Goodbye ponies

Lee Taylor · Oct 30, 2008

I am a recreational diver. My dives are typically between 70ft and 100ft in 75 degree seawater. I dive single, nitrox, +/-100 cu ft, steel tanks. I always dive with a backup regulator and a partner. Years ago my dives were made with a 30 cu ft pony strapped to my single tank. I have recently quit using the ponies and I have begun to rethink the desire for using the pony. I have been thinking a lot lately about air-delivery, failure modes, between the tank and my lungs. I have read that if one were to have a free flow, that one can fold the hose over and crimp it off. Somewhat like one does a garden hose.

I have heard that primary regulator failures (the one on top of the tank), under the conditions of which I dive, are practically unheard of.

Here are the questions: I have heard o-rings pop (fail) topside, but do o-rings ever fail during a dive? Do primary regulators ever just stop working? Do hoses suddenly rupture?

I am trying to build an argument for not carrying pony bottles around in my travels.

Anti-Hero · Oct 30, 2008

Lee Taylor:
I am a recreational diver. My dives are typically between 70ft and 100ft in 75 degree seawater. I dive single, nitrox, +/-100 cu ft, steel tanks. I always dive with a backup regulator and a partner. Years ago my dives were made with a 30 cu ft pony strapped to my single tank. I have recently quit using the ponies and I have begun to rethink the desire for using the pony. I have been thinking a lot lately about air-delivery, failure modes, between the tank and my lungs. I have read that if one were to have a free flow, that one can fold the hose over and crimp it off. Somewhat like one does a garden hose.

I have heard that primary regulator failures (the one on top of the tank), under the conditions of which I dive, are practically unheard of.

Here are the questions: I have heard o-rings pop (fail) topside, but do o-rings ever fail during a dive? Do primary regulators ever just stop working? Do hoses suddenly rupture?

I am trying to build an argument for not carrying pony bottles around in my travels.

I've seen O-rings on yoke valves fail underwater due to the first stage twisting. To be more specific, there were a small stream of bubbles and the buddy moved the reg back and fourth to seat it better and caused the o-ring to fail completely.

shoredivr · Oct 30, 2008

Lee Taylor:
I am trying to build an argument for not carrying pony bottles around in my travels.

I carry a stage bottle kit and a spare reg with SPG. It's not heavy, and you can convert any 30, 40 80 cuft into a sling stage in a few minutes.

rstofer · Oct 30, 2008

Lee Taylor:
Here are the questions: I have heard o-rings pop (fail) topside, but do o-rings ever fail during a dive? Do primary regulators ever just stop working? Do hoses suddenly rupture?

My 100th dive was a night dive in 60 fsw with a strong current at the surface. My tank o-ring blew out as I reached the bottom. This was no bubble leak - it was a roar of discharging air.

Fortunately, the tank blew enough air into my 1st stage that I was able to ascend in a somewhat controlled manner.

On the surface my buddy and I were caught in the current and had a very difficult swim back to the boat. In the end, the boat had to drive around fetching the other divers.

I have a picture of myself, dressed in my Lycra suit, giving the finger to the world. I will never forget the event even if it was a hoot.

I always blame myself for not correctly mounting the regulator to the tank. I remind myself, and others, that somewhere around your 100th dive you start to think you know it all. Well, I was careless and that's what happens. It hasn't happened since.

There is a small possibility it wasn't my fault. These were boat tanks, who knows what kind of condition the o-ring was in? Still, it's better to assume is was my fault and learn from the 'near miss'.

Richard

dumpsterDiver · Oct 30, 2008

Lee Taylor:
I am a recreational diver. My dives are typically between 70ft and 100ft in 75 degree seawater. I dive single, nitrox, +/-100 cu ft, steel tanks. I always dive with a backup regulator and a partner. Years ago my dives were made with a 30 cu ft pony strapped to my single tank. I have recently quit using the ponies and I have begun to rethink the desire for using the pony. I have been thinking a lot lately about air-delivery, failure modes, between the tank and my lungs. I have read that if one were to have a free flow, that one can fold the hose over and crimp it off. Somewhat like one does a garden hose.

I have heard that primary regulator failures (the one on top of the tank), under the conditions of which I dive, are practically unheard of.

Here are the questions: I have heard o-rings pop (fail) topside, but do o-rings ever fail during a dive? Do primary regulators ever just stop working? Do hoses suddenly rupture?

I am trying to build an argument for not carrying pony bottles around in my travels.

Nope, O-rings never fail (except on the space shuttle) and hoses last forever!!!!

Gene_Hobbs · Oct 30, 2008

Some reading on equipment failures...

Acott, CJ. (2001) 457 Equipment incident reports. South Pacific Underwater Medicine Society Journal 31(4) RRR ID: 7743

This one has a nice several nice tables that summarize the issues with each piece of equipment. Each table includes the problem defined with the major contributing factors associated with each issue. At the end the is a table of "Suggested strategies to minimise outcome associated with equipment problems".

Acott, C. (1999) Equipment malfunction in 1,000 diving incidents. SPUMS Journal Volume 29 Number 3. RRR ID: 6009

Acott, C. (1996) An evaluation of buoyancy jacket safety in 1,000 diving incidents. SPUMS Journal Volume 26 Number 2. RRR ID: 6288

Acott, C. (1995) A pre-dive check; An evaluation of a safety procedure in recreational diving: Part 1. SPUMS Journal Volume 25 Number 2. RRR ID: 6411 (NOTE: I have not seen a "Part 2" of this article, we are still actively adding to this collection.)

spectrum · Oct 30, 2008

You can't rule out o-ring failure.

You are talking about dives where you need a better solution than CESA.

Options are carrying a redundant air supply or diving effectively with a buddy. If you dive with a good buddy and dive as a team then you might consider that as ample back-up.

If you dive in poor visibility or as a loose team then carry your own back-up.

Pete

TSandM · Oct 30, 2008

Oh, man, that last paper gives me the chills. But it's exactly what we saw in two weeks in Tahiti.

ianr33 · Oct 30, 2008

You forgot about the burst discs on the tank.

At 100 feet I want either a reliable buddy or redundant gear.

String · Oct 30, 2008

Lee Taylor:
"I have read that if one were to have a free flow, that one can fold the hose over and crimp it off. Somewhat like one does a garden hose.

Try it. You havent got a chance with one of the newer hoses, especially in a sensible timeframe.

I have heard that primary regulator failures (the one on top of the tank), under the conditions of which I dive, are practically unheard of.

Not at all. They can happen anywhere from the pool to the arctic. Rubber perishes, metal works loose, rubber perishes.

Here are the questions: I have heard o-rings pop (fail) topside, but do o-rings ever fail during a dive?

Yep.

Do primary regulators ever just stop working?

Yep - see above

Do hoses suddenly rupture?

Can do yes.

Goodbye ponies

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Lee Taylor

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Anti-Hero

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shoredivr

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rstofer

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dumpsterDiver

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Gene_Hobbs

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spectrum

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TSandM

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ianr33

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String

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