مشخصات مقاله:
عنوان فارسی مقاله:
ارزیابی نرخ FAC و تخمین عمر سرویس تحت داده های کنترل عملیاتی
عنوان انگلیسی مقاله:
Substantiation of FAC rate and service life estimation under operation control data
کلمات کلیدی مقاله:
پوششی از خوردگی جریان، رسوب محصولات خوردگی، داده های اندازه گیری ضخامت، روش محاسبه نرخ FAC، طول عمر باقی مانده، ضخامت مجاز حداقل
مناسب برای رشته های دانشگاهی زیر:
فیزیک
مناسب برای گرایش های دانشگاهی زیر:
فیزیک هسته ای
وضعیت مقاله انگلیسی و ترجمه:
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فهرست مطالب:
Outline
Abstract
Keywords
Introduction
Review of approaches to the evaluation of FAC rate applied on foreign and Russian NPPs
Correction coefficients
Calculation of residual life time of pipelines
Recommended methodology for calculation of FAC rate and of residual life time of pipelines for indigenous NPPs
Analysis of control data on the basis of the developed methodology
Conclusion
References
قسمتی از مقاله انگلیسی:
Abstract
Flow-accelerated corrosion (FAC) wear is the complex mechanism of damage of elements of NPP equipment and pipelines. FAC rate is determined by such factors as corrosion of metal, flow hydrodynamics, geometry of equipment elements and pipelines, applied water chemistry regimes (WCR), duration of operation, chemical composition of the metal, thickness of deposited corrosion product film and others. Approaches to the assessment of FAC rate according to the control data are addressed in the present study. Implemented investigation was aimed at the substantiation of the methodology of calculation of FAC rate. Absence of the methodology for calculation of FAC rate does not allow verification of calculation programs, as well as the use of data of regulatory documents on the minimum permissible thicknesses [1] for evaluating the residual lifetime.
Processing of measured data allowed determining the main indexes of FAC process such as the values of wall thinning and thickening, rates of wall thinning and thickening, residual operation time to the moment of reaching the minimum permissible thickness. Reduction of thickness is determined by corrosion of metal and its increase is determined by the formation of deposited film of corrosion products. The process of corrosion products deposition on the internal surfaces of the element proceeds simultaneously with the process of thinning of the wall. Presence of this process results in the situation when the residual lifetime of equipment elements under the conditions of deposition of corrosion products is technically increased. At the same time the real state of the wall under the layer of deposited corrosion products is unknown, as well as the initial wall thickness. In order to bring the calculated results closer to the real situation it is necessary to use substantiated and verified methodology in the calculations of FAC rate according to the data of control measurements. The implemented study allowed suggesting the methodology of calculation of FAC rate taking into account the technological tolerances on the sizes and taking into account the influence of deposits on the initial and minimum thicknesses. Safety factor was also introduced for calculating the residual lifetime which is taken into account in the international practices because of the same reason. Introduction of correction coefficients allows enhancing the conservatism of calculations of residual lifetime characteristics by approximately 2.5 times compared with calculations performed on the base of nominal thickness.
Introduction
Estimation of FAC rate on the base of control data contains significant uncertainties associated with presence of depositions on the inner surfaces of pipeline elements because measurement performed on the wet pipes corresponds to the combined thickness of the wall and the deposits. The problem is also further aggravated by the fact that the data of acceptance control of wall thickness of equipment elements are not available.