Analysis of above-ground pipelines on unilateral supports: a neural network approach

A neural network approach is proposed for the effective numerical treatment of the analysis problem of above-ground pipelines on unilateral supports. As is well known, the structural response of such pipelines can be effectively described by monotone problems having the form of quadratic minimization problems with inequality constraints. In order to numerically treat these quadratic problems, the methods of the theory of neural networks are applied. Within such a neural network computing framework, the Hopfield model is first appropriately generalized, and then a neural network model covering the case of inequalities is proposed. A numerical application illustrates the proposed neural network method.     

深圳市某河道截污管道近距离上穿既有大直径地下供水管道有限元分析

城市建设过程中各类地下管线交叉不可避免,由于地下管线材质、管径、使用功能、荷载不同,常规计算方法繁琐且不够直观。为此,通过有限元方法分析了深圳市某河道截污管道近距离上穿既有大直径地下供水管道问题,为既有管道安全和正常使用提供了直观的计算结果,亦为工程设计和施工方案提供了技术支撑。     

泵站压力管道振动特性分析及减振优化设计

为探究泵站压力管道的不同布置形式对管道振动的影响,选取宁夏盐环定泵站工程二泵站#1压力管道为研究对象,建立基于流固耦合的泵站压力管道水流ALGOR数值模型,并采用DASP振动测试系统获取振动信号对模拟结果进行验证,分析压力管道水流流态对管道振动的激励特征并提出优化设计方案。结果表明,压力管道进水管处、支管总管相接处及总出水管处均有强烈的振动,但进水管的振动较出水总管振动更为强烈;减振优化设计方案中,调整支管距离对降低水流对管道振动的激励效果微弱,增大管径及改变总管走向对其效果较好,其中总管走向在2°～5°之间较佳,不仅能降低管道振动,而且能减少泵站能耗损失。研究结果可为高扬程泵站压力管道的优化设计提供理论依据。     

Reliability-based assessment of polyethylene pipe creep lifetime

Lifetime management of underground pipelines is mandatory for safe hydrocarbon transmission and distribution systems. The use of high-density polyethylene tubes subjected to internal pressure, external loading and environmental variations requires a reliability study in order to define the service limits and the optimal operating conditions. In service, the time-dependent phenomena, especially creep, take place during the pipe lifetime, leading to significant strength reduction. In this work, the reliability-based assessment of pipe lifetime models is carried out, in order to propose a probabilistic methodology for lifetime model selection and to determine the pipe safety levels as well as the most important parameters for pipeline reliability. This study is enhanced by parametric analysis on pipe configuration, gas pressure and operating temperature.     

南方LNG低温管道保冷层厚度计算的分析

目前在中国南方地区远离天然气长输管线的县城,几乎全部都采用投资建设LNG(液化天然气)气化站,然后通过LNG槽车把LNG运送到LNG气化站,然后经气化后经管道输送到各燃气用户。由于LNG是低温储藏,因此在气化前LNG低温管道需要进行保冷设计。保冷厚度的大小对工艺管道的正常运行起到重要的作用。通过对几种保冷层厚度计算方法的分析,并通过举例说明,对LNG低温管道保冷层厚度的计算方法进行阐述。     

架空热力管线管托散热修正系数研究

炼化公司内存在大量架空热力管线.为安装固定管线,承受管线自重载荷,架空热力管线安装了大量管托.管托与热力管线直接接触,一方面起承重作用,另一方面向外损失热量.然而目前所进行的管线保温效果测试与评价多数未考虑管托的影响.本文提出了架空管线管托散热修正系数的概念,用管托散热修正系数给出了管线保温效果以及管托散热量测试计算方...     

Fracture response of pipelines subject to large plastic deformation under bending

Demand for long-distance offshore pipelines is steadily increasing. High internal pressure combined with bending/tension, accompanied by large plastic strains, along with the potential flaws in girth welds make the structural integrity of pipelines a formidable challenge. The existing procedures for the fracture assessment of pipelines are based on simplified analytical methods, and these are derived for a load-based approach. Hence, application to surface cracked pipes under large deformation is doubtful. The aim of this paper is to understand and identify various parameters that influence the fracture response of cracks in pipelines under more realistic loading conditions. The evolution of CTOD of a pipeline segment with an external circumferential surface crack is investigated under pure bend loading as well as bending with internal pressure. Detailed 3D elastic–plastic finite element simulations are performed. The effects of crack depth, crack length, radius-to-thickness ratio and material hardening on fracture response are examined. The results show that at moderate levels of CTOD, the allowable moment capacity of the pipe decreases significantly with increase in internal pressure. Further, the variation of CTOD with strain can be well approximated by a simple linear relationship.     

Failure analysis of corroded high-strength pipeline subject to hydrogen damage based on FEM and GA-BP neural network

The pipeline is a major approach to achieving large-scale hydrogen transportation. Hydrogen damage can deteriorate the material performance of the pipe steel, like ductility and plasticity reduction. Corrosion is dominating damage that impairs a pipeline's bearing capacity and structural reliability. However, previous research barely investigated the effect of hydrogen damage on failure behaviors, residual strength and interacting effect between adjacent corrosions of corroded high-strength pipelines transporting hydrogen. Besides, hardly any burst pressure model considers hydrogen damage. In this paper, several approaches, including the finite element method (FEM), regression analysis, the orthogonal test method, and the artificial neural network method, are applied to fill the gap. First, a series of finite element models with different geometric features and hydrogen damage is established to investigate the effects of hydrogen damage and corrosion on failure behaviors and residual strength. The results show that hydrogen damage can change the corroded pipeline's failure behaviors and reduce the residual strength. Second, based on the simulation results and regression analysis, a new burst model is developed to consider the hydrogen damage and improve the estimation accuracy. Third, based on the genetic algorithm (GA), a GA-BP neural network is established and trained for accurate and efficient residual strength estimation considering hydrogen damage. Furthermore, an orthogonal test is designed and performed to investigate the effects of critical parameters on the burst pressure of the corroded pipeline after hydrogen damage. The results indicate that hydrogen damage and corrosion length have similar contributions to the residual strength. Finally, the simulation results of pipelines with multiple corrosions show that hydrogen damage has a significant impact on the interacting effect between adjacent corrosions. The results obtained are valuable for further integrity management of steel pipelines carrying hydrogen.     

Prediction of remaining strength of corroded pressurised pipelines

In this paper a deterministic model is developed which can be used to evaluate the remaining strength of corroded steel pipeline over time. This model also can be used to evaluate the maximum allowable failure pressure of corroded pipelines. The motivation for the development of the model is that during in-service conditions the strength of pressurised pipelines may be impaired, for example, from the failure of the protective coatings, paint surfaces or cathodic protection or as a result of externally applied mechanical damage or as a result of ageing (e.g. fatigue). Any of these may lead to the initiation of corrosion at the damaged area if it is not repaired. Once initiated, corrosion increases gradually both in extent and depth with increased exposure period. This results in the reduction of the remaining strength and hence a reduction in the carrying capacity of a pipeline. It also creates uncertainty about the future capacity. The proposed model is related to accepted methods for estimating the remaining strength of pipelines, but uses a simple corrosion model to estimate future remaining life. A sensitivity analysis can be used to investigate the effect of corrosion parameters on the pipeline carrying capacity. A simple example is given to illustrate the approach.     

Failure pressure analysis of hydrogen storage pipeline under low temperature and high pressure

Low temperature and high pressure line pipes are widely used in hydrogen storage, air separation plant, liquefied natural gas (LNG) transportation etc. The material properties of pipes at low temperature are different from those at room temperature. If the medium in the pipe is corrosive, it will cause the pipe wall thickness to decrease. However, the failure pressure of the corroded hydrogen storage pipeline at extremely low temperature is lacking of adequate understanding. In this paper, we provided a novel failure pressure equation of the mild steel line pipe with corrosion defects at extremely low temperature. Firstly, a mechanical model of the line pipe with corrosion defects is established. And then, an analytical solution of the mechanical model is obtained based on elastic theory. Next, a failure pressure equation of the corroded hydrogen storage pipeline at extremely low temperature is developed. In the end, the accuracy of the failure pressure equation is verified by comparing with finite element method (FEM). The results suggest that the calculated value of the failure pressure equation is consistent with that of FEM. This paper provides a theoretical basis for the safety assessment of low temperature hydrogen storage pipeline. The new equation presented in this paper can provide useful guidance for the design of low temperature and high pressure pipelines.     

蒸汽管网模拟优化技术应用

洛阳分公司蒸汽管网包括10MPa、3．5MPa、1.0MPa和0．3MPa共4个等级．其中3．5MPa和1．0MPa蒸汽管网是主要管网。两套管网均存在供汽结构不合理,管段散热损失大,管网保温材料老化及破损严重,管段外表面温发较高（在50℃以上,局部管段超过80℃）等问题。为此．根据3．5MPa和1．0MPa蒸汽管网平衡数据．作出流量平衡表．利用蒸汽管网模拟分析软件（SNAMER）建立蒸汽管网模型并进行离线模拟分析。根据模拟分析结果,提出增设一条蒸汽跨线,以提高1号汽轮机发电机入口压力和汽轮机输出功率;将热电站至化纤装置3．5MPa蒸汽母管管径改为DN500,以减少压降;将部分管线保温材料改为硅酸铝镁纤维,保护层材质改为镀锌铝皮．以减少散热损火。模拟结果显示,实施上述措施后,1号汽轮机发电机入口压力约提高0．3MPa,在耗汽量不变的情况下,输出功率可提高3％：3．5MPa年1．0MPa蒸汽管网总散热损失将分别下降24％和31％;若对部分管线进行改造,每年将节约费用500万元。     

Creep damage prediction of the steam pipelines with high temperature and high pressure

Creep is the significant factor that caused failure of steam pipelines with high temperature and high pressure in the period of long-term service. In this paper, the creep tests were performed at serviced temperature of 520 °C for 1.25Cr–0.5Mo pipe material, and the creep and fracture constants were obtained by fitting the creep test data. Based on the modified Karchanov–Rabotnov constitutive equation, compiled the user subroutine computing the damage of the pipe element or 3D solid element, the creep damage prediction was carried out by finite element methods using ABAQUS codes for the steam pipelines with high temperature and high pressure, which serviced in a petro-chemical plant, the damage distribution and maximum damage location of the pipelines were obtained, which is testified by metallographic examination result. Furthermore, the local creep damage analysis of a tapered pipe serviced for 100,000 h was also carried out because tapered pipes used in the main steam pipeline is one of weakness in the piping system. Damage distribution and evolution in the analyzed tapered pipe were obtained. The location with the maximum damage value was determined, which is coincident with cracking position of the actual tapered pipe.     

基于3S技术构建华东成品油数字化管道系统

"数字化管道"是当前国内外油气管道管理技术应用的热点。通过引进ArcGIS和skyline两款国际领先的软件,并利用3S(RS、GPS、GIS)技术构建了集管道完整性数据管理、GIS业务应用、管道智能巡检、应急分析决策及站场三维可视化于一体的华东成品油数字化管道系统。该系统采用先进的技术架构和设计理念进行规划设计,强调数据的服务共享;关键技术包括基于SOA的服务体系、松耦合方式集成及OPC接口支持。华东成品油管道覆盖江浙沪两省一市,其海量数据库是否完备是系统建设成败的关键。通过该系统的实施,为数字化管道提供了数据规范和管理规范,实现了管道全生命周期内各类资源的有效利用以及完整性数据管理,为管道运维提供了科学的管理和有力的支持。未来将重点从管道完整性的风险识别、高后果区分析、风险综合治理方案设计等方面对系统进一步完善。     

船舶汽轮机蒸汽管路流动噪声源的声类比计算研究

针对某船舶动力系统蒸汽调节管路在不同阀门启闭状态下的流动噪声源空间分布,开展了详细的计算气动声学数值研究工作。采用剪切应力输运湍流模型(SST,shear stress transport)获取了管内复杂三维蒸汽流场分布;结合Curle声类比模型和Proudman声类比模型分别计算得到管路壁面偶极子噪声源和管内流体域四极子噪声源分布特性。研究结果表明：相比于阀门关闭状态下的一进一出“T型”和“Z型”管路,阀门开启后的两进一出“h型”管路内流动噪声源强度上升明显;偶极子噪声源主要分布在管路汇聚处与出口弯管区域壁面,与此区域流体剪切应力相关;由于出口弯管直径突然变小,且流体流向发生变化,导致此处管内流场湍流度较高,故而产生了较为强烈的四极子噪声源。     

The synergistic effects of hydrogen embrittlement and transient gas flow conditions on integrity assessment of a precracked steel pipeline

We are reporting in this study the hydrogen permeation in the lattice structure of a steel pipeline designed for natural gas transportation by investigating the influence of blending gaseous hydrogen into natural gas flow and resulted internal pressure values on the structural integrity of cracked pipes. The presence of cracks may provoke pipeline failure and hydrogen leakage. The auto-ignition of hydrogen leaks, although been small, leads to a flame difficult to be seen. The latter makes such a phenomenon extremely dangerous as explosions became very likely to happen. In this paper, a reliable method is presented that can be used to predict the acceptable defect in order to reduce risks caused by pipe failure due to hydrogen embrittlement. The presented model takes into account the synergistic effects of transient gas flow conditions in pipelines and hydrogen embrittlement of steel material due to pressurized hydrogen gas permeation. It is found that blending hydrogen gas into natural gas pipelines increases the internal load on the pipeline walls due to overpressure values that may be reached in a transient gas flow regime. Also, the interaction between transient hydrogen gas flow and embrittlement of API 5L X52 steel pipeline was investigated using Failure Assessment Diagram (FAD) and the results have shown that transient flow enhances pipeline failure due to hydrogen permeation. It was shown that hydrogen embrittlement of steel pipelines in contact with the hydrogen environment, together with the transient gas flow and significantly increased transient pressure values, also increases the probability of failure of a cracked pipeline. Such a situation threatens the integrity of high stress pipelines, especially under the real working conditions of hydrogen gas transportation.     

Pipeline Heating Method Based on Optimal Control and State Estimation

In the production of oil and gas in deep waters, the flow of the produced hydrocarbon through pipelines is a challenging problem. High hydrostatic pressures and low seabed temperatures may result in the formation of solid deposits, which in critical operating conditions like unplanned shutdowns can cause pipeline blockages. One of the possible methods for flow assurance, which can be jointly used with other approaches, is to heat the pipeline. This design concept aims at heating the produced fluid, if needed, to above a safe reference temperature in order to avoid the formation of solid deposits. The objective of this article is to utilize the particle filter method for the solution of a state estimation problem, in which the state variables are considered as the transient temperatures within a pipeline cross section. In addition, the minimum temperature in the region, predicted with the particle filter method, is used in the optimal control theory as a design tool for a typical heating system, during simulated shutdown conditions. An application example is presented to illustrate the control of the minimum temperature in the region, from an observer based on the particle filter method, where temperature measurements are assumed to be available on the external surface of the pipeline.     

An MILP model for the reformation of natural gas pipeline networks with hydrogen injection

A mixed integer linear programming (MILP) model is proposed for the reformation of natural gas pipelines. The model is based on the topology of existing pipelines, the load and pressure at each node and the design factors of the region and minimizes the annual substitution depreciation cost of pipelines, the annual construction depreciation cost of compressor stations and the operating cost of existing compressor stations. Considering the nonlinear pressure drop equations, the model is linearized by a piecewise method and solved by the Gurobi optimizer. Two cases of natural gas pipeline networks with hydrogen injection are presented. Several adjustments are applied to the original natural gas pipeline network to ensure that our design scheme can satisfy the safety and economic requirements of gas transportation. Thus, this work is likely to serve as a decision-support tool for the reformation of pipeline networks with hydrogen injection.     

Evaluation of the safe separation distances of hydrogen-blended natural gas pipelines in a jet fire scenario

The desire for sustainable development in various countries has increased the use of hydrogen energy. Considering cost and time savings, the introduction of hydrogen into existing natural gas pipelines is an excellent option, and the failure consequences of hydrogen blending in natural gas pipelines should be considered. In this study, a solid flame model is used to calculate the thermal radiation intensity of a hydrogen-blended natural gas jet fire. A method is proposed to modify the calculation of the view factor in the near field, and parameters such as the specific heat capacity and calorific value of pure gas are replaced by the parameters of the mixed gas. The data of the Thornton and modified models are compared with the experimental results, and the modified model result is found to be more accurate. Using the modified model, the variations in different hydrogen blending ratios, internal pressures, and pipe diameters with the safe separation distance of the thermal radiation intensity in a pipeline accident are investigated, and the relationships between them are analyzed.     

交流输电线路对埋地金属管道稳态干扰的影响规律

随着电力和石油能源需求不断发展,电力线路和埋地金属油气管道建设在全国各地迅速展开。土地资源紧张的地区,高压输电线路和油气管道往往面临同走廊并行走线的状况。高压交流线路正常运行时,线路上的电流周期性变化产生交变磁场会在管道上产生纵向感应电动势从而引起交流稳态干扰。探讨并获得了管道外径/壁厚、管道埋深、防腐层厚度、管道防腐层绝缘电阻率等参数对交流稳态干扰的影响规律,可供电力和管道设计单位参考之用。     

支吊架附重对管系应力的影响分析

管道支吊架在火力发电厂四大汽水管道中主要承担承受管道荷载、限制管道位移和控制管道振动等作用。针对某300MW机组的再热管道系统,分析支吊架附属重量对管道一次应力和二次应力的影响,对考虑支吊架附重和不考虑支吊架附重两种情况对管道一次应力及二次应力影响进行对比,得出大型支吊架的附属重量在管道的应力分析中不容忽视,对管道的应力分布有较大影响。