Innovative safety valve selection techniques and data

The new valve data resources and modeling tools that are available today are instrumental in verifying that that safety levels are being met in both current installations and project designs. If the new ISA 84 functional safety practices are followed closely, good industry validated data used, and a user's maintenance integrity program strictly enforced, plants should feel confident that their design has been quantitatively reinforced. After 2 years of exhaustive reliability studies, there are now techniques and data available to support this safety system component deficiency. Everyone who has gone through the process of safety integrity level (SIL) verification (i.e. reliability math) will appreciate the progress made in this area. The benefits of these advancements are improved safety with lower lifecycle costs such as lower capital investment and/or longer testing intervals. This discussion will start with a review of the different valve, actuator, and solenoid/positioner combinations that can be used and their associated application restraints. Failure rate reliability studies (i.e. FMEDA) and data associated with the final combinations will then discussed. Finally, the impact of the selections on each safety system's SIL verification will be reviewed.     

环境噪声对语言识别率的影响

本文比较了４种干扰声源声级（ｄＢＡ）和语言干扰级（ＳＩＬ）的关系,观察了不同ｄＢＡ,ＳＩＬ和信噪比（Ｓ／Ｎ）对语言识别率影响的规律,结果表明ｄＢＡ与ＳＩＬ有很好的线性关系,但不同性质的噪声源,两者间的差值相差很大,４种干扰声源下的语言识别率都有随ｄＢＡ和ＳＩＬ的增加而减少,随ＳｄＢＡ／ＮｄＢＡ和ＳｄＢＡ／ＮＳＩＬ的增加而提高的趋势,但语言识别率与ｄＢＡ,ＳｄＢＡ／ＮｄＢＡ的相关性因噪声的性质不同有     

The accidental risk assessment methodology for industries (ARAMIS)/layer of protection analysis (LOPA) methodology: A step forward towards convergent practices in risk assessment?

In the last ten years, layer of protection analysis (LOPA) emerged as a simplified form of quantitative risk assessment (QRA). The European Commission funded project Accidental Risk Assessment Methodology for Industries in the context of the Seveso 2 Directive (ARAMIS) has recently been completed. ARAMIS has several modules which give a consistent simplified approach to risk assessment which does not approach the complexity or expense of full QRA. LOPA is potentially a means of carrying out the assessment of barriers required in ARAMIS. This paper attempts to explain the principles of LOPA and the means by which it can be used within ARAMIS.     

Probabilistic assessments in relationship with safety integrity levels by using Fault Trees

In this article, we study the assessment of safety integrity levels of safety-instrumented system by means of Fault Trees. We focus on functions with a low demand rate. For these functions, the appropriate measure of performance is the so-called probability of failure on demand (PFD) or probability of not functioning on demand. In order to calculate accurately the average PFD as per IEC 61508 standard, we introduce distributions for periodically tested components into Fault Tree models. We point out the specific problems raised by the assessment of safety integrity levels (SILs), which restrict the use of the formulae proposed in the standard. Among these problems there is the fact that SIL should be assessed by considering the time-dependent behavior of the system unavailability in addition to its average value. We check, on a simple pressure protection system, the results obtained by means of the Fault Tree approach against those obtained by means of stochastic Petri nets with predicates.     

结合解释结构模型与网络分析法于FMEA的应用

引入解释结构模型法,分析出控制措施之间的层次、顺序关系,再用网络分析法考虑控制措施间的相依关系,进行客观权重的计算,作为FMEA中的新探测度,再进行新RPN的计算。以回炉焊接制程提升为研究案例,比较新方法与传统方法的差异,发现优先改善项目与改善顺序的不同产生不同结果,提升了改善的效果。     

The role of manufacturing defects in munition component failures

The U.S. Army Research Laboratory, Weapons and Materials Research Directorate performs numerous failure analysis investigations on munition-related components. Many of the failures are attributable to defects that can be traced back to the manufacturing process. Typical manufacturing defects encountered include those associated with the material, forging, casting, welding, and heat treatment processes. Dimensional anomalies have also been noted. Munition component failures are very costly and may seriously affect the safety and readiness of the armed forces. Additionally, repeated failure may lead to the grounding (removal from service) of a system, depending on the severity of the problem. Specific examples of component defects/failures discussed in this report include bomb fin retaining bands, general purpose bomb suspension lugs, missile launcher attachment bolts, cluster bomb tailcones, general purpose bomb fins, and Gatling gun breech bolt assemblies. This paper focuses on the importance of proper manufacturing techniques to the munitions industry and, by inference, to numerous other industries.     

钢筋混凝土框架结构基于可靠度的最可能倒塌失效模式分析

在建筑结构的抗震设计中,常常希望通过合理的设计,使结构能按预期的强柱弱梁失效模式破坏,通常通过提高柱端弯矩增大系数(COF)使结构满足“强柱弱梁”的要求。该文考虑上层、下层、中间层这3 类层间失效模式,采用结构可靠度理论,对钢筋混凝土框架结构最可能倒塌失效模式及完全梁铰式失效模式的相对发生概率进行研究。算例结果表明:当COF 较小时,结构最可能失效模式为中层失效模式;当COF 较大时,则结构倒塌由上层失效模式控制。研究结果可为罕遇或特大地震作用下结构的抗倒塌设计提供参考。     

Early failure analysis of machining centers: a case study

To eliminate the early failures and improve the reliability, nine ex-factory machining centers are traced under field conditions in workshops. Their early failure information throughout the ex-factory run-in test is collected. The field early failure database is constructed based on the collection of field early failure data and the codification of data. Early failure mode and effects analysis is performed to indicate the weak subsystem of a machining center or the troublemaker. The distribution of the time between early failures is analyzed and the optimal ex-factory run-in test time for machining center that may expose sufficiently the early failures and cost minimum is discussed. Suggestions how to arrange ex-factory run-in test and how to take actions to reduce early failures for machining center is proposed.     

基于可靠性理论的包装振动试验方法改进

目的基于可靠性理论改进包装件的振动试验方法。方法通过界定产品平均寿命、试验截止时间和失效数,研究了样本大小对整个试验可靠程度的影响,以及改变包装阻尼与振动频率对试件振动幅值的影响。结果保证包装产品的可靠性有必要明确样本的大小,样本过小将不能完全体现该批产品的可靠程度;样本过大,虽然能充分体现该批产品的可靠程度,但试验费用将大大提高。随着产品样本的增大,使用者的风险降低。结论在包装件振动试验中融入可靠性理论,并在试验标准中加入失效率验证程序和失效率等级等内容,提高了包装件的可靠性。     

FMEA在商品包装设计中的应用

介绍了FMEA的思想和应用特点,以啤酒包装为例分析了商品流通过程中包装所起的作用和可能出现的失效模式,并讨论了其影响;通过风险矩阵等方法对这些潜在的风险进行了分析,针对可能造成的影响给出了相应的措施,分析了其效果。以商品在流通中的物流过程为对象,提供了包装设计的具体步骤,对包装的绿色设计和最优应用提供了一条新颖的思路。     

关于先进制造设备故障规律的新认识

通过大量的故障记录数据的统计分析,结合专家的经验,描绘出先进制造设备(Advanced Manufacturing Eguipment,AME)的故障率特征曲线;在分析AME各个使用阶段故障原因的基础上,提出了有关AME故障规律的新认识。     

FMEA下的超市食品HACCP计划制定与实现

结合故障模式与影响分析(FMEA)以及危害分析和关键控制点(HACCP)方法,可以分析超市食品供应中的潜在故障模式和决定给予风险优先级的关键控制点,从而可以产生一个HACCP计划.这一方法在一个超市产生猪肉的供应计划中成功地得到应用.     

双向应力状态下混凝土的动态压缩试验研究

利用大连理工大学自行研制、改造的液压伺服静、动态三轴试验系统对71个立方体混凝土试件进行双轴应力状态下的动态压缩试验,侧压比例为0:1、0.25:1、0.5:1、0.75:1、1:1五个级别,加载速率为10^-5s^-1、10^-4s^-1、10^-3s^-1、10^-2s^-1四个量级。系统研究了不同应变速率以及不同应力比例条件下混凝土的破坏模式以及极限强度变化规律。试验表明:在双向应力状态下,极限强度随着应变速率有一增加的趋势;侧向压力的大小是影响破坏模式和极限强度的最重要因素。提出了综合考虑应力组合与应变速率影响的统一强度准则。     

FMEA在过程管理中的应用

2000版的ISO9000标准明确提出过程管理的方法。分析了质量管理体系的现状和实施过程管理的必要性。把失效模式及后果分析（FMEA）作为过程管理的一种工具提出来,并通过一个实例具体介绍了在过程管理中使用FMEA的步骤。     

塔里木油田氮气钻井内防喷器组的可靠性分析

综合应用故障模式影响及危害度分析（FMECA）与故障树分析(FTA)对氮气钻井内防喷器组进行可靠性分析。首先对氮气钻井内防喷器组进行系统级和设备级的故障模式影响及危害度分析,找出各个设备的常见故障模式,提出对应的改进措施,并定量计算出故障模式的危害度和系统内各个内防喷工具的危害度,为故障树分析确定顶事件。故障树分析,求出导致氮气钻井内防喷器组主要故障的所有底事件和最小割集,进而确定底事件的结构重要度的大小和底事件的组合方式对系统故障的影响力,对结构重要度大的底事件和底事件的组合方式对系统故障的影响力高的故障形式优先采取改进措施,并对薄弱零部件进行可靠度计算,更有针对性地对薄弱零部件进行设计改进和故障监测。鉴于对氮气钻井内防喷器组的可靠性研究,得出箭型止回阀锥面密封故障、翻板浮阀的复位弹簧失效、投入式止回阀的投球被压溃、旁通阀的扣断裂和旋塞阀的旋球被“抱死”是导致系统失效的主要故障模式,分析5种故障模式的所有可能的原因并提出了相应的改进方案。     

基于改进EMD与有限元的测力轮对组桥方案比较

基于有限元方法和改进的经验模态分解方法,研究测力轮对两种组桥方案信号输出的特点。建立测力轮对三维有限元模型,施加边界条件和载荷,计算轮对辐板面弹性应变以及两种组桥方案的电桥输出。提出改进的EMD方法,以改进的极值域均值提高局部均值的求解精度,用边界波形匹配预测法来抑制端点效应,结合差分与累加求和法抑制出现的模态混叠现象。运用改进的EMD方法对两种组桥方案电桥输出进行经验模态分解,提取并分析了电桥信号的各个谐波分量。研究结果表明：GB5595-85电桥输出主要为幅值波动较大的低频分量;最佳组桥方案输出主要为幅值小的高频分量,能有效减小电桥的幅值波动,具有更高的测量精度。