考虑腐蚀储罐底圈壁板的时变可靠度分析

Time-variant reliability analysis of tank bottom shell considering corrosion

关键词:  腐蚀  储罐  可靠性  灰色理论  广义随机空间

Key words:  corrosion  storage tank  reliability  grey theory  generalized random space

摘要:

准确掌握在役储罐的健康状况可以为储罐维修维护提供决策支持。通过分析储罐底圈壁板强度失效的影响因素,建立底圈罐壁结构抗力的衰减模型;根据灰色理论建立非等间距GM(1,1)的底圈罐壁腐蚀速率预测模型,采用储罐历年的检测数据对底圈壁板的腐蚀速率进行预测,并对预测的精度进行检验;通过对实测数据的统计分析得到底圈壁板腐蚀深度及罐内液体载荷的分布特征,根据可靠性理论建立底圈壁板的时变可靠性模型,并利用广义随机空间内改进的一次二阶矩法求解可靠性指标。结果表明:底圈壁板的腐蚀深度和罐内油、水的高度符合正态分布;预测模型的拟合精度较高;储罐在服役22　a后其失效概率超过10-3,应对底圈罐壁进行适当的维修与维护。

Abstract:

The grasping of accurate knowledge of the health status of storage tanks in service can provide decision support for their maintenances. Various factors impacting the strength failure of the bottom shell were analyzed, and the degradation model of structural resistance of the bottom shell was established. Then, a corrosion rate prediction model based on non-equidistance grey model GM (1,1) was proposed according to the grey theory, and its prediction precision was validated by using the past inspection data. Finally, the distribution types of corrosion depth and liquid load were acquired based on the analysis of the measured data. And a time-variant reliability model for the bottom shell was established according to the structural reliability theory, where the reliability indices were solved via modified first-order second-moment method in generalized random space. The results show that, the corrosion depth of the bottom shell and the height of oil, water in tank fit the normal distribution. Fitting accuracy of the prediction model is high. The failure probability of storage tank is more than 10-3 after serving 22 years, and the appropriate repair and maintenance measures can be taken for the bottom shell.