When she finishes today's excursion, the 7470 will officially run out of service days and will come due for a 1,472-day inspection, as required under the Code of Federal Regulations, Title 49, Part 230. I often hear folks refer to this requirement as an "overhaul" or "rebuild", but neither is correct. The 1,472 is a boiler inspection. First, the flues must be removed....not because they "expire"....but because the required inspection is virtually impossible with them still installed. Once the boiler shell is cleared of the flues, all boiler surfaces must be cleaned down to the bare steel, inside and out. Then a complete ultrasound survey must be done, to ascertain the thickness of the steel throughout the pressure vessel. Any spots which do not meet FRA requirements must be either patched, or replaced, depending on the extent of the non-conformance. In addition, hundreds of rigid and flexible staybolts that hold the firebox and crown sheet areas together must all be inspected, and if necessary, replaced. The dry pipes, water glasses, safety valves and a host of other boiler features must also be inspected and repaired as needed. When the inspection is complete, a Professional Engineer must then recalculate the maximum operating pressure, based on a complex formula. For a boiler that is in good shape, this inspection can take anywhere from a few months to several years, depending on the manpower and money available. If any significant repairs are required, such as replacement of entire firebox sheets, one can pretty much throw the schedule out the window. Folks, this is why there are only perhaps 150 steam locomotives in this country that can operate, and this is why running steam is so expensive. A 100-year old steam boiler can be very dangerous if it is not cared-for properly, and the 1,472-day inspection was put in place by the Feds to ensure that all railroads that are operating steam are running safe operations.