Why Do Steam Engines Have to Be Torn Apart Every 15 Years?

Every operating steam locomotive in America has a federal clock running on it. After 1,472 days with a fire in the firebox, or 15 years, whichever comes first, the boiler has to be opened up and inspected from end to end. Tubes come out, staybolts get hammer tested one by one, and the boiler is pressure tested with water at 25 percent above its working limit. This documentary explains how the 1,472 service day rule works and why an engine that never moves still burns days off its clock. It also explains where the odd number 1,472 comes from. It traces the rule back to the Locomotive Boiler Inspection Act of 1911 and the March 18, 1912 boiler explosion of engine 704 in San Antonio, which the Texas State Library calls the worst railroad boiler explosion in American history. We follow real teardowns at the Illinois Railway Museum, the Southern California Railway Museum, the Boone and Scenic Valley Railroad and Union Pacific's Cheyenne steam shop, where 844 spent three years in the shop. We compare the American rule with British boiler tickets. Then we look at what the clock means for Big Boy 4014 after its 2026 coast to coast tour.