چكيده به لاتين
One of the main reasons for the boilers to be shut down and removed from the circuit and, as a result, out of the operational network, is the occurrence of leakage as a result of the failure of the boiler tubes, especially in the superheater and reheater tubes. Since most of the vandalism in the boiler occurs in the superheater tubes, and these vandalisms cause the boiler to fail and cost wastage in the power plants, therefore, this study investigates the causes of superheater tube vandalism of a boiler and a power plant, and the factors The main root is found and interpreted. The purpose of this project is to investigate the causes of destruction in the superheater steam production pipe in the boiler. The failed pipe was removed from its place and examined and various tests were performed on it. Because investigating the effects of different parameters of repair welding on damage and susceptibility to stress corrosion is a very important issue in power plants and the mechanical properties of the steam transmission pipe change during repair welding, so after analyzing the failure, in order to optimize the welding process Repairing and improving the service life of repair structures, the effect of repair welding parameters on the mechanical properties of the superheater tube will be investigated. Then the effect of repair welding parameters on the mechanical properties of the pipe will be investigated. With the study done in this research, it was found that due to the lack of proper purification of boiler water and lack of boiler temperature control, it has led to the formation of a thick oxide layer on the inner wall of the pipe. It led to the lack of heat transfer, which caused the temperature of the metal to rise to more than 640 degrees Celsius, which led to a transformation in the microstructure, carbides were deposited on the boundaries and inside the crystals, causing creep. Due to corrosion, it led to the thinning of the pipe wall in the fracture area and the inability to withstand the steam pressure, which led to the pipe explosion. To restore the boiler to operation, repair welding was performed by removing the damaged part and replacing it with a new bend, and before welding, the remaining life of the old pipe was calculated and it was determined that the pipe could work. For another 20 years, GTAW welding was performed through tests before and after heat treatment. Before heat treatment, the hardness in the weld and HAZ zones was high, after heat treatment in the laboratory at 740 °C, the hardness decreased, but above the standard. The temperature setting time should be from 1-30 hours.
