johnsmachines

machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment.

6″ Vertical Boiler- First silver Brazing

So what is the big deal?

Well for a start, this is a big deal financially.  The materials to be joined are expensive, and some are difficult to obtain.

And the silver solder itself is expensive.  We ended up using 4 sticks of 45% silver solder, and an unknown quantity of oxygen, acetylene and propane.

And the end result will be inspected by an expert boiler inspector, and if it is substandard, it will be rejected.  No argument.

So yeah, it was a big deal.  Look at the pics.   A few friends called in to watch and help.  It was a cold wet winter day, and I had the workshop wood heater working to keep the troops happy.

IMG_6578.JPG

I used steel wool to expose the elemental copper.

IMG_20180711_141605

Me applying flux.  Note the silver solder rings which were made on the lathe.  Don’t ask where the brush originated.

IMG_6580.JPG

The firebox wrapper was placed on the aerated concreted form to keep the tubeplate level, and allow the tubes to penetrate exactly 2mm.  The tube ends were fluxed, and silver solder rings placed into the join.

IMG_6582.JPG

The 44 fluxed firetubes with their rings of silver solder are in place.  The top tube plate will not be brazed at this time.  It is there to keep the firetubes in the correct position.  The firebox tubeplate is also fluxed and sitting in position on its Hebel block.

IMG_20180711_151431.jpg

Me on the left with the propane weed flamer applying gross heat, Stuart with oxyacetylene applying local heat and silver solder, and Swen cheering.  Brendan is the photographer, trying not to get burnt.

IMG_20180711_151114.jpg

We probably should have reshaped the forge to reflect the heat more efficiently.

IMG_6584.JPG

When the brazing seemed to be finished, the work was allowed to cool to 200c, then quenched in water then a 15″ soak in 20% sulphuric acid to remove any remaining flux, then a further water soak to remove any acid.  Yes, the top plate is upside down.  Yes, it will be reversed eventually.

IMG_6586.JPG

Inspection from inside the firebox.  Most firetubes have taken the silver solder properly, but a few of the inner circle and the flue require a second application.  The brazing heat looks to have been inadequate near the centre, probably due to the density of the firetubes.

So, not a perfect result, but not bad for a beginner.  Stuart opined that the job would have been better if my silver solder was the older, (more dangerous) but more runny type which contained cadmium.

Turning Concrete on a Metalworker’s Lathe

OK.  The concrete is aerated… Hebel.

But, it does turn easily and cleanly.

IMG_6577.JPG

But it is concrete, and probably very abrasive, so I have covered everything in plastic, and used an old carbide cutter.

I needed to refine the dimensions and shape of the supporting block while brazing  my 6″ vertical boiler, so I turned it.  And it worked brilliantly.

 

%d bloggers like this: