Wassup with Cave Fills?

[boulderjohn]

I get that John and it makes sense...... but as long as some shops turn a "blind eye" are OK overfilling steel tanks then why shouldn't all of them do it.

Yes...because most charge by the cubic foot.

In cave country, they are meeting a demand. Divers need those big fills there because cave diving gas planning protocols mean you need way more gas than you do in an OW dive. There's no "be back on the boat with 500 PSI." In the best case scenario, you are diving thirds into the current, so you come out of the cave with half your gas left over. You need oodles of gas because you can't just head for the surface if you have a problem. A cave country shop that refused those big fills would be out of business in no time.

There is no such demand on OW dives, so there is no need for a shop to meet it. They can stay within standard pressures without losing customers.

The point Tursiops is making is that pricing is different as well. In an OW shop, you pay so much per fill. In cave country, they charge per cubic foot, so they make more money for overfills. OTOH, because they charge by the amount of the fill, the returning diver gets credit for what is left over in the tank that is being filled.

 

[PEDiver]

I feel like this is a very simple concept.

There are some shops, primarily in FL, who are comfortable with overfilling LP steel tanks to ~3800-4000 psi (cooled to 3600 psi). This has been happening for decades and is an accepted practice among the cave community.

Outside of FL (and maybe some other regions, I am not sure), this practice is not really necessary since the vast majority of the world uses aluminum tanks.

If you dive in an area where steel tanks are more beneficial (thinking cold OW), and you want "cave" fills, that is a conversation you will need to have with your LDS or purchase your own compressor.

 

[NDonahue]

Could it be that the "deviance" is the act of gathering data, and when enough data has been gathered, it's not normalization of deviance but rather persuasive evidence that the norm was incorrect to begin with?

absolutely. The is the basis for scientific innovation!

with my original comment I was just taking the piss.

I just think it’s pretty funny that the same group (FL cave divers) that gave us DIR / GUE, and who have constantly reinforced the critical importance of consistent practices and adherence to standards, willingly ignores the juxtaposition of cave fills.

again, just taking the piss.

 

[JoeTPhilly]

absolutely. The is the basis for scientific innovation!

with my original comment I was just taking the piss.

I just think it’s pretty funny that the same group (FL cave divers) that gave us DIR / GUE, and who have constantly reinforced the critical importance of consistent practices and adherence to standards, willingly ignores the juxtaposition of cave fills.

again, just taking the piss.

I think GUE has adherence to safety and the standards are to support safe dives. As mentioned a couple posts above cave divers need the extra gas to make those cave dives safe, no?

 

[boulderjohn]

just think it’s pretty funny that the same group (FL cave divers) that gave us DIR / GUE, and who have constantly reinforced the critical importance of consistent practices and adherence to standards, willingly ignores the juxtaposition of cave fills.

Cave divers do rigidly stick to established standards--their established standards, not somebody else's.

 

[NW Dive Dawg]

are you flipping the bird?

Just happened to notice that my wingman buddy was snapping a pic and wanted him to know that he's No. 1. It's a term of endearment among friends!!

 

[BoundForElsewhere]

Just happened to notice that my wingman buddy was snapping a pic and wanted him to know that he's No. 1. It's a term of endearment among friends!!

Figured as much.

 

[Divin'Papaw]

I think HP steels get pumped to 4000 psi but I am not 100 percent on that -- a Florida local will correct me if I am wrong.

At the shop I use most frequently in southeast FL, my HP steels regularly come off of the fill station at 4000, sometimes a mere 3800 if the banks are low. Once allowed to fully cool, if that is possible being Florida, I have 3600-3800 in my HP steels. The other shop that I use requires me to leave them over night. When I pick them up the next day they have 3500-3600. I rarely, if ever, have a short fill from either shop.

 

[pauldw]

Yes...because most charge by the cubic foot.

Not that this is at all important, but I'm just curious. Do they measure the pressure before the fill, and then after the fill, and subtract the first measurement from the second and then charge by that measure of cubic feet? And is the second measurement when hot or cold? Or do they just fill it and charge according to the final pressure without reference to how much air was already in the tank? Or do they have something that meters air as it goes in?

 

[rx7diver]

... Are HP steels rated with the same conservatism as LP steels or less?

When I lived in SE Michigan, diving the Great Lakes, my PST 3,500 psig HP80's, HP100's, and HP120's, routinely left my LDS cool, showing 4,000 psig. I was using Poseidon Odin's (300 Br. regs) on my cylinders at that time, which certainly can handle this fill pressure.

rx7diver