Pony use when assisting an OOA diver

[Cave Diver]

It didn't work well for me - I went from 1000psi to 300psi in the time it took to surface from 16fsw. I'm not sure I had the grip to kink it, though.

You might have to fold it over twice to completely stop it if the tank is full. I can hold a full tank with a single kink in the hose to just a slight dribble. Two kinks fully stop it. Of course that's all relative to where the burst in the hose is and whether you have enough hose to kink. If it goes at the fitting on the first stage, you're SOL.

 

[MXGratefulDiver]

Yes. I've actually tried it when me and my buddies decided to test the whole "which is worse, a blown lp or hp hose?"

If you want to try it without cutting an old hose in half, hook your reg up to a tank, pressurize it, kink the hose then purge the reg.

I've never seen a hose completely blow either. I suppose it's possible, where you've got a broken end flapping around, but usually the covering lets go. Now a burst disk on the other hand, that's a pretty eye opening experience...

I wouldn't kink a hose unless I was prepared to replace it afterward ... they weren't designed for that sort of stress.

And has anyone ever actually blown a burst disk underwater? Seems to me it's more likely gonna happen when you're filling a tank ... not when you're emptying one ...

... Bob (Grateful Diver)

 

[kanonfodr]

Now a burst disk on the other hand, that's a pretty eye opening experience...

Ya, had that happen to one of my tanks during filling. It was shocking when the tank was outside in a shed with a loud compressor running next to it, I'd hate to imagine it happening right behind my head :shocked2::shocked2: .

Peace,
Greg

 

[Cave Diver]

I wouldn't kink a hose unless I was prepared to replace it afterward ... they weren't designed for that sort of stress.

And has anyone ever actually blown a burst disk underwater? Seems to me it's more likely gonna happen when you're filling a tank ... not when you're emptying one ...

... Bob (Grateful Diver)

I've been around one that blew that wasn't being filled. It wasn't underwater though, but I've heard of it happening.

 

[Jax]

You might have to fold it over twice to completely stop it if the tank is full. I can hold a full tank with a single kink in the hose to just a slight dribble. Two kinks fully stop it. Of course that's all relative to where the burst in the hose is and whether you have enough hose to kink. If it goes at the fitting on the first stage, you're SOL.

I was fortunate it was at the inflator, but grabbing it, and folding it over, was more instinctive than anything. Folding it a second time didn't occur to me; I'll know better next time . . .

 

[flots am]

Exactly! It's one thing for to adjust gas reserves for buddies you're familiar with, but how much do you need to reserve in the case of an unknown diver interrupts your solo dive with an OOA situation.

You don't need to know the specific diver, and can make a reasonable assumption that a freaked out large diver is good for a 2+ CFM SAC rate.

It all boils down to each person answering "How much do you care about a stranger's life?" I care enough to leave enough gas in reserve, whether diving solo or with a buddy. It's just a tank and it's just gas. If that means that I take a 120 and a 30' pony on a deep dive instead of a 95, or a 95 instead of an 80 on a shallow one, it's just not a big deal.

On a boat dive with rental tanks, it might mean selecting sites where the planned depth allows for handling emergencies with the available equipment. It might mean not signing up for a dive that's "unsafe by design." A 100'+ dive from a boat full of random strangers diving 80 Cu Ft tanks would qualify as a dive I'd pass by.

flots.

 

[DaleC]

In OW conditions I plan for one failure at max depth/duration which then precipitates an immediate (but environmentally prudent) ascent to the surface with some time allocated for problem solving. I do not plan for three failures by a stranger (repetitive diving close to NDL's, loss of buddy, loss of gas) who may or may not be appear out of nowhere. In that situation, I will share my resources if I can, but the stranger will have to make do with what I have planned for my dive.

I am not a diving St. Bernard.



I am also not a fan of the 1/3 rule for OW diving (unless the specific dive calls for it):

It's a general rule that avoids specific thinking. If your relying on 1/3's you're not thinking about individual dive calculations.
It's a strategy adopted from a different environment, with very different parameters, and does not take into account the variable profiles an OW diver may encounter. Too bad it's taught to a certain group of divers who's greatest asset ought to be their ability to think critically about a situation.

In the OP's scenario I don't think Paul did anything wrong and planned his reserve gas as I might when soloing (enough gas to ascend properly with some problem solving and an increased resp. rate). He had a redundant airsource with the same amount of reserve gas. If one uses a pony one does not need to reserve gas for two divers in the back gas. Because he has a short primary and an Air2 he should donate the pony reg, attempt to calm the diver and ascend with them to the surface. Pretty basic. If they have to ascend a little sooner because Sam blows through the gas too quick and he gets bent because of it, that's his (Sams) problem - not Pauls. I don't believe in assuming guilt that does not belong to me.

The acceptable modern ascent rate for OW diving is 30'/min. with an optional 3 min. SS, manditory if close to the NDL's, so Paul is doing nothing wrong there either. Blowing the SS (or omitting deep stops [if one ascribes to that philosophy]) may have an adverse effect on Sam because of his profiles but I do not assume that Paul is in the same nitrogen boat. Nothing in the OP states that Paul dove the same profiles as Sam or even knows of his existance until meeting him OOA.

 

[MXGratefulDiver]

I've been around one that blew that wasn't being filled. It wasn't underwater though, but I've heard of it happening.

Was it a hot and/or sunny day?

... Bob (Grateful Diver)

 

[Cave Diver]

Was it a hot and/or sunny day?

... Bob (Grateful Diver)

No. It was fairly late at night. Several of us were sitting around the shop after it closed, just hanging out and BANG! I don't know when the tank was filled, but it wasn't being filled at the time. Made a helluva racket banging around in the back of the shop. Between the bang, the clanging and the woosh of air you could barely hear over, it just about scared the crap out of us for a minute.

 

[MXGratefulDiver]

No. It was fairly late at night. Several of us were sitting around the shop after it closed, just hanging out and BANG! I don't know when the tank was filled, but it wasn't being filled at the time. Made a helluva racket banging around in the back of the shop. Between the bang, the clanging and the woosh of air you could barely hear over, it just about scared the crap out of us for a minute.

Blown disks indoors are always an exciting time ... had one "redecorate" the shop once ... it even blew tiles off the floor!

... Bob (Grateful Diver)