Dive Cylinder Explodes - Sydney

[Hemrick]

I was part of a committee that set the Australian Standard, but my spot on it was replaced before it actually was adopted. The committee was dominated by people who had a vested interest in having pressure tests done as often as possible. That is, dive shop owners, testing stations etc. It was inevitable that this would be the outcome.

As I fill my own cylinders, I only get them tested every three years or so. I make sure that I have at least a few cylinders in test in case we travel somewhere and need to get a refill.

PS I have corrected the typo in my previous post about the alloy type.

How long ago was the standard set clownfish? What were the time intervals prior to it being set?

Was there any input from cylinder manufactures? I'm genuinely interested in what going through a hydro every year does to a tank

 

[clownfishsydney]

As far as I recall, it used to be hydro one year, visual the next, then hydro again. I assume this is what it is in US. In Germany I know it is even more relaxed than this.

 

[Hemrick]

I've come from the US where it is hydro every 5 years and vis every 12 months, which is why I'm blown away by the Australia Requirements.


My research is mainly wikipedia

• In the United States, an annual visual inspection is not required by the USA DOT, though they do require a hydrostatic test every five years. The visual inspection requirement is a diving industry standard based on observations made during a review by the National Underwater Accident Data Center.[73]
• In European Union countries a visual inspection is required every 2.5 years, and a hydrostatic test every five years.[74][75]
• In Norway a hydrostatic test (including a visual inspection) is required 3 years after production date, then every 2 years.
• Legislation in Australia requires that cylinders are hydrostatically tested every twelve months.[76]
• In South Africa a hydrostatic test is required every 4 years, and visual inspection every year. Eddy current testing of neck threads must be done according to the manufacturer's recommendations.[39]

It makes me want to buy a compressor just so I'm not feeding this over the top the system

 

[clownfishsydney]

That is why we have about 20 compressors now in our dive club.

I also have spoken to a neighbour tonight who told me she works next to the dive shop. She advised that she thought a gun had been fired, but heard no screaming afterwards. She thought that it was something in the backpackers' lodge which is above the shops (police are there always raiding for drugs).

 

[Peter69_56]

I have old aluminum tanks. How do you find out if the alloy is the 6051 alloy? Do they have a marking somewhere? I don't own a tank less than 10 years old, and they have passed hydro but sounds like the failure can occur anyway. Maybe it's time to replace.

Embarrassed to say I assumed a tank was safe to fill if it passed a hydro.

Never assume that because a cylinder has been hydro'd it will therefore not fail before the next test period. A hydro only proves non failure on the day of the test (and also proves that the cylinder meets expansion and return to normal specifications). It is my belief that the hydro is more to test the pliability of the material rather than an actual failure test, although pumping to 5/3 pressure does test integrity at the actual time. The more important test is actually the visual and eddy current test.

My Technician course instructor said that he has hydro'd tanks and occasionally have failed in use some time later. He usually visually tests and eddy tests all tanks now to ensure this is prevented or minimised. He has also had manufacturers state that if a tank crack is not picked up visually then its nothing to worry about (which both he and I disagree with). Our approach is to always state that the crack is visual regardless of how it was found (in particular with new tanks), in that way its replaced no questions.

 

[Peter69_56]

This is nuts. Empty and drill holes in every one of these things. 1 person decides these tanks are ok to fill, and then exposes everyone within blast radius of your poor decision making. Let me guess, the person(s) injured are often not the person who decided the tank was ok to fill. Eddy testing isn't foolproof either.

I recommend not drilling holes in a failed tank but to use a chisel on the neck and thread. A tester on OZ used to drill holes on failed tanks but then had one come back in for fill with a bolt screwed into the drill hole and taped over. Yes idiots do come up with some great ways to live on the edge.

I think in OZ you have to either cut the tank in half or crush it. Usually you sign a release statement to allow destruction if it fails.

 

[w3dge]

Seems we're even more lenient in the UK, with a hydro every 5 years and a vis every 2.5 years.

Quite surprised how much variation there is in this...

 

[Peter69_56]

I was part of a committee that set the Australian Standard, but my spot on it was replaced before it actually was adopted. The committee was dominated by people who had a vested interest in having pressure tests done as often as possible. That is, dive shop owners, testing stations etc. It was inevitable that this would be the outcome.

As I fill my own cylinders, I only get them tested every three years or so. I make sure that I have at least a few cylinders in test in case we travel somewhere and need to get a refill.

PS I have corrected the typo in my previous post about the alloy type.

I am with you, I inspect yearly and clean, and test 3 yearly, however I am the only one to fill all my tanks unless in test. I am anal about how my tanks are filled to ensure no water in them, and that the air is not contaminated in any way. I have LDS compressors that I will not allow their air in my tanks as I dont trust them. I agree with you that in OZ its all about vested interest rather than safety of divers and the public. We are well known in OZ to be always ripped off by those with vested interests in many things.

Overpressurisation is one of the worst things for pressure vessels, and we regularly do this to our scuba tanks when standards are followed. Funnily, commercial pressure cylinders are only hydro'd 10 yearly?

 

[Goingforsound]

Just a question on the side, since filling tanks has its risks, could they put the tank being filled in a protection enclosure?

I remember that they now fill truck tires in a sort of cage because they had explosion in the past. Maybe it could be applied to scuba tanks?

 

[Shotmaster]

Just a question on the side, since filling tanks has its risks, could they put the tank being filled in a protection enclosure?

I remember that they now fill truck tires in a sort of cage because they had explosion in the past. Maybe it could be applied to scuba tanks?

Trucks used two piece rims, if the steel band slipped off it became a room clearing missile. Hence the safety cage required.

They make safety cabinets for scuba and scba tank filling. They are big, take up a lot of space and expensive. Here is an example. Just wait and see what it would cost to get your fills if they had to buy these at you LDS.

High Pressure Fill Stations And Containment Systems - Compressors - Fill Stations - For Fire Service and Scuba Diving - Poseidon Air Systems - Colchester Vermont