Lifetime estimation of superheater header
| Autor: | Yuri Lapusta, Yuriy Pyndus, V. Iasnii, O. Yasniy, Vitaly Brevus |
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| Rok vydání: | 2016 |
| Předmět: |
residual lifetime
Materials science business.industry 020209 energy Boiler (power generation) Thermal power station 02 engineering and technology Structural engineering Mechanics Atmospheric temperature range Residual Finite element method 020303 mechanical engineering & transports superheater header 0203 mechanical engineering fatigue crack Header 0202 electrical engineering electronic engineering information engineering business finite element modelling Superheater Stress intensity factor Earth-Surface Processes |
| Zdroj: | Procedia Structural Integrity. 2:840-846 |
| ISSN: | 2452-3216 |
| DOI: | 10.1016/j.prostr.2016.06.108 |
| Popis: | The safe operation of thermal power plants (TPPs) is largely determined by the reliability of main components of steam systems of power units, to which belong the headers of boiler superheaters. The aim of the study is to estimate the residual lifetime of superheater header starting from the initial defect size and up to the maximum allowable one. The above-mentioned lifetime is affected by the fluctuations of temperature under steady mode of operation of TPP superheater header. Superheaters headers operate in a steamy environment under the pressure of 15.5 MPa at temperature of 545 oС. The header is a thick-walled cylinder with a length of 2314 mm, outer diameter of 325 mm and thickness of 50 mm. The header contains three rows of 27 holes with a diameter of 22 mm and step of 80 mm in the axial direction and 57.6 mm in the circular. The header is made of 12Cr1MoV steel. To estimate the residual lifetime of header, the registered operational data of steam temperature in header were used. The temperature range of header under quasi-stable operational mode was divided into three classes: the temperature range (1) T 30 °C. The local minima and maxima were determined using the obtained steam temperature history. The stresses in the wall of header for the given temperature fluctuations were calculated by finite element method (FEM). The residual durability was evaluated taking into account the effect of thermo-mechanical stresses and also the stresses caused by internal steam pressure. The stress intensity factors at the crack tip in the ligament between the holes of superheater collector were estimated by FEM. Based on the analysis of header defects, the proposed front shape was taken in the form of semi-ellipse. The crack growth at 500 ° C was modelled by Paris equation. The number of cycles for a crack to grow from the initial crack depth of 25 mm up to final size of 35 mm is calculated, taking into account the mean of temperature fluctuations. With the increase of temperature difference between the external and internal header surfaces from 10 °С to 50 °С, the number of cycles, that is necessary for the crack to reach 35 mm in depth, decreases approximately in 25 times. It was calculated, that the average value of temperature fluctuations is 15°С for the 2 nd class, and is 46.2 °С for the 3 rd class. It takes 112000 and 10200 hours of operation for the crack to grow from initial depth of 25 mm to final defect depth of 35 mm at temperature fluctuations of 2 nd and 3 rd class, respectively. The lifetime of header can be extended due to the decrease of fluctuations of temperature range and their frequency. |
| Databáze: | OpenAIRE |
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