I had the boiler seems brazed again, all that is good. But I misunderstood the construction of the boiler, the group bulkheads were riveted to the copper boiler and I assumed the rivets were water tight, alas they are not. So the heads of those rivets will be brazed over. And that should do it. Hopefully. But I had the boiler up to 1.5 bar using air and just a few of the rivets were leaking.

My guess is that the hot lead wicked into the rivets when they sealed it at the factory kind of like solder does on water pipes. Probably easier to seal it with lead than brazing.

Yes that is what I am leaning towards. Will have a go later.

I had a go, not that easy but the solder seems to have been drawn down into the rivet. I shall continue next week, there are a lot of rivets to go over.

The boiler is holding with compressed air, I had it up to a max of 2 bar. Of course the real test will be with a heat cycle which I should be able to do later this week once I feel a bit more comfortable.



The lead solder worked a treat and was quite good fun. Towards the end I got better and was able to do neat work on the rivets, the early efforts were more blobs. A nice touch was that all the lead work was done with the original lead from the boiler that I saved. Although this is lead there is hardly any chance of contact with the drinking water as it is all on the outside.



It's also worth pointing out again I would never mess around with these boilers normally, but the soldering and brazing is sealing the joints only. The structural integrity of the boiler is achieved by the numerous rivets they used, and all fittings and steam pipes are also secured to the boiler with a nut inside the boiler.

Nice work on getting those rivets to seal with the lead. I can imagine how finicky that job must have been.
Getting it sealed sufficient to take 2 bar air pressure is a great result. Interested to see how it will go at temperature as you say.

Keep the pics coming.

Out of interest, what sort of mechanism is used for maintaining the boiler pressure? Is it a Mercury bulb switch?

Edit: I just re-read all 15 odd pages of this thread to remind me of the work you've done. What a marathon, and you're well and truly on the home stretch. Inspiring work to say the least.

There was no pressure switch, and judging by the condition of the boiler it was probably run on the gas burner with the flame adjusted by hand

The boiler has been up to temperature a few times but the main boiler end plate gasket needs redoing as it is weeping a little. It has been on and off several times now so it is not surprising that it is not sealing.

Paul_Pratt wrote:There was no pressure switch, and judging by the condition of the boiler it was probably run on the gas burner with the flame adjusted by hand

Certainly adds a new dimension to the last of the 4 M's ("Mano", i.e the skilled 'hand' of the barista)

The boiler is in the frame and all the taps and the sight glass have been fitted. I did the wiring today and added a small Sirai switch and a resettable safety thermostat. The original safety valve works well. The lead weight is not as heavy as other valves like this and is venting steam from 0.6 bar.





I still have the big job left of getting the group piston seals in place, it's a curious arrangement and will need some thought.

I think I'm about ready to pay you to allow me to apprentice in your shop!
I can hardly believe it's the same machine. Fantastic job so far! Can't wait to see the final product.