Re: Boiler design question

Im going to give this a shot at answering it...The boiler shell or what we sometimes call the boiler barrel is generally the thickest area of the boiler. The thickness depends on the pressure that the boiler is intended to operate at. On most all locomotives the boiler barrel is protected with a jacket and insulation. The main reason of the jacket is to reduce heat loss and to protect the crew. However the Jacket also protects the boiler from the elements and corrosion. As for the tubes and firebox sheets they are thinner. The reason they are thinner is to maximize the transfer of heat from the fire to the water. The tubes will generally wear out the fastest cause when the locomotive is working it is pulling cinders thru the tubes along with the fire the combination of the two will sand down the interior of the tubes and especially where the tubes are rolled and/or welded to the flu sheets. The firebox sheets are subject to similar wear from the fire and coal working on the sheets in a similar manner. Also the water will wear on the sheets, flues, and staybolts, The hardest thing on a boiler is firing it up to fast, cooling it to fast and poor firing which causes the pressure to fluctuate along with the temperatures of the water and fire. If a boiler is taken care of it will last many years. Both of our engines still have there most of their original firebox sheets. #12 is 93 yrs old and #190 is 67 yrs old.