Overfilling and life expectancy. (LP Tanks)

[Leadking]

These threads are always used as some excuse to ignore some rules of safety. I have driven well over the speed limit from time to time and never had an accident at high speed, so it must be safe. All those numbers stamped on the tank must be there for our entertainment. Why would they bother to put on serial numbers, lot numbers, pressure ratings and hydro data on cylinders? It appears this is some kind of government make work project. Goofy engineers. Going to school for years. What do they know? Get off my back!

 

[p1p]

There ya go...

I speed in my car @100, even though designed for 70
I Overclock my xbox and PC's though designed for lower clock speeds.
I eat persishables past their due date.
I run my air below 500psi in my tank

I'm just doomed to die a horrible death.

 

[ajduplessis]

Hydro failures during testing don't make any noise. You clearly don't know how tanks are hydro'd. So let me help you out.

During a hydro, a tank is filled with water. That water is pressurized to 5/3'rds the working pressure of the tank (on most tanks anyway) When we attempt to pressurize this water in the tank, the water is pushed into a graduated cylinder and measured at 5/3'rds working pressure. Then we drain the tank. The volume of water in the graduated cylinder must return to our starting level +/- 10%. If it doesn't, the tank fails. No big boom, no cracks, no wooshes. Just a water level not returning to the proper mark on a graduated cylinder. Of course this is a mundane description, but you get the point. I hope.

With all that knowledge and experience and never had a cylinder rupture during a hydro?? Or is a rupture not considered a failure? Not sure what you guys do but our are cylinder ruptures make a huge BANG!!!!! It was also a pleasure helping you out :mooner:

My apology for not clearly defining my reference to ruptures. Guess that's two halves of a story.

 

[Superlyte27]

What is rupturing? The scuba tank is rupturing during the test? Or the burst disk on the hydro machine is rupturing? If you are saying the scuba tank is rupturing, you are clueless. That NEVER happens during a hydro, probably because the difference in the pressure on the water outside the scuba tank is very close to the pressure inside the scuba tank. If you are saying the burst disk on the hydro machine fails, that does happen, rarely (in 10 years, and literally 10's of thousands of tanks, it happened twice). But that's not a "cylinder" rupture.


EDIT**
Let me be more specific.

The Hydro Machine is a giant VAT with 1" thick steel walls. It is filled with water and has a 1" thick glass burst disk in the back of it. It has a 2" thick steel lid. It comes with valves and ports to allow water to enter or exit, it has ports a quick disconnect to pressurize the water with air, powered by a scuba tank.

We drop a scuba tank into the Hydro machine and screw the lid into the scuba tank, then bolt the lid down to the 1" thick walls of the hydro machine. We purge any remaining air out of the scuba tank and out of the Hydro machine. We now have a vat full of water, with a scuba tank full of water, and a big huge lid screwed into the tank and screwed down tight. Now.... There's a graduated cylinder that is connected to one of the ports on the hydro machine. We set the level of water in the graduated cylinder to ZERO, and begin to pressurize an AL80 to 5/3 working pressure (if it were really possible to pressurize a liquid). The tank stretches due to the added pressure, and that stretch is evident by the water column moving up the graduated cylinder. We started at ZERO and now we are at say 100ml, or whatever. We bleed down the pressure and the water level in the graduated cylinder must drop to +/- 10% of zero. So if the water in the graduated cylinder is at 11+ or -11, the tank fails. What this means is, that when the tank pressure was released, the tank didn't come back to it's original size. Most often, the tank shows that it's now stretched out, doesn't come back to it's original size, and that's a failure.

In 10k + hydros we had that glass burst disk fail twice (which is quite a fright). That spanned 30'ish years. Tanks don't rupture during hydro because the difference in pressure from the outside of the tank and the inside of the tank (inside the vat) is very close.

 

[ajduplessis]

Very nice! Let me enlighten how we do the same test $5k cheaper with the same results. Around here we put the cylinders in bucket filled with water and check the water level via a very expensive $2 tube. We then fill the cylinder with water and increase the pressure beyound the cylinder working pressure as per manufactures spec. We then check the water levels again, take the measurements and do the same calculations you so expertly descrided. Once in a while a abused cylinders ruptures, not the burst disc (we dont have any remember, just a bucket). Most of the owners admit overfilling there cylinders and pitting is also involved.

Nice chatting to you.
PS the cylinders still make a huge BANG if they go.

 

[Superlyte27]

Total BS.
At least in the USA where DOT is king.

Dude, you're caught. You haven't a clue what you're talking about. Let it go. I understand the need to try to convince us, but you don't have enough knowledge on the subject to sway us that far. You lose. It's ok. Just walk away.

 

[Superlyte27]

To answer the OP's original question. In my experience, with countless sets of doubles, some spanning decades, and I promise they've never been filled below 3600psi, it's never been a problem. But it's completely up to you what you do.

I gotta live my life, and you gotta live yours. I promise if you fill them to rated pressure, they'll work just fine until they don't. Just like anything else.

 

[DepthCharge]

I am speaking of catastophic failures and the actual number, not percentage.

Percentage would be more meaningful. Say 10 out of 10,000,000 steel vs 5 out of 1,000,000 ali (don't know the actuall numbers just for illustration purposes). Do the math and steel is much safer.

 

[ajduplessis]

Total BS.
At least in the USA where DOT is king.

Dude, you're caught. You haven't a clue what you're talking about. Let it go. I understand the need to try to convince us, but you don't have enough knowledge on the subject to sway us that far. You lose. It's ok. Just walk away.

Sure, live in your little box.

 

[Superlyte27]

I'll continue if you wish. If the tank is in an unsealed bucket, with walls capable of being expanded, how do you force the water into the measuring tube? The only reason it works in a hydro vat is because there is NO WHERE else for the water to go EXCEPT the tube. I'm sorry but a "bucket" just won't fly.

Next question please.