聚乙烯及其复合管道安全检测与评价方法

聚乙烯及其复合管道广泛应用于油气输送、城市燃气等能源领域,其安全性至关重要。焊接接头的安全检测及评价是聚乙烯及其复合管道系统安全的关键技术。介绍了聚乙烯管道焊接接头的无损检测原理及方法、冷焊检测技术以及缺陷分类与失效模式三方面内容。对电熔和热熔焊接接头分别采用超声相控阵和耦合聚焦技术进行超声检测,并给出了缺陷剖切与检测结果的对比图。提出了物理概念清晰、工程应用方便的冷焊超声检测方法。将电熔接头中的缺陷分为熔合面缺陷、孔洞、结构畸变和过焊。分别对含不同类型和大小缺陷的电熔接头进行力学性能测试,发现电熔接头存在三种典型的失效模式,即沿电熔套筒壁贯穿裂纹失效、熔合面失效以及沿电阻丝所在平面贯穿裂纹失效。根据试验测试与理论分析结果,提出了相应的安全评定方法。所提出的方法,填补了国内外在聚乙烯管道安全检测与评价方法方面的技术空白,提高了燃气管道的本质安全性。     

聚乙烯管道电熔焊接超声相控阵检测技术研究

电熔焊接是聚乙烯管道的主要连接方式之一,由于聚乙烯材料声波衰减系数较大,电熔焊接接头内部金属丝对检测干扰较大,利用常规超声检测手段很难有效检出聚乙烯电熔接头内的各类缺陷。制作了聚乙烯管道电熔焊接接头内部典型缺陷,使用超声相控阵检测技术对其进行了可靠性试验测试。结果表明,提出的超声相控阵检测技术能可靠地检测出聚乙烯电熔焊接头内的典型缺陷。     

聚乙烯燃气管道热熔接头主要缺陷及无损检测技术研究进展

本文将常见的聚乙烯燃气管道热熔接头缺陷形式分为未熔合、孔洞、工艺缺陷三类。同时,详细介绍了近年来聚乙烯燃气管热熔接头的超声相控阵检测、红外热成像检测、超声波耦合聚焦检测、微波扫描法检测、X射线检测等无损检测技术的研究进展。     

聚乙烯电熔焊接新方法及工艺优化研究

在电熔接头相控阵检测中首次发现接头内部存在一条由超声信号组成的特征线,进一步研究表明,可以根据特征线移动速度以及特征线与电阻丝的距离变化情况,估评聚乙烯（PE）电熔接头的焊接工艺是否合适。在PE电熔接头新产品开发中采用超声检测实时录像,通过特征线的移动情况对焊接工艺参数进行优化,从而可大幅降低电熔接头的开发时间和成本。     

聚乙烯(PE)燃气管焊接及焊工培训考核探讨

简述了聚乙烯管道在燃气管道工程中相对传统金属管道的优势,重点分析了聚乙烯管的热熔焊接和电熔焊接之间的异同及应用情况。分析表明:在燃气管道工程中采用热熔和电熔焊接两种方法相结合的方式比较合理。文章最后对聚乙烯管的焊接培训考核提出了相关建议。     

聚乙烯管道电熔焊焊接缺陷及焊接质量影响因素分析

分析了聚乙烯管道电熔焊的缺陷类型和影响电熔焊质量的因素,提出了控制聚乙烯管道电熔焊质量的措施。     

聚乙烯及其复合管电熔接头的失效模式与爆破压力研究

通过Abaqus有限元分析软件,建立聚乙烯（PE）及其复合管电熔接头受内压和轴向力作用下的有限元模型,分析电熔接头的应力分布规律,研究管材种类、强度对电熔接头的失效模式与爆破压力的影响规律,结合电熔接头短时爆破实验验证模型的有效性。结果表明,PE管电熔接头的失效模式是管材韧性破坏;增强热塑性复合管（RTP）电熔接头的失效模式和爆破压力受管材强度影响,随强度增加,失效模式由管材破坏转变为电熔套筒破坏,爆破压力随RTP管材强度增加先升高,随后趋于稳定。     

聚乙烯管道热熔焊接技术研究进展

简述了聚乙烯（PE）管道热熔焊接接头的影响因素,对国内外热熔接头可靠性测试方法的研究进展进行了综述。总结了焊接参数对接头质量的影响规律,并分析了接头的失效机理。焊接参数的改变能显著影响热熔接头的性能,选择最优焊接参数能提高接头乃至整个管道系统的可靠性。分别从力学性能、有限元模拟和无损检测3个方面总结了热熔接头相关研究,期待未来建立一种全面的热熔焊接接头力学性能评价标准,能减少实验时间、降低测试成本。随着材料的创新和科技手段的发展,未来有限元模拟和无损检测技术有望代替力学实验,成为热熔接头可靠性检测的主要方法。     

聚乙烯管材热熔对接接头抵抗慢速裂纹扩展性能评价

采用应变硬化试验(SH)对不同焊接工艺下的聚乙烯管材热熔对接接头抵抗慢速裂纹扩展（SCG）性能进行评价。通过建立焊接温度梯度（190~250 ℃）、焊接压力梯度（0.6~1.4 MPa）和吸热时间梯度（40~140 s）试验,分析在不同焊接工艺参数条件下,不同聚乙烯管材热熔对接接头耐SCG性能的变化规律,探索冷焊及过焊2种典型缺陷对管材接头耐SCG性能的影响。结果表明,焊接温度、焊接压力和吸热时间都是影响管材热熔对接接头耐SCG性能的重要工艺参数,试验测得PE100, d_n110, SDR11型管材的最佳焊接参数为焊接温度230 ℃,焊接压力1 MPa及吸热时间100 s,当焊接参数选取过高或过低时,会造成管材接头出现过焊或冷焊缺陷,降低管材接头的耐SCG性能。     

燃气用聚乙烯管道热熔焊接工艺研究现状

介绍了各研究院在燃气用聚乙烯管道热熔焊接工艺优劣判别方面发展的新动向。聚乙烯管道在燃气管道等市政工程中的大量运用,迫切要求聚乙烯管道焊接工艺出台一套焊接工艺操作标准和评价体系。根据热熔焊接过程中的温度变化和压力变化来控制焊接接头的耐冲击性能、拉伸屈服强度以及避免焊接物理缺陷是一个值得研究和考虑的方向。     

PE100管及其热熔接头的蠕变裂纹扩展行为

聚乙烯(PE)管性能优异,广泛应用于城市水及燃气供应系统。PE管的主要破坏形式是长期静压载荷下的慢速裂纹扩展失效。在蠕变条件下,采用光滑试样和裂纹圆棒试样对PE100管及其热熔接头进行了测试,得到了基于蠕变断裂参数C*的蠕变裂纹扩展动力学关系式。利用扫描电子显微镜(SEM)分析了裂纹圆棒试样的断面形貌,对比分析结果发现,蠕变裂纹扩展失效模式对应的最大应力为15.05 MPa,热熔接头熔合面分布有约11个/mm^2、直径范围为1~5μm的微气孔,热熔接头断裂微纤平均长度比母材约小20%~45%。当热熔对接时,熔合面存在的微气孔以及系带分子的浅渗透是导致PE100热熔接头蠕变裂纹扩展抗力降低的主要原因。     

Evaluation of polybutene electrofusion joint performance

This paper describes methods of evaluating polybutene electrofusion joints and results of mechanical strength measurements for an electrofusion joint. Suitable fusion conditions were determined qualitatively through measurement of fusion interface temperatures and observation of the fusion zone. A method of determining standard fusion conditions, based on the relation between heating time and tensile strength, is also indicated. Differences in thermal properties between polybutene and polyethylene resins are discussed. It was found that polybutene required less supplied power per unit fusion area for suitable fusion. It was also confirmed that an electrofusion joint required a cold zone.     

Digital image analysis of coating defects

A simple, low cost, easy to use computer-based Digital Image system has been developed for characterizing defects which occur in various types of organic films. The system uses an optical microscope, high resolution TV camera, frame grabber to display the image on Macintosh computer and software to analyze and characterize the image. All components are commercially available. Using this system, many different defects which are typically seen in organic coatings and the support on to which they are coated, such as spots, bubbles, reticulation streaks and pinholes can be rapidly characterized. Quantitative information about the defect, such as size and frequency can be rapidly obtained to assist in determining the cause. Images obtained of the defects can also be enhanced to obtain characterization information not easily seen in the defect. The system has applications in the R and D laboratory for understanding defect mechanisms, in trouble-shooting plant and end-use problems and in the control laboratory. It can also be used to provide routine quantitative testing information on defects that have been typically evaluated by subjective tests and comparison with go/no-go standards. The system is easier to use than viewing with a glass or conventional microscope and a permanent record of the defects can easily be stored and retrieved in a computer database to assist in troubleshooting.     

基于GPRS的油田抽油机远程在线监控系统的设计与实现

针对油田抽油机的监测仍采取传统人工方式,设计了基于GPRS的油田抽油机远程在线监控系统.系统采用高精度专用传感器实时采集抽油机运行的各种数据,然后将采样数据送入智能监测仪,并通过基于GPRS的通信模块将监测数据上传到监测中心的大型数据库中,以实现数据的共享.对该系统的硬件结构和软件设计均做了介绍.该系统可及时发现、消除由于抽油机故障引发的油田作业缺陷,确保油田安全作业.     

The joining of biaxially oriented polyethylene pipes

Die-drawing techniques recently developed at Leeds University make it possible to produce oriented polymer tubes with both axial draw and hoopwise expansion. These products have increased axial stiffness, improved barrier properties, and excellent resistance to chemical reagents. Normally mechanical methods are used to join such tubes in order to preserve their orientation: however we show that electrofusion techniques produce joints of strengths such that in tensile tests, failure always occurs in the fittings, not at the joint interfaces. Optical and electron microscopy reveal different zones in the welds and indicate that only 20 percent of the wall thickness is affected by the electrofusion process. The pipe studied was biaxially drawn medium density polyethylene of outside diameter 63 mm with draw ratios of 4 in the axial direction and 2, inner hoop. Optimum welding conditions were determined using socket and saddle electrofusion fittings. The joints did not fail in a standard crush test. Careful control of welding parameters is essential in butt fusion welding when the maximum weld strength exceeds that of the undrawn polymer.     

聚乙烯电熔接头管材熔融区深度与焊接性能关系研究

在聚乙烯管道电熔焊接过程中,形成接头强度主要取决于套筒和管材界面聚乙烯高分子链的扩散缠结阶段经历的时间,该时间与熔焊区扩展到管材内部的熔融区深度存在一定的对应关系。为探索聚乙烯电熔接头管材熔融区深度与接头焊接性能的关系,提出了一种管材熔融区深度的超声测量方法,开展了管材熔融区深度测量和焊接性能试验。结果表明,管材熔融区深度与界面焊接强度有明确的关联,管材熔融区深度在一定范围内时,就能保证基本的剥离强度值和界面韧性;在此基础上提出一种以管材熔融区深度确定电熔接头焊接时间的新方法,该方法充分考虑到环境温度、焊接电压、电阻丝电阻等各种偏差,更能适应实际工程。     

Fusion simulation of electrofusion polyethylene joints for gas distribution

Fusion simulation is one of the key techniques used in designing and producing electrofusion joints for gas distribution and in evaluating fusion joint integrity. This paper describes the results of numerical simulation of the thermal fusion process, using the finite element method. A nonlinear heat transfer computer program was used to obtain the temperature profile of an electrofusion joint at fusion. It was found that the temperature experimentally measured at the fusion interface by insertion of a thermocouple agreed with the temperature computed by fusion simulation. In addition, as both the temperature at the fusion interface and the resin temperature close to the wire corresponding to the mechanical strength of the fusion part were measured, it was confirmed that the proper heating conditions for each joint could be determined based on the results of the fusion simulation.     

A review of the electrofusion joining process for polyethylene pipe systems

Electrofusion joining is now an essential and widely used method to assist in the creation of polyethylene pressure pipe systems. The process of electrofusion joining is reviewed by examining the experimental and some computer simulation literature relating to the temperature and melt pressure changes during the fusion process, and on how varying fusion time and pipe/fitting gap influences the strength of electrofusion joints. From this literature review, four key stages in the joining process are identified. First, an incubation period where the joint has no strength. Second, a joint formation and consolidation stage where an increasing joint temperature aids molecular diffusion to both increase the joint strength and promote a more ductile mode of failure. A plateau region then follows where the joint strength, and ductility, remain reasonably constant despite the fusion time increasing. This plateau is thought to allow some welding variables, such as gap, to have only a small influence on joint strength (for gap maintained within reasonable limits). Finally there is a cooling stage where the joint bridging “tie molecules” become locked into either side of the joint. It is these tie molecules that give the joint its ductility and strength. The concluding section of the review notes some of the important on-site practices that, if followed, allow electrofusion joints to acquire their good strength properties, and hence give polyethylene pressure pipe systems of a high integrity.