A WATERTUBE BOILER FOR MY TRIPLE EXPANSION ENGINE

[Laurentic]

John - thanks for the heads up on the tube

Chris 

[crueby]

What type of torch is it - oxy/acetylene, propane, other? Also, was looking at the tubing you showed in that link that you were using, the walls seem awfully thin?

[Vixen]

What type of torch is it - oxy/acetylene, propane, other? Also, was looking at the tubing you showed in that link that you were using, the walls seem awfully thin?

Did you use thin wall hydraulic brake pipe or thicker wall steam boiler pipe?

Silver solder melts at around cherry red temperature, Copper melts at bright orange temperature. A darkened room will help you see the colour of the metal. you may need to move the torch away, for a moment, to see the metal colour, hence temperature.

Mike

[simplyloco]

Guilty as charged Your Honour!  I used a big propane burner on thin brake pipe even though it takes high pressure. I seek clemency and I promise not to do it again...

[crueby]

On parole for now!   

The reason I asked about the torch type is that some fuels burn a lot hotter than others. Even a propane torch can easily hit 1200C or higher, well above copper melt temps. I've had cases where I overdid things and had copper and brass parts soften and sag. Even steel parts can soften enough to sag under their own weight. Watching the color/glow of the metal is very important, as was said by others doing this work in dimmer light makes it a lot easier to see where the metal is starting to glow.


For the piping like that in boilers, better to use the thicker walled stuff anyway. The times I've used smaller diameter tubing it was much thicker walled, which made it heat up more like the larger boiler shell, still had to aim the flame more at the larger shell and let it heat the smaller tube rather than direct flame on the smaller tube. Silver soldering thin parts, or thin parts to thicker parts, is definitely tricky, must put the flame more on the thicker/heavier parts to even out where the heat flows.

Hope you can get it reworked or remade, it was going so well!

[MJM460]

Hi John, that doesn’t look so good.  Just as well you have your holiday coming to allow your subconscious to work on how to repair it.

I have to agree with others on the thin wall tube, it holds lots of pressure, but only when cold.  Not really good for boiler making without some serious heat transfer analysis.  Probably even contributed to the failure by the thin metal heating quickly and more locally while the more massive shell was coming up to temperature, but not the sole cause.

Do enjoy your holiday, we will all be still ere when you return.

MJM460

[Laurentic]

Well, I have to say that others have confirmed my fears when i saw it was brake and refrigeration tubing, not boiler tubing.    Yes it will stand the pressure, cold. but when hot?  Though of course here it was also hit with a big flame in a small congested localised area.  C106 copper tube is what is needed for boilers (in the UK).

Such a shame as it was going so well and was looking good.  Not to worry, tell your Mum, I will look forward seeing to Part 2 after Spain!

Chris