Your not the first one to re purpose the disposable gas cylinders ! I have seen it used before for brakes.  Another High pressure cylinder often found is the Nitrous Oxide ones these have a test pressure of many hundreds of PSI. I would remove the valve body, remove the valve and then re thread to suit the new use or silver solder into a boss that will take the thread you need. Good Luck. Noel.

Having double-checked that the cylinder is EMPTY, a decent vice will often grip the edges of the valve and enable the body to be unscrewed from it.

However the little regulators that attach these bottles to cheap welders are usually rubbish and it shouldn’t be hard to find a donor to supply the manifold / threaded bush.

I think the threads are 1/8 BSP..

On 4 October 2025 at 22:31 Nigel Graham 2 Said:

I have a couple of empty, Clarke-labelled, CO2 cartridges, and now a possible use for one as a vacuum reservoir on a locomotive driving-truck. (Vacuum Reservoir: A tank to hold a lot of nothing!)

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The label says empty cartridges must not be refilled but “recycled” with ordinary steel scrap or empty food tins!

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Point to note, there’s a good reason these cylinders should not be refilled.   Cylinder life is determined by both the pressure and the number of charge / discharge cycles it can take.  Disposable cylinders are made of remarkably thin metal because they are single use only.   There is no allowance for metal fatigue caused by charging and discharging cylinders.

I don’t see much risk in repurposing a 900psi CO² cylinder to hold  a 14psi vacuum –  the metal isn’t flexed much by changes of a few psi and shouldl survive many cycles before cracking.   Conversely very foolish to recycle a disposable cylinder in an diving breathing set: if it fails underwater, you drown.   Likewise, I wouldn’t advise refilling them to 900psi in an air-gun because the cylinder is close to the users eyes, should it go bang.

The Comet airliner is a famous example of a thin pressurised vessel failing due to pressure cycling metal fatigue.  The cabin skin was just a little too thin, and – worse – penetrated by many stress-raising holes, including square windows.

Dave

The current craze for using Nitrous Oxide as a recreational aid has resulted in some high pressure disposable cylinders. These can often be found in parks and other places where people gather(and not just the young). These have a test pressure stamped on the bottle of some 2000psi as I recall or 150 bar. These are quite heavy/thick walled compared to the Co2 bottles and a little larger. I have one or two, if your near me N Norfolk I can give you one.  Noel.

Small airbrush compressor tanks?. Gang a few together.

Hi Noel,
The NO cylinders being discussed arn’t the little “sparklets” sized ones, They are ones used with catering cream whippers and are similar in size to te disposable MIG gas ones.
Another option for vacuum or low pressure with more volume is a “ballon gas” cylinder. These have a non return valve in the ste whih needs removing. A request on freecycle or local yahoo groups will normally turn one up.

Robert.

Robert, the ones I have are of the catering size, may be 2 pint or 1 L. The OP whilst telling us what it’s for has given no real idea of the capacity he needs ? One could be easily welded up to suit the purpose from big tube or rolled sheet or a breakers yard for a commercial vehicle air brake tank – they come in many sizes. In the days of vacuum wipers the reservoir was a thin pressed tank. Noel.

I’ve had this video bookmarked for several years, couple of nice engines made from old gas bottles. may get round to making one along those lines some day.

I meant no dis-respect, Noel … simply stating a fact.

MichaelG.

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Incidentally, I may be the only person on this forum who has come near to being prosecuted by HSE for an incident with a vacuum vessel … but that’s another story, for another day.

I turned one into a compressed air whistle – interesting project, but of no practical use.

ķ

Hi Nigel Graham 2, when I say low pressure, I mean compared with non-liquefied gases, typically Propane is stored at about 7 ish bar, which is low compared with the 60 bar in my Argon cylinder, and other gases that don’t liquefy. Liquefied gases have to absorb heat from the atmosphere in order for the gas to boil, so you don’t want a cylinder to have a too thick a wall section, as it will struggle to boil enough gas for your needs. We all know that Propane cylinders often get a layer of frost on the outside during cold weather, and very often you’ll get a lower flame than usual, this is more pronounced with Butane, as its boiling point is higher.

Regards Nick.