What's a cave fill?

[tfsails]

A tank is pressurized to 5/3 of rated pressure during a hydro check. That means 5000psi for an AL80, 4000 for a steel LP tank, and 5833 for a steel HP tank. The pressures stamped on the tank is working pressure which should not be exceeded, but it's probably exceeded every fill. If the tank passes hydro, these "cave fills" shouldn't be a really big deal. Just about every reg is limited to 4500 psi if it's got a DIN fitting. The limiting factor for a yoke reg is the yoke itself.

All this being said, I once picked up a nitrox tank at a famous Bonaire resort that had 4200psi in it. It was an AL 80, and God only knows when it was last hydro'd and VIP'd. Since I was diving with a gas-sipping female buddy, I decided to use it. It was nice having all that extra gas on that dive! Did I feel like I had a nuke on my back? Nah, I'm a fatalist--when it's my time, it's my time.

I would not advocate overfilling tanks regularly, but I'm not above using one if I find it.

 

[SparticleBrane]

A tank is pressurized to 5/3 of rated pressure during a hydro check. That means 5000psi for an AL80, 4000 for a steel LP tank, and 5833 for a steel HP tank.

To the best of my knowledge, HP cylinders and 'exempt' (3442psi series) cylinders are actually hydro'd at 3/2 of rated pressure, or essentially 5,250psi.

 

[JCDdiver]

I like 3600 'cos it makes the math easy.

That way I just turn when my tank is "full."

I like easy math.

 

[jeandiver]

Alright, any of you that know me are probably wondering WTH! But it's a serious question. What is a cave fill these days? I'm still getting my tanks slow filled to 3700-3800 so they cool off to 3600. However, in this thread there is talk of some shops filling tanks to 4000+. Is this becoming standard practice in central cave country now?

I didn't read the rest of the tread but down here around the Gainesville are shops , 3600 is still the standard. At least that is what I have been getting the last month or so.

4000 seems a TAD HIGH (EEK).

Thanks!
Da Beano

 

[jimdiverman]

We've been discussing just that, Jean, the psychological barrier that those extra few hundred pounds get you at 4000 psi.

 

[jeandiver]

We've been discussing just that, Jean, the psychological barrier that those extra few hundred pounds get you at 4000 psi.

Ah , gotcha.

See , 4000 doesn't divide by 3 easily. That's why I like 3600
As far as a psychological barrier , er ...
I keep on singing no-matter-what-fill-I-get.

Seriously , it's hard enough on dem LP tanks at 3600. 4000 , well , er , uh ...
more hard enough. But I'll leave that to minds smarter than myself.
(And YES , I dive LP's)

(makes no comment on gas-sipping female divers)

LOL

Jean

 

[jimdiverman]

Ah , gotcha.

See , 4000 doesn't divide by 3 easily. That's why I like 3600

(makes no comment on gas-sipping female divers)

LOL

Jean

HA! One day I'm going to figure out how your 85s hold more than my 130s.

 

[jeandiver]

HA! One day I'm going to figure out how your 85s hold more than my 130s.

Maybe we should start a new thread

Jelly Bean

 

[marchand]

4000 may not divide easily by three, but 3900 sure does.

 

[ucfdiver]

4000 may not divide easily by three, but 3900 sure does.

Really, you only get 100psi more of penetration, for the 400psi extra on your tank. Seems like nothing, but 100psi is like getting a fresh set of tanks at the lips.

Figure my tanks have a fresh hydro. If they fail in 5 years, I'm getting around 75-100 dives a year on them, so 400-500 dives. I got them used for $650, so it's like renting for $1.50 a dive if they fail the hydro. I usually ask for 3600, which I think is fine, seeing how many tanks that are 20 years old in cave country still pass that are rentals and filled way more than 100x a year.