gas tank construction

[Dougie SwanParticipant @dougieswan43463]

Thanks to all who posted replies to my request for gas tank filler valves

 

The thread went well OT towards the end but it was interesting all the same.

 

My next question regards the tank itself, and what sort of pressure I should test it to?

The commercial ones I have seen say they have been tested to 300 odd psi, is this what I need to achieve?

If so what guage of copper tube will I need? I was planning to use an offcut of 2.5″ which has a wall thickness of 1mm or so. With the pressures above it seems unlikely that my tank will survive the test.

Any thoughts/help will be greatly appreciated

Dougie Swan

Edited By Dougie Swan on 06/01/2011 20:56:34

[Dougie SwanParticipant @dougieswan43463]

[James fortinParticipant @jamesfortin46829]

i dont know if this will hep but ‘pure copper in its cast form has a tensile strength of around 125n/mm² 

though drawing increases this to 275n/mm²

 

from; ‘workshop materials by alex weiss’

 

james 

[John OlsenParticipant @johnolsen79199]

This would be drawn tube so the higher figure would apply. A rough calculation suggests a bursting pressure for that tube of over 1000 psi, so a working pressure of 150 (for propane) with a test pressure of twice that would actually look OK.Since you would probably use butane the safety factor would be even higher.

 

The general idea is as with boilers, you design for a generous safety factor, typically 8 times. Then you test to say twice (sometimes 1.5) times working pressure. The idea is to discover any leaks or major problems, without overstressing the vessel such as to create them. It does not pay to over test, since stressing to near the limits could cause damage that will cause problems later.

 

If you are in a club, it might pay to talk to the boiler committee.

 

regards

John

[TerrydParticipant @terryd72465]

Hi There,

 

Dave Watkins built a small model De Winton type loco and eventually made a gas burner and gas tank for it.  It is detailed here and may give you some pointers.  Scroll down about 2/3 of the way down the page and look for the ‘Idris Story’.  There are complete drawings as well to download for free. 

 

Let us know how you get on.

 

Beast regards

 

Terry

[Martin WParticipant @martinw]

Terry

 

Can’t get your link to work under ‘It is detailed here …’. Is the link OK or is it me and my system?

 

Cheers

 

Martin

 

PS Like the typo in your salutation .

[TerrydParticipant @terryd72465]

Hi Martin,

 

It appears to be the link in the original posting, why that is I’m not sure it’s never happened before .

Try again here.

 

It appears to be working now.  The links to the ‘Idris Story’ and drawings are about 2/3 of the way down the page beneath a picture of the loco.

 

regards

 

Terry

Edited By Terryd on 07/01/2011 09:30:34

[TerrydParticipant @terryd72465]

Hi there,

 

the drawing for the butane gas tank is here and the gas regulator here. the latter is a variation of the boiler regulator (see notes on drawings).

 

Hope this helps,

 

Terry

[Dougie SwanParticipant @dougieswan43463]

Thanks for the above, it has helped a lot

 

I have alo seen advertised “gas filler nozzles” not the same as the fill valve on the tank but something that looks like it would fit onto the top of a blowlamp gas canister.

 

Are these used to fill the gas tank from a blowlamp refill?

Once again any info would be very welcome

 

If anyone is interested, I have posted a couple of pics of the engine that will be powered by the gas boiler under construction. It’s still very much a work in progress but any thoughts/comments are welcome

Thanks

 

Dougie Swan

[TerrydParticipant @terryd72465]

Hi Dougie,

 

Not sure about the proposed filler valves/nozzles but I did notice that on Dave Watkins detailed description of building Idris and burner he did describe methods of pressure testing.  I thought that may be of use to you.

 

Regards,

 

Terry

[Dougie SwanParticipant @dougieswan43463]

Hi Terry

 

Yes it was, that information and some of the replies above made me feel a lot better about tesing to 300psi. I liked Dave’s design of regulator and might try it 

 

The filler valve I’m referring to looks like it screws onto a blowlamp fitting and has a length of copper pipe sticking out there is one on ebay and another sold by Bruce Engineering,

it’s just the use I’m not sure of

Regards

Dougie

[Richard MarksParticipant @richardmarks80868]

Gentlemen

Please enlighten me, I dont dispute any statement regarding the working pressures stated for our friends gas tank but the aerosol and gaz canisters I have handled have been made tinplate or aluminium, neither canister capable of handling 300psi,is it me or am I missing something?

Regards

Dick

[mrsgogginsParticipant @mrsgoggins14041]

Dick,

The answer lies in the controls over material properties, the manufacturing process and the filling ratio. Steel and aluminium are much stronger than copper when selected and processed correctly, (eg not subjected to uncontrolled heat treatment) and safety factors can be lower because of the level of control. Disposable gas canisters are for single use only and do not need to include a fatigue allowance in any safety factors.

 

Keith

[Ian S CParticipant @iansc]

There have been articals on pressure testing disposable gas cylinders to destruction, by lighting a fire under the cylinder(with gauge), an retreating to a safe distance with a pair of binoculars, don’t remember the pressures reached, but it was considerable, getting up 400psi+.  Ian S C

[Gordon WParticipant @gordonw]

Pressure testing is simple and safe, just fill with water, or similar, make sure everything is filled with water, pump up to required pressure. Any leak and pressure drops immediatly. Anybody interested in pressure vessels should look at the plastic lemonade bottles, a work of art IMHO.

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