【作者】 王洋；

【导师】 兰惠清；

【作者基本信息】 北京交通大学 ， 载运工具运用工程， 2019， 博士

【摘要】 天然气是一种优质清洁的能源,对改善人民生活、支持国民经济发展、保护环境方面发挥着重要作用。天然气管道运输系统是天然气生产和运用过程中的重要环节,其中城镇天然气管道运输系统与人民的生产生活息息相关。由于聚乙烯管道具有使用寿命长、耐腐蚀能力强、柔韧性好、低摩擦阻力、重量轻、连接方便等特点,广泛使用于城镇天然气管道运输系统中。城镇燃气PE管道多位于人口密集区域,失效后果严重。随着使用时间的增加,部分燃气PE管道已接近设计寿命,因此城镇燃气PE管道老化失效已成为安全问题之一。研究表明,聚乙烯材料的老化寿命受环境因素的影响,且微观性能变化可以反映其老化速率。因此,根据城镇燃气聚乙烯管道的实际工况,研究温度、压力对城镇聚乙烯管道的影响规律,探寻宏观性能研究与微观机理研究的关系,改进已有的聚乙烯管道老化试验平台和计算方法,提出在役城镇燃气PE管道承压热氧老化寿命预测计算模型,为城镇燃气管道安全运行及延寿提供技术支持和安全保障。论文主要从以下方面进行研究:(1)改进燃气聚乙烯管道承压热氧老化试验平台,完成不同温度(353 K,363 K,373 K和383 K)和不同压力(0 MPa,0.1 MPa,0.2 MPa,0.3 MPa和0.4 MPa)下燃气聚乙烯管道承压热氧老化试验,得到承压老化聚乙烯管道。(2)利用拉伸测试方法,测量承压老化聚乙烯管道的最大拉力,分析不同老化时间、环境温度和压力对燃气聚乙烯管道最大拉力的影响。根据试验数据,分析了最大拉力在阿伦尼乌斯公式中的适用性,根据阿伦尼乌斯公式计算在不同压力下聚乙烯管道的老化速率,分析了最大拉力与老化速率间的影响关系,建立了基于拉伸测试的燃气聚乙烯管道承压热氧老化寿命预测模型,但此方法不适合在役检测。(3)对老化聚乙烯管道的内壁,中层和外壁三层分别使用DSC测量承压老化聚乙烯管道的氧化诱导期测试,分析管道壁厚对氧化诱导期的影响和不同老化时间,环境温度和压力对燃气聚乙烯管道的氧化诱导期的影响。根据试验数据,分析了进行差示热量扫描法测试采样点的合理选取位置及氧化诱导期在阿伦尼乌斯公式中的适用性,根据阿伦尼乌斯公式计算在不同压力下的聚乙烯管道的老化速率,分析了氧化诱导期与老化速率间的影响关系,建立了基于DSC测试的燃气聚乙烯管道承压热氧老化寿命预测模型。此方法适用于在役检测,但仍基于单一温度因素的计算,缺乏基于压力和温度因素的计算方法。(4)对不同温度和压力下承压热氧老化聚乙烯管道进行熔体流动速率测试,分析不同老化时间,环境温度和压力对燃气聚乙烯管道密度的影响。并基于分子动力学模拟的方法,对聚乙烯管道的微观分子模型进行不同温度(313 K,323 K,333 K,343 K,353 K,363 K,373 K和383 K)和不同压力(0MPa,0.1 MPa,0.2 MPa,0.3 MPa和0.4 MPa)下承压热氧老化仿真,分析不同老化时间,环境温度和压力对聚乙烯管道密度的影响,探寻微观性能变化与宏观性能变化之间的关系,为建立符合工况条件下的微观老化聚乙烯管道的寿命预测奠定基础。(5)研究压力对于老化燃气聚乙烯管道寿命的影响。完成不同温度(318K,328 K,338 K和348 K)和不同压力(0 MPa,0.1MPa,0.2 MPa,0.3 MPa和0.4 MPa)下燃气聚乙烯管道承压热氧老化试验,得到相应的承压老化聚乙烯管道。然后分别进行拉伸测试、差示热量扫描法测试和熔体流动速率测试,分析最大拉力、氧化诱导期和熔体流动速率的比例变化关系,提出采用氧化诱导期进行寿命预测的合理性。根据测试结果,建立含有压力因素的燃气PE管道寿命预测模型,提出承压下城镇燃气PE管道的剩余寿命预测方法。此方法是基于压力和温度因素的计算方法,可作为城镇燃气PE管道的剩余寿命预测方法。(6)研究一种对在役城镇燃气PE管道寿命评估方法。依据某在役燃气PE管道的使用情况,运用承压下城镇燃气PE管道剩余寿命预测方法进行工程验证,提出一种不会影响天然气PE管道正常运行的寿命检测方法。这种方法不仅适用于燃气PE管道,对于其他相似工况的塑料管道也适用。更多还原

【Abstract】 Natural gas is a kind of high-quality and clean energy,which plays an important role in improving people’s life,supporting national economic development and protecting the environment.Natural gas pipeline transportation system is an essential link between the process of natural gas production and application,among which urban natural gas pipeline transportation system is closely related to social production and people’s life.Polyethylene(PE)pipes have the advantages of low density,corrosion resistance,long service life,high impact resistance,superior flexibility and convenient connection,therefore,have been widely used in urban gas engineering.There are a large population living nearby urban gas PE pipes,so the failure of PE pipes would cause serious loss of life and property.With the increase of service life,life of some PE pipes is close to design life,therefore the aging of PE pipes has become a safety issue that needs to be solved.The results show that the aging lives of PE are affected by environmental factors and aging rate can be reflected by the change of its microscopic properties.Therefore,under the actual working conditions of urban gas PE pipes,effects of temperatures and pressures on urban PE pipes are focused on to research in the dissertation,the relationship between the macro performance and the microscopic mechanism is explored,the existing PE pipes ageing test platform and calculation methods are improved,and in-service lifetime prediction model is put forward,which can provide technical support and security for urban gas pipeline safety operation and prolong life.The paper mainly studies in the following aspects:(1)Thermal oxygen aging(TOA)test platform of pressured gas PE pipes was improved and tested under different temperatures(353 K,363 K,373 K and 383 K)and different pressures(0 MPa,0.1 MPa,0.2 MPa,0.3 MPa and 0.4 MPa)by this platform.Therefore,aging PE pipes were obtained.(2)The maximum tensile force(TF)of the aging pressure PE pipes was measured by tensile test.Temperature and pressure effects on TF of the aging PE pipes were discussed under different aging times.According to test data,the maximum tensile force was shown to be calculated by Arrhenius equation.Aging rate of the PE pipes was calculated by Arrhenius equation to analyze the relationship between the TF and aging rate.Pressured thermal oxygen aging lifetime prediction model was built by tensile test.But this method is not suitable for in-service inspection.(3)Oxidative induction time(OIT)of the aging PE pipes was measured by Differential Scanning Calorimeter(DSC).According to the test data,OIT from inner,middle,and external for the aging PE pipes was tested to analyze effects of test site for the aging PE pipes.Temperature and pressure effects on OIT of the aging PE pipes were discussed under different aging times.According to test data,OIT was shown to be calculated by Arrhenius equation.Aging rate of the PE pipes was calculated by Arrhenius equation to analyze the relationship between the OIT and aging rate.Pressured thermal oxygen aging lifetime prediction model was built by DSC.This method is suitable for in-service inspection,but it is based on the calculation of single temperature factor,and the calculation method based on pressure and temperature factor is still lacking.(4)The aging pressured PE pipes were tested by melt flow rate(MFR).According to the test data,temperature and pressure effects on MFR of the aging PE pipe were discussed under different aging times.The density of the aging PE pipes was analyzed under different aging times,temperatures and pressures.Moreover,based on the molecular dynamics simulation method,microscopic molecular model of PE pipes was built to simulate pressured TOA process under different temperatures(313 K,323 K,333 K,343 K,353 K,363 K,373 K and 383 K)and different pressures(0 MPa,0.1 MPa,0.2 MPa,0.3 MPa and 0.4 MPa).The simulation results were analyzed effects of temperatures and pressures for the density of the aging PE pipes and explored the relationship between micro and macro performance to establish relationship macro and micro lifetime prediction.(5)Pressure effects on in-service lifetime of aging gas PE pipes under different temperatures(318 K,328 K,338 K and 348 K)and different pressures(0 MPa,0.1 MPa,0.2 MPa,0.3 MPa and 0.4 MPa)by pressured TOA test platform were researched.Aging PE pipes were tested by tensile test,DSC and MFR to analyzed relationship among TF,OIT and MFR.The results showed that OIT of test data was fit for the residual lifetime prediction for urban gas PE pipes.Therefore,a residual lifetime prediction method contained pressure was proposed.Based on the pressure and temperature factors,this method is used to predict the residual life of urban gas PE pipes.(6)A method for evaluating in-service lifetime of urban gas PE pipes was studied.According to the usage of in-service gas PE pipes,the residual lifetime predicting method was used to carry out engineering verification.A residual lifetime predicting method under actual urban gas working condition was proposed for in-service gas PE pipes.This method is applicable not only to gas PE pipe,but also to other plastics pipes under the similar conditions.更多还原