# Scorce ofLarge Copper Tube.



## smokey (Nov 24, 2009)

Can anyone advise please if there is a dealer that sells large diameter copper tube in millimeters, i require a piece 63mm od x 2mm wall for a boiler shell.


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## Jasonb (Nov 24, 2009)

Sounds more like a metric conversion of imperial tube, 63mm is the usual metric size given for 2 1/2" inches but the thickness is not one of the more common SWG thicknesses. 16g is the usual thickness for that dia which is approx 1.6mm.

Whats the boiler drawing?

Jason


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## cobra428 (Nov 24, 2009)

Hi,I don't know where you are located but.....
http://www.mcmaster.com/#copper-tubing/=4n9c3i

Tony


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## smokey (Nov 24, 2009)

Hi Jasonb.

The drawings i downloaded off the net, they are of a 0-4-0 live steam French narrow gauge Decauville for G scale. All measurements are in millimeters, soes this help any.


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## Jasonb (Nov 24, 2009)

I've had a look at the drawings and without going into calculations for the boiler its hard to say if 1.6 (16swg) tube will be OK but that metric size is not commonly available in the UK unlike 2 1/2" x16g which several of the ME suppliers stock, Reeves, LSM etc.

Its possibly a French size as that seems to be where the design originates.

Jason


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## smokey (Nov 24, 2009)

Hi Jason.

Many thanks for your advise, it appears to me that most of the small boilers must be made useing imperial copper tube, i think this is what i will have to do, there is a safety valve fitted and one can always adjust the burner. I don't feel like importing copper tube from France.


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## Artie (Nov 24, 2009)

I notice on the site that Cobra put up that 1mm thich walled, seamless 14mm pipe is rated at 1060psi at 100 deg F. Perhaps 2mm thick might be some state of overkill as the site states that this is simply general purpose copper. I assume this to mean that its not some form of super duper alloy (did I use that phrase?). Or does Pascals Law come into play as we increase the surface area of the tubing up to 63mm (yes it does but without complex calculations....)

Anyone have any thoughts on exactly what is safe in boiler construction of this size (or a link to a site that has this sort of info?).

I also think that the potential for home builders to solder "below par" may be of more concern. its all good fun... looking forward to learning more.. cheers guys.

Artie


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## shred (Nov 24, 2009)

Boiler safety and design is driven by a lot of factors; working pressure, construction, materials, build quality, etc. Don't underestimate it.

For example, a 2.5" tubing shell (1.6mm thick) by itself might rate 100 psi when used in a silver-soldered boiler, but without stays on the end plates wouldn't even qualify for 30 PSI according to the boiler code (a derivative of the ASME, different regions have different codes) in the back of Kozo's New Shay book.


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## GWRdriver (Nov 24, 2009)

Smokey,
It really doesn't matter whether the tube is Imperial or Metric, the requirement will be the same for a given tube size. The first basic requirement is that the barrel tube be seamless hard drawn copper. As pointed out 63mm is approximately a 2.5"OD tube but US standard 2.5" tube will have an actual OD of 2.625". You could order tube from the UK, but it's perfectly acceptable and was at one time commonplace to split and re-size a larger tube to a smaller size and use a lap or strip joint at the seam. The internally reinforced seam was far more popular as it left no awkward "bump" on the OD to be dealt with.

As an example, a US standard 2.5" (nominal) copper tube would be available in three wall thickness . . . Type K (.095" or 2.5mm), Type L (.089" or 2mm), and Type M (.065" or 1.65mm). The wall thickness of each type varies with the nominal OD of the tube. For most copper model boilers a Type L tube would meet most wall thickness requirements, as it would for yours. By the time you get up to a 6" nominal tube (6.125"OD) the wall thickness has risen to .140" (3.56mm) which is actually a bit too much for a 6" boiler shell, at which point you would drop down the Type M which is .125".

Published copper tube bursting pressures are, first, for COLD bursting and don't take into consideration loss of tensile strength as the boiler tempreature rises and don't specifiy what gauge or wall thickness the tests have been done on. Secondly model boilers are traditionally (at least in British practice) designed for an 8X factor of safety and that standard has been generally accepted by the other model boiler building nations, except France, who don't give a rat's bum what the rest of us do. Model boilers sometimes fall short of the 8X design safety factor but the very least acceptable is 6X. The safety factor is achieved by introducing 8 into the barrel and head design formulas. (from Harris, Evans)

I don't recall that you stated an operating pressure but for the G1 Deceauville guess it would not exceed 60psi and for that pressure 2mm would be the minimum I could be comfortable with and again this will depend upon WP (design working pressure.) A peculiarity of copper in miniature boilers is that for the same WP, as the OD becomes larger the wall thickness must also be increased. The wall of a 4"OD boiler running at 60psi must be thicker by a numerical factor than the wall of a 2"OD boiler running at 60psi.

1/16" or 1.6mm head thickness could possibly be adequate for a 63mm OD barrel provided the pressure was not above 50 psi and there was at least a half the head area stayed (by flues for instance.) Additional staying would allow the WP to be increased slightly but lacking this, or for higher pressures, heads would need to be thicker, at a minimum 2.5mm perhaps, or 13ga (.090") copper. The staying pattern of each boiler design must be deveopled individually to suit the size and WP.

Is this the loco? If so I know of it.


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## Steam4ian (Nov 24, 2009)

G'day Smokey

Rather than guesses, no matter how well educated, let's look at a Code. I refer to the AMBSC Code Part 1 Copper Boilers.

Table 3.3.2 allows a minimum thickness for boiler barrels up to 96mm diameter of 1.6 mm for a working pressure of 700 kpa; this table 3.3.6 states is equivalent to 16 gauge.

I don't know where home is for you, but this tube is available in Australia as DN65 type A, it has a 50 degC safe working pressure rating of 1840 kpa At 700 kpa steam the safe working pressure rating is 1256 kpa. The test pressure is 1.5 times safe working pressure and the testing is done at under 50 degC so tha 2 x hydro test can be done. Refer AS1432.

If you refer to Part 3 of the AMBSC Code (Sub-miniature boilers) you can use 1.2mm Gauge 18 thickness for pressures up to 520 kpa (75psi) and diameters up to 77mm. The equivalent tube is a DN65 type B which is commonly used for mains pressure water piping in Australia; this should be the case elsewhere.

If I haven't said it here before and even if I have. Anybody contemplating building a boiler should get themselves copies of the AMBSC Codes. They may not have jurisdiction in your province but they are a great source of design data, they offer both recipe and regulation.

Regards
Ian


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## Artie (Nov 25, 2009)

Thanks Ian, Ive included the link for the AMBSC site (Australian Miniature boiler Safety Committee) http://www.pnc.com.au/~wallison/AALS/AMBSC/AMBSC.htm

You have to order a copy of the code as the site only gives you a list of contents.This is current info as of Sept 2008.

Cheers

Artie


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## Jasonb (Nov 25, 2009)

Subject to working pressure you may well be OK with 16g. The minnie in my avitar uses 2 1/2" OD x 16 and there have been hundreads built. 

Can you add at least a country to your profile so we have an idea of where you are as supplies, terms and codes will vary

Jason


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## smokey (Nov 25, 2009)

Hi All.

Many thanks for the information it was most informative, you have put my mind at rest in more ways than one . I live in Telford, Shropshire,UK, an ex fireman on Brittish Railways W/R.

GWRDRIVER.

That is the loco in question.

Best Regards to All.    Theo.


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## ianjkirby (Nov 26, 2009)

Steam4ian  said:
			
		

> ... they offer both recipe and regulation.
> 
> Regards , Ian.
> 
> ...


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