腐蚀和残余应力对油气管道不规则区可靠性的影响分析

Corrosion and Residual Stress on Reliability of Irregular Area of Pipeline

目的针对油气管道的运行安全问题,建立油气管道局部腐蚀模型,对管道不规则区域的可靠性进行准确分析。方法首先,对管网中不同的不规则区域管道的腐蚀进行简单分析,每个区域都有局部腐蚀缺陷,任何区域的破坏都会导致整个管网的破坏。其次,定义各区域的有限元模型,考虑文献中给出的局部腐蚀模型和常用应力模型。再次,利用概率分析方法给出真实的腐蚀参数和时间模型,并采用蒙特卡洛模拟算法进行求解,得出不同腐蚀速率下管道的不规则区域的失效概率。最后,以三种不同腐蚀速率的数值算例分析各种因素对腐蚀管道可靠性的影响。结果受腐蚀和残余应力的影响,不规则区域的可靠性明显大于规则区域。考虑不同区域的残余应力,破坏概率随残余应力的增加而增加,特别是高腐蚀速率时,失效概率增加,而低腐蚀速率时,这种敏感性降低。法兰的可靠性更受有无残余应力腐蚀的影响。常规区(基)的可靠性最好。结论管道不规则区域对腐蚀和残余应力的响应机制不同于规则区域,所提出的方法相比于传统方法,能够更有效地评价不规则区域的可靠性。

The work aims to establish a local corrosion model for oil and gas pipelines to solve the problem of operation safety and analyze the reliability of irregular areas.The pipeline corrosion in different irregular areas was firstly analyzed.Each area had local corrosion defects,and the failure of any area would lead to the failure of the whole pipeline network.Secondly,the finite element model of each region was defined.The local corrosion model and stress model given in the literatures were considered.Finally,the real corrosion parameters and time models were given by probability analysis,and the actual life of each area was obtained.Finally,three numerical examples with different corrosion rates were given to illustrate the influence of various factors on the reliability of corroded pipelines.Due to the influence of corrosion and residual stress,the reliability of irregular region was significantly greater than that of regular region.Considering the residual stress in different regions,the failure probability increased with the increase of residual stress,especially at high corrosion rate,the failure probability increased;while at low corrosion rate,the sensitivity decreased.The reliability of flange was more affected by whether there was residual stress corrosion.The conventional zone(base)had the best reliability.The response mechanism of irregular area to corrosion and residual stress is different from that of regular area.Compared with traditional method,the method proposed in this paper can evaluate the reliability of irregular area more effectively.