汽泵前置泵基础沉降对给水管道支吊架及受力的影响

针对某电厂1 000 MW机组汽动给水泵的前置泵基础沉降问题,首先对基础沉降前后管系应力及管道系统对汽泵前置泵推力和力矩进行了静力计算、分析与对比,研究了基础沉降对给水管道支吊架及管系受力的影响,分析评估了管道系统对汽泵前置泵推力和力矩的影响;然后针对基础沉降后支吊架受力异常和管道系统对汽泵前置泵的推力和力矩超标问题,提出了支吊架优化调整方案。经优化调整后,管道支吊架受力状态正常,管道系统对汽泵前置泵推力和力矩合格。     

某火力发电厂四大管道支吊架检查与调整

从四大管道支吊架安装、质量、管道设计和运行的角度,阐述了某电厂330MW机组主蒸汽、再热蒸汽管道支吊架的运行现状和存在的问题,对管道支吊架进行了状态检查、支吊架载荷性能检测、在综合分析的基础上提出了支吊架调整方案,并进行了工程实施,最后还对机组支吊架的运行监督提出建议。     

浅谈模块化施工中管道支吊架的安装

介绍了模块化施工过程中管道支吊架的安装原则。详细描述了AP1000核电项目中箱型支吊架、弹簧支吊架及阻尼器的安装要求。提出模块化施工对管道支吊架安装的不同要求。     

去除堵阀后低温再热蒸汽管道应力计算及分析

对某低温再热蒸汽管道去除堵阀后支吊架的工作载荷、管道受到的应力及管道对低温再热器入口联箱的推力进行了计算分析。结果表明:去除堵阀后管道的一次推力及力矩极大地升高了,更换部分恒力支吊架、调小部分恒力支吊架载荷后,可以保证低温再热蒸汽管道的正常运行。     

某600MW机组再热蒸汽冷段管道倾斜变形原因分析与处理

针对某电厂600MW机组试运期间发现的再热蒸汽冷段管道倾斜变形问题,通过管道热膨胀及支吊架状态的现场检查、管系静力计算分析,找出了管道倾斜变形的原因,提出了有效的处理措施。管道的倾斜变形主要是因为再热器入口集箱前冷段管道向下的热位移受阻造成,而支吊架设计不合理、载荷偏大是管道向下的热位移受阻的主要原因。     

45000m~3/h空分装置配套汽轮机管道整改总结

阐述了45000Nm~3/h(氧)空分装置配套汽轮机在试车时出现振动异常,通过对汽轮机前猫爪膨胀量的监控,利用受力分析软件重新对管道及机组进行核算,确定汽轮机的异常振动是由入口蒸汽管道拉动缸体而引起的。对蒸汽管道,选用弹簧力较小的恒力弹簧支吊架及把支架更改为吊架,使用限位硬性拉杆等措施降低了蒸汽管道热膨胀产生的力和力矩对汽轮机的影响,消除了汽轮机的异常振动。     

民用建筑机电安装工程中综合支吊架的选型与设置

综合支吊架作为管线综合平衡后的支撑体系广泛应用于民用机电安装工程中.本文从综合支吊架的整体安全性、经济性、美观性角度,详细介绍了综合支吊架选型及设置总体原则.     

核电厂用管道系统支吊架布置的优化

针对核电站用管道布置变更或设备变化引起的管道应力较大的问题,采用管道应力分析工具,计算管道及支吊架在复杂工况下的受力情况,并对芰吊架的布置进行优化,改善管道系统的应力状态。     

超超临界机组蒸汽吹管管道支吊架设计及安装

在禹州二期工程超超临界机组#4机吹管试运工作中,本文接合以往工程的经验,对蒸汽吹管管道支吊架设计选型和施工进行了规范和改进,以期作为相似工程中的蒸汽吹管管道支吊架设计及施工依据。     

超超临界机组蒸汽吹管管道支吊架设计及安装

在禹州二期工程超超临界机组#4机吹管试运工作中,本文接合以往工程的经验,对蒸汽吹管管道支吊架设计选型和施工进行了规范和改进,以期作为相似工程中的蒸汽吹管管道支吊架设计及施工依据。     

去除水压试验堵阀后电厂主蒸汽管道支吊架整改及应力计算

采用等值刚度法计算程序对某电厂主蒸汽管道在水压试验堵阀去除后其附近支吊架的工作载荷、管道受到的应力以及管道对锅炉末级过热器出口联箱的推力进行了计算分析。结果表明:去除堵阀后,其附近支吊架的工作载荷减小,主蒸汽管道受到的一次应力极大升高,且最大应力点发生了转移。因此,需要对管道上的支吊架结构进行整改,将堵阀附近的一横担恒力吊架改为单个恒力吊架。等值刚度法计算结果表明:该整改方法即可保证主蒸汽管道在水压试验堵阀去除后能够正常运行,同时利于水压试验堵阀的回装。     

Failure analysis of a leak-off oil pipe from injection valves of an off-shore operating diesel engine

The failure analysis of a four-stroke 3000 kW off-shore operating diesel engine is presented. The failure occurred during engine normal operation period in the leak-off oil pipe from the injection valves, which experienced a fracture through the pipe wall and a diesel engine fire as a result. A detailed analysis of all elements which had an influence on the failure initiation was carried out, namely leak-off oil pipe vibration level, pipe stress level, presence of corrosion pits on the pipe external surface under the zinc coating and engine components temperature distribution in the failure zone. It was found that the crack initiation and propagation of the leak-off oil pipe from injection valves was driven by a fatigue mechanism, which was facilitated by loose pipe supports (excessive pipe vibration) and corrosion pits on the pipe surface that acted as stress concentrators. The contact of leak-off atomized oil due to the pipe through wall fracture with the hot engine exhaust muff (390 °C approximately) caused local fire of the diesel engine.     

基于试验模态安全吊焊缝开裂原因分析

GQ70型轻油罐车上拉杆安全吊在车辆运行过程中经常发生焊缝开裂。安全吊不承受大载荷,可排除强度断裂原因。运用试验模态分析的方法,对关键部位安全吊进行锤击法模态试验,找出各个安全吊模态频率,并经过对比分析找出易裂部分安全吊焊缝开裂原因,提出改进建议。     

Further experimental study on the failure of fully clamped steel pipes

In the present study experimental data recorded from 226 impact tests on seamless mild steel pipes are reported. The pipe specimens with different geometries were fully clamped at both ends, and impacted transversely by rigid wedge-shaped indenters at the positions of mid-span, one-quarter span and very close to a support, respectively. In order to model the fully clamped boundary conditions, a special clamping system was designed to hold the pipe specimens rigidly at each end to prevent any significant inward displacements from the supports. The impact velocities ranged up to 10.69 m/s and caused large inelastic indentations for the lower values and at higher values a loss of integrity near the supports. Particular attention was paid to obtaining the threshold value of initial impact energy that caused the onset of material rupture. Discussion is made for the influences of pipe geometry, impact position and internal pressure on the critical value of initial impact energy.     

汽车排气系统吊耳动刚度优化方法的研究

基于汽车排气系统吊耳传递的动态载荷最小、吊耳耐疲劳性最好,建立了考虑动力总成在内的排气系统振动分析模型。进行了排气系统的自由模态和约束模态的测试,并和计算值进行了对比分析,证明了所建立的排气系统振动模型的正确性。以吊耳的垂向动态载荷最小和其静变形量在一定范围内为优化目标,建立了排气系统吊耳动刚度优化模型。优化后,在怠速工况和2档全负荷加速工况下对车身底板驾驶员位置进行了振动响应测试,测试结果表明,利用优化后的吊耳刚度,能够有效降低车身底板的振动加速度,表明了阐述的排气系统建模和吊耳动刚度优化方法的有效性。文中建模与优化方法,对排气系统的吊耳动刚度计算与优化具有指导意义。     

Non-destructive testing and assessment of a piping system with excessive vibration and recurrence crack issue: An industrial case study

Flow in piping generates random excitation which is non-periodic and that means resonance will not be the key factor to pipe failure. One of the main causes of pipe failure is weak supports. Due to their dissimilar stiffness in the piping system, it leads to low frequency and high amplitude flow induced vibration that causes high cyclic stress resulting in high cycle fatigue failure of the joints. Other contributing factors in pipe failure are poor or inadequate design, poor workmanship during installations or maintenance and inadequate or weak and flexible support. These pipes are usually required to work non-stop for 24 h a day 7 days a week for weeks, months or years at a time. Regular monitoring and in-service dynamic analysis should ensure continuous and safe operation. This paper presents a case study on monitoring, diagnosis, and maintenance of a piping system. High vibration was observed during routine maintenance, in a 30 m high, 24 in. diameter amine pipes at an oil and gas processing plant in southern Thailand. Amine liquid leakage due to high cycle fatigue crack was reported at the piping bearing and this remained a major concern for the personnel at the plant. A non-destructive testing approach which relies on a combined experimental techniques (i.e. Operating Deflection Shapes (ODS)) and computational mechanics (i.e. Finite Element (FE) modal analysis, Computational Fluid Dynamics (CFD) Analysis, Fluid-Structure Interaction (FSI) Analysis) was used to assess the structural integrity of the piping and in the effort of proposing a suitable recommendation in rectifying the high vibration issue. The analyses concluded that the root cause of high vibration was due to inadequate and weak piping support. As a result, additional supports were proposed to counter the deflection of the piping generated by the flow. The supports were found effective in reducing vibration in which the stress concentration at the new supports and the piping was considered relatively low.     

恒力吊架力学性能对低温再热蒸汽管道热位移的影响

采用JY—20便携式测试系统,对某火电厂低温再热蒸汽管道恒力吊架的恒定度和载荷偏差进行了测试,探讨了恒力吊架力学性能对低温再热蒸汽管道热位移产生的影响。结果表明:恒力吊架载荷偏差及恒定度不合格是造成低温再热蒸汽管道无法复位的主要原因;更换性能合格的恒力吊架后,恒力吊架的位移指针基本能回复到原位,管道热位移正常,且各主要管种的最大一次应力和二次应力均在其允许值范围内。     

Failure analysis of a high pressure natural gas pipe under split tee by computer simulations and metallurgical assessment

Crack failure of a 36 inch high pressure gas pipe observed during regular inspection of a station has been investigated and the results are presented in this paper. The crack, approximately one meter long, was initiated from a notch inside the hot tapped hole in a pipeline installed about 30 years ago. The study was conducted by reviewing the design history and construction data, visual inspection, pipe material characterization, stress and modal analysis by using finite element method. Investigations revealed that the valve, directly connected to the split tee, faced large dynamic periodic forces due to a pressure drop between two pipelines. Metallurgical evaluation of the pipe material by optical microscope and fractography of the crack surface by scanning electron microscopy indicated the presence of elongated inclusions in the steel microstructure together with some indications of fatigue fracture as a poorly formed sawtooth profile. Based on dynamic analysis, it was found that the first mode shape, the maximum displacement and, therefore, the maximum stress were exactly situated within the crack initiation zone. It was concluded that the notch effect in the hot tapped hole, the position of the supports under the split tee and the presence of a large periodic stress were responsible for the initiation and fatigue propagation of the crack in the gas pipe.     

悬索桥短吊索索力测试的探讨

因难以准确确定吊索的计算长度和抗弯刚度,按照公式法计算短吊索的索力误差一般较大。以新沟河大桥悬索桥吊索索力测试为研究背景,分析了吊索的边界条件、抗弯刚度、计算索长及线密度等因素对索力测试精度的影响,表明公式法的简化假设对短吊索不适用。介绍了有限元法分析吊索索力的方法,按吊索的实际尺寸建立有限元模型,首先识别出吊索的抗弯刚度,然后建立各吊索的索力—频率对应表格,查表即可得到实测频率对应的索力。该方法应用到新沟河大桥的施工监控,证明是一种行之有效的方法。