Reliability Analysis of Repairable Systems Using Stochastic Point Processes

In order to analyze the failure data from repairable systems, the homogeneous Poisson process (HPP) is usually used. In general, HPP cannot be applied to analyze the entire life cycle of a complex, re-pairable system because the rate of occurrence of failures (ROCOF) of the system changes over time rather than remains stable. However, from a practical point of view, it is always preferred to apply the simplest method to address problems and to obtain useful practical results. Therefore, we attempted to use the HPP model to analyze the failure data from real repairable systems. A graphic method and the Laplace test were also used in the analysis. Results of numerical applications show that the HPP model may be a useful tool for the entire life cycle of repairable systems.

Analysis of the Reliability Model of the Tool Magazine Subsystem in the Processing Center

Tool magazine is an important part of a processing center.Tool magazines have the advantage of reducing work parts turnover,handling,and storage time.In addition,some research shows that the use of tool magazine in machine tools in the machining center can make the cutting time utilization rate of machine tools 3-4 times higher than that of ordinary machine tools,and has better machining consistency,thus improving processing accuracy and processing efficiency,shortening the production cycle.Therefore,the reliability,efficiency and accuracy of the tool magazine have a crucial impact on the stability of the machine tool.Therefore,the reliability analysis of CNC machine tool magazine is considerably important.In view of this problem,this paper puts forward that the reliability model of the tool magazine is established after the parameter estimation and hypothesis test,and then the maintainability model of the tool magazine is built,it ends with the fault analysis of the tool magazine.

Method of Estimating Human Error Probabilities in Construction for Structural Reliability Analysis Based on Analytic Hierarchy Process and Failure Likelihood Index Method

Human error(HE) is the most important factor influencing on structural safety because its effect often exceeds the random deviation.Large numbers of facts have shown that structural failures may be caused by the gross error due to HE.So it is essential to analyze HE in construction.The crucial work of human error analysis(HEA) is the estimation of human error probability(HEP) in construction.The method for estimating HEP,analytic hierarchy process and failure likelihood index method(AHP-FLIM),is introduced in this paper.The method also uses the process of expert judgment within the failure likelihood index method(FLIM).A numerical example shows the effectiveness of the methods proposed.

Effect of Healthcare Failure Mode and Effect Analysis on Reducing Error Risk of Neonatal Parenteral Nutrition Solution Dispensing

[Objectives]To investigate the effect of healthcare failure mode and effect analysis(HFMEA)on reducing error risk of neonatal parenteral nutrition solution dispensing.[Methods]A research team was established to identify the failure mode(FM)in each link of the formulation process of neonatal parenteral nutrition solution by HFMEA,quantify the severity(S),occurrence(O)and detection(D)of FM,and evaluate FM by risk priority number(RPN).For FM with the values of RPN>16,failure cause analysis was conducted,and corresponding improvement measures were formulated.The weight coefficient and random consistency ratio(CR)of deployment process were calculated in Matlab R2018a by compiling the Analytic Hierarchy Process(AHP)program.Six months after the implementation of improvement measures,the implementation effect was evaluated by comparing the changes of the values of RPN which was evaluated comprehensively and the rate of dispensing errors before and after the implementation of HFMEA.[Results]In the preparation process of neonatal parenteral nutrition solution,a total of 13 FMs with medium and above risk were found,the weight coefficient of medical order review,dosing and mixing was 0.2703,the weight coefficient of drug dispensing check and review was 0.1432,the weight coefficient of print label was 0.1015,the weight coefficient of distribution was 0.0716,and CR=0.0491<0.1.After six months of intervention,the total RPN value decreased by 64.81%from 127.8 to 45.0.The deployment error rates were significantly lower after the implementation,and the difference was statistically significant(P<0.05).[Conclusions]HFMEA can effectively reduce the error risk in preparation of neonatal parenteral nutrition solution,improve the quality of dispensing and promote the safety of neonatal medication.

An Evaluation of Human Error Probabilities for Critical Failures in Auxiliary Systems of Marine Diesel Engines

Human error,an important factor,may lead to serious results in various operational fields.The human factor plays a critical role in the risks and hazards of the maritime industry.A ship can achieve safe navigation when all operations in the engine room are conducted vigilantly.This paper presents a systematic evaluation of 20 failures in auxiliary systems of marine diesel engines that may be caused by human error.The Cognitive Reliability Error Analysis Method(CREAM)is used to determine the potentiality of human errors in the failures implied thanks to the answers of experts.Using this method,the probabilities of human error on failures were evaluated and the critical ones were emphasized.The measures to be taken for these results will make significant contributions not only to the seafarers but also to the ship owners.

Development of Optimal Maintenance Policies for Offshore Wind Turbine Gearboxes Based on the Non-homogeneous Continuous-Time Markov Process

Gearbox in offshore wind turbines is a component with the highest failure rates during operation. Analysis of gearbox repair policy that includes economic considerations is important for the effective operation of offshore wind farms. From their initial perfect working states, gearboxes degrade with time, which leads to decreased working efficiency. Thus, offshore wind turbine gearboxes can be considered to be multi-state systems with the various levels of productivity for different working states. To efficiently compute the time-dependent distribution of this multi-state system and analyze its reliability, application of the nonhomogeneous continuous-time Markov process(NHCTMP) is appropriate for this type of object. To determine the relationship between operation time and maintenance cost, many factors must be taken into account, including maintenance processes and vessel requirements. Finally, an optimal repair policy can be formulated based on this relationship.

APPLICATION OF STOCHASTIC FINITE ELEMENT METHOD TO STRENGTH AND STABILITY ANALYSIS OF EARTH DAMS

This paper applies the stochastic finite element method to analyse the statistics of stresses in earth dams and assess the safety and reliability of the dams. Formulations of the stochastic finite element method are briefly reviewed and the procedure for assessing dam's strength and stability is described. As an example, a detailed analysis for an actual dam Nululin dam is performed. A practical method for studying built-dams based on the prototype observation data is described.

STPA和CREAM方法在飞行冲突调配人因差错研究中的应用

为了研究管制员飞行冲突调配的人因差错问题,进而有效评估管制员解决飞行冲突的可靠性,以保障空中交通的安全运行,提出系统理论过程分析(System Theoretic Process Analysis, STPA)与认知可靠性与失误分析方法(Cognitive Reliability and Error Analysis Method, CREAM)相结合的人因可靠性分析方法。首先,通过STPA方法构建系统控制模型,识别不安全控制行为(Unsafe Control Action, UCA)以及致因因素,找到管制员在调配飞行冲突过程中可能存在的差错行为;其次,基于CREAM扩展法对管制员的差错行为进行定量分析,得到管制员调配飞行冲突的人因失误概率。研究显示:使用该方法能够系统、全面地识别出管制员在调配飞行冲突过程中出现的差错行为,进而计算管制员飞行冲突调配的人因失误概率。实例分析表明该方法可以预测管制员在飞行冲突调配过程中的人因失误概率及可靠性,为管制员人因可靠性分析提供了新思路。

电缆接头在10 kV配电施工中的质量控制与可靠性分析

立足于10kV配电工作环境,文章对电缆接头部分进行了研究,并对其质量控制与可靠性进行了分析。概述了电缆接头组装技术,提出了针对性的质量控制方法。在设计上合理规划,施工严谨,可大幅提高电缆接头的可靠性,从而保障电网安全稳定运行。同时,针对电缆接头设计不合理、材料质量问题、施工工艺不到位、施工环境恶劣等易引发故障因素,提出了具体措施,以提高电缆接头可靠性。

机械零部件的动态可靠性灵敏度分析

传统的零部件可靠性模型不能很好地反映变幅随机载荷和强度退化对可靠性的影响,忽略可靠度和失效率随使用时间的变化规律。研究机械零件强度、载荷和可靠度随时间的变化规律,运用随机过程和顺序统计理论建立考虑变幅随机载荷和强度退化下机械零件的动态可靠性功能方程模型,利用二阶矩和摄动方法求出机械零部件的动态可靠性指标,并计算出零部件的动态可靠度。以建立的动态可靠性数学模型为基础,将可靠性设计理论与灵敏度分析方法相结合,提出动态可靠性灵敏度设计的计算方法,讨论动态可靠性灵敏度设计问题,以扭杆为例,给出各参数动态可靠性灵敏度的变化规律,分析设计参数的改变对扭杆可靠性的影响,为机械零部件的动态可靠性设计和动态灵敏度设计提供理论依据。

我国大型工艺压缩机故障情况调研及失效预防对策

调研了我国石化企业大型工艺压缩机失效破坏现象,在相关数据的基础上,分析了压缩机关键部件的故障模式与故障原因,归纳了压缩机失效破坏现象的共性问题,提出了极端条件和复杂工况下工艺压缩机可靠长周期运行的对策与建议,对共性关键技术的发展进行了展望。

一种适用于可靠性评估的电网设备时变停运模型

建立精确的元件停运模型是电力系统中长期可靠性评估的基础工作,现有的元件停运模型通常不能反映元件时变的运行工况和维修对元件的影响。采用阶梯函数来近似模拟元件老化故障率曲线,并基于更新过程理论建立了元件时变停运模型。该模型可以反映中长期可靠性评估中时间对老化故障率的增长效应和维修对老化故障率的降低效应。实际的变压器算例表明,该模型适合模拟任意老化故障率曲线,可用于老化模式已知的元件寿命分布函数和可用度稳态值的评估。相比于传统模型,所提模型具有更好的精度和更广的适用性。

基于CREAM的电网人为可靠性定量分析方法

目前电网可靠性的相关研究主要集中在输变电设备或是电网供电可靠性,人为操作可靠性的研究尚不多见。首先叙述了电网人为操作可靠性概念及认知可靠性和失误分析模型(CREAM)基本法,然后借鉴了核工业领域的人为可靠性分析模型,结合电力操作特点和已有的安全相关的规章制度,给出9类通用效能条件的评估细则,提出一种基于CREAM的电网人为操作可靠性定量分析方法。通过不同环境条件下某变电站倒闸操作的案例分析,验证了模型的正确性。

边坡失效概率估计的高斯过程动态响应面法

针对传统响应面法在求解具有高度非线性隐式功能函数边坡可靠性问题上的局限性,采用适用于处理高维度、小样本、非线性回归问题的高斯过程回归模型构建隐式功能函数的响应面,将高斯过程响应面与蒙特卡罗模拟法相结合,通过构造合理的迭代方式,在利用高斯过程回归模型的不确定性评价功能获取最优采样点的基础上,实现了高斯过程响应面动态更新,由此提出了边坡失效概率快速估计的高斯过程动态响应面法。利用数值算例验证了该方法的有效性,在此基础上对3个边坡算例进行了可靠性分析。结果表明,与传统响应面法相比较,该方法计算精度与计算效率明显较高,易于与既有的边坡分析软件相结合,且实现容易,适用于边坡可靠性的快速分析。

电梯检验过程中的人因失误分析与管理对策

近年来,我国电梯行业发展迅速,但电梯安全事故频发。导致电梯安全事故的原因中,人为失误占很大比重。因此,研究电梯检验过程中的人因失误及管理对策具有重要意义。应用层次分析法构建了理论模型,对可能的人因失误的关键要素进行提取并按相对重要性进行排序,确定了影响人因失误的重要因素。结合近6年南京市电梯检验人因失误的统计数据,应用灰色关联度理论对操作因子进行关联分析,并由此提出了减少电梯检验过程中人因失误的管理建议。

基于CREAM方法的人因失效概率预测模型研究

认知可靠性与差错分析方法(CREAM)是第二代人因可靠性分析方法中的代表方法之一,通过对任务环境进行分析从而直接确定人为差错发生概率。本文分析了该方法及其后续研究在人因可靠度评估时存在的主要问题,并以CREAM方法为基础建立新的人因失效概率预测模型。模型首先要求有针对性的对具体任务环境确定通用性能影响因子(CPC)权重,然后通过对CPC进行打分对任务环境进行量化,通过加权求和的方式分别计算出CPC的改进总分值G和降低总分值J,最后运用新建的预测模型计算出人因失效概率。新模型提出了三点改进:第一将任务环境设定为连续的空间;第二提出了不同的工作环境(任务环境)应该有其对应的CPC因子权重;第三考虑正影响CPC因子和负影响CPC因子的双重影响,建立双变量预测模型,预测结果更加合理。

复杂系统中人误原因因素的层次分析法

介绍和评析了人误分析历史上有重要影响的几种人误原因因素分类方法:传统人因分类法、信息处理分类法和认知系统工程分类法。基于认知可靠性及失误分析方法(CREAM)的人误原因因素分类,运用层次分析法(AHP)基本原理,建立了大规模复杂人-机系统人误原因因素层次结构模型及相应的AHP程序,并以JCO公司超临界事故为实例进行了分析。分析和应用结果表明,本文所建立的人误原因因素层次结构模型及AHP程序能够辨识出大规模复杂人-机系统中人误的主要原因因素,进而寻找出最优预防方案,对预防和减少此类人误事故的发生有积极意义。

认知失误定量分析方法及其在PSA中的应用

认知可靠性和失误分析方法(CREAM)是第二代人的可靠性分析方法中的代表方法之一。以CREAM的核心思想为基础,对定量分析方法进行了改进,给出了共同绩效条件(CPC)对人的可靠性影响的量化指数。提出了用环境影响指数来定量计算情景环境迫使人的认知失误的发生概率,给出了概率安全评价(PSA)中人误概率的分析方法,并用于诊断核电站蒸汽发生器传热管破裂和蒸汽发生器隔离时的人误概率分析。

离散时间修理延迟单部件可修系统的可靠性分析

针对离散时间下修理有延迟的单部件可修系统,建立了系统状态转移的数学模型。该模型假定系统有正常、维修和故障后待修三种状态,并且系统寿命、修复时间和等待修理时间均遵从一般离散分布。利用随机过程的方法,研究了该可修系统状态之间的转移关系。在该模型的基础上得到了系统可靠度、可用度、平均故障次数等常用可靠性指标。最后,通过一组算例来说明了该模型的有效性。