PURPOSE: To sprinkle rustproof agent on the surface of heat transmitting pipes easily and surely by a method wherein a tube type nozzle body is provided and plural nozzles are arranged on it. The nozzle body is supported parallel in the axial direction through a flexible suspending member hanged from a free moving carrier on a rail parallel to the axial direction.

CONSTITUTION: A carrier 5 which is free moving mono-rail type is arranged on a cable rail 4. The flexible suspended member 6 is hung at the lower end of the carrier 5, and the tube type nozzle body 7, which is parallel to the axial direction of the first group of heat transmitting pipes, is suspended at the end of this member 6. Many nozzles 8' spouting rust proof agent are formed on the axial direction and along the circumference direction on the tube type nozzle body 7. The tube type nozzle body 7 is inserted in the arbitrary space in the first pipe group of the heat transmitting pipes, and can be equipped freely in the whole space in the first group of the heat transmitting pipes of the heat exchanger, because it is movable to the axial direction of heat transmitting pipes by the carrier 5.