Leak rate calculation for LBB analysis in high temperature gas-cooled reactors

Leak rate calculation is very important for Leak Before Break (LBB) analysis. Helium is used as coolant in high temperature gas-cooled reactor (HTGR). Therefore the flows in the cracks of HTGR vessels and pipes are single phase, which are different from the two phase critical flows in the cracks of water reactors. In the present paper, simple leak rate calculation formulae for compressible laminar and turbulent flows in HTGR cracks are introduced. The velocity and pressure distributions in cracks as well as the leak rates are calculated using the formulae. Numerical simulations are also conducted for compressible laminar, turbulent and critical flows with different crack widths and depths. The results of the numerical simulation and theoretical formulae are compared with experimental data. The comparison shows that both the simple theoretical formulae and the numerical simulation can achieve good results.     

长输油气管道泄漏检测方法概述及实用性分析

随着我国国民经济的迅速发展,石油与天然气作为主要能源的代表,其需求量不断增大,长输油气管道的安全风险问题也备受关注。尤其是,近几年来管道泄漏爆燃事故时有发生,不仅给人民生命安全和财产造成了极大的损失,也给生态环境造成了污染和破坏。因此,将智能、高效的泄漏检测定位方法应用于油气管道及时制止次生灾害的发生显得至关重要。通过分析管道泄漏产生的主要原因,概述了目前常用的几种管道泄漏检测方法,并采用负压波和流量平衡法相结合的方法在原油管道进行泄漏检测实验。结果表明,该方法可以对输油管道泄漏进行实时监测,尤其是微小缓慢的泄漏,同时也可以准确定位泄漏点。     

A risk-based methodology for the optimal placement of hazardous gas detectors

Hazardous gas detection systems play an important role in preventing catastrophic gas-related accidents in process industries. Even though effective detection technology currently exists for hazardous gas releases and a majority of process installations have a large number of sensitive detectors in place, the actual operating performance of gas detection systems still does not meet the expected requirements. In this paper, a risk-based methodology is proposed to optimize the placement of hazardous gas detectors. The methodology includes three main steps, namely, the establishment of representative leak scenarios, computational fluid dynamics (CFD)-based gas dispersion modeling, and the establishment of an optimized solution. Based on the combination of gas leak probability and joint distribution probability of wind velocity and wind direction, a quantitative filtering approach is presented to select representative leak scenarios from all potential scenarios. The commercial code ANSYS-FLUENT is used to estimate the consequence of hazardous gas dispersions under various leak and environmental conditions. A stochastic mixed-integer linear programming formulation with the objective of minimizing the total leak risk across all representative leak scenarios is proposed, and the greedy dropping heuristic algorithm (GDHA) is used to solve the optimization model. Finally, a practical application of the methodology is performed to validate its effectiveness for the optimal design of a gas detector system in a high-sulfur natural gas purification plant in Chongqing, China. The results show that an appropriate number of gas detectors with optimal cost-effectiveness can be obtained, and the total leak risk across all potential scenarios can be substantially reduced. This methodology provides an effective approach to guide the optimal placement of point-type gas detection systems involved with either single or mixed gas releases.     

基于D-S理论和AMESim技术的液压缸泄漏故障诊断仿真研究

将D-S数据融合技术引入液压缸泄漏故障诊断领域,通过异类传感器获取液压缸泄漏故障下的多模信息,将多源信息进行融合,有效解决了单传感器判别精度不高的问题.利用AMESim软件分别对液压缸的内泄漏和外泄漏故障状态以及正常工作状态进行仿真,提取其压力、流量、行程信号,并利用数据融合技术进行故障诊断判别.     

Android平台下井下安全监控系统内存泄露分析

Android平台下井下安全监控系统存在内存泄露问题。经过分析认为Java内存泄露是破坏系统的主要因素。文章着重介绍了在Android平台下开发应用程序中,内存泄露出现的原因及相应的解决办法,并通过示例程序进行说明。     

泄漏油品在雨水作用下渗透范围模拟计算

对埋地管道下部泄漏油品在雨前、雨中和雨后的不同水分分布土壤中油品渗透扩散进行模拟分析,借助CFD软件建立土壤多孔介质中油水两相流动的三维流动传质耦合模型。模拟计算结果表明:油品在地下渗透扩散范围受水分分布影响明显,泄漏油品在下雨前的土壤中地下扩散区域以不倒翁状向四周渗透;雨中泄漏油品受雨水冲带后在地下四处流窜并以极不规则形状区域向四周扩散;雨后泄漏油品以烧瓶状区域向四周扩散。在雨前、雨中和雨后三种工况下,扩散速率稳定后,雨后的泄漏范围及地表扩散面积均是最小;雨中油品泄漏范围最大且增长速率比雨前高约3%;雨前油品地表扩散范围最大且增长速率比雨中高约2%。     

低充氦浓度氦质谱检漏技术应用研究

为解决不允许抽真空和充压的密封装置的密封性能检测问题,开展了较低充氦浓度的氦质谱检漏模拟实验。实验采用通道型标准漏孔和模拟密封容器,在容器内的氦气浓度为0.5‰,1‰,3‰,5‰时分别实测了混合气体中氦气通过漏孔的漏率,基于混合气体以同种比分通过分子流漏孔的假设,不同浓度下测得的漏率结果与理论计算相比较;实验得出了在一定体积的空间内定点释放少量的氦气自由扩散至基本均匀分布所需时间。在实验的基础上,专门设计低充氦浓度检漏的标定装置,可降低因标准漏孔的氦浓度与检漏充氦浓度相差较大而引入检漏结果的不确定度。     

芳烃装置锅炉给水泵密封失效分析及改进

介绍了冷凝水回收泵在实际生产运行几年里发生的因机械密封泄漏导致密封失效故障的详细分析,查找到了解决问题的途径和办法。问题发生的现象分别为:密封面出现损坏、动环发生断裂、动环的弹簧全部断裂、静环、静环承磨台被磨掉、动环的辅助密封损坏,并通过对实际运行参数的密封系统理论核算与实际运行密封型号相关尺寸及材质的对比提出了改进方案即:改善静环的材质,采用石墨浸金属锑、对弹簧的参数和弹簧座结构进行改动、改进辅助系统,增加换热器的换热面积、改进冷却水系统等措施解决了密封失效故障,从而保障设备长周期安全平稳运行。     

防漏早强韧性水泥浆体系的室内研究

大庆、长庆、克拉玛依等老区油田油气资源埋藏浅、井底温度低,加之长期注水开发等增产措施的广泛应用,储层地质结构复杂、压力系统紊乱,大斜度井、水平井钻遇溢漏同存的几率增加,固井过程中漏喷风险增大,对水泥浆体系提出了更高的要求。从材料学角度出发,利用经过表面预处理的新型油井水泥增强剂DRB-3S的低温增强、自悬浮稳定、混配性好的特点,将其与膨胀材料和抗窜增韧材料进行复配,制得了防漏早强韧性水泥浆体系。实验结果表明,该体系施工性能好,稠化过渡时间短,API失水量小,游离液为0,55℃时4 h抗压强度为7.2~11.5 MPa,还可有效封堵毫米级的渗透和裂缝性漏失,为复杂区块大斜度井、水平井固井质量的改善提供了有力的技术支持。