Filling LP tanks to high pressure

[Jared0425]

I'm sorry if this has been covered before, but I am looking for a definitive answer. I just inherited 2 LP Faber 130s that has the 2400+ symbol on them and the guy told me you could pump these tanks up to 4000psi in "cave" country. Then I ran across a thread that said LP tanks are made with a different material than HP tanks. So are we wrong about pumping the tanks up past their rated pressure that we have heard and done for many years?

 

[AfterDark]

That there + is 10% over the 2400psi or 2640psi. If ya'll are takem to 4000psi stand back some.

 

[scubadiver888]

Use search. Enter "cave fill" and use the quotes. You will find hundreds of posts about this.

If the tank has 2400+ stamped on it then someone claims it is rated for 2400 PSI + 10% or 2640 PSI. Anyone should be willing to fill the tank to 2640 PSI so long as it is current for visual inspection and hydrostatic testing. There are people will will fill it to higher than 2640 PSI. This was popular in "cave" country and is now referred to as a "cave fill".

Some will claim it is fine to fill the tank beyond the recommended rating. I personal don't do this nor would I fill someone else's tank beyond the recommended rate.

 

[boulderjohn]

To summarize scubadiver888: in cave country, lots of people overfill LP tanks to a large degree, but it is not "officially" sanctioned, and many others will not do it.

 

[Nwcid]

You have "working" pressure, Hydro pressure and then burst pressure.

Working pressure is usually one that a tank can be filled to over and over again with no ill effects and be in a "very safe" limit.

Hydrostatic testing is done to 5/3 of working pressure. The amount of stretch is measured to determine the "health" of the tank.

Then there is burst pressure, this is where there is a catastrophic failure.

Lets just take the tank you are talking about with a standard working pressure of 2400 psi. Every time it gets hydro tested it is pressurized to 4000 psi, so this is obviously not the burst pressure or your tank would be no good. From what I have read in general (can't find any sources right now, my googlefu is weak) bursting pressure it about double testing pressure.

So many people "cave fill" LP 2400psi tanks in the 3500-4000 psi range. [-]Due to the extra stress of the extra pressure when frequently used it sounds like most fail hydro on their first or second hydro. [/-] Sounds like this might be false info. I thought it was one of the things I read a couple years ago while looking for tanks.

That is the basic theory of it all. As stated you can look up more on "cave fills". You can also google each type of working pressure and see how they relate.

 

[AfterDark]

To summarize scubadiver888: in cave country, lots of people overfill LP tanks to a large degree, but it is not "officially" sanctioned, and many others will not do it.

Yes, but is it usually almost 2x's the rated pressure? I've got 1800psi tanks that get to 2200psi regularly and some 2250psi tanks that get to 2400psi. Going to 3000 / 4000 psi would send me seeking cover.

 

[boulderjohn]

Yes, but is it usually almost 2x's the rated pressure? I've got 1800psi tanks that get to 2200psi regularly and some 2250psi tanks that get to 2400psi. Going to 3000 / 4000 psi would send me seeking cover.

If you get your LP tanks filled in cave country, most shops that I know will expect you to want something between 3500-3800. I have never heard that they routinely fail hydro on the first or second try. Some of the instructors there have been doing it for decades.

 

[SeaCobra]

If you need 100 cubic foot tanks, then buy them. Don't try to make them out of 72's.

 

[AfterDark]

If you need 100 cubic foot tanks, then buy them. Don't try to make them out of 72's.

Will you carry them for me?

 

[Omisson]

From an ENGINEERING perspective, there is no inherent danger to filling a 2600 psi tank in Hydro to the typical "cave fill" of 3500 psi. The tanks are DOT tested to withstand 5/3 rds of their rating pressure WITHOUT straining the steel.

The "burst disk" in the valve to prevent overfilling is usually rated to either 4000 or 5000 PSI and will prevent a fill which compromises the metal's integrity.

There is no demonstrable reduction in lifespan of 2400/2600 tanks filled routinely to 3500 because the metal is well within its tolerance (usually 4500psi) pressure per square inch. The DOT sets standards to ensure safety by deliberately under-rating 3AA tanks.

Never overfill an aluminum tank... it lacks the stress qualities of steel..... that said... Cave fills under 4000 psi should not, under normal conditions (not over heated, properly cleaned, not banged up, recently hydroed and VIP'd) cause any safety issues.