Bonjour George,
Thank you for the drawing and thank you for the warning but I think I have not been accurate enough. The copper pipe will rolled around the body of the torch outside the boiler, not directly in contact with the fire and the pipe wil be full of water. I will use a 4 mm pipe, which let a lot of room to the water. In this configuration, I think there is no heat enough to generate flake, would you agree with me ?
Raphael,
I can only comment on what I have experienced in the past.
I machined a flame tube from a piece of Stainless steel tube down to a wall thickness of .025" thk and from memory it was 1" dia.
I wrapped 5/32" copper pipe ( 4mm ) around the tube as a water heater, when the burner was lit the stainless tube glowed red as did the copper pipe,
I turned of the Gas and filled the boiler with water and proceeded to fire up the burner , when the boiler came to 60 p.s.i. I opened the water feed which was driven by a D10 engine, no water came from the water supply to the boiler, so after some consideration I fitted an over flow valve between the delivery side of the pump and the boiler Clack.
With the same proceedure the water feed was opened and the by pass was opened which produce a blast of steam from the over flow so it was obvious to me that the burner was producing too much heat to the water supply and the flame tube and the coil were glowing red, the overflow valve was closed but the pump refused to pass water to the boiler at 60 p.s.i.
On examination of the coil flakes of copper were clearly visable on the out side so it must have been flaking on the inside.
The copper coil was removed and when the water supply was fitted the pump had no problem on filling the boiler, unfortunately I have no pics of the installation.
So in conclusion, when the boiler was filled manually and the coil was empty it was that period that turned the water coil into a flash steam situation before the pump took over.
So my experiment with the coil around the burner was abandoned and I used the exhaust to heat the boiler feed water as per the sketch which I use to this day with no problem and it also means that I don't have to uncouple the water feed supply to fit a new gas bottle, I use camping gas bottles.
I see no reason why you should not do as you have suggested but make sure that there is water in the coil while you fire up to bring your boiler to W.P. and your burner may not be a powerful as mine with a No 10 jet
George..