tanks are cycled pretty much daily, ought to use a more frequent inspection standard, based upon usage rather than simply time.

 

[grf88]

I would assume that the majority of risk of failure and explosion if not 100% of it, is during the filling, and not afterwards while using it. I may be wrong but I suspect the number of tank explosions are statistically non existent when comparing them those exploding while in use compared to exploding while being filled.

I am sure that statistics would suggest a tank exploding other than when being filled is probably very small. What are the chances that you can have a first stage diaphragm let go and get the only contaminated tank, out of approx 100 that I tested, over the course of 3 dives which is what happened to my son on his last two dive trips, second to last dive on the first trip and first dive on the second trip. Probably not exponentially higher so I will play it safe and stay away from "old alloy" tanks that I suspect have not had a recent eddy current test. I already retired my own pre 1988 Luxfer even though my LDS still fills them.