Overfilling LP Steel Tanks -- How bad is it?

[PhilEllis]

Since Luxfer is no longer in the scuba market I'd like my cylinders to last as long as possible.

PARDON THE HIJACK

Actually, Luxfer has JUST re-entered the scuba cylinder market with 4 cylinders. They will only be available in the brushed aluminum finish. Among them will be the brushed aluminum 40CF and the brushed aluminum 80CF. They will be available almost immediately. The old "cheap" Luxfer days are gone, but I think the news of continued availability is welcome.

More information will follow.

Phil Ellis
www.divesports.com

 

[rjack321]

I'd like to see the section in the standards of any of the mentioned agencies that covers that.

Not a caver so I won't dispute that it's common practice, but if anything ever happened they would be pretty much on their own in court.

Agencies don't set fill pressures. This is left up to divers and fill stations.

Working pressures are legal things set by DOT, in this case they conspire against bringing as much gas as you can into a cave. 100x (maybe 1000x) more people have died from running out of gas in caves than from bursting 3AA cylinders. I'll take the overfills thank you.

 

[rjack321]

We are forgetting something here...
Every tank is required to be brought to well over it's service pressure once every five years for hydrostatic testing. This is required by DOT to keep the tank in service. What are the pressures during hydrotest? Yes this is done under controlled conditions by trained personel. But the point is that pressures of a overfilled LP cylinder are substancially less and the safety at those pressures are substancially greater. Granted not as safe as HP cylinders that are rated for higher pressures to begin with.

Hydrostatic test pressure for a 2400psi 3AA cylinder is 4000psi. Just a bit above typical cave fill usage at 35-3600psi. LP cylinders from 15-20 years ago which have seen regular 3000psi+ overfills seem to still be fine.

 

[tc]

Agencies don't set fill pressures. This is left up to divers and fill stations.

Working pressures are legal things set by DOT, in this case they conspire against bringing as much gas as you can into a cave. 100x (maybe 1000x) more people have died from running out of gas in caves than from bursting 3AA cylinders. I'll take the overfills thank you.

You're correct, the agencies don't set fill pressures. Tank manufacturers, the CGA and DOT do. OSHA might also have a few things to say about it if an employee is filling the tank.

I was simply addressing the implication in the post I responded to that the listed agencies allowed/accepted/condoned/advocated? filling to the higher pressures.

If the shop owner and employees (or owner of the compressor) are aware of the slight added risk and the added liabilities that go along with it then it's their choice to do so.

 

[Leadking]

Any answer that isn't a NO is a wrong answer.

I'm disappointed to see Dive Masters, Asstinant Instructors and Instructors advising someone that's ok to over pressurize a tank.

DOT Regs are very specific and can only be filled to the operating pressure stamped on the tank - period - no exceptions.

Giving advice to the contrary exposes one's self to liability, not to mention most likely a violation of your own certifying agency standards.

Any question can be answered based on "experience" or the "Right Answer"....sometimes these answers differ.

The "right" answer is: You should never overfill your tank.

You just don't get it!!!

These tank jockies know more than trained engineers!! Those engineers just pull numbers out their a$$'s just to make life difficult for us. Wise up, removing the safety factor is the smart way to go.

 

[H2Andy]

removing the safety factor is the smart way to go.

do you know what that safety factor is?

what is the probability of a 2400+ LP tank blowing up on you after 20 years of fills to 3400 psi?

do you know?

 

[SparticleBrane]

PARDON THE HIJACK

Actually, Luxfer has JUST re-entered the scuba cylinder market with 4 cylinders. They will only be available in the brushed aluminum finish. Among them will be the brushed aluminum 40CF and the brushed aluminum 80CF. They will be available almost immediately. The old "cheap" Luxfer days are gone, but I think the news of continued availability is welcome.

More information will follow.

Phil Ellis
Discount Scuba Gear at DiveSports.com - Buy Scuba Diving Equipment & Snorkeling Equipment

Thanks for the update, Phil!

 

[jmorriss]

You just don't get it!!!

These tank jockies know more than trained engineers!! Those engineers just pull numbers out their a$$'s just to make life difficult for us. Wise up, removing the safety factor is the smart way to go.

Yes, we should go ahead and remove the safety factor on bridges and buildings too-it would make them cheaper! The engineers have put hours of work into something before it gets used in public. If that design is proven to be faulty they can be civilly or criminally liable for anything that happened as a result. Its good practice and in the best interest of the public to have a safety factor since you can Q/C test every last ounce of steel that goes into the factory and comes back out.

do you know what that safety factor is?

what is the probability of a 2400+ LP tank blowing up on you after 20 years of fills to 3400 psi?

do you know?

Exactly-that being said I see no issue with mild overfills. In fact I am gonna dust off my pressure vessel design notes from college and see that the safety factor is on those tanks.

 

[Leadking]

do you know what that safety factor is?

what is the probability of a 2400+ LP tank blowing up on you after 20 years of fills to 3400 psi?

do you know?

No I don't, that is why we have PROFESSIONALS who do understand the these things.

When I'm sick , I go to a doctor. Have a legal problem? I go to a lawyer. Why does society bother to spend the billions of dollars educationg these people if what they learn means nothing. Just because you're getting away with it does not make it "safe".

And god forbid when a tank let's go on some tank monkey (and it has happened) remind him of ridiculous safety factor. I don't mind if you take all the risk you want, the rules are there to protect the rest of us.

 

[redacted]

When I'm sick , I go to a doctor. Have a legal problem? I go to a lawyer. Why does society bother to spend the billions of dollars educationg these people if what they learn means nothing. Just because you're getting away with it does not make it "safe".n't mind if you take all the risk you want, the rules are there to protect the rest of us

So doing 60 MPH in a 55 zone would just be out of the question?