Comparative Evaluation of the Resistance of Polyethylene and Steel Pipelines to a Frost Crack

We have carried out a comparative evaluation of the resistance of polyethylene and steel pipes to the action of a frost crack, i.e., to the discontinuity in the near-surface ground layer resulting from the occurrence of complex geocryological processes in the season-thawing layer of ever-frozen grounds.     

Investigation of the Hydraulic Resistance of a Combined Dust Collector

A new structure of a combined dust collector, in the unified energy field of which suspended particles are separated in interacting swirling flows, with subsequent aftercleaning of the gas by filtration has been developed. The hydraulic resistance of the combined dust collector has been investigated. The change in the pressure loss as a function of the total rate of flow of the gas in the apparatus and the flow-rate ratio has been determined. The dependence for calculation of the hydraulic resistance of this dust collector has been obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 158–162, July–August, 2005.     

Mechanical Analysis of Buried Polyethylene Pipelines under Ground Overload

Journal of Failure Analysis and Prevention - Polyethylene (PE) pipelines are widely used in natural gas transmission systems in urban areas. With the acceleration of urbanization, the scale of PE...     

Delamination Controlled Ballistic Resistance of Polyethylene/Polyethylene Composite Materials

We have investigated ballistic response of polyethylene/polyethylene (PE/PE) composites to impact by Uzi bullets. For comparison, limited work was carried out on PE/aramid fiber hybrids and PE fiber/Polycarbonate plate laminates. The plates exhibited an average ballistic resistance, V ₅₀, of approximately 90 m/s per 1 kg/m² area density. In term of the protection level per thickness, the ballistic resistance was 76 m/s per 1 mm. Visual and microscopic examinations identified indentation and delamination as the prevailing failure mechanisms. The delamination, energy calculated on the basis of a simple delamination model considering the fracture surface energy of the matrix, was shown to fully balance the dissipated kinetic energy of the bullet, while the contribution of the fiber fracture process was negligible. This is taken as strong circumstantial evidence for the significant role of this failure process in the ballistic resistance of these composites.     

TBM液压管道等效固有频率及稳定性研究

针对TBM掘进过程中产生的基础振动对液压长管道稳定性的影响,选取长管道相邻两固定支承及其之间的管道作为一个单元,建立基础振动下管道单元的非线性微分方程,并通过实验验证振动微分方程的正确性,运用等价线性化推导出管道的等效固有频率的数学模型。研究输流管道系统固有频率与稳定性的相关性,分别讨论流体参数和结构参数对等效固有频率的影响规律。结果表明:利用等效固有频率能很好地反映系统的稳定性,两者相关系数大于0.85。随着流速、压力及单元管长、内径的增大或刚度、壁厚的减小,管道系统的等效固有频率降低,系统稳定性降低;随着基础振动的增大,系统等效固有频率越低,越容易失稳。     

Investigation and Recommendations on Bottom-Dented Petroleum Pipelines

On September 21, 2015, the National Transportation Safety Board responded to a petroleum leak from a transmission pipeline in Centreville, VA. A small through crack was found leaking at a dent on the underside of the pipe, located away from any welds. The investigation found that corrosion fatigue could initiate at small dents, typically caused by impingement. While top-side dents from excavation and servicing have well-been documented and regulated, bottom-side dents, deemed acceptable per regulations, were found to be susceptible to stress corrosion and fatigue cracking. This investigation explored multiple and fundamental aspects of cracking in steel pipe dents, including nondestructive inspection, electron microscopy, finite element modeling, and long-term cyclic loading tests to characterize the cause of this pipeline accident.     

管道三层热缩套(带)现场补口应注意的问题

为解决三层聚乙烯热缩套(带)管道补口的质量问题,通过现场考察,总结出4类主要质量问题和4方面的现场条件问题,提出了与操作和检查有关的改进意见以及与套(带)选型选材有关的建议.结果表明,补口施工中的6个质量控制点是进行科学的质量检查和制定合理的质量标准;根据施工环境选择用套还是用带(定向钻工程中不应用带);套(带)收缩率不宜太高和收缩速度不宜太快;在保证底层质量的条件下允许有较小的空鼓或气泡;安装后边缘应有可见厚度的胶条;使用具有感温颜色显示功能的套(带),才能凭视觉控制最重要的温度指标.     

一种新型液压管道抗振支承研究

根据管道减振原理,设计一种新型管道液压抗振支承。该液压管道支承通过弹簧、弹簧片对振动能量进行吸收,并具有结构简单、安装方便的优点。建立振动环境下液压管道振动的数学模型,通过仿真分析安装抗振支承前后管道应力的波动响应,并进行实验验证。结果表明:该抗振支承能有效减小管道应力和流体波动,减振后管道应力最大值和流体压力平均波动幅值分别减小了14.80%、40.49%,有关结论能为在基础振动环境下的管道抗振提供一定的依据和参考。     

TBM液压管道频谱特性分析和结构优化

考虑到全断面硬岩推进机(TBM)掘进过程中轴向基础振动对流体流速和压力波动的影响,运用输流管道流固耦合轴向运动4-方程模型,分析基础振动的影响,建立轴向基础振动下的TBM液压管道轴向耦合振动方程组,并用直接解法在频域内对其进行求解,再运用MATLAB软件对管道出口处流速和压力的频域响应特性进行仿真计算,随之分析基础振动和不同结构参数对流体频域响应的影响规律。同时,为减弱基础振动对流体出口参数的影响,运用正交实验法对管道进行结构优化,优化后的管道系统流速的频域幅值整体上减小了48.61%,从而在一定程度上抑制了因基础振动带来的流体波动。     

高韧性聚乙烯合金的制备与性能

采用氢化苯乙烯-丁二烯-苯乙烯共聚物(SEBS)、二元乙丙橡胶(EPR)、三元乙丙橡胶(EPDM)及乙烯-辛烯共聚物(POE),分别与高密度聚乙烯(HDPE)以不同比例在双螺杆挤出机中熔融共混,制备高韧性聚乙烯合金。冲击测试表明,在四种共混物中,HDPE/POE具有较佳的力学性能;Vu-Khanh方程表明,Gi与冲击性能有很好的对应关系;扫描电镜表明,弹性体在HDPE中有很好的分散,橡胶粒径较小,分散均匀;形变区观察显示,纯HDPE为脆性断裂,而HDPE/弹性体断裂表面发生塑性形变,发生剪切屈服,呈明显的韧性断裂。     

Influence of Microadditions on the Resistance to Brittle Fracture of Welded Joints of Oil Pipelines

On the basis of the results of testing of influence of modifying microadditions (Ce, Y, Ba, Ca, and Zr) on the characteristics of the resistance to brittle fracture of a weld metal of welded joints of oil-and-gas pipelines, their optimal content in welds is determined. We propose mathematical models for numerical prediction of the crack resistance of welded joints.     

Determination of the Resistance to Light of Polyethylene Shrink Films Used for Pallet Loads

The shrink films used to fix the loads on pallets are subjected to outdoor exposure and, particularly, to temperature changes and light. The resistance to photodegradation of these films must be taken into account in the design of a quality certificate. The natural degradation of the films was carried out in the natural environmental testing station in Bandol (south of France). The climate of this area represents the conditions encountered around the Mediterranean (moisture, temperature and radiant energy), which are as severe as those in most temperate countries. The accelerated tests were made at 60°C in a Sairem-Cepap 12/24 cabinet comprising four mercury gas-filled arc lamps of the mean pressure type. The quality of the light is representative of natural photoageing. Any radiation of wavelength lower than 290 nm, which is absent from the solar spectrum, is carefully eliminated. The light sources radiate light rich in photons that have wavelengths between 290 and 450 nm, and provide one of the main factors of degradation. The intensity of emission and the spectral composition were constant during 5000 h. Three kinds of films of 120 μm thickness were tested: (i) four films with ‘medium’ protection against sunshine (6 months resistance in a very sunny country); (ii) four films with ‘high’ protection against sunshine (12 months resistance in a very sunny country); (iii) one reference film without any protection. A film was considered acceptable if its mechanical properties (tensile strength and elongation) did not fall more than 50% after exposure to natural radiations for 6 or 12 months, respectively. Comparative tests have shown that for these particular kinds of polyethylene films, exposure to natural radiations at Bandol for 6 or 12 months is equivalent to an accelerated ageing in a Sairem-Cepap cabinet of 350 or 500 h, respectively.     

Industrial Synthesis and Evaluation of the Hydrodynamic Efficiency of Potential Agents for Decreasing Resistance in Petroleum Pipelines

The influence of antiturbulence additives on the decrease in the hydrodynamic resistance in main pipelines is investigated. The dependence of the Thoms effect on the physicochemical properties of a polymer obtained on an industrial plant is analyzed. The method for evaluating the efficiency of potential agents of decreasing the hydrodynamic resistance is proposed.     

聚对苯二甲酸乙二酯轧制及加热过程中的织构研究

用X射线面探测器研究了半结晶态聚对苯二甲酸乙二酯(PET)在轧制和随后的加热过程中的织构变化.实验结果表明,PET的初始取向接近随机分布状态,轧制形变后的织构包括{100}<001>组分和不完全纤维织构(<001>∥轧制方向),并且形变量愈大,织构愈强;对轧制形变后的PET进行加热处理,发现上述织构组分增强,并且随加热温度升高和加热时间延长进一步增强.X射线平均衍射强度法计算PET结晶度的结果表明,结晶度在轧制形变后大幅下降,然后随加热温度升高和加热时间延长逐渐上升.分析认为,PET在轧制形变后的织构演化符合(100)[001]分子链滑动机制.     

Hydraulic Resistance of a Random Spiral Packing for Regenerators

Results of an experimental investigation of two types of metallic spiral packings for regenerative heat exchangers are considered. They are compared to packings of other types used in regenerators; a method of calculation of the hydraulic resistance of the packings investigated is proposed.     

聚乙烯外防腐管线液体环氧补口技术的应用

聚乙烯外防腐层管线液体环氧补口技术首次在我国大型管线施工中试用时,通过现场指导试用过程与标准编制过程相结合的方式,提出了实际应用与这种补口技术的涂料供货和现场施工有关的技术标准,同时总结出补口技术具有以下特点:涂装过程简单、界面粘结牢固、修补容易、检验结果可靠、材料价格较低、能源消耗较少、流水作业较快、没有阴极保护电流屏蔽,为推广使用这种补口技术确立了初步的技术标准.     

海流冲击对深海采矿装备液压管道流固耦合振动的影响

为研究海流冲击对深海采矿装备液压管道流固耦合振动的影响,利用伯努利—梁模型,对内流作用下的柔性管道进行受力分析,建立管道流体流固耦合振动方程。根据有无外部周期性冲击作用力两种情况对液压系统管道进行了仿真。仿真结果表明:(1)外部周期性冲击力加剧了管道内部的油压波动。(2)外部周期性冲击力增大液压管道振动的最大位移。     

Diagnostics of the Engineering State of Steam Pipelines of Thermal Power Plants by the Hardness and Crack Resistance of Steel

Materials Science - We propose a nondestructive method for the diagnostics of the current state of heat-resistant steels after long-term operation in the steam pipelines of thermal power plants...