液化气脱硫装置再生塔返塔管线弯头腐蚀失效机制分析

弯头在管路系统中主要起到改变介质流动方向的作用,是油气输送中最常用的管道部件之一。重点研究了液化气脱硫装置再生塔返塔管线弯头的腐蚀失效机制。从宏观和微观两个角度入手,研究了失效弯头部位的腐蚀孔孔径分布、减薄规律,进而利用X射线衍射(XRD)和扫描电镜-能谱仪(SEM-EDS)对样品进行了系统的理化分析。结果表明:沿流体流动方向,腐蚀逐渐加剧,在弯头的中部和出口形成完全破坏区;流体冲刷会破坏电化学腐蚀形成的产物保护膜,减弱产物膜对基体的保护作用,导致内壁不断被腐蚀,这是弯头腐蚀失效的主要原因。此外,热稳定性盐(HSS)的存在也加剧了弯头的腐蚀。

热高分油管线弯头开裂的失效分析

热高分油管线中的不锈钢弯头在停车检修中大量开裂 ,经检查 :外壁发生含有微量Cl-离子的高温水蒸汽引发的奥氏体沿晶型的应力腐蚀破裂 ,裂纹较浅 ,呈网格状 ;内壁发生连多硫酸引发的应力腐蚀破裂 ,穿透管壁的裂纹都是起源于内壁 。

确定地下金属管线弯头位置和埋深的实用技术

地下管线普查对于城市的规划、建设、管理等具有重大意义。在用电磁类地球物理方法探查热力、自来水等硬管类金属管线实际工作中,在管线弯头处会出现定位和定深不准确的问题。以实际工作为例,探索性地提出可以利用交汇法确定此类管线弯头处的平面位置,使用平均值法确定管线的埋深,从而解决管线弯头处定位、定深不准确的问题。实际应用检验证实该方法能快速、高效、准确地确定地下硬管类金属管线弯头位置和埋深,提高普查工作效率和精度,方法有效可行。

Fatigue crack in large-scale tubular joints for offshore structures

Tubular members have been used for constructing offshore structures. Large-scale fatigue tests of welded tubular K-joints under the balanced in-plane bending brace were carried out to investigate the fatigue behavior of API 2W Gr.50 steel produced by POSCO. The experimental results were verified by numerical approaches and compared with the IIW, DnV RP-C203 and API RP 2A-WSD design curves. The test results based on the hot spot stress were in agreement with the design curves. The SCF factor for tubular K-joint was also obtained. The numerical parametric study of the K-joint (using the finite element program) was described and its results were compared with experimental results. The stress effects of various parameters including α, β, γ, τ and θ on the stress in the K-joint were investigated. The stress distribution for each parameter was introduced. The study showed that the maximum stress of the joint varied according to the variation of joint parameters.