Stress Corrosion Cracking of High-strength Drill Pipe in Sour Gas Well

In high sour gas reservoir drilling process, it happens occasionally that high-strength drill pipe suffers brittle fracture failure due to stress corrosion cracking, and poses serious hazard to drilling safety. To solve this problem, this paper studied the stress corrosion cracking mechanism and infl uencing factors of highstrength drill pipe in sour environment with hydrogen permeation experiments and tensile tests. We simulated practical conditions in laboratory and evaluated the stress corrosion cracking performance of the high-strength drill pipe under conditions of high stress level. For the problems occurring in use of high-strength drill pipe on site, the paper proposed a technical measure for slower stress corrosion cracking.

Nonlinear Static Finite Element Stress Analysis of Pipe-in-Pipe Risers

Owing to the complexity of the pipe-in-pipe (PIP) riser system in structure, load and restraint, many problems arise in the structural analysis of the system. This paper presents a new method for nonlinear static finite element stress analysis of the PIP riser system. The finite element (FE) model of the PIP riser system is built via software AutoPIPE 6.1. According to the specialties of a variety of components in the PIP riser system, different elements are used so as to model the system accurately. Allowing for the complication in modeling the effects of seabed restraint, a technique based on the bilinear spring concept is developed to calculate the soil properties. Then, based on a pipeline project, the entire procedure of stress analysis is discussed in detail, including creation of an FE model, processing of input data and analysis of results. A wide range of loading schemes is investigated to ascertain that the stresses remain within the acceptable range of the pipe material strength. Finally, the effects of the location of flanges, the thermal expansion of submarine pipelines and the seabed restraint on stress distribution in the riser and expansion loop are studied, which are valuable for pipeline designers.

STRESS ANALYSIS OF FREEZING PIPES BY MODELLING

Using the simulation test facility designed on the basis of similitude principle,the authors of the paper carry out a series of simulation tests and study the influence of effective factors on the stress in the freezing pipes during both periods of active freezing and excavating-lining.They obtain preliminarily the regularity of stress variation and discuss the causes of freezing pipe fracture.

Surface stress effect on the vibration and instability of nanoscale pipes conveying fluid based on a size-dependent Timoshenko beam model

Presented in this paper is a precise investigation of the effect of surface stress on the vibration characteristics and instability of fluid-conveying nanoscale pipes.To this end,the nanoscale pipe is modeled as a Timoshenko nanobeam.The equations of motion of the nanoscale pipe are obtained based on Hamilton＇s principle and the Gurtin-Murdoch continuum elasticity incorporating the surface stress effect.Afterwards,the generalized differential quadrature method is employed to discretize the governing equations and associated boundary conditions.To what extent important parameters such as the thickness,material and surface stress modulus,residual surface stress,surface density,and boundary conditions influence the natural frequency of nanoscale pipes and the critical velocity of fluid is discussed.

Comparative study of weld residual stress on steel pipes with different weld types

This study developed a sequential coupling finite element procedure to predict residual stresses of steel pipes with longitudinal wela／ circumferential weld and spiral weld.The results show that the residual stress in heat affected zone（HAZ）is higher than that in weld for spiral weld pipe.For the circumferential weld pipe and spiral weld pipe,the residual stress in inner surface is higher than that in outer surface.However,for the spiral weld pipe,the residual stress in inner surface is smaller than that in outer surface.The hoop residual stress of circumferential weld pipe is higher than that of longitudinal weld pipe,while the axial residual stress of circumferential weld pipe is smaller than that of longitudinal weld pipe.The hoop stresses for circumferential weld pipe and axial stress for longitudinal weld pipe have exceeded the yield strength of base metal.With the increase of helix angle,the hoop stress decreases while the axial stress increases.For the spiral pipe（α=30° to 50°）,both the hoop stress and axial stress are relatively small.The spiral pipe（helix angle ranging from 30° to 50°） is helpful to reduce stress corrosion cracking（SCC） and it is recommended to manufacture the steel pipe.

Stress and Fracture Strength Analysis for Three-Way Pipes

Three-way pipes, T and Y pipes, are very important connecting components in pipeline systems, their strength are related to the safety of pipelines. In the case that crack is not detected in the three-way pipe, ANSYS finite element program version 5.6 is applied to study the stress distribution of the three-way pipe and to obtain the optimum fillet radius in the crotch region of the two pipes. The reasonable intersection angle of the two pipes is also obtained. In the case that a surface crack is detected in the three-way pipe, the maximum stress intensity factor (SIF) near the front of the surface crack is studied.

The Interlayer Stress Analysis of Polyethylene-steel Composite Pipes

Polyethylene-steel Composite Pipes is widely used in conveying corrosive media occasions,but the pipe may lose effectiveness in the process of transporting hot and cold media,so the research of stress distribution and variation in polyethylene-steel composite pipes is very necessary.This article first assume that a thin adhesive layer is in between the polyethylene and steel,the adhesive layer along the axial shear stress is the major cause of the polyethylene layer and the steel pipe off sticky.Secondly,we use a method of finite element to computer simulation by ANSYS,and verify initial assumptions.Finally,based on simulation data,we analyse the adhesive layer stress distribution and the variation with different parameters to change.Through the above research,preliminarily summarize the variation and distribution of interlaminar stress,and provide technical support for future design and process improvement of polyethylenesteel pipe.

The Challenges of the Engineering Inspection of Pipelines and Heat Engines by Temperature Deformation and Stress

Pipelines and engines are studied under the thermal stress during operation. With the calculated ratios obtained, it is possible to settle practical issues in operation in order to increase the reliability and safety of equipment. To this end, it is first necessary to investigate the thermal mode of the pipeline, the engine for the planned period by the operations control centre. At the same time, the equipment with the average temperature at a certain time of the year exceeding the design value should be identified. In addition, the equipment concerning the nature of jamming should be studied at the sections specified in such a way. In case of identifying the jammed sections based on the above calculated ratios by thermal deformation and stressing the necessary value of movement of the sections, it should be determined that the actual voltage does not exceed the permissible level.

Study of relieving weld residual stresses in large pressure steel pipes of hydropower station by local explosion treatment

From comparing the test of local explosion treatment(LET)with the locaf heat treatment (LHT)in welded plates and welded steel pipes in field,LET has excellent effect of stress relief and high efficiency. Whereas the effect of stress relief for LHT with 575℃×1.5hr is poor.The mechanical properties of welded joints after LET are basically the same as those of as-welded joints.The practically measuring results on 4 large steel-pipe surfaces indicate that the welding residual tensile stresses in welds,which mostly is compression residual stress,are basically relieved.

Prediction of welding residual stress in multipass narrow gap welded pipes with large thickness

The objective of this study is to investigate the influence of post weld heat treatment （PWHT） on the distribution of residual stress in welded pipes with large thickness. The detailed pass-by-pass finite element simulation was developed to study the residual stress in narrow gap multipass welding of pipes with a wall thickness of 150 mm and 89 weld beads. The effect of PWHT on welding residual stress was also investigated by means of numerical analysis. The simulated results show that the hoop stress is tensile stress in the weld region and compressive stress in the parent metal areas adjacent to weld seam. After heat treatment, the residual stresses decrease substantially, and the simulated residual stress is validated by the experimental one. The distribution of the through-wall axial residual stress along the weld center line is a self-equilibrating type.

不锈钢内衬修复复合管层间缺陷处应力分析

为研究不锈钢内衬修复前后复合管道内腐蚀缺陷处的应力分布规律以及修复效果,基于有限元软件,建立含单腐蚀坑缺陷的管道模型,改变腐蚀坑的深厚比,忽略黏结层厚度及对腐蚀坑的填补影响,层间采用黏接行为建立界面相互作用分析模型,将修复前后腐蚀缺陷处的应力进行对比。随着腐蚀缺陷深厚比的增加,管壁腐蚀缺陷处的径向应力、周向应力、Mises应力都有增大的趋势;修复前缺陷处的周向应力最大,且其值与Mises应力相近;经不锈钢内衬修复后,缺陷处的周向应力下降了11.3%,Mises应力下降了7.12%。腐蚀缺陷的深厚比对管道的应力分布有着显著的影响,所以在进行复合管线安全评估时应注意腐蚀深度的影响;在修复前后,管道腐蚀缺陷处的控制应力一直是周向应力,复合管道的失效可依据周向应力进行判断;经不锈钢内衬修复后,原始缺陷处的应力发生了重分布,其周向应力与Mises应力均有减小,修复效果明显。

钻杆在扭转作用下的变形及抗扭性能分析

钻杆在煤矿勘探开发过程中占据着重要地位,因工作条件恶劣,易失效并造成钻井事故。基于材料力学、工程力学等对钻杆扭转时的切应力及变形量进行分析,建立钻杆在施加纯扭矩作用下的剪应力、单位长度扭转角及抗扭强度计算的力学模型。同时,通过ANSYS仿真得出切应力分布规律及扭转变形量。通过对比,ANSYS仿真结果与理论模型计算结果基本一致,为钻杆失效等进一步研究提供了理论依据。

某高压管汇Y型三通管开裂原因分析

[目的]某高压管汇Y型三通管在酸压施工作业过程中发生泄漏。[方法]通过无损探伤、宏观分析、金相分析、化学成分分析、力学性能分析、微观分析、应力计算等手段,对某高压管汇Y型三通管的材质、断口特征、应力场分布等进行了研究。[结果]现场发生泄漏的三通管在化学成分、拉伸性能、耐冲击性能、金相组织等方面都与库房完好的三通管基本一致,但冲击功均较低,断口呈脆性断裂特征,内壁存在明显的腐蚀产物及腐蚀坑。[结论]三通管发生纵向开裂的主要原因为地面交联酸的腐蚀导致大量腐蚀坑的形成,并在较高的内压作用下造成局部应力集中,超过管材的强度极限。

冷热原油顺序输送管道热应力与疲劳寿命分析

近年来,随着国外原油进口量的持续攀升以及国内油田产量的下降,管道输送出现了不同油品需要用同一条输油管线共同输送的情况。以庆铁四线管道为例,结合实际参数,应用ANSYS有限元分析方法,采用六面体结构性网格对管壁进行离散化处理,对埋地管道热结构耦合问题进行求解,分别计算了直管段和弯管段在不同温度下的热应力;基于断裂力学理论,计算了不同服役寿命下的年循环周期极限,分析了温度交替变化对管道疲劳寿命的影响。实验结果为冷热原油管道安全输送提供了理论依据。

埋地燃气PE管道在地面沉降作用下的应力分析

为了研究在地面沉降作用下PE燃气管道的受力特性及失效原因,借助ANSYS软件,探究了在地面沉降作用下PE100、管径DN110、e=10的燃气PE管道的应力-应变响应情况,分析了管道失效影响因素以及失效原因,并得出管道的失效危险点、管道极限沉降位移及极限截面变化率。结果表明:在地面沉降作用下管道的失效危险点出现在沉降区与非沉降区交接处的管道内表面;且在地面沉降作用下,管道产生的压缩变形是导致管道失效的主要原因,管道弯曲变形的存在会使管道的压缩变形更加严重。这为防治埋地燃气聚乙烯管道在地面沉降作用下的管道安全评估提供理论参考。

某1400 MW等级核电汽轮机中低压连通管应力分析

以管道应力分析软件ROHR2为计算平台,对某1400 MW等级核电汽轮机组中低压连通管在冷态、热态、抽真空以及地震等不同工况下的应力水平进行了详细的计算分析。结合相关设计规范以及工程实际对各工况进行匹配组合,得出了管系整体的应力计算结果以及接口的荷载,以期向设计人员提供连通管道的应力评判、结构设计以及支吊架选型设计的相关理论依据,确保管系的安全可靠运行。

装配应力对飞机管道随机疲劳寿命的影响分析与试验验证

针对飞机液压管路连接件疲劳断裂问题,基于随机振动理论对带有轴向装配偏差的液压导管进行疲劳寿命预估。从建立真实飞机液压系统管路连接件有限元模型入手,分析轴向装配偏差产生的装配应力对结构的影响规律,通过试验获取不同轴向偏差下的管路连接件的阻尼比。利用有限元分析软件进行随机振动分析,获取危险部位的应力响应功率谱密度函数,结合Miner线性损伤理论,对含有装配应力的管路连接件进行了随机振动疲劳寿命预估。设计并进行了管路共振疲劳试验,发现管道裂纹萌生位置及疲劳寿命下降趋势与仿真结果契合,仿真及试验结果表明当轴向偏差达到0.8 mm时,严重影响到了飞行安全。研究成果为航空液压管路的设计及装配理论研究提供理论参考和技术支撑。

法国核电应力腐蚀问题对我国核电技术发展的启示

2022年,法国电力公司(EDF)大量核电机组因一回路管道应力腐蚀开裂(SCC)问题而停堆检修,对法国甚至欧洲的生产生活造成巨大影响。针对该事件,在总结国内外核反应堆类似失效案例及材料老化研究成果的基础上,对反应堆不锈钢部件的SCC问题的机理、影响因素、抑制措施开展了分析,并结合我国核电机组服役时间逐渐延长,材料老化、设备失效问题日益突出的现状,提出我国核电运维改进措施,如优化残余应力、加强监督和检查,研发更有效的无损检测技术等。同时,探讨了我国在反应堆材料老化研究方面的发展方向。

AutoPIPE软件在氧化铝工厂管道设计中的应用

随着我国氧化铝工业进入百万吨级时代,大型化将成为今后的发展趋势。大型化设计不是简单的放大,已有的设计经验不一定适用。管道设计是氧化铝工厂设计过程中不可缺少的组成部分,涉及各种工况、介质的压力管道,工厂大型化后管道直径必然加大,这样管道布置走向、支架型式都会发生改变。为了确保压力管道设计安全、可靠,设计人员常借助应力分析软件来进行柔性设计。AutoPIPE作为国内外应用广泛的应力分析软件,其应用涵盖了许多领域。本文以某氧化铝厂母液蒸发工序的铝酸钠溶液压力管道为例,利用AutoPIPE应力分析软件进行了柔性设计、弹簧选型设计、泵设备分析,探究了该软件在氧化铝工厂管道设计中的应用情况,为管道设计的安全提供保障。