Hank has only known Francisco from his reputation in the papers, which has been deliberately slanted to give the impression that he is an inveterate, dissipated playboy. Hank, though he doesn't know it at this point in the novel, is also the rival for Dagny's affections. He doesn't know that Francisco learned his engineer's trade as thoroughly as Dagny has learned hers, and that he is every bit as hard a worker as Hank has ever been; Francisco has been working to destroy d'Anconia Copper so that the "looters" can't profit from it, after he has gone to live in the valley in Colorado with John Galt and the rest of the people who believe Galt's philosophy.
Francisco not only works hard to fix the broken furnace, but he risks his life in doing so. Even more amazing, to Hank, is that Francisco knows what to do. Francisco, an engineer who has been involved with metal and smelting his entire life, knows that quick action -- and a particular kind of effort -- will be the only thing that can save the situation. And this playboy, who has been working silently in Hank's mills for some time, Hank realizes, is nothing of the kind.