How does "real life" OOA looks like?

[Uncle Pug]

frogxman once bubbled...
Uncle Pug, can you explain how this device works?

An SPG is a rather simple device that connects to the first stage regulator's high pressure port via a suitable high pressure hose.

The SPG allows one to instantly determine the pressure in the scuba tank just by looking at it!!!

I won't go into the details as to how the SPG actually measures and displays the tank pressure... just know that it does... unless of course the indicator needle should *stick*... but I will explain how to tell if that is the case.

How to use an SPG is the important thing here.

You should check your SPG reading at the beginning of a dive to see how much breathing gas you have. I will leave out a discussion of gas management practices here but we do have excellent threads on Scuba Board covering this topic.

Before beginning the dive it is a good idea to watch the SPG while taking a couple of breaths off of the regulator. This will confirm that you have actually turned and left your tank valve on. If you have turned your tank on and then back off... the needle on the SPG will fall to zero as you breath off of the regulator. This is why you should do this before the dive. BTW if you have turned the valve on and then almost off the SPG will drop as you breath and then rebound. Always open your valve all the way to dive the tank.

During the dive you should check your SPG every 5 minutes and consciously note your pressure. Do not stare incessantly at the SPG as this is counter productive. After several times doing this you should try to guess what your SPG will read before you look at it.

It won't be long and you will have developed the ability to *know* your tank pressure just by looking at your bottom timer! Of course you should still look at your SPG every 5 minutes just to make sure.

Thanks for asking this question Froggy... SPGs are a great adjunct to diving and have truly made the J valve with its reserve lever obsolete.

Oh, I almost forgot... about that sticking needle problem... it doesn't happen often... but if you have used your SPG as I recommend you will instantly know that it has a stuck needle when you look at your SPG and it reads significantly higher than you have guessed!! This is why incessant staring at the SPG is not good... it doesn't give you the same effect as, "Hey, I've been breathing off of this thing for 5 minutes and the needle hasn't moved!"

 

[frogxman]

Am I stupid or jus lacking sense of humor? If yes, then I grant my permission to make fun of me. Isn't the SPG just a pressure gauge that you have on your console???

 

[Uncle Pug]

frogxman once bubbled...
Am I stupid or jus lacking sense of humor? If yes, then I grant my permission to make fun of me. Isn't the SPG just a pressure gauge that you have on your console???

Not at all... it is obvious that many folks do not know what an SPG is or how to use one. That is why we have so many OOA threads on Scuba Board.

And yes... as in my first post:

Uncle Pug defined SPG as:(submersible pressure gauge.)

But it is not just a pressure gauge on the console... it is the tool that insures you will not have an OOA!

 

[Uncle Pug]

frogxman once bubbled...
Uncle Pug, can you explain how this device works?

Perhaps I misread your question... and you were asking how the obsolete J valve works!

Well... the J valve has a lever that when activated makes the remaining 500psi of air in the tank available. The diver sensing that he is OOA simply pulls the lever and (hopefully) has the 500 psi to end the dive in a successful ascent and egress.

I say hopefully since the reserve lever points forward it can be bumped into the reserve available position and then when the diver hits his OOA he or she really is OOA.

Also these valves must be serviced to function properly as a sticking J valve will make its malfunction known at the worse possible moment... unlike a sticking SPG needle.

 

[divedude]

frogxman once bubbled...
Am I stupid or jus lacking sense of humor? If yes, then I grant my permission to make fun of me. Isn't the SPG just a pressure gauge that you have on your console???

Yes, a spg is your pressure gauge.

BUT old fart's like me and I think UP. used to dive without a SPG, We had a J-valve and when you ran out of air you pulled the valve which gave you about 500 PSI to get your butt back to the surface.

 

[frogxman]

Uncle Pug once bubbled...

Not at all...

Thanks.

But it is not just a pressure gauge on the console... it is the tool that insures you will not have an OOA!

I absolutely agree. I am trying to stress that out for the students too. I am just so used to use it all the time that I thought you are talking about something else. Sorry - lesson for me - always to use the full names of the things to avoid misunderstanding.

As well thank you for the techniques of using the SPG - this can really build up your confidence under the water.

And thanks for explaining what is the J valve is

 

[frogxman]

divedude once bubbled...


Yes, a spg is your pressure gauge.

BUT old fart's like me and I think UP. used to dive without a SPG, We had a J-valve and when you ran out of air you pulled the valve which gave you about 500 PSI to get your butt back to the surface.

You are probably right! Here you go - the example of misunderstanding between the generations

 

[Uncle Pug]

Froggy I figured you were intentionally opening the door for me to explain why an SPG is important and how it should be used.

I launched into the didactic not because I figured folks didn't know what an SPG is but because its proper use is so obviously neglected.

For example the premise of this thread that I quoted in my first post and paraphrase here:

"How can you tell an OOA is about to happen?"

The old way was: the regulator breaths harder... use your reserve by pulling the J valve and hope it works.

The new way is: the bottom timer tells you that you have used up your planned gas supply and your SPG confirms this (you never get to OOA)... egress on the remaining gas as per plan.

 

[the sharkman]

It just goes to show you that it is so important to practice this situation. Being relatively new to diving, my wife and I practice OOA often. In fact each trip we go on. Actually, the last time we tried it, we had a little mishap, which caused us both a lot of panic. Let's just say that Mr. Murphy was present and one thing led to another, and I kind of sucked down some salt water. That urge to just rocket to the surface is VERY hard to fight I can tell you. Better to happen in practice I'll say...

sharkman
:guitar:

 

[Conor]

UP - In the case I discribed above, the needle wasn't sticking (there was 50ish bar left), and the needle didn't dip as I breathed. Do you think this would indicate a fault in the guage or just one of those things ? or maybe it is just an indicator of a fault in the diver.