AN INVESTIGATION ON THE CAUSES OF A ROTOR BENDING A.ND ITS THERMAL STRAIGHTENING

Distortion or bend in a turbine rotor (especially HIP rotors) may be caused by a number of factors, either singularl) or in combination. In general. the causes of rotor bend can be classified invartably in two categories: Rapidly forming permanent rotur bends and/or Slower forming rotor bends. which could trip the turbines emergency stop. One of the major modi fy ing solutions for rapid repairing or bent rotors is hot spotting. For this purpose. after the initial tests (visual inspection. chemical analysis, nondcstr ict ive hardness). the hot spotting was performed seven consecutive times. The results of experimental investigations and experiences with different temperatures and times showed that, the 690 ± 2U C and 210 S. nrc as an optimum t mperaturc and time respectively. I I hot spotting which c: n provide. a noticeable srraightening in bent areas, in addition to having no affects on mechanica l properties. Also. this results were simulated by F.E,M in view or heat distribution in different temperatures in three states (without insulation. with moisture and dry insulation). in order In find out the optimum restra ii t effects around hot spot area.