Metric and Imperial tanks.

[Kim]

Clearly I meant "regardless of rated pressure."

This is confusing me a little. I can see that an 80cf and a 100cf tank have a difference in volume of 20cf when filled to their rated pressure. Surely that difference will change when not? For example - if the rated pressure of both tanks is 3000psi, then when both tanks are at 1500psi I would only expect a difference of 10cf. Is this wrong?

edit:
never mind, I have just re-read what you wrote both times and you are only talking about full tanks - albeit with different rated pressures, right?

 

[jonnythan]

This is confusing me a little. I can see that an 80cf and a 100cf tank have a difference in volume of 20cf when filled to their rated pressure. Surely that difference will change when not? For example - if the rated pressure of both tanks is 3000psi, then when both tanks are at 1500psi I would only expect a difference of 10cf. Is this wrong?

No, you're absolutely right. I was unclear in my original statement.. sorry about that.

Let me rephrase, even though you understand perfectly not everyone will:

A 100 cf tank has the capacity to hold 20cf more gas when filled to its rated pressure than an 80 cf tank when filled to its rated pressure, no matter what those rated pressures are.

For instance, an HP100 has a capacity of 100 cf at 3500 psi. An LP80 has a capacity of 80 cf at 2640 psi. However, fill both to 2640 psi and the LP80 will be holding 80 cf in it whereas the HP100 will have 75 cf in it.

 

[Kim]

see my edit above!

 

[jonnythan]

You got it

 

[barc802]

I am a Nitrox Gas blender and A guy dropped off a metric tank last year and we we all confused!
Reading this thread answered a lot of questions I had about metric tanks.
Thanks

 

[Kim]

I am a Nitrox Gas blender and A guy dropped off a metric tank last year and we we all confused!
Reading this thread answered a lot of questions I had about metric tanks.
Thanks

Metric tanks/bar is very easy for blending. I recently did Thailand liveboard and watched my 32% fill being done many times. Basically they emptied the tank - filled 64 bar of 100% O2 then topped it up to 200bar.

 

[barc802]

Metric tanks/bar is very easy for blending. I recently did Thailand liveboard and watched my 32% fill being done many times. Basically they emptied the tank - filled 64 bar of 100% O2 then topped it up to 200bar.

The tank did not look like it was AL or Steel. Do they use different meterials over there? It almost looked like a fiberglass weave. It also had a big black and white tralgular marking on the top.

 

[Kim]

The tank did not look like it was AL or Steel. Do they use different meterials over there? It almost looked like a fiberglass weave. It also had a big black and white tralgular marking on the top.

You've got me there! In Japan almost everyone dives steel. On the liveaboard in Thailand the tanks were also all steel. Aluminium isn't very popular in these parts!

 

[grazie42]

Originally Posted by OffTheWal:l
The tank did not look like it was AL or Steel. Do they use different meterials over there? It almost looked like a fiberglass weave. It also had a big black and white tralgular marking on the top.

I THINK what you got was the kind of tanks that firefighters use...I won´t swear to it but that´d be my guess...

Almost all tanks here are steel except for deco/stage bottles which are usually but not always aluminium (for obvious reasons)...

 

[barc802]

If it helps the Guy was German. The tank was short and fat. shorter than a PST 80 and about 9 inches in diamiter.