Summertime is outage time, and many of CAP’s millwright mechanics are spending their days at Mark Wilmer Pumping Plant. On this day, they were working on a “thrust runner,” a large piece of metal that carries the entire weight of the motor rotor and pump impeller – the two components that spin and allow the pump to operate. The approximate weight of that rotating assembly is 280,000 pounds or 140 tons.

These craftsmen are using torches to thermally expand the thrust runner so they can remove and work on it. Once the work is complete, the thrust runner will be reheated so it will expand and slide back into place. As it cools, it will then shrink onto the shaft, essentially making it one piece.