11 Boiler parts namely furnaces, down comers, stay tubes, stay bars, generating tubes, superheated tubes, manholes, hand holes, domes, steam spaces, lower tube plates, [upper tubes plates,] * upper tube plates, * throats, wall tubes, roof tubes, floor tubes, screen tubes, shell plates, uptakes, raisers, pin tubes, fin tubes, spiral tubes, coils, elements, casings, headers and ring headers