Double Discing???

[jeepster0000]

I have a set of double faber lp 108's. The tanks bought brand new this year so I still have the + rating for 5 more years. I was thinking about double discing my tanks. I have the dive rite 300 bar manifold, so I know my tanks and valves can handle the pressure. Would this put in extra strain on the tanks like a shorter life? If so about how much shorter. I would only be filling my tanks up to 3200 PSI and no more. From what I read, and correct me if I am wrong, If you do not go beyond 3200PSI, You tank will last just as long as if you dont.

Please Help
Thanks
ADAM

 

[BUBBLETRIBE]

I have seen some serious pressure cracks in Aluminum tanks. They call them sustained load pressure cracks. Many times I also see these cracks only with an eddy current tester. To me it is the fill station that is at highest risk here. Do you really have such ease in getting such a substantial overfill? 2400psi + 10%= 2640psi.
Perhaps I am just ignerant as to what is going on in the Steel market. Interested to hear the poop on that.
Cheers

 

[Iguana Don]

In this Forum "Tanks and valves" and you will get more information than you can shake a stick at.

But beware, this is just information in a discussion group and you should follow the manufacturer's advice.
"Legal Disclaimer"

ID

 

[Goldminer]

jeepster0000 once bubbled...
I have a set of double faber lp 108's. The tanks bought brand new this year so I still have the + rating for 5 more years. I was thinking about double discing my tanks. I have the dive rite 300 bar manifold, so I know my tanks and valves can handle the pressure. Would this put in extra strain on the tanks like a shorter life? If so about how much shorter. I would only be filling my tanks up to 3200 PSI and no more. From what I read, and correct me if I am wrong, If you do not go beyond 3200PSI, You tank will last just as long as if you dont.
ADAM

I am still not sure why you want to double disc. The burst disc is not designed to fail at the working pressure of the tank. Rather it is designed to fail before the tank reaches its test pressure, thereby preventing catastrophic failure.

Contact the manufacturer of your valves to find out what the test pressure for you burst disc's are. I suspect that they will easily handle 3200 psi. I have PST LP95's that have been filled to 3,000 psi several times.

Another thing to consider is I suspect that double discing can get you into a liability nightmare.

 

[Genesis]

the tank is double-disced and IF it blows up you will have major problems - like perhaps living in a refrigerator box or even the graybar motel for quite some time.

If someone was to die as a consequence you could easily be charged with involuntary manslaughter.

Think long and hard before removing the safety systems in this fashion. If you fill in your own garage off your own compressor then its your own butt - and that's a choice I argue you have a right to make.

Ditto if your LDS knows you did this (and you can prove it - say, with a written document) and they will fill you anyway (ha! fat chance there!)

Otherwise, I wouldn't.

 

[MikeFerrara]

The burst disc is there, I believe, to protect firemen in burning buildings. Some say that the neck o-ring will fail before the tank(steel) gets hot enough to fail. Being an x-blacksmith I have seen Al heated. It disintegrates very quickly. I think that when exposed to fire the Al will give befero the presure gets high enough to blow a burst disc. It sounds good but I don't know. Here is what I do know...I have seen burst discs blow just because and I did see it happen in a cave. My tanks have never been in a burning building with firemen present but they are frequently on my back in a cave. IMO, the chances of me having trouble because a burst disc is there is much much greater than a firemen getting hurt because it's not there.

I have never heard of a tank blowing because of the "fail" presure being exceeded. Has a burst disk ever helped anyone?

All that said, the law is the law and it is the law that our legeslators can kill who they want.

 

[Ray2]

Jeepster,
The + rating will last the enire life of your tank,when its time to retest, take it to your local welding supply distributor they should understand this very well and they usually charge approx.$12.00 to$15.00 per cyl.Diverlink has good info on the 10% overfill,if you want to find out more on the subject.

 

[Genesis]

you are right about the REALITY of it, but the unfortunate liability russian roulette game is that if you have a tank go "boom" and you double-disced it, you are hosed - whether the disc would have blown or not.

By tampering with the overpressure device you void the tank's DOT certification - a very un-good thing when you are playing the liability russian roulette game.

I have seen a disc blow during filling when the tank was nowhere near rated pressure. If that happened underwater in a cave (or in any other overhead environment), it would suck badly and might kill you due to loss of backgas before you could isolate the remaining supply.

There is no real "good" answer to this.

If you're going to do it, arguably the proper way is to put in two discs "accidentally"; it could always be argued that the error was not yours, although quite frankly you're rather likely to lose at least on the civil end of that one. If you soldered in the relief hole or put in a solid plug instead of a burst disc the evidence would be conclusive...