Union Pacific Big Boy, 4014 Steam Train Accelerating and Sanding Flues (8, 27, 21)

READ: Working HARD on the Big Boy 2021 Tour: Supercut of the two best pacing shots from this date. Accelerating out of Walnut Ridge, AR and sanding the flues just south of Knobel, AR. Enjoy ) Oil burning locomotives must have their flues and tubes sanded every few dozen miles because any oil that does not fully combust in the firebox will end up coating said tubes and flues and hinder heat transfer to the boiler. When the locomotive is working hard, a heavy draft is induced from the firebox, through the tubes and flues to the smokebox and out the stack. The sand that is poured through the firebox peep hole in the cab is sucked through the tubes and flues and scours them clean of the oil deposits, hence the short periods of black exhaust.