How Long For Freeflow To Empty Tank?

[Rick Murchison]

If I inflate my wing on the surface it takes about 10 seconds from empty to 1/2 full. At depth it takes longer to inflate it to equal size. I use a balanced diaphragm so the reg is flowing the same amount of air and its going through the same inflator... but it takes longer at depth.
So why is it that it takes longer to flow enough air to inflate the wing to the same size if the tank will supposedly empty 5x faster?

Your observation is correct. See my explanation above.
Rick

 

[H2Andy]

And if you wanted to measure the flow rate in CFM or liters per minute at the ambient pressure of, say 5ATA, then that same 1430 grams/minute would yield not 1100 liters/minute, but 220, and the tank would empty at essentially the same rate as it did on the surface.

wow.. that, like... made sense

 

[pufferfish]

Any chance somebody with a spare tank could do this experiment to settle this discussion?
Take a full tank,hit the purge and time how long it takes to drop to ,say ,300 psi.
Thanks

I tried that last summer with a Scubapro Mk25/S600 and timed 90 seconds to from 3000 psi to 500 psi with purge fully depressed. Nice layer of ice built up on the outside of the reg too. Not enough time to safely ascend if you are at 100 feet and plan to ascend 30 ft/min and do a safety stop.

 

[Warren_L]

I tried that last summer with a Scubapro Mk25/S600 and timed 90 seconds to from 3000 psi to 500 psi with purge fully depressed. Nice layer of ice built up on the outside of the reg too. Not enough time to safely ascend if you are at 100 feet and plan to ascend 30 ft/min and do a safety stop.

Pufferfish, what size tank was that?

 

[truva]

Is we are assuming 2 different things:

1: the failure is at the tank valve (meaning the first stage isn’t doing anything). This one hurts to think about

2: The failure is after the first stage and at a secondary.

OK?

Assuming the first, I have no scientific idea which would empty before the other, however I think they’d be about the same…….This is just a guess….

If it is a failure of a secondary, the relative volume coming from the leak at the surface or at 100-feet is the same. Because the air/gas is denser at depth (the same volume of gas is heavier) the tank will empty a lot faster.

Truva

I think I’ll go drink more beer now….

 

[H2Andy]

darn it... now i'm confused again...

ok... here's my new question:

why does air go much quicker at depth when you INHALE it but would not go quicker
in case of a free flow?

what's the difference?

 

[NEWreckDiver]

darn it... now i'm confused again...

ok... here's my new question:

why does air go much quicker at depth when you INHALE it but would not go quicker
in case of a free flow?

what's the difference?

I beleive it would go quicker.

 

[Warren_L]

darn it... now i'm confused again...

ok... here's my new question:

why does air go much quicker at depth when you INHALE it but would not go quicker
in case of a free flow?

what's the difference?

Because when you take a normal breath off your reg, the flow rate is nowhere near the maximum flow rate from the valve. As such, then the limiting factor is the amount of air in each breath, which, as you know, is more at depth than at the surface.

 

[truva]

darn it... now i'm confused again...

ok... here's my new question:

why does air go much quicker at depth when you INHALE it but would not go quicker
in case of a free flow?

what's the difference?

I hope I didn't indicate that it didn't! It does, but if you were to just open a tank valve? I have no idea on the result there.

Truva

 

[H2Andy]

Because when you take a normal breath off your reg, the flow rate is nowhere near the maximum flow rate from the valve. As such, then the limiting factor is the amount of air in each breath, which, as you know, is more at depth than at the surface.

ah yes... ok... it's all clear again, thank you.

now i'm going to stop reading this thread to prevent re-confusion

(can you de-confuse? what's the minimal surface interval away from
this thread? *punches numbers into calculator*)