scuba tanks and refills

[rider-m]

Anyone who is filling their own hpa tanks, i have a couple of questions. Out of a 80 ft^3 tank, how many refills of a 68 in^3 tank can I expect (and at what pressure)? Also any idea where to get a 4500 psi scuba tank and cost ?



TIA

[SkyBoySurfer]

ya i run that set up....


you will get about:
4 hits at 3000psi
5 hits at 2000psi
and about 5 hits at 1500psi
(I get somewhere around there)

"sports chale" I think have the best prices on tanks and fills...

Now if you want to save more gass...fill your tank slow...try not to cause your tank to heat up to much...so it wont drop as far.

And if its possible...fill it with nitro....its the same price...and it doesnt drop as far...

[akscubainst]

This question can't be answered because of the variables.

It depends on how low you drain the 68 each time prior to filling, the temperature, the speed of the fill, etc.

An AL80 holds 77.4ft^3 when full at 3000psi and 70 degrees F. A 68/3000 holds 8.02ft^3 when full at 3000psi and 70 degrees F.

According to the gas blenders of the diving industry, 1cf in an 80cf is 37.5 PSI. So if you hooked up your empty 68/3000 to a full 80 you'd equalize somewhere around 2700psi the first time and it would drop with each fill depending on how low you drain the 68.

As far as the higher pressure SCUBA cylinder. Luxfer has a 4350psi carbon fiber 80cf cylinder that you could buy for a small fortune. Fire Dept SCBA cylinders run up to 4500psi but cost about $700 new.


I would recommend getting 2-3 80's and using the first 2 for your volume and the last one for you final topoff. Always use them in the same order and you'll maximize you air efficency. This is how we fill dive tanks from our air banks so our compressor doesn't have to start and stop so much.

We had a lond discussion thread about all of this a few months back. Do a search for Scuba and you should find it.

DM

[Caffiend]

wow, that was alot of good info akscubainst. thanks.

[akscubainst]

Don't mention it! I've gained ton's of knowledge from AO and just share what I know in return.

DM