管线探测中不可忽视的问题--电流方向

根据作者实际工作经验 ,分别从并行管线中不同电流方向的异常特征、产生背景及探测结果的修正作了一些介绍 ,并且进一步对并行管线中同向电流和反向电流的相互干扰结果作出了阐述。列举了实际工作中造成并行管线中产生同向或反向电流的一些工作方法 ,引用实例加以说明并行管线中同向或反向电流在实际工作中的特征、探测结果及应用计算机进行反演计算后的效果     

Modeling of Shallowly Embedded Offshore Pipelines in Calcareous Sand

The results of centrifuge modeling of pipe–soil interaction for shallowly embedded offshore pipelines are presented. A non-associated bounding surface model is constructed in vertical–horizontal (V–H) load space on the basis of test data and the theory of plasticity to simulate the response of a pipeline embedded in sandy soil under combined (vertical and horizontal) monotonic loading, taking into account possible pre-loading effects. The model needs nine parameters that can be back calculated from model or field tests and in some cases estimated theoretically. It provides a suitable basis for modeling the load-displacement response of shallowly embedded offshore pipelines. The model reproduces the key features of the load-displacement response of pipelines observed in centrifuge model tests. In particular, the adoption of bounding surface plasticity allows a gradual transition from elastic to plastic response to be simulated and the introduction of a non-associated flow rule allows the model to predict the strain-softening behavior of pipes under horizontal loading. The lateral breakout resistance predicted by the model agrees very well with experimental data.     

焦炉炉床板内高精度预埋管安装新工艺

简述了在新钢公司4号焦炉底板埋管的施工中，采用预埋管安装新工艺，达到操作简便，成本低，本效性的效果。     

Failures of 108‐Inch Steel Pipe Water Main

The paper describes the analysis of failures of a 108‐in. (2.74 m) diameter steel pipe water main. Total pipe separations occurred because of large unrelieved thermal stresses and stress amplification caused by the eccentricity of the welded bell‐and‐spigot joints. The pipeline designer ignored these aspects in his design, thus grossly underestimating the stresses in the pipe. This could easily have been recognized by performing an elementary longhand calculation. The failure analysis described in this paper demonstrates that the asdesigned pipeline was incapable of safely withstanding even the incorrectly defined design conditions. The designer attributed the failures to low toughness of the bell steel. Conversions of Charpy impact test data and J‐integral analysis of compact tension test data are used to demonstrate that the steel had normal fracture toughness. Nonlinear finite element stress analysis and elasticplastic fracture mechanics demonstrate that for the measured range of fracture toughness the failures were inevitable.     

Integral buckle arrestors for offshore pipelines: Enhanced design criteria

Integral buckle arrestors are relatively thick wall rings periodically welded in an offshore pipeline at intervals of several hundred meters in order to safeguard the line in case a propagating buckle initiates. They provide additional circumferential rigidity and thus impede downstream propagation of collapse, limiting the damage to the length of pipe separating the two arrestors. The effectiveness of such devices was studied parametrically through experiments and numerical simulations in Park and Kyriakides [On the design of integral buckle arrestors for offshore pipelines. International Journal of Mechanical Sciences 1997;39(6):643–69]. The experiments involved quasi-static propagation of collapse towards an arrestor, engagement of the arrestor, temporary arrest, and the eventual crossing of collapse to the downstream pipe at a higher pressure. The same processes were simulated with finite element models that included finite deformation plasticity and contact. The experimental crossover pressures enriched with numerically generated values were used to develop an empirical design formula for the arresting efficiency of such devices. A recent experimental extension of this work revealed that for some combinations of arrestor and pipe yield stresses, the design formula was overly conservative. Motivated by this finding, a new broader parametric study of the problem was undertaken, which demonstrated that the difference between the pipe and the arrestor yield stress affects significantly the arrestor performance. The original arrestor design formula was then modified to include the new experimental and numerical results producing an expression with a much wider applicability.     

能量平衡结合有限元数值计算分析天然气管道裂纹稳定扩展问题

本文提出了在天然气管道裂纹稳定扩展问题中，应用能量平衡方法结合有限元数值计算结果来分析计算裂纹驱动力。能量数值计算采用了可模拟动裂纹在管道上扩展的有限元程序ＰＦＲＡＣ，它包括了对未开裂管道和裂纹扩展管道的能量计算。通过分析外力作功和内部能量在裂纹扩展时的变化率，应用能量平衡方法计算了裂纹驱动力，并与在ＰＦＲＡＣ程序中应用节点力释放方法计算的裂纹驱动力的结果进行了比较     

Effectiveness of evacuating combustible gases by two parallel expellers closely coupled at one end of a gas pipeline

Expeller performance has been formulated in terms of its capability to create suction pressure at the throat. This formulation has been used to assess the effectiveness of evacuating combustible gases from a pipeline section from one end using dual expellers mounted in parallel on two adjacent blow-down stacks. A general formulation was derived to address any situation of asymmetry in the stack resistance, asymmetry in the expellers' power as well overall pipeline resistance to suction flow. Solutions of the closed-form equations were obtained and presented on performance graphs showing the ratio of the suction flow using dual expellers to that using either one in a single mode. It was found that there are conditions at which expelling with dual expellers exceed that of either expeller operating alone. It was also shown that when asymmetric expellers are used, where one expeller is more powerful than the other, the benefits of using two expellers is realized up to a limiting degree of asymmetry, beyond which the weaker expeller could be stalled and then reverse flow.     

核电管系的焊接自动化研究

核电再热管及辅助管系为公司重要生产部件,焊接量大,形状复杂,现多采用手工氩弧焊打底、半自动气保焊填充方法焊接,生产效率低、焊接质量不高。文章通过对产品结构分析,提出各自适合于再热管及辅助管系适合的自动焊方法,逐步实施,效果显著。     

油气管道施工焊接质量管理措施

准确描述油气管道的定义。根据已有的多年施工管理及焊接质量控制经验,结合国内油气管道焊接施工主要特点,有针对性地提出了"人员、焊材及保护气体、焊接及相关设备、焊接工艺评定、焊接工艺规程、焊接过程控制、补焊及返修"等一系列焊接质量管理措施。对油气管道焊接施工及油气管道安装质量保证体系的建立和运行具有实际参考价值和指导意义。     

阴极保护试片在土壤环境中的腐蚀失效分析

目的 针对埋地管道阴极保护测试用试片的失效问题进行原因分析,阐明了管道阴极保护测试用试片的失效现象及原因,为准确检测试片的阴极保护电位提供指导。方法 以野外埋地管道相连接的试片为研究对象,采用数据记录仪采集试片的阴极保护参数,利用采集失效试片的通断电电位、交直流电流密度,干扰电压及试片表面腐蚀产物等来综合分析试片失效原因。结果 试片表面宏观分析发现,试片表面腐蚀产物聚集,腐蚀产物和土壤夹杂在一起,形成坚硬的硬块,除去表面腐蚀产物后,试片表面有大小不均的腐蚀坑,最大坑深1 mm。试片表面腐蚀产物的元素面分析结果表明,锈层中的主要元素以Fe和O以元素为主,腐蚀产物以铁的氧化物为主,并夹杂有土壤杂质及钙镁难容盐等。试片历史数据显示,阴极保护电位满足规范要求,但交流电流密度较大,最大交流电流密度208.3 A/m²,最大交流干扰电压7.52 V。结合试片表面形貌,试片发生了交流腐蚀。结论 阴极保护测试用试片的失效与交流腐蚀有关,试片在交流杂散电流和阴极保护电流的作用下,表面腐蚀产物聚集,难容盐与铁的氧化物形成厚厚的隔离层,隔离了试片与土壤介质,造成阴极保护电流流入困难,无法准确测量阴极保护电位。