Differences between tank sizes

[Tantell]

Hi all, bit of a noob question here.

Currently I rent my tanks from my LDS and they are 10.5 liter steel tanks (200 bar).

As you can get bigger and smaller tanks, is it correct to say that they carry more and less air respectively?

Thanks!

 

[DevonDiver]

Yes.

A 10.5 L tank at 200 bar holds 2100L of gas (10.5 x 200 = 2100).

The capacity of the tank is a proud of its internal volume x the pressure (it can be filled to).

 

[Tantell]

So are they all filled to 200bar? Or maybe bigger to 250 bar and smaller to 175bar etc...

 

[DevonDiver]

Aluminium cylinders are limited to 200 bar. Steel can be rated to 200 or 300 bar. 300 bar is less common.

Those are the maximum 'working pressures'. They're normally filled to that max pressure.

The following link will give you an idea of the tank specifications available :

Scuba Cylinder Specifications | Metric & Imperial

 

[clownfishsydney]

I doubt that any steel tanks in Sydney are 200 bar tanks. They are more likely to be 232 bar as this is what all the common steel ones sold in Australia are now and have been for at least 15 years. You might only be getting 200 bar fills as the Australian standard says 207 bar is maximum unless you are using DIN or the yoke on your reg is rated higher (pretty sure that is what it is, almost 15 years since I got a fill in a dive shop).

So, if a tank is 11.2 litres and it is 232 bar, it will hold more than a 10.5 litre 232 bar tank. However, if the 11.2 litre tank is a maximum of 200 bar (as an example), it will only hold 2240 litres compared to 2436 in the "smaller" tank. Therefore, real size is a combination of internal size times pressure in the tank. In metric system, this is very easy to work out.

 

[DustyC]

What's a bar, and how do you get 232 of them into a cylinder?

 

[Lorenzoid]

Yeah, you people with metric tanks have it easy. The answer to the same question in the context of tanks measured in cubic feet of capacity is not as straightforward.

 

[Banyan]

As you can get bigger and smaller tanks, is it correct to say that they carry more and less air respectively?

If you can stand the imperial measurements, this chart is very helpful for understanding the capacity and buoyancy of different tanks.
Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

 

[Tantell]

Thanks everyone. I guess what I was trying to ask is will a bigger tank let me dive longer? I realise now that the pressure would be similar across the different sizes.

 

[ajduplessis]

What's a bar, and how do you get 232 of them into a cylinder?

Bar is an unit measurement used in modern countries