Scuba accident in a swimming pool close to my house

[BlueTrin]

Final report: Veiligheidswaarschuwing duikflessen

Article is in Dutch. The accident was caused by a wrong valve. The cylinder had a G3/4 thread, the valve had a M25x2 thread. These threads will only fit if you use a hammer for the final turns. And this stupidity has now taken the life of a diver.

How does the wrong valve cause exploding out of curiosity?

Or was the original article wrong and only the valve got loose?

 

[fsardone]

How does the wrong valve cause exploding out of curiosity?

Or was the original article wrong and only the valve got loose?

My first tank a steel 232 bar 18 liters is a G3/4 tank. Bought in 1984 and still going strong and in excellent internal conditions.
I had to replace the valve and it was hell to find one. I ended up buying a used one from a scrapped tank …. maintained to new and installed.
Be careful out there: compressed gas stores and incredible amount of energy, that can be release rather quickly.
This missmatched valve/tank thread is doing quite a few victims…. many times unsuspecting ones!
The mechanism is simple the thread are damaged by the force needed to screw the wrong valve on and now are unable to hold the force that the gas pressure puts on them.

 

[SlugLife]

Also out of curiosity:

Is there a good way to identify different threads, except the valve almost-but-not-quite screwing in all the way?

From what I hear, an my experience with some pony-tanks, you should just be able to easily hand-tighten most valves.

 

[goldfishtornado]

Also out of curiosity:

Is there a good way to identify different threads, except the valve almost-but-not-quite screwing in all the way?

From what I hear, an my experience with some pony-tanks, you should just be able to easily hand-tighten most valves.

According to the advisory, the threads on the tank and valve are supposed to be marked. If you need a quick id there are any number of quick reference gauges available. If a set of threads is suspected of having been damaged from galling etc. There are special thread gauges that can be used to check if they are still in spec.

The point about hand-tightening is the most practical one.

Fingers are very sensitive, and should be able to detect most situations where threads are not engaging properly. Almost all threaded devices should be at least started by hand. If they don't go together with fingertip pressure something is wrong, wrong size, cross-threaded, corroded, etc. Modern tank valves only need to be hand-tight since they have a captured o-ring. The old 1/2"-14 NGT threads are the only semi-common ones that are not like that.

 

[DandyDon]

Is there a good way to identify different threads, except the valve almost-but-not-quite screwing in all the way?

Yep, posted earlier...

So, it's a simple step of reading and matching the tank and valve that's missed with deadly possibilities?

View attachment 749273

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From what I hear, an my experience with some pony-tanks, you should just be able to easily hand-tighten most valves.

Yeah, but fill stations usually tighten my phone with a wrench beyond that.

 

[Bob DBF]

Is there a good way to identify different threads, except the valve almost-but-not-quite screwing in all the way?

Assuming one doesn't, or can't, read the thread stamped on the tank or valve, one should be able to easily hand tighten the valve all the way into the tank until the o-ring compresses, if it's the wrong thread it will get hard to turn, which means it's the wrong thread or cross threaded, either of which is a serious problem.

 

[SlugLife]

Does anyone have a guide to the actual markings on the VALVE? I tried finding one, but no luck.

For example, I see: "07-04E" and "B-1" (or 8-1) on valves on my steel tanks. Another tank has "05-03" and "0-7" marked on the valve. Perhaps there are other markings on the valve-base (inside the tank?) I could check my other tanks and loose valves in the morning.

 

[ijdod]

Does anyone have a guide to the actual markings on the VALVE? I tried finding one, but no luck.

For example, I see: "07-04E" and "B-1" (or 8-1) on valves on my steel tanks. Another tank has "05-03" and "0-7" marked on the valve. Perhaps there are other markings on the valve-base (inside the tank?) I could check my other tanks and loose valves in the morning.

One of the issues is that not all tanks and/or valves are marked with this particular information. Ideally they should be, of course, but there is no legal requirement here from a tank certification perspective. It'll only fail if the threads are damaged; I'm not clear this troublesome combinaties does so to the extend it fails. My tanks are stamped M25, and my valves M25x2. The G3/4 tanks I've seen were marked 3/4, as were the valves.

 

[Bob DBF]

One of the issues is that not all tanks and/or valves are marked with this particular information. Ideally they should be, of course, but there is no legal requirement here from a tank certification perspective. It'll only fail if the threads are damaged; I'm not clear this troublesome combinaties does so to the extend it fails. My tanks are stamped M25, and my valves M25x2. The G3/4 tanks I've seen were marked 3/4, as were the valves.

It's like a lot of changes, the new tanks and valves are much more likely to have the information stamped on them, the older ones will not, kind of like the REE numbers now stamped on tanks. The takeaway is not to take anything for granted.

 

[SlugLife]

I took a closer look at some of my valves, now that I have some daylight. Of the valves I checked so far.

• 4 valves have marking indicating threading
• 5 do not.

As far as tanks with markings? Don't know, because markings can be a pain to read, and I have a very random assortment of tanks.