RE CO2 cylinders/fittings/refilling

Greetings Steven,

>BOC / CIG will only rent me a huge bottle (not very attractive in the lounge!)
>and I've tried Coca-Cola and other people but no-one wants to sell me CO2!! I
>thought about fire extinguisher people, but now I'm not so sure.

>have you ever seen a Dupla CO2 bottle? Mine is 500g capacity at a max of
>250bar.  The thread is a bit of a mystery.. on the side of the box it says 21.8
>x 1/14". A few measurements have led me to believe that the outside diameter >of
>the thread is 21.8mm and there are 14 'winds' in one inch.  I work in an
>Engineering group and none of us can find refernce to such a thread.  What is
>it? Can someone fill it for me without going to a special Dupla shop in

There are a few ways of getting around the problem of refilling. 

Standard Primus or LPG bottles can be used to decant from a large cylinder
You could rent a G size cylinder, and decant into a small Primus cylinder. 
We do this here at work, to create calibration gas test bottles, but the quantity
you get into them is not huge.

Another way, is that we use a bottle that we buy from BOC is called a 
Spectroseal bottle (0.93kg) and is designed for high pressure situations
especially CO2. The bottle looks similar to the dupla bottles, but is actually
normally used for fire extinguishers. We then fit a needle valve to the top 
( costing about $80 ) as the bottle does not come with fittings. We buy them
from BOC here in Sydney, and if you ask them for this bottle and they deny
knowledge of it, ask for the ones that they sell to Gastech Australia, else 
you might be able to write to my company and try and buy one through us. 

The best way to do that is to contact Stuart Campbell on 02 9979 6979 
and say that you heard that Gastech has a high pressure test gas cylinder used 
for calibration gas and that it is a Spectroseal bottle. I dont know what they
would charge for it, you'll have to ask.

The thread that you are refering to is a special gas thread and is the same 
thread that is used on the Spectroseal bottle. We have a fitting that we get
made especially that converts it to a standard 1/8" fitting that fits our needle

I personally use the 6kg D size cylinders, and hire them from BOC at about
$55 per year and about $20 per refill. The bottle is about 700mm tall and lasts
me approx 9 months between refilling.

Hope this is of some use, I'm afraid that I cannot help with prices, but I am 
in the R & D section and marketing is not my bag.

Let me know how you go.

Marque Crozman  -ANGFA- NSW