80cu Tank at 800 Feet ????

[Akimbo]

Multiple.

There would be one on my backgas and then one on every one of my deco bottles.

Gas reserve planning would allow for the loss of small amounts of gas such as a HP leak. If necessary, feathering the valve would allow you to reduce the loss of gas further.

On such a dive it's not likely that you'd take all your tanks down with you, rather they would probably be staged on a line. IF you did take them all down, it's unlikely they would all implode at the same time. First failure means you call the dive, so you're still only dealing with one failure.

SPG is a nice feature to have, but it's not a necessity. Your deco schedule is going to run on a time factor and as you deco out either you have enough gas to do the deco or you dont. If your backgas SPG implodes, then your dive is ending sooner so you have even more sufficient deco reserves when you start back up.

If a deco SPG implodes, you complete your schedule til you run out of gas. At that point you either adjust the schedule and move up to your next deco gas, or you switch back to backgas until you can make your next deco switch.

Of course a good understanding of deco is imperative to making these on the fly adjustments.

I'd probably be more concerned about the concussive force and shock wave of an imploding SPG near my head at depth than I would about the loss of gas.

I hope anyone reading this keeps your answer in mind when contemplating the OP's original question.

Wanna start a petition? The tech market is large enough that several manufacturers court you. Why not start a movement for someone to make a much safer depth rated and tested SPG? What do you all think about a 200 M/660' rating? Maybe start a new thread with a poll, petition, and additional suggestions for a tech (or tek for our Euro friends)? I am not the one to start it but I would sign on.

I bet more "depth rated SPGs" would be sold to new divers with money just for the prestige factor. The increased manufacturing volume would just reduce prices for people who really need it.

 

[Cave Diver]

I hope anyone compares reading this keeps your answer in mind when contemplating the OP's original question.

I bet more "depth rated SPGs" would be sold to new divers with money just for the prestige factor. The increased manufacturing volume would just reduce prices for people who really need it.

Hopefully, no one reading this would ever seriously contemplate the OP original question to begin with.

I've been to a bit past 300' and I can assure anyone reading along that looking up at the surface from that depth is pretty damn daunting and not someplace I want to be on a single AL80. Ever.

 

[Akimbo]

Hopefully, no one reading this would ever seriously contemplate the OP original question to begin with.

I've been to a bit past 300' and I can assure anyone reading along that looking up at the surface from that depth is pretty damn daunting and not someplace I want to be on a single AL80. Ever.

This is the Internet after all.

It was not that long ago that the diving we both do would be considered equally insane. Without the hard-won knowledge, experience, developments in decompression theory, and a minor boost from technology it still would be. In the big picture, the single 80 is the least important part of the equation. This is not a criticism of the OP for asking the question as an intellectual exercise, only a warning to the ill-informed who may read this.

 

[Jax]

Bend the hose back on itself and secure it with a spare double ender. I'd likely also start feathering the tank valve to conserve some air since that may not completely stop the leak.

It is however, fairly effective. I've tested low and high pressure hose failures on the surface and at depth before.

Okay, I'll bite. How does one test such things and better -- why? Since the data exists, it seems a moot point.

 

[Cave Diver]

Okay, I'll bite. How does one test such things and better -- why?

Several of us sitting around the dive shop one day arguing over what would empty a tank faster, burst LP hose or burst HP hose. So someone whips out a knife, we find a couple of old hoses and test it to see which drains a tank faster.

To test it underwater, loosen up the second stage to hand tight on a stage bottle and unscrew it on the training platform and see how long it takes.

IIRC, Joel ([user]JS1Scuba[/user]) did a test of HP and LP hoses at various depths and published the results here a few years back.

Since the data exists, it seems a moot point.

Where do you think data comes from?

As I recall, we tested this before I ever found SB.

 

[Jax]

Where do you think data comes from?

As I recall, we tested this before I ever found SB.

Then you'd better beat up the SSI manual for failing to pay proper attribute to you work! :shocked2:

BTW, what did you come up with? SSI says the LP hose will drain an AL80 in 83 seconds.

 

[Cave Diver]

Then you'd better beat up the SSI manual for failing to pay proper attribute to you work! :shocked2:

BTW, what did you come up with? SSI says the LP hose will drain an AL80 in 83 seconds.

I'm sure we're not the only group of guys to ever get bored enough to test a theory. Hell, the Mythbusters get paid to do stuff like that (although I'm not always impressed with their methods or their results).

I don't recall the exact times since this was probably 10 years ago. I do remember that the LP hose drained a tank significantly faster than HP and it was a lot faster than we expected.

 

[Jax]

I'm sure we're not the only group of guys to ever get bored enough to test a theory. Hell, the Mythbusters get paid to do stuff like that (although I'm not always impressed with their methods or their results).

I don't recall the exact times since this was probably 10 years ago. I do remember that the LP hose drained a tank significantly faster than HP and it was a lot faster than we expected.

Surprised me, too; but I got serious about "why was this" after the inflater hose blew on me. Some of our physics guys did computations on oriface sizes and flow, and 'proved' it mathmatically . . . . Bored engineers are scarey.

 

[Cave Diver]

Surprised me, too; but I got serious about "why was this" after the inflater hose blew on me. Some of our physics guys did computations on oriface sizes and flow, and 'proved' it mathmatically . . . . Bored engineers are scarey.

I don't recall it draining it quite that fast. If memory serves me correctly a blown hose on a full tank still gave us time to shut down the valve with close to 2/3's the tank left. But it's definitely something that requires immediate response.

Blown burst discs can be pretty exciting too.

 

[Jax]

I don't recall it draining it quite that fast. If memory serves me correctly a blown hose on a full tank still gave us time to shut down the valve with close to 2/3's the tank left. But it's definitely something that requires immediate response.

Blown burst discs can be pretty exciting too.

That was something like 72 seconds . . . So, when SEA HUNT comes by, hope they cut that HP hose! :laughing:

Have you actually blown one?