The Fracture Failure Analysis For Air Preheater Using Centre Drive Device

With rotary air preheater widely used in modern thermal power generation unit as a kind of heat transfer, there is a increased discuss about the advantage and disadvantage between pin rack drive device and centre drive device. The pin rack drive device has simple structure and can run for a long time even under the condition of lack of lube oil. But when we assemble the pin rack drive device, we need take more time on the work of assembling, welding and debugging, to make sure the pin rack can engage with wheel gear on output roller of the reduction box well.While the centre drive device can be assembled easily, but require better lube grease and to add it at regular time.In this paper,the research object is the rotor structure of the air preheater.According to the rotor structure feature of the air preheater with the centre drive device,I make the force analysis when the rotor is assembled and running,and understand the stress distribution on the rotor structure.The research suggests that there is a point taking the maximum stress and easily cracked by twisting stress and shear stress located in the join of the radial plate root and the lug assembly outer edge.In Lue Yang power plant, there were two air preheaters where found cracks on the radial plates when examined.These two air preheaters use the centre drive device. The fracture of the radial plate is analyzed in welding quality, stress distribution and material quality by means of metallographic microscope, SEM and EDS.The study finish the location of the position easily cracked by twisting stress and shear stress in the air preheater with the centre drive device, which provides important suggeations about choosing driving solution during the air preheater design.