The invention relates to a dual drive device for an Airpreheater comprising a speed reducer having a base, at least two input shafts eccentrically disposed and an output shaft, the base being mounted on the Airpreheater rotor housing ; an electric motor coupled to one end of the input shaft via a fluid coupling; an air motor coupled to the other end of the input shaft via a Bibby coupling; a pinion rack rigidly fixed on the rotor of the Airpreheater; a pinion centrally mounted on the output shaft of the speed reducer adaptable to engage or disengage with the pinion rack. ‘A sliding means comprising atleast one crank mounted on the base, is provided which accommodates the output shaft such that a rotation of the crank causes forward or backward movement of the speed reducer in reference to the Airpreheater thereby allowing engagement or disengagement of the pinion with the pinion rack. Thus, in the present invention two separate drive means are installed for one Airpreheater. Only one drive means is engaged at a time for operation of the Airpreheater. If any problem arise in the drive means, then the drive means can be disengaged from the rotor for maintenance. Simultaneously, the other drive means can be engaged for operation of the Airpreheater, thereby stoppage of the Airpreheater can be avoided and the down time of the boiler reduced. (FIG.1).