Analysis And Diagnostic Method Research Of Turbo-generator Rotor With Cracks

Rotor crack is one common fault of rotating machinery. When a rotor contain cracks in turbo-generator set, the vibration will increase gradually, affecting the safe and stable operate, it will broken shaft and destroy unit when seriously, threatens the equipment and personanl safety. Therefore, studying how to accurately and timely diagnosis the crack fault and preidct the development tendency of it, is important for the safety and reliability operation of unit,reduce economic losses and prevent a sudden disaster.Based on a large number of domestic and foreign turbine rotor crack fault cases, the paper deeply study the crack fault of turbo generator set.. the mechanism of occurrence and development and the sepcific reasons and influencing factors of the rotor crack were analyzed and summarized. Based on the statistical analysis, the thermal stress, environmental corrosion and stress concentration is the main reason leading to crack. A simplified rotor crack model is established, the vibration mechanism and the effect of the crack to the unit are studied. Combined with the engineering, the vibration characteristics of the rotor crack are studied, the crack development is divided into early, middle and later stages, each stage has the corresponding characteristics.Then the characteristics of the process of start-up(stop) and load operation are analyzed,which can comprehensive reflect the characteristics of crack fault.Based on the FTA and FMEA comprehensive analysis,list all the basic events may lead to crack, find out the important events,analysis the effect, then gives the corresponding prevention measures. Based on Rough sets, sums up all the vibration and related characteristics and analysis, constructing fault decision table, then reducing the scale of the fault characteristic parameter, remove redundant information, obtain positive region of set, that is the most representative signs of crack fault, as the fault diagnosis rules, and give the crack propagation control and maintenance methods. According to the data features, proposes the online monitoring requirement, briefly introduced the vibration diagnosis and ultrasonic flaw detection method, and give practical application case.The paper’s research results providing technical references for the similar fault.