Re: A question for all you boiler specialist

Welding tubes in a locomotive boiler is generally a bad idea. Many boiler shops simply roll the tube into the tube sheet, then put a bead of weld around the tube attaching it to the sheet. This does not allow for expansion of the tube and sheets during normal operating conditions. The result is that the weld cracks, and the joint between the tube and sheet leaks. Re-rolling the tube will seal it up, but there is now scale between the tube and sheet and the joint will eventually start to leak again, even if you touch up the weld. I have always called this a "power plant tube job" as this is what most modern day boiler companies do. This method works fine on a power plant boiler that sits on a nice concrete slab and gets fired at a constant rate all day long. Locomotives have huge differences in firing rates in very short periods of time, resulting in significant expansion and contraction forces

There are many ways the RR applied tubes, but the most common way is to roll (expand) the tube into the sheet, then on the firebox end, roll the end of the tube back on itself to form a "bead" around the end of the tube. This keeps the action of the fire off the end of the tube. Most roads then seal welded the edge of the bead to the sheet to further keep the fire away from the edge of the bead. Some roads also "prossered" (sp?) the flues by expanding them inside of the flue to lock them into the sheet on both inside and outside.

On the smokebox end, there was less expansion/contraction to deal with. Tubes were rolled and few were beaded, usually in an "X" pattern to hold the tube sheet in place.