A few tank questions

[walke121]

I don't have an air integrated computer but couldn't it have a beep or alarm feature that could be optionally turned on once you reach a certain tank pressure? Do these exist? Personally I feel proper air management is a key skill that should be mastered from the get go and it not necessary but could give some divers added comfort.

Yes they do.

 

[captain]

There were several audio low tank pressure devices in the past. Heathways made the Scubair Sonic regulator that produces a loud clicking noise beginning at about 300 psi. Scubapro and U S Divers had a valve with a bell clapper like device in the tank that banged against the side of the tank.

 

[pittyyofool]

I'm a total newbie to diving (though I'd really like to sometime) but I recently thought of a warning system for if you're running low on air, I don't think it would be popular with people who dive regularly for fun but it might be useful for commercial stuff like diving schools, police divers etc. places which need to cover themselves more in the case of health and safety. I don't want to go too deeply into how it works because this is really just the beginnings of the idea and I'm not even sure it's viable yet.
there are already systems in place; pressure gauges, wrist mount and in mask dive computers.
Anyway... in diving
You know how much air you have by the pressure in your breathing tank(s) right? correct, in most tanks 3000psi is 80 cubic feet of air=1500psi is 40cf and so on. basic math
Are tanks refilled? yes
How is a tank refilled? you connect it up to a compressor and pump more air in to it until it is up to its "full" pressure.
Do you need special qualifications to refil a tank? If you don't own a compressor any scuba shop will fill a tank for a certified diver.
Is all pressure within the tank lost to refil? you just add more air, you don't drain the tank
How much time is an adequate warning to have if you are running low on air and you need to get up? (at average levels under the water) depends on where and how you are diving
How much time left in your tank is usually left as a safety margin if all goes well? depends on where and how you are diving

In deep sea diving...
What happens to the pressure in the tank the deeper you go? Insert [HUGE] physics lesson here, in short no measurable change.
Do the different gases in deep sea diving tanks create different pressures to normal diving tanks, less or more or the same? same
Are tanks refilled? If so... Same as above
How is a tank refilled? Same as above, and you blend other gasses in from other larger higher pressure tanks
Do you need special qualifications to refil a tank? Same as above
Is all pressure within the tank lost to refil? Same as above
How much time is an adequate warning to have if you are running low on air and you need to get up?Same as above
How much time left in your tank is usually left as a safety margin if all goes well?Same as above

 

[Bonairetrip]

Anyway... in diving
1 You know how much air you have by the pressure in your breathing tank(s) right?
2 Are tanks refilled? If so...
3 How is a tank refilled?
4 Do you need special qualifications to refil a tank?
5 Is all pressure within the tank lost to refil?
6 How much time is an adequate warning to have if you are running low on air and you need to get up? (at average levels under the water)
7 How much time left in your tank is usually left as a safety margin if all goes well?

In deep sea diving...
8 What happens to the pressure in the tank the deeper you go?
9 Do the different gases in deep sea diving tanks create different pressures to normal diving tanks, less or more or the same?
10 Are tanks refilled? If so...
11 How is a tank refilled?
12 Do you need special qualifications to refil a tank?
13 Is all pressure within the tank lost to refil?
14 How much time is an adequate warning to have if you are running low on air and you need to get up?
15 How much time left in your tank is usually left as a safety margin if all goes well?

I modified your quote above to make it easier to respond. I am also making lots of assumptions and leaving out some nuances.

First, such devices already exist. Firefighter SCBA kits often have a bell that rings at a certain point. Air integrated dive computers offer the low pressure alarm. The old J valve. The regs that used to honk (was that a Scubapro?).

1. Correct -- there is a pressure gauge that reads the pressure in the tank. But the size of the tank also matters. For example, a 80 cubic foot tank has that much air in when filled to the working pressure of the tanks (lets say 3000 psi). Some dive computers will make an estimate of remaining air time based on actual air consumption.
2. Yes. They are not single use items. A tank is typically insepected every year and hydro tested perioidcally (every five years?)
3. Typically a high pressure fill whip is attached to the tank. The other end is attached to a bank of tanks or a high pressure compressor. The tanks is filled slowly so as to not over heat the tank.
4. Not sure. But you are dealing with something that is high pressure and tank failure, while rare, is the real deal. Also, it is very important that the air be properly filtered (keeps out oils, CO, moisture, etc.). You need to be trained on the setup that is sued to fill tanks.
5. Typically, air is just added to top of the tank pressure. I start with an empty tank (brand new). Fill to 3000 PSI. Dive and use 1800 PSI. I take it back to the shop and they fill it back to 3000 PSI. It does not get reset to zero.
6. No easy answer -- depends on depth, deco obligations, size of the tank, surface air consumption rates, etc. Many use the rule of thirds -- you use 1/3 of your air going out, 1/3 coming back and have the other 1/3 as a reserve. Others rely on surfacing with a target pressure (most often 500 or 750 psi)
7. Again time is a hard thing to explain. All other things being equal if X PSI of gas last 12 minutes at the surface it only lasts 6 minutes at 33 FSW. So time is really a function of tank size (although you don't need that info to calculate remaining air time if you plot pressure change over time with depth), pressure, surface air consumption rate and depth.

Not sure what deep sea means but I will assume you are not talking about surface supplied air. Say, tri-mix or something similar.
8. Nothing. That said, all other things being equal, you consume air faster (see #7) as the ambient pressure increases.
9. There are some high pressure steel tanks that are also used in the rec world. Not a huge difference either way.
10. Yes.
11. Similar to 3 but with gas blending. A few different techniques are used. See something like Blank (new air system)
12. Similar to 4 but more training is typically required.
13. No.
14. See #6. Also, this can get more complicated as a diver may have deco obligations that prevent a direct ascent to the surface.
15. See #7

 

[Garth]

Okay, i'm lost here. I read your thread ( i don't want to call it a question because I don't know the question or more like multiple questions). What is the main question? Are you trying to get information about creating a product? If so, maybe a better idea would be to go to an instructor at a dive shop. Another option would be to look at some of the alarms already created. Are you saying that you have an idea that no one has thought of?
Good luck in your search.
If your just interested in being a diver, then good luck in that too.

 

[SCUBASailor]

I have used a friend's 20 year old SCUBAPro regulator that has a "honker" built into it. Once the tank pressure falls to 500 psi, it makes a loud, irritating honking noise with each inhalation. It sounds like a freight train horn. I always thought it was a great safety feature, but apparently, it has fallen out of favor.

 

[1_T_Submariner]

Welcome to Scubaboard Fey!

Get certified and learn about the sport you might find something then that will really make a great tool for scuba divers. Just my 500 psi but I think you are trying to do this backwards.