Investigation of microdamage of metal pipes of high-temperature steam pipelines from Cr-Mo-V steels of thermal power plants under long-term operation

The paper gives an overview of structural changes and the development of metal damage of power equipment operating in creep conditions at a high operating temperature. Alternatively, the use of regenerative heat treatment (RHT) is considered replacing the depleted metal resource efficiency. The RHT technology is described to be used in industrial conditions without removing the steam line and using induction heating by the electrothermal high frequency installation. For the first time the industrial experiment was made on the application of this method to extend the service life of metal bends of steel steam pipelines of two steam generating units of 200 MW, which exceeded the standard service life (210 thousand hours) with the damage of more than the maximum permissible level specified by technical norms. The results of the study of the microscopic metal damage before and after the RHT indicate resuscitation patterns and healing creep pores in the form of chains formed during the prolonged high-temperature operation. A comprehensive study of the structure, microdamage, short-term mechanical properties and durability, made in the laboratory on model bends showed regulatory strength reserves and the possibility of extending the service life of the restored metal for the next 100 thousand hours with nominal steam operating parameters.