This paper reports on the results obtained on the diagnostics of a steam pipeline of a thermal power plant; it analyzes the effect of thermal fatigue on the structure and properties of the 12Kh1MF steel and possible reasons for the emergency destruction of steam pipeline elements before the exhaustion of economic life. Ultrasonic testing and additional heat treatment are proposed to be used for the detection and elimination of structural inhomogeneity in the metal. The applicability of statistical technique to analyzing data on the loading history of a steam pipeline is studied, which enables us to evaluate the damaging effects of loading cycles and to develop a plan of preventive measures, as well as to increase the accuracy of predicting the residual life of steam pipeline elements.

Keywords: metallic structure, diagnostics, degradation, steam pipeline, thermal fatigue, microstructure, mechanical properties, residual life

The paper studies the applicability ofthe coercive force (Нс) as a parameter for measuringthe wall thickness ofpipelines,vessels,andother metallic structuresthroughnonmagnetic insulationduring material degradation undercorrosion conditions. A procedure is developedfor remote inspectionof metallic structures atsites of maximum corrosion rateby the coercimetricmethod,withoutbreaking the insulationandstopping the operation ofthe object being tested.The effects of metal thickness, the size ofthe poles of the magnetizer, andthe thickness of non-ferromagneticinsulationon the absoluteand relativevalues of the coercive force are comparatively analyzed. The application of theproposed relative value methodis shown to be able to decrease significantlythe effectof steel composition and structureonthe metal thickness dependence of Нс. The results of measuring the coercive force of differently thick 09G2S steel specimens through non magnetic insulation are presented, as well as the behavior of the relative values of the coercive forceas dependent onmetal and insulation thickness.Foridentical metal thicknesses, the absolute values of the coercive force of different steels may differby a factor of 10 ormore, whereasthe difference in the relative values of Нс with equally decreasing metal thickness does not exceed 15%. The developedtechnique isinsensitivetothe misalignment of the outer and innermetal surfaces,and itenablesthe thickness oflow-alloysteels like 09G2Sto be measured witha relative error of 10%.

Keywords: metallic structure, diagnostics, degradation, corrosion, coercive force, thickness measurement, nonmagnetic insulation

The methods of the diagnostics and oil-and-gas installations state analysis reliability increasing based on usage of the parametric methods of statistics are discussed in this paper. The variance analysis of the mechanical properties of the pump rods made of normalized steel is given in this paper (according to the data of the manufacturing plant for the period of 10 years). It is found that breaking point and yield stress are distributed with the truncated normal laws in the region of minimum values. The obtained average values and variation coefficients of the mechanical properties within the steel grade permit to calculate the statistically significant changes of the mechanical characteristics. The correlations between Vickers hardness and breaking point (Vickers hardness and yield stress) in the case of steels produced in the Russian Federation for the pressure-operated vessels are also presented in this paper. These correlations permit to determine the strength characteristics with the relative error of 12% according to the hardness value. In the case of transferring the obtained correlations on the steels produced in Japan the systematic underestimation of the yield stress is 0,85 fold with respect to the value given in the certificate. The factors that influence on the microanalysis sensitivity and accuracy are revealed, the optimal scanning electron microscope mode and research conditions for the chosen patterns are also determined. Evaluation of the systematic inaccuracy of determining the carbon content in the steel is obtained in this paper. It is found that the measurement error for the scan area from 3 x 3 to 20 x 20 mm and accelerating voltage from 10 to 15 kv is minimal. The usage of the obtained results permits to increase the validity of the findings in the diagnosed installations condition evaluation and determining the conditions of their further exploitation.

Keywords: diagnostics, oil field equipment, parametric statistics, variance analysis, precision of measurements, mechanical properties, microanalysis