| With the increasing consumption of resources in the world, the development of resources is gradually transferred from land to sea and the development of seabed oil-gas resources is of great significance to promote the economic development of our country. Based on grey system theory, this paper mainly studies the uncertain corrosion system of pressure vessel, pressure pipe and carbon steel under the influence of multiple corrosion factors in the marine engineering platform.The basic content of the grey system theory is described. By studying the modeling process of grey theory, it is divided into three main parts: grey generation,struction of background value, definite conditions. On the basis of this, the traditional GM(1,1) modeling theory is analyzed and found that the traditional model has certain theoretical defects in the above three parts.As an important part of the marine oil and gas gathering and transportation, the marine riser is a channel connecting the sea surface and the seabed. Once the corrosion leakage accident occurs, it will cause huge economic losses and serious damage to the natural environment. Focus on the problems that traditional GM(1,1)does not have the data pretreatment and the background value causes the lag error,this paper proposes an improved model of combinating the logarithmic transformation to background value. The improved model was applied to the prediction of corrosion rate of ocean riser and the accuracy test was carried out. The improved model is applied to the prediction of corrosion rate of ocean riser and the accuracy test is carried out. The average relative error is only 1.27%, which is lower than the traditional model error and lower than the improvement of logarithmic transformation or the improvement of background values.In view of the problem that the triphase separator of offshore platform is confronted with serious partial corrosion which has less corrosion data and more corrosion factors. Grey prediction model is established for residual thickness of nozzle, at the entrance of separator, taking the phenomenon of the thickness with the corrosion reduction as grey global parameters. In view of the data are not pre-processed and the new information is not fully utilized in traditional GM(1,1),moving the data and using the latest accumulated value as the setting condition to improve the original prediction model. Analyzing the problems happened in theprocess of improvement at the same time. The effectiveness of the improvement is proved by comparison with the accuracy of other three grey forecasting models.According to the change of corrosion rate of carbon steel in different marine environment, the gray correlation analysis of 5 factors affecting the corrosion rate of3 C steel was carried out, to quantify the relationship between corrosion factors and corrosion rate. According to the calculation results, the effect of oxidation reduction potential and temperature on corrosion rate is greater, followed by salinity, p H,dissolved oxygen content.Grey prediction model is used on corrosion rate of marine riser and the residual life of three phase separator of offshore platform. Grey relational analysis is used to analyze the relationship between corrosion rate and influencing factors of carbon steel in marine environment. All this will help managers to develop a reasonable testing cycle and take appropriate corrosion protection measures to avoid the risk of leakage of corrosion, So as to ensure the safe production of marine engineering platform. |
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