Cave fills?

[Brett Hatch]

Does cave filling a lp steel tank reduce it's lifespan?

I'm obviously not an expert here, but I have heard that overfilling reduces their lifespans from decades to years.

EDIT: This was clarified to be false downthread.

 

[NAM001]

Does cave filling a lp steel tank reduce it's lifespan?

I think technically you have to say yes. There is no way around saying other than YES. They are supposed to handle I think 10000 2400 psi fills w3hile still passing a hydro. Over filling may reduce that to perhaps 6000 fills. that is a lot of fills if you dive once a week using 2 fills thats 100 fills a year or 60 years worth of over filllng on that dive schedule. pick your techinical or reality answer?? I would say that amount of tanks I have results in perhaps a dozen fills a year each. None of my tanks has evre failed a hydro and they IN the words of the hydro guys they fully recover fromthe expansion . Ive had my lp 95's since 2003.

 

[W W Meixner]

I currently do (strictly rec) single-tank dives in the Monterey area with HP100 steel tanks filled to ~3442 psi. I have heard that filling LP tanks (2400 psi or 2640 with the + rating) up to ~3500 psi is very common in some places of the world, such as Florida cave country. The result is a smaller tank containing a lot more gas than my HP100's. It's my understanding that this practice is safe for divers (read: nearly no more risk vs diving an HP tank at the same pressure). Rather, it is the tank filling operator who takes on additional risk, since there is a non-zero chance of tank failure during the fill.

My primary LDS's operators don't do this. Are there any dive operators in the Bay Area who do these "cave fills"? If so, I might consider picking up some LP85's (or similar).

Thanks.

Brett...

There is no such a thing as a ''cave fill''..there is only filling to working pressure as identified by cylinder stamping...and over-pressurizing...regardless of sector within our industry...

The + stamp only allows for 10% over stamp identified working pressure...

Buy larger cylinders...HP 117's/133's/149's...either as singles or any combination of doubles...for your purpose double HP steel 80's will serve your purpose very nicely...

I can get 45 minutes at 130 ft including all stops...with 1200 PSI remaining from single HP 117's...

Retailers who value the safety of their staff...as well as safe-guarding their liability...will not/should not over pressurize any cylinder over stamped working pressure...if they do not take the time to fully verify the cylinder before filling...you should find another retailer...they're not doing themselves...you...or your cylinders any favor...

W.M...

 

[MichaelMc]

Some older threads have more info.
- Steel is not stressed by pressure below some point (a bit higher than what they are filled to), so no to a point. Presumably a reason springs are made of steel, but have limits which if stretched past they no longer return.
- Aluminum is stressed by every fill, so yes, with every fill.

 

[Brett Hatch]

I have LP50s for sidemount. My experience in the Monterey area is most shops fill them to 2650. One filled to 2200 or 2400 and had to be questioned about whether they saw the + rating. As a gentle way of asking if they knew what they were doing.

I've had casual conversations about the statistical safety of cave fills on LP tanks when such things came up. But not asked them explicitly to do it. I don't know their rules or liability and I'm not doing anything where I can't just surface or take more or bigger tanks.

I might end up trying sidemount or tiny-doubles for improved redundancy w/o necessarily having a lot more gas (and a lot more crap to lug around). But at some point I am going to want more gas; seems theres basically 1) bigger tank, 2) over-filled tank, 3) multiple tanks. I do have a 40cuft that I occasionally sling for redundancy, but it has never been a part of my gas plan -- maybe some day (with sufficient training .

Do any local ops fill to the 3k-4k range? That's where LP tanks start to hold more gas than HP tanks.

Brett...

There is no such a thing as a ''cave fill''..there is only filling to working pressure as identified by cylinder stamping...and over-pressurizing...regardless of sector within our industry...

The + stamp only allows for 10% over working pressure...

Buy larger cylinders...HP 117's/133's/149's...either as singles or any combination of doubles...for your purpose double HP steel 80's will serve your purpose very nicely...

Retailers who value the safety of their staff...as well as safe-guarding their liability...will not/should not over pressurize any cylinder over stamped working pressure...if they do not take the time to fully verify the cylinder before filling...you should find another retailer...

W.M...

W.M.: Thank you for the advice, I appreciate it. Larger tanks might indeed be the best option for me, I'm still doing research.

I do not wish to start a religious war over whether over-filling LP tanks to HP pressures is safe, legal, advisable, smart, or what have you. There are threads and threads of this already on SB, and I'm not in a position to add value to that conversation. What I'm trying to do is evaluate what options are available in my area.

 

[MichaelMc]

Do any local ops fill to the 3k-4k range? That's where LP tanks start to hold more gas than HP tanks.

In my experience, Monterey and Bay Area shops do not fill LP to the 3k-4k range, as an occasional person bringing tanks to the shop. A few might be less exact at staying down at 2650 and might venture boldly up to 2850. That is appreciated, but mostly irrelevant in your calculations of tank choice.
(The specs for fill pressure do list a reference temperature pressure and a warmer temp pressure that is greater, either of which can be met, so they might be in spec, details in earlier threads talking about stamped/cool pressure.)

Tiny doubles are great, and come in a few sizes. I highly recommend them from a redundancy yet ease of use standpoint. I went sidemount, but that is more effort to get into. You might look at double 72s. Either steel or aluminum. I've got double AL40s. but that would be a step down in volume.

 

[SandyRobinson]

I'm obviously not an expert here, but I have heard that overfilling reduces their lifespans from decades to years.

No expert here either but I would guess the reduction may be from centuries to decades In the FWIW category, my Faber 95s are 15 years old, are normally stored with 3600 +/- and have always passed. Many of my buddies dive the same tanks that are older with no issues. The only tanks I have heard of failing were LP PSTs which could have been a tester issue, and it seems like that was 10+ years ago.

 

[runsongas]

@Brett Hatch i'll send you a pm

 

[Dominick Gheesling]

Does cave filling a lp steel tank reduce it's lifespan?

I am currently diving (overfilling/cave diving) a set of PST lp104s that have a born on date of 1978. The previous owner was Forrest Wilson (Inventor of the Wilson Line Arrow) who certainly overfilled and dove them for years. So far so good. From what I have seen, overfilling is not nearly as destructive to a tank as saltwater anywhere, water in the tank, and tank boots.

 

[dewdropsonrosa]

I've heard a well-known cave instructor say, "Yes, I hydro my tanks... EVERY TIME I FILL THEM."