【作者】 纪大伟；

【导师】 黄一；

【作者基本信息】 大连理工大学 ， 船舶与海洋结构物设计制造， 2010， 博士

【摘要】 管道运输是现代工业生产中一种重要的运输方式,其运行的安全可靠性已经引起了高度的重视,针对管道外壁腐蚀状况的监、检测技术已经日趋成熟,但目前对于管道内壁腐蚀状态的实时监测尚无法实现。本文依托“中国海洋石油总公司海底管道内腐蚀及磨损监测技术研究”项目,应用传感器结合计算机技术开发了管道内壁腐蚀实时监测系统,并且在实验室的模拟管道中进行了试验研究。本文所开展的主要工作以及结论归纳如下：(1)针对密闭管道腐蚀环境提出了通过管道内流质环境监测评估管道内壁平均腐蚀厚度的监测方法。管道内流质中腐蚀性物质成分的含量是环境介质腐蚀能力的主要因素,通过监测管道内部流质在管道的入口和出口处的腐蚀能力的变化,分析确定监测期内腐蚀性物质成分的消耗量,根据腐蚀反应的当量关系即可估算出管道内壁的平均腐蚀厚度,作为评估管道内壁腐蚀状态的重要依据。(2)应用传感器结合计算机技术研发了管道内壁腐蚀监测系统。针对管道内电解质流质和非电解质流质,设计制作腐蚀电偶式传感器和电阻探针式传感器,并设计制作了DG-OF3型数据采集仪实时监测管道内流质的腐蚀能力；以DG-OF3型腐蚀监测仪、腐蚀传感器为核心硬件,以VB及SQL Server为开发工具,基于TCP／IP的客户机与SQLServer网络数据库技术,开发管道内腐蚀监测系统,实现了在远程客户端实时获得现场采集数据并以图形、数表方式显示管道内壁的腐蚀状态。(3)分别对腐蚀电偶式传感器和电阻探针式传感器进行基础试验研究,通过长期试验,发现传感器监测信息与管内流质的温度、流速以及腐蚀性物质成分的含量之间存在复杂的非线性关系,应用BP神经网络方法,实现了通过传感器监测信息及管内流质的流速、温度等参数评价环境腐蚀能力的功能。(4)建立了基于最大蚀坑深度的管道内壁腐蚀状态评估方法。基于点蚀形貌的统计特征,建立管道内壁腐蚀模型；通过腐蚀模型建立点蚀形貌特征参数与对应总腐蚀体积的数据库,经数学分析后得到最大蚀坑深度与总腐蚀体积之间的非线性关系。基于上述非线性模型,腐蚀监测技术得到的管道内壁总腐蚀体积可以进一步求解得到管道内壁的最大蚀坑深度,对管道内壁腐蚀状态做出更加详细的评估,进而为管道安全评估提供依据。更多还原

【Abstract】 Pipeline transportation occupies a very important position in modern industry, and high attention has been paid to the safety reliability of the pipeline operation. The detection technique and the monitoring technique of external corrosion are maturing, but there is no completed real-time monitoring system for the internal corrosion of pipeline. To ensure the security of pipeline operation, Dalian University of technology and CNOOC applied for the project of monitoring technology of the internal corrosion in submarine pipeline. In this paper, the relevant researches were carried out, and the internal-pipeline real-time monitoring system was developed; moreover a new safety evaluation method of internal-pipeline corrosion was proposed. The major contents and conclusions are surmmarised as follows:(1) An indirect monitoring method was put forward. It is indicated that the corrosion rate is closely related to the corrosion capability of the fluid in the pipeline. Corrosion capability is decided by the content level of the corrosive conponents. There is a corrosion equivalent relationship between the consumption of corrosion capability and the consumption of metal. The internal-pipeline corrosion monitoring system was developed to evaluate the consumption of metal based on monitoring the changes of the corrosion capability of the fluid.(2) Real-time monitoring system, centering on the sensors and corrosion monitoring instrument, is developed by VB and SQL Server 2000. The connection based on TCP/IP between client and the web database server, which has more flexibility and is available for long-distance safeguarding.(3) Galvanic sensor and electric resistance sensor were respectively developed to the electrolyte environment and the non-electrolyte environment, and fundamental researches on the sensors were carried out in the laboratory. Artificial seawater was applied to the test as the corrosion medium, and consequently concentration of dissolved oxygen was the scale of corrosion capability. After long-term testing in a 50-metre-long pipeline and analysis, the effective working period of the sensors were found, and the influence caused by the oxidative film on the electrode working face was eliminated by an amendatory coefficient; a complex and nonlinear relationship, among the monitoring signals and the temperature, velocity and the concentration of dissolved oxygen of the fluid in pipeline, is acquired. Finally, BP artificial neural network is applied to estimate the concentration of dissolved oxygen of the fluid through other factors. In this way, the consumption of the dissolved oxygen can be estimated by the galvanic sensors setting at the entrance and the exit of the pipeline. Furthermore, the corrosion condition of the internal pipeline, which was evaluated by the average corrosion thickness, can be evaluated in the monitoring system.(4) A new safety assessment method by the max pitting depth was put forword. Based on the topography characteristics and optimal distribution of pitting corrosion, a statistical model was established by assuming the diameter and the depth of pitting subordinated to log-normal distribution. Thereby, the total volume consumed by corrosion can be calculated by the model. Quadratic polynomial curve-fit was used to build the non-linear relationship among the total corrosion volume, pitting number, diameter-depth ratio and shape factor and the max pitting depth. Consequently, the max pitting depth can be calculated by the average corrosion thickness, and the internal-pipeline corrosion safety assessment can be given according to SY/T6151.更多还原