Pony tanks Good or Bad? - POLL

[pipedope]

Uncle pug's answer was that we carry an octo for our buddy but that is only half the answer.

Under the ice, solo diving is safer and far simpler than trying to manage 2 divers and 2 lines under the water at once. A pony provides additional saftey without the weight or bulk of doubles on what are normally relatively short and shallow dives.

Under the ice requires a teather so I like to go to surface supplied air and a bailout bottle. With surface supply I can use a full face mask or helmet and my face stays nice and warm. The first stage is in the warmed tent on the surface so it doesn't freeze and it is only a backup to the compressor. Heck, I can even use a free flow air hat like the Desco and don't even have a second stage to free flow.
Hook up the diver radio and the surface crew knows right away if I have a problem and can take the best action right now.

Tended diving is NOT SOLO.
Tended diving is usually safer than buddy diving.
Of course, you do need some additional training as tended/surface supplied is different and some of the procedures are also different.

If I have to drag a teather line you can bet there will be an air hose in there at the very least.

Under the ice there is another risk. When You start breathing from a full tank the air in the tank is at the water temperature. The temperature drops in the first stage directly in proportion to the pressure drop. You now have *very* cold air going to the second stage where is is colled again. The air coming out of the second stage can be as cold as -50 degrees F. A deep breath of air this cold can cause a spasm in your throat. Air in your mouth does no good unless you can get it into your lungs.
Using a low pressure tank for the bailout reduces this risk. There are also systems in the commercial world that warm the IP air to ambient before it gets to the second stage eliminating this problem.

Most questions in diving are not yes or no, but are a series of pluses and minuses. By looking at the big picture and thinking about the risks and solutions we make choices for the gear and procedures we use for a given dive. In commercial diving we do this for *every* job. There are often substantial changes from dive to dive. Not a problem for the pros but not reccomended for the sport diver who is not diving several days a week.

The DIR system as taught by GUE strives to minimize the changes so the gear and procedures are as nearly the same as possible from dive to dive. This saves you having to learn more procedures and more importantly to remember which configuration you are diving and how to respond to an incident underwater, right at the time it is most difficult to think clearly.

The problem with the pony is that it is a *small* redundant gas supply. This greatly limits the rage of dives where it is helpful. No overhead, no staged deco required and deep enough that a CESA is not dirt simple.

No matter how you carry it a pony is added weight, complexity, more things to break, and is additional entanglement hazzard. Is the extra gas worth the added risks? Sometimes!

 

[Big-t-2538]

O.K. how's this?

Equipment configuration:

PS HP120 tank (3500 psi), 300 BAR DIN K-valve

<snip>
Dive Plan:

Descend following the anchor line to wreck and swim around the wreck.
Return to anchor line when first buddy down to 2300 psi (2/3) or at ½ NDL for 120 feet.
Surface, hopefully on the anchor line NLT when the first buddy hits 1200 psi
Ascent rate 30 FSW/min with 1 min stop at 50 fsw and 5 minute stop at 15 fsw.


<snip>
Analysis Questions:

Is there a better configuration for obtaining the same or similar option?

O.K...here's my question. How much gas do you need to reserve in your HP 120 to make your desired ascent with your buddy (assuming he had the problem)...and what is the corresponding pressure at that point?

Essentially can't you plan to figure out how much gas you're going to need to have on reserve in the event of an emergency instead of "hopefully being back at the anchor line"

 

[Uncle Pug]

O.K. how's this?

...tropical diving to me!

About the dreaded bursting LP hose:
Have you ever noticed all the little holes on a LP hose? Have you ever had an LP hose *blow* before? What happened? And do you periodically check your LP hose condition?

 

[Dive Source]

...tropical diving to me!

About the dreaded bursting LP hose:
Have you ever noticed all the little holes on a LP hose? Have you ever had an LP hose *blow* before? What happened? And do you periodically check your LP hose condition?

FYI - I has heard first hand of two different incidents where the pressure gauge loosened and spun off leaving the HP hose to blow air quite forcefully( even through that little hp hole)

The tell tales which are on the hose did not fortell this nor would they have made any difference as it was a case of poor assembly

HP and LP hoses are pretty robust, threaded items however do become loose on occasion and bear watching.

 

[Big-t-2538]

FYI - I has heard first hand of two different incidents where the pressure gauge loosened and spun off leaving the HP hose to blow air quite forcefully( even through that little hp hole)

I find it hard to believe that the SPG just all of the sudden "spun off" wihtout showing any sign of a leak first which would easily be found on a pre-descent check.

 

[Uncle Pug]

I haven't had an SPG spin off Brian... but I might give it a try sometime... or at least open a bottle with the SPG already off to see how much gas could be lost per minute.

I might give it a try with a lp hose as well. Have you ever done this?

In the scenario I outlined above... I started the dive with 2500 psi in a lp 72 and 6 minutes into the dive the o-ring let go. I spent 6 minutes ascending from 122' and had 1400 psi left on the surface.

 

[MikeS]

O.K...here's my question.

How much gas do you need to reserve in your HP 120 to make your desired ascent with your buddy (assuming he had the problem)...and what is the corresponding pressure at that point?

Per the plan 1200 psi. This equates to approximately 40 cubic feet.

1 min at depth
30 ft/min ascent rate
3 min safety stop at 17 ft.
SACR of 2.0 cu. ft. min. ( 1.0 for me 1.0 for my buddy)
Comes out to 40.9 cubic feet.

Essentially can't you plan to figure out how much gas you're going to need to have on reserve in the event of an emergency instead of "hopefully being back at the anchor line"

The plan is to return to the anchor line. However, we’re not going to run out of air looking for it. If we havn’t found the anchor line by then, when the first diver get’s to 1200 psi (approximately 40 cubic feet) it’s time to float a marker and head for the surface.

 

[Dive Source]

I haven't had an SPG spin off Brian... but I might give it a try sometime... or at least open a bottle with the SPG already off to see how much gas could be lost per minute.

I might give it a try with a lp hose as well. Have you ever done this?

I will do it tommorrow, if I have time

The person I know who had the SPG come off was holding their gauge console in their hand trying to figure out where the bubbles were coming from during the dive when the hose came off then flew out of the console actually cut their hand. ( if your familiar with the way the hp spool seals inside the SPG it is possible to have a slightly loose hose and no bubbles - to answer Big T)

Scared the heck out of them and got them a couple stitches. They managed a safe ascent ( don't think they cared what the loss of gas rate was and there was no way to measure it since the SPG was at the bottom of the ocean)

I didn't bring this up to justify Pony pony use as it wasn't relative in this case - I just thought I would bring it up so people thought to check the things attached to their Hoses once in a while. ( an once of prevention is worth a pound o pony bottles)

I have seen my fair share of second stages that loosened off on regs as well.

On another note - 15 years ago Aqualung had a recall that involved the possible failure of the hose at the octo which of course would empty a tank pretty quickly. ( bad octo case design which could break off)

I'll do the test and get back to you which should make for even more debate.

( PS - I see by the poll the Pony users are still winning)

 

[WRKNUT]

Redundancy is a good thing ( pony bottle or Doubles )! I believe in the buddy system, but the more self sufficient you become the better diver you're going to be! what I don't believe in are Spare Air's!!

 

[Genesis]

A HP leak (even a SPG loss) won't be a huge deal. There's a pinhole orifice in all of "today's" regulator HP ports to restrict flow dramatically in the event of a HP leak.

A blown LP hose, on the other hand, is a very big deal indeed. 100cf/min+ flow rates are not unacheiveable by today's high performance regulators. No, that's not a misprint.