Tank overfill

[Leadking]

It's always nice to know that we can change the rules/laws if it's inconvenient.

 

[mxracer19]

yes, infact it is.

 

[roakey]

It's always nice to know that we can change the rules/laws if it's inconvenient.

That's the concept behind jury nullification!

Roak

 

[Tom Winters]

I'd be bummed out if my LP85's only had 3000psi in them.

 

[SouthEastFloridaDiver]

I have Faber 85s (2400 + 10%). So far every single dive shop has filled them to 3300-3600. So it seems to be very common to overfill them, and I have not heard yet of a single case where this caused any problems.

 

[Lightning Fish]

We've been round and round this argument, on this board and every other, the fact of the matter is there is only one recorded incident of a steel tank exploding, but it was badly rusted 72 that was out of hydro and no sane person overfills 72s or any other "old" tank for that matter.

Question: If no sane person overfills 72s, then why would they overfill 80s, or 104s? What is special about the other tanks that they can be overfilled whereas 72s can't?

Cheers,
Bill.

 

[Leadking]

A quote from PSI's (Professional Scuba Inspectors) website

"Several of the recent aluminum cylinder ruptures have attracted considerable industry attention while the more than 24 steel cylinder ruptures over the years are forgotten. The prudent dive industry professional should be very cognizant that ALL high-pressure cylinders contain phenomenal energy and ALL should be given great care. Every ruptured cylinder had obvious damage whether it was a crack in the threads, damage from excessive heat, extensive corrosion or other abuses."

 

[Tom Winters]

Question: If no sane person overfills 72s, then why would they overfill 80s, or 104s? What is special about the other tanks that they can be overfilled whereas 72s can't?

Solely because they're old. I used to fill lots of steel 72's in Honolulu. I failed more than a few because serious external rust - chunks flaking off. No way I was going to fill those things. The guys who owned them had NEVER argued with me when I condemned one of them too.
Sane people do not overfill LP steels by the way.
I never overfilled aluminum tanks though - if someone pumped them up to 4000psi, well, that was their call, not mine. I could live with 3000psi.
You read all the reports over the years of tanks exploding - it's those aluminum bombs. More than once, I opened up an aluminum 80 for a VIP and found lots of powder inside. Scary stuff. One had been VIP'ed just 6 months earlier.

 

[RedCash02]

I'm going to have to agree with markfm on this topic, being a fellow engineer. Design specifications are there for a reason when it involves fluids. I work for the world's largest hyrdaulics company and we use a large factor of safety. If we have a fitting that fails at approximately 40,000psi in the lab then we will only rate it at 10,000psi at the most. Why? Liability for one, and the increased wear and shortened life.

Also we will not rate it at a higher pressure than what the fatigue limit of the steel is. When you say it will last 10,000 cycles that means you're above the limit and the cylinder WILL fail eventually (no matter what). However 10,000 is just an estimate. If you're cylinder does have any flaws such as cracks and grain boundaries (which it does) they are at risk of growing and increasing the localized stress in those region.

I'm not saying you will all kill yourselves, because nothing will probably happen. But don't completely ignore these specifications, they were put in place to protect you.

 

[Lightning Fish]

Solely because they're old. I used to fill lots of steel 72's in Honolulu. I failed more than a few because serious external rust - chunks flaking off. No way I was going to fill those things. The guys who owned them had NEVER argued with me when I condemned one of them too.
Sane people do not overfill LP steels by the way.
I never overfilled aluminum tanks though - if someone pumped them up to 4000psi, well, that was their call, not mine. I could live with 3000psi.
You read all the reports over the years of tanks exploding - it's those aluminum bombs. More than once, I opened up an aluminum 80 for a VIP and found lots of powder inside. Scary stuff. One had been VIP'ed just 6 months earlier.

So in other words, 72s are no longer available to be bought? I have found a couple of website where they list MP-72s for sale.

Bill