Boiler Construction

Soft Solder vs Bronze Welding
by L.B.S.C.

The Live Steamer, May-June 1950

Question: Is a boiler safe to use if it is sweated at the joints, tubes and stays with soft solder?

Answer: Whilst a boiler can be safe to use with riveted and soldered joints, it rapidly deteriorates and eventaully leaks. The reason is that the solder gets hard, just like the whitemetal in the big ends of an automobile engine, and presently cracks under the stresses of continued expansion and contraction. Also, a riveted boiler can never be as strong as a brazed or bronze-welded one, for this reason: The perforations where the rivets go thru weaken the plates just like the performations in a sheet of postage stamps; and given sufficient stress, the plate would tear along the line of holes, just like you can tear the sheet of stamps. This was the cause of several boiler explosions in the early days of steam locomotives.

It is many years ago that I abandoned riveting, except for just a few needed to hold the parts of a boiler together while bronze-welding. In my experience, the most satisfactory construction is all bronze-welded seams, and silver-soldered flues. Thinner metal can be used, with a greater factor of safety, than if the joints are riveted and sweated.