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.

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.

Finite Element Analysis of Modeling Residual Stress Distribution in All-position Duplex Stainless Steel Welded Pipe

On the basis of the thermal-elastic-plastic theory, a three-dimensional finite element numerical simulation is performed on the girth welded residual stresses of the duplex stainless steel pipe with ANSYS nonlinear finite element program for the first time. Three-dimensional FEM using mobile heat source for analysis transient temperature field and welding stress field in circumferential joint of pipes is founded. Distributions of axial and hoop residual stresses of the joint are investigated. The axial and the hoop residual stresses at the weld and weld vicinity on inner surface of pipes are tensile, and they are gradually transferred into compressive with the increase of the departure from the weld. The axial residual stresses at the weld and weld vicinity on outer surface of pipes is compressive while the hoop one is tensile. The distributions of residual stresses compared positive-circle with negative-circle show distinct symmetry. These results provide theoretical knowledge for the optimization of process and the control of welding residual stresses.

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.

常减压装置高温热油管道的应力分析及优化设计

为了确保管道布置和法兰连接的可靠性和安全性,高温管道的应力分析十分必要。利用CAESAR II软件对常减压装置的高温热油管道进行了一次应力和二次应力校核。分析了各节点的热态位移、约束力和力矩等关键数据。采用L型和Z型自然补偿方案,合理规划了管道布置,优化了支吊架设计。进一步采用Kellogg当量压力法校核了热油泵和常压塔设备管嘴与管道之间法兰连接的可靠性,最终确保了该热油管道的安全、长周期运行。

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。

爆破振动下城市管架型热力管道响应与安全研究

以下穿热力隧道的北京冬奥支线区间隧道爆破为背景,建立热力管道三维动力有限元模型,利用锤击测试试验验证了数值模型的可靠性.在数值模型中输入实测的爆破振动波,研究爆破地震波作用下管架型热力管道动态响应.结果表明:爆破地震波作用下,管道结构的有效应力为45.89 MPa,有效应变仅为0.02%,与重力初始作用时结构应力应变分布保持一致,爆破振动对管道结构的作用效应较小;放大输入地震波5~100倍,管道结构的PPV随之等倍数增大,而最大等效应力和最大等效应变的增幅仅为4.5%左右;提取实测地震波低频成分并施加在管道结构上,并不会引起热力管道的应力和应变大幅度增加,管道材料的等效应力均在50 MPa以下.由此可见,地震波峰值和主频对管道应力应变分布影响均较小。具有波纹管膨胀节的架空管道结构受力均匀,变形协调性和抗震性能较好,因工程爆破振动造成破坏的可能性不大.

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。

水冷壁管接头开裂原因

某电厂发生锅炉水冷壁管开裂现象。采用宏观观察、化学成分分析、金相检验、硬度测试等方法分析了水冷壁管开裂的原因。结果表明:水冷壁管接头对接环焊缝焊接产生了残余应力,材料中存在焊接缺陷,在高温、高压环境下,缺陷逐渐扩展为孔洞,并对其他管壁造成冲蚀破坏,最终导致水冷壁管开裂。

储气库注采管柱屈曲后表面半椭圆裂纹力学分析

采用有限元方法,研究了注采管柱屈曲后表面半椭圆裂纹的应力强度因子K_(Ι)和J积分。首先,由于储气库注采管柱是长直圆管结构,通过建立含外表面裂纹直管的有限元模型,对其进行有限元验证。然后,基于子模型法,建立了管柱屈曲后裂纹力学计算模型,计算了屈曲后不同裂纹形状参数、裂纹相对深度和轴线夹角下的应力强度因子K_(Ι)和J积分,分析了管柱不同螺距数对K_(Ι)和J积分的影响规律。结果表明,有限元法在计算应力强度因子时精度较高,造成有限元法误差明显的主要因素是网格尺寸和裂纹前缘网格划分份数;管柱螺旋屈曲后,K_(Ι)和J积分随裂纹形状参数的增加而减小,随裂纹相对深度的增加而增大;随着注采管柱屈曲螺距数以及轴线夹角的增加,K_(Ι)和J积分均呈增长趋势,且裂纹为周向裂纹时的增长速率最大。

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。

大跨度料场封闭结构设计问题探讨

针对大跨度料场封闭结构设计中的关键问题,对预应力管桁架弧段的模拟、节点分析、等效风荷载取值等进行了研究并给出建议。

加氢装置原料运输线排污管节腐蚀失效原因

某加氢装置原料运输线排污管节发生了腐蚀开裂。通过宏微观形貌观察、化学成分分析、腐蚀产物成分分析、金相检查等手段分析了管节腐蚀失效的原因,并提出了相应的改进措施。结果表明:管节化学成分和组织正常,管节材料未敏化;裂纹从管节内壁开始扩展至外壁,分叉特征明显,为穿晶裂纹;断口表面腐蚀产物中残存着氯元素。综合裂纹特征和腐蚀产物成分可以推断该管节发生了由氯离子引起的应力腐蚀开裂。管节两端存在较大的温差,造成了局部水相析出,介质中的腐蚀性氯元素在水相中聚集,形成应力腐蚀开裂的环境。

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。