Boiler material

just a thought, and welcome views of others. I use disposable CO2 mix gas bottles, 300 mm high 100mm diameter and wall thickness of 3mm. These have a working pressure of 100 bar at 20 deg C and test pressure of 145 bar. Made of steel and about 2.5 litre capacity. Could these be used for a vertical boiler, drilling the end caps for fire tubes etc etc.?
I have no idea as to the steel specification and just pose this as a question and in no way suggest or recommend their use.

Ps Usual excuse for horizontal picture (Horizontal boiler ??).
Another use could be to use the end cap of the cylinder for a smokebox door.
BobH

You can do what you like with them in your own shed but would not be able to run in public and if anyone did get hurt in private the ambulance chasers will also be after you for a bob or two.

Having said that I have seen a couple of boilers complete with small engine made from these and they looked very good, will see if I can find the video.

J

It depends what temperature you will running at. There must be a formula for calculating heat versus strength of steel. The higher the temperature the weaker the steel becomes. The comes a point where you get a sudden catastrophic failure, that's why steel beams in buildings have to be incased in plasterboard.

What sort of temperature would you envisage running a vessel that boils water at? Are you talking flash steam generators here? Considering iron derivatives have been used for boilers since the industrial revolution and most full size boilers are steel, running at far higher loadings than proposed here I hardly think the material properties of the gas bottle will be a problem. It may be commercially un certifiable for other reasons such as traceability but as a small boiler operating at up to say 80psi temperature isn't going to be a factor.

Paul.

Here you go, couple of really nice engine/boiler combinations. Jump to a bout 2mins in to see one under steam.

Using something outside normal design parameters is an 'unbounded risk', that is there are too many unknowns to allow a prediction to be made. The absence of data makes repurposing the cylinder as a boiler component a bit dodgy.

On the plus side the cylinders are professionally made of steel and pressure rated at 20C to 100 bar (about 1400psi). That's substantially stronger than a typical small copper boiler.

On the negative side, we don't know how good the steel is at resisting hot wet corrosion, or if the construction is in any way vulnerable to heat. Also, the pressure rating is for a disposable item, ie. a gas cylinder not designed to withstand more than one cold pressure cycle in it's entire working life. As such the build is likely less strong than would be used for a hot boiler cycled several hundred times.

Although uninsurable my feeling is that the pluses outweigh the negatives as a way of occasionally making low pressure steam in a private workshop. Up to, say, 60psi with suitable precautions like a shield. As the cylinders are cheap the risk could be reduced by changing the boiler shell before fatigue or corrosion have had time to cause damage.

It would be interesting to comprehensively test a boiler made from a gas cylinder over a few months and then take it apart. If all was well inside, confidence would rise. Or the opposite!

Dave

Edited By SillyOldDuffer on 10/03/2019 17:32:13

I was thinking of using then filled with compressed air for running simple steam engines with a suitable regulator fitted. Filling from a compressor to about 100 bar

Sorry should have said 100 psi

Edited By Brian Rutherford on 11/03/2019 22:19:16