Cave Fills on LP tanks

[northernone]

I won't cave fill aluminum. A good condition LP steel, I'll cave fill without hesitation. There's a low enough global rate of reported incidences that's it's practice that's within my risk tolerances.

Filling strangers tanks, I'd be nervous but that's true regardless if it is to 2250 or 4000.

I take it back. Have since got burning throat and lungs on bigger dives than I was doing back then. It’s a real thing

Thanks for the update. I've suspected this from my o2 rebreather, I had first discounted it as sorb related irritation. Might be an interesting thread topic.

Cameron

 

[LiteHedded]

I won't cave fill aluminum. A good condition LP steel, I'll cave fill without hesitation. There's a low enough global rate of reported incidences that's it's practice that's within my risk tolerances.

Filling strangers tanks, I'd be nervous but that's true regardless if it is to 2250 or 4000.



Thanks for the update. I've suspected this from my o2 rebreather, I had first discounted it as sorb related irritation. Might be an interesting thread topic.

Cameron

On dives with a lot of o2 time I'll get out of the water having lost my voice with an irritated throat. Not always but sometimes

 

[Charles2]

I won't cave fill aluminum. A good condition LP steel, I'll cave fill without hesitation. There's a low enough global rate of reported incidences that's it's practice that's within my risk tolerances.

I partially agree with you - I won't cave fill aluminum either. However, I don't agree that having a "low enough" global rate of reported incidences makes the overfilling of cylinders an acceptable practice. If both tanks were in "good condition" why would the filling of a 3AL cylinder to 90% of its test pressure be more of a risk than taking a 3AA cylinder to 90% of its test pressure?

 

[northernone]

I partially agree with you - I won't cave fill aluminum either. However, I don't agree that having a "low enough" global rate of reported incidences makes the overfilling of cylinders an acceptable practice. If both tanks were in "good condition" why would the filling of a 3AL cylinder to 90% of its test pressure be more of a risk than taking a 3AA cylinder to 90% of its test pressure?

Way up thread there's a nice metallurgy explanation of why over repeated cycles the aluminum fatigues more quickly (potentiality catastrophically) than steel.

Cameron

 

[Charles2]

Way up thread there's a nice metallurgy explanation of why over repeated cycles the aluminum fatigues more quickly (potentiality catastrophically) than steel.

Cameron

If you are talking about post #51, it is a well written and informed post. As alluded to in that post; however, steel does have an "endurance limit". If the design stress is kept below that "endurance limit", steel can be cycled almost indefinitely without fatigue. Once that "endurance limit" is exceeded, steel no longer enjoys that same resistance to fatigue and will, in fact, fatigue in a similar fashion to aluminum. "Cave filling" of 3AA steel tanks increases the stress in the steel tanks to above that "endurance limit". I am sure that the metallurgists with the manufacturers could predict the number of cycles before failure at a 50% overfill of both 3AA and 3AL designed tanks. I suspect that we would all be surprised at that number and might even agree that the number is within our risk tolerance. We all pays our money and takes our chances.

 

[KevinNM]

Steel is really damn strong. I’d bet you are above 10,000 cycles before it fails hydro.

 

[АлександрД]

I know many people, who overfilling their tanks (steel), but most of them not over 10-20%...
My opinion - tanks overfilling - it the same as Russian roulette
Any overpressured 10-25 bar is the same, as another shell in revolver for Russian roulette...
WP filled tank is like empty revolver, and 360 bar filled tank with wp200 is the same as full-charge load of six shooter

 

[victorzamora]

I know many people, who overfilling their tanks (steel), but most of them not over 10-20%...
My opinion - tanks overfilling - it the same as Russian roulette
Any overpressured 10-25 bar is the same, as another shell in revolver for Russian roulette...
WP filled tank is like empty revolver, and 360 bar filled tank with wp200 is the same as full-charge load of six shooter

Outside of the US, these matters seem to be pretty different. In the US, the "LP" tanks being discussed here are rated for ~180bar and being filled to ~245bar.

The reason for the ratings has less to do with design and engineering than it does Government regulations. This was per a rep for one of the major manufacturers.

 

[АлександрД]

Outside of the US, these matters seem to be pretty different. In the US, the "LP" tanks being discussed here are rated for ~180bar and being filled to ~245bar.

The reason for the ratings has less to do with design and engineering than it does Government regulations. This was per a rep for one of the major manufacturers.

Ok, I understood....
In States you are using S&W mod 60 (.38), instead of us with S&W mod 17 (.22) for this game...

 

[Diver-Drex]

I’ve posted before about the code and regulatory issues with overfilling cylinders and won’t rehash that. But from a straight common sense perspective I just don’t get this. Someone please explain the thought process behind getting lp85s and overfilling them instead of getting hp100s? If you need 200cf of gas why don’t you just get the correct cylinders?
Here are the dimensions to compare.
Faber LP85 at +10% 7” dia., 26” height, 31lbs empty, -6.7lbs full buoyancy, neutral buoyancy empty given you 85cf.
Faber FX100 7.25” dia., 25.4” height, 34lbs empty, -8.4lbs full buoyancy, -.6lbs empty buoyancy giving you 100cf.
Over filling a LP85 has no advantage over a correctly filled 100. The weight and bouyancy differences are negligible at best. A quarter less diameter?
For all of the talk of standards, doing things the right way and normalization of deviance I’m puzzled that many in the ‘cave community’ accept this practice.