Tank / 1st Stage Flow Question

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syruss32

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Yippee I finally got the last of my gear tonight! So to commemorate it I went pool diving in our apartments pool. I saw no cool fish, no other divers, not even a turtle to speak of....

Now to the question when my tank was full 3000psi I found that I was gulping air then when it was down to 2000psi it seemed to be more relaxed breathing. My question is does the 1st stage provide the same air pressure at 3000psi vs say 2000psi? Is the difference in breathing because I get more relaxed as I dive and I tend to breathe much more relaxed?

I did pretty good for a 5 foot deep dive (do I have to log this) 1 hr 11 minutes on 1900 psi. Heck I got enough I can go diving again tomorrow. It was beneficial as I noticed several tiles that were placed to make lap lines were broken before they grouted them in place. Shame that a pool company would do that knowing that no one but a scuba fin-atic would ever notice the tiles that were grouted in place with chips off the side and broken corners....

I wonder if there is a job for underwater pool inspectors?
 
Like the underwear I will soon be wearing... it Depends!

You failed to mention the type/make of the regulator. If it is supposed to have a "balanced" first stage, then you would not notice an appreciable difference until the tank pressure hit the intermediate pressure (usually below 150 psi).

A "simple" or non-balanced first stage however, will exhibit those properties you mentioned. Too easy when full and increasingly harder till the air runs out. I hope this helps!!!

:tease:
 
syruss32,

That dive had a SAC (surface air consumption) rate of 0.64 cfpm (cubic feet per minute) assuming you're using an AL 80 tank. Not too bad. The regulator, if functioning properly had no effect on your air consumption rate. You may have lost 100 to 200 psi due to tank cooling in the water and the rest of the difference was due to relaxation as you settled into the dive.

Ralph
 
Originally posted by NetDoc
Like the underwear I will soon be wearing... it Depends!

You failed to mention the type/make of the regulator. If it is supposed to have a "balanced" first stage, then you would not notice an appreciable difference until the tank pressure hit the intermediate pressure (usually below 150 psi).

A "simple" or non-balanced first stage however, will exhibit those properties you mentioned. Too easy when full and increasingly harder till the air runs out. I hope this helps!!!

:tease:

It is a U.S. Divers Impulse 1st & second stage and is balanced diaphram. It sure works nice!

Thanks for the info Ralph. I will keep practicing till I get better times on the tank at depth. But hey we are all air suckers when we start from what I hear.
 
I concur with Ralph's analysis, especially the part about you becoming more relaxed as the dive progressed. Your air consumption rate will continue to improve the more you dive.

As for your employment prospects as an 'underwater pool inspector', you'll never know until you ask around . . .

Good luck and have fun with your new gear.

Warren

 
A "faster" air consumption at the beginning of the dive often happens to me as well. It seems like the SPG moves fromm 3000psi to 2500 almost as fast as the second hand on my watch, but once I'm settled into the dive, it slows down.

Things I've done lately to counter this:
  • If it was a longer surface swim to the descent spot, I try to rest a for a few minutes on the surface before descending.
    As I descend, I try to breathe deeply to clear out dead air and establish my breathing rythm.
    Then once I'm down, I take about 30 seconds to relax and do a gear check with myself and my buddy.
Congrates on getting the new toys. I hope you have lots of years of enjoyment out of them.
 
Originally posted by TexasMike
A "faster" air consumption at the beginning of the dive often happens to me as well. It seems like the SPG moves fromm 3000psi to 2500 almost as fast as the second hand on my watch, but once I'm settled into the dive, it slows down.

Things I've done lately to counter this:
  • If it was a longer surface swim to the descent spot, I try to rest a for a few minutes on the surface before descending.
    As I descend, I try to breathe deeply to clear out dead air and establish my breathing rythm.
    Then once I'm down, I take about 30 seconds to relax and do a gear check with myself and my buddy.
Congrates on getting the new toys. I hope you have lots of years of enjoyment out of them.

Alright Mike, enough you are scaring me now. The fact that we could be alike scares the bajeebers out of me. (I gotta ask what the hell is a bajeebers?) Just kidding

Thanks for all your advice, I think I am on the right track so all I need to do is keep practicing!

 
https://www.shearwater.com/products/swift/

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