Copper tubing specs

[Bernd]

There has been quite a bit of discussion going on about boilers and there safety. I decided I needed to look at some specs for copper tubing that would be used in the making of a model boiler for the small engines the we are building here. The diameter of the boiler would be in the area of about 2" to 4" dia.
I did a google and came up with two links for copper tubing specs and there use.

Here is the first. http://www.engineeringtoolbox.com/astm-copper-tubes-d_779.html

Here is the second. http://www.indpipe.com/images/PDF/copper_tube_federal_and_astm_specifications.pdf

Note in the second link that a color code is given. The specs given are ASTM specs. The color code red and blue can be gotten at any of the home improvement stores in the US. The red code is type "M" and is used for general plumbing and light pressures. The blue code is type "L" and can be used for steam but does not give a pressure rating. The code green, which I haven't seen in the home improvement sotres, is type "K" and can also be used for steam and also does not give a pressure rating. All these tubes are seamless. That is what one wants to use in building a boiler, seamless tubing or DOM (drawn over mandrel). The code black which no type is given can be used for steam since the spec sheet says "including high pressure industrial applications".

I'm sure if any body goes and prices a piece a foot long their heart will stop.

Back in April 1979 Jan Gunnarsson wrote a 5 piece series in Live Steam called "For marine or stationary use, a Miniature Boiler Works. All of his dimensions is in metric. The boiler is a piece of copper tubing 54mm in dia or 2.1259" in dia. with a wall thickness of 1.5mm or 0.059". He states that is roughly equal to 16 SWG and will allow a maximum working pressure of 150 psi or 10.5kg/cm2 with a safety factor of 8. The boiler would only be required to put out a pressure of 30 psi or 2.1kg/cm2.
If you look at the first spec sheet for the links you find that type "M" could be used since it has a wall thickness of .058" for a 2" dia. pipe. I definitely would not use that for a boiler. I would use type"K" with a wall thickness of .083".

So with all the specs listed above I would like to build a boiler using type "K" tubing and "test to destruction" to see how high a pressure it would take before bursting and were the failure would occur.

Bernd

 

[shred]

A local live-steamer makes his own copper boilers in the 2-3" sizes and they're almost all rolled from 1/16" copper sheet. He runs upwards of 100 PSI in them without trouble.

 

[Bogstandard]

Shred,

Very good boilers can be made by the rolling technique, in fact some model loco boilers have to be made that way, as they have a tapered form.

There are basically two type of joint that are recommended, one is where the butting ends are cut with dovetails that interlock, then silver soldered, a very skilled and time consuming method. The other is where the butting ends are brought together, and a reinforcing plate is rivetted over the joint, then the whole area, including rivets, is silver soldered.

I should somewhere have the specs for doing this type of joint. If I can find them.
Slightly difficult at the moment.


John

 

[Loose nut]

If you get the boiler making books that Model Engineer put out years ago, one was by Martin Evans
"Model Locomotive boilers, their Design and Construction",
these will tell you everything you need to Know about boiler making. I believe that they are still available for sale if you google the title.