Are you still imperial?

[Arnaud]

drbill once bubbled...
Arnaud- Just happened on this thread and being the far left-leaning pinko that I am, of course I dive imperial... this is an imperialistic country...
Dr. Bill

You know I don't drink sodas much, but if I did, I would have spilled my 12 oz can

 

[kelpmermaid]

and my 750 ml bottle of wine, Arnaud!
Let's get our priorities straight!
Funny, there are some things that I know both ways (height and weight, although I choose not to dwell on the latter these days,) some things that are definitely imperial (fuel for the car), and some things where I have gone metric (vino). Honestly, I believed in our teachers in third grade when they said the US would be converting, and I'm still confused. The only way I remember the liquid measures is from visualizing the milk containers in the supermarket.

 

[KOMPRESSOR]

I grew up in Australia, which converted to the metric system in the 60's. My father, being in trade, used both imperial and metric, so I'm pretty comfortable using either. But here in the States I have to use imperial measurements for diving, because no-one else knows how deep a metre (sorry, meter!), or how much pressure a bar is. Isn't bar a type of DIN valve? ut:

Metric measurements also make great sense for diving - each 10msw is an additional ATA. So surface = 1ATA, 10m = 2ATA, 20m = 3ATA, 30m = 4ATA, etc.

Tanks are measured in litres (sorry, liters!) of water capacity. A common size is 12L - that's how much water the tank would hold if you pulled the valve out and held it under a tap (sorry, spigot!). Because 1 bar is approximately ambient pressure at the surface (that's where the standard comes from), it's easy to convert how many litres of air are left in your tank at any given pressure. A 12L tank, full at 200 bar, holds 2400L of air. If you breath it down to 100 bar, you've got 1200L of air left, etc. So it's easy to calculate at the beginning of the dive how much gas you have - over here in the US, if you've got an 80cf tank, it's stuck in your head that there's 80cf of gas. No-one works out that they've got 73cf because they had a hot fill, or 83cf because they had a guy at the shop stuff it for them. Everyone works in PSI, and you need to know the working pressure of the tank, tank's capacity at working pressure, and actual pressure, to determine how much gas you have. With metric system, you just need to know the water volume, and actual pressure. Makes the math simpler.

My 2c (because you still use the penny over here!).

I'm lifting up an old thread here. Sorry, but I need some help, and you guys seem to be the ones to help me

Could someone with knowledge please inform me what these tanks would be described as in "imperial" measures?

6 liter 200 bar
6 liter 300 bar
7 liter 200 bar
7 liter 300 bar
8 liter 300 bar
10 liter 200 bar
10 liter 232 bar
10 liter 300 bar
12 liter 200 bar
12 liter 232 bar
12 liter 300 bar ( My single tanks!)
15 liter 200 bar
15 liter 232 bar
15 liter 300 bar
16 liter 232 bar
18 liter 200 bar
20 liter 200 bar


Now these are available sizes "overe here". The imperial system is just immmmmpossible for me to figure out. Someone, please???

 

[Manfred]

I live in Canada, and dive all metric. My tanks are 100 cu feet 3600psi in metric they would be 10l 232bar.
a 12l tank would be 130 cu feet 300 bar wow that's a lot of pressure.
1 bar equals 14.7psi so your tank is good for 4400 psi.
hope this helps

I'm lifting up an old thread here. Sorry, but I need some help, and you guys seem to be the ones to help me

Could someone with knowledge please inform me what these tanks would be described as in "imperial" measures?

6 liter 200 bar
6 liter 300 bar
7 liter 200 bar
7 liter 300 bar
8 liter 300 bar
10 liter 200 bar
10 liter 232 bar
10 liter 300 bar
12 liter 200 bar
12 liter 232 bar
12 liter 300 bar ( My single tanks!)
15 liter 200 bar
15 liter 232 bar
15 liter 300 bar
16 liter 232 bar
18 liter 200 bar
20 liter 200 bar


Now these are available sizes "overe here". The imperial system is just immmmmpossible for me to figure out. Someone, please???

 

[Charlie99]

I'm lifting up an old thread here. Sorry, but I need some help, and you guys seem to be the ones to help me

Could someone with knowledge please inform me what these tanks would be described as in "imperial" measures?

<snipped long list of tanks>

Now these are available sizes "overe here". The imperial system is just immmmmpossible for me to figure out. Someone, please???

Imperial system refers to tanks by the total free air capacity at rated pressure. Your 12 liter 300bar tank has about 12 * 300 = 3600 liters of gas available for use (ignoring the deviation from ideal gas law, and the 1.325% difference between bar and atm). There are 28.3 liters in each cubic foot, so 3600 liters/ 28.3 = about 127 cu ft.

In the reverse direction, you can tank the free gas capacity of an imperial tank, divide by the rated pressure and get the water volume or internal volume in cubic feet. Then convert to liters.
The standard AL80 tank is an 11.1 liter 207 bar tank.

(Doing the calculations the way described above, it comes out at as a 10.8l tank --- I'll let someone else figure out where the 3% descrepancy comes from ).

 

[SeanQ]

The standard AL80 tank is an 11.1 liter 207 bar tank.
(Doing the calculations the way described above, it comes out at as a 10.8l tank --- I'll let someone else figure out where the 3% descrepancy comes from ).

Did you remember that an AL80 is actually 77.4 cu ft at 3000psi?

It's all terribly confusing. I find it expecially irritating that most Canadian dive gear is in Imperial units despite being a Metric country. At least I grew up close enough to the US to learn both systems.

Whew... It's getting cold today. Only 283 kelvin. (~510 rankine for you imperial folk)

 

[Rick Murchison]

It's all terribly confusing.

Yes, yes.... that's why I prefer furlongs per fortnight as a measure of speed.
For example, a good rate of ascent for scuba is about 1000.
Oh, so much easier.
Rick

 

[abitton]

Nooooooooooooooooooooooooooooooooooooooooooooooooooooo!!!!!!!!!!!!!!!!!!!

:monkeydan

Yes, yes.... that's why I prefer furlongs per fortnight as a measure of speed.
Oh, so much easier.
Rick

 

[Don Burke]

Here is what I came up with right off the calculator.

The actual capacities for the 300 bar cylinders will be a little lower as air is very "non-ideal" at that point.

This all assumes that the water capacities of the cylinders are as stated. As mentioned above, the "AL 80" you have been reading about has a nominal capacity of 77.4 cuft, with considerable variation from that. Considering the variation in the actual displacement of a "two liter" engine, I find it hard to believe there is no creative rounding in the water capacities.

Another interesting note is that most steel cylinders here are known by the capacity at 110% of rated pressure.

6 liter 200 bar - 42.4 cuft 2940 psi
6 liter 300 bar - 63.6 cuft 4410 psi
7 liter 200 bar - 49.4 cuft 2940 psi
7 liter 300 bar - 74.2 cuft 4410 psi
8 liter 300 bar - 84.8 cuft 4410 psi
10 liter 200 bar - 70.6 cuft 2940 psi
10 liter 232 bar - 81.9 cuft 3410 psi
10 liter 300 bar - 105.9 cuft 4410 psi
12 liter 200 bar - 84.6 cuft 2940 psi
12 liter 232 bar - 98.3 cuft 3410 psi
12 liter 300 bar - 127.1 cuft 4410 psi
15 liter 200 bar - 105.9 cuft 2940 psi
15 liter 232 bar - 122.9 cuft 3410 psi
15 liter 300 bar - 158.9 cuft 4410 psi
16 liter 232 bar - 131.1 cuft 3410 psi
18 liter 200 bar - 127.1 cuft 2940 psi
20 liter 200 bar - 141.3 cuft 2940 psi

 

[KrisB]

I thought a standard-pressure (~3000 psi) AL80 was equivalent to a 12L tank...