| With the development of the national economy, The security and stability of equipments of thermal power plants has been attached greater importance increasingly. For example,some diaphragm's stiffness less is found in heavy maintenance since units put into service in the thermal power plant to be provided with four 600MW Subcritical Coal-fired turbine-generator units. So the design of diaphragm may have some defects. As a result, the deformation of diaphragm is tested by power plant in every times heavy maintenance. And the 11th diaphragm has been found that it exist a deformation of 1.7mm, which seems abnormally large by the current standard. It may bring about some uncertainties or hidden troubles to the units. In order to evaluate the security of the diaphragm in its long running time especially during the interval of heavy maintenances'time, this research aims to analyze the process and mechanism of the creep and deformation of the diaphragm under the conditions of the high temperature.At first, the shape of the interior and exterior ring for the 11th diaphragm of NO.4 unit is measured on the spot, the expansion quantity of cylinder and difference between cylinder and rotor is gained in the process of units startup , and all the data from the usual running statistical parameter, previous records, testing statistics of the turbine are collected. Solid foundation is built by these data for the study of the diaphragm.Secondly,the deformation of diaphragm and the location of maximum stress in the static state,based on the aerodynamic and strength calculation model and made a raise of material characteristic parameter of the diaphragm and static blade,is gained. Besides, comparing calculation with experiment results and continuously modifying calculation model and material characteristic parameter until the error less than standards given, then the reasonable evaluation model is made ultimately.Finally, according to the creep material parameters, the process of the creep in the future is predicted. What is more, it concludes that the diaphragm will be safe in the next 30 years and the diaphragm can be maintained in the major repairs. The cost of power plant is saved by this research's help.This research brings forward the way of getting the creep material parameters through combining the all previous recorded deformation data during heavy maintenances and actual calculation data together. The problem will be solved by using this way that creep material parameters can be hardly got because the creep parameters, material and the process of making are closely related. Moreover, the parameters can be amended at any time when the unit is running. In addition, the Conclusion can be universally applied in other power plants, an effective methodology is offered to evaluate the creep life of steam turbine and gas turbine's parts under the conditions of the high temperature. |
