关于设备大修理中沉没成本的商榷

设备在使用过程中会有经常性的有形磨损,当有形磨损达到一定程度后,就会遇到对原有设备进行更新还是大修理的决策问题.常用的单位产品生产成本比较法中,成本的确定还存在着争议.本文根据现金流量分析和决策图示,辨析了设备大修理中沉没成本的概念,提出更为合理的成本确定方法,在实践中有一定的指导作用.     

对休哈特控制图中平均值控制界限的商讨

采用休哈特控制图的方法可以对测量过程是否处于统计控制状态进行控制.但是,对于平均值控制界限的确定则认为不妥,根本原因是,平均值控制界限依据重复性条件下所得数据的标准偏差来设置,用它来控制复现性条件下子组的平均值的波动性,由于条件不同,因此,前者不能来控制后者.依据计量保证方案(MAP)提出的控制界限的确定,是用在复现性条件下各子组的平均值的组间标准差来设置控制界限,也就是用组内平均值的分散性来控制组内平均值.通过对二等电阻、直流电压和电能表标准装置同一组试验数据进行上述两种控制图的制作比较,以及对确定控制界限的理论分析,证明了休哈特控制图平均值控制界限的确定不妥.     

低渗透油田产能建设区块经济合理采油方式的确定

通过建立油井经济产量界限模型,确定了不同采油方式下油井的经济产量界限,对比分析了低渗透油田抽油机与提捞采油方式的经济性,为降低低渗透油田产能建设投资,提高油田开发经济效益,优化地面工艺流程,选择经济合理的采油方式提供依据。     

线性与非线性传热情况下卡诺制冷机的最优性能

通过制冷系数与制冷率的一般关系,导出卡诺制冷机工作于线性与非线性传热情况下最佳制冷系数ε与制冷率 R 的关系。据此可确定不同制冷率所对应的制冷系数界限。最后,讨论了上述关系的一些应用。     

一种准确可靠的期间核查方法

通过对选定的核查标准的测量,利用被核查标准的最大允许误差和校准证书给出的校准结果及其不确定度,来确定核查测量控制图的“中心线”、上下控制界限和警戒线,利用Excel电子表格绘出这些控制界限,使每次核查测量结果在图中直观准确地反映被核查标准的误差或量值的变化方向和大小。该结果也可作为计量标准稳定性考核的依据。     

论设备大修理的依据、原则及修前准备

<正>一、大修的概念目的和意义设备的大修理是指工厂在生产过程中定期对设备进行全面的修理,通过对设备上的所有零件进行清洗、检查、调整、更换。对需要加固稳定的重要零部件进行加固稳定;对需要调整的机械结构和操作系统进行调整,对需要配齐的安全装置和主要附件进行配齐。最后打底喷漆,进而恢复设备机器的精度和性能,以保证生产的顺利进行。大修理应该达到以下要求:一是以购置机器时的标准为基础;二是修后的设备性能和精     

硬度法测定渗氮层深度结果的测量不确定度评定

主要以综合评定法对硬度法测定渗氮层深度结果的测量不确定度来源进行了分析,分别讨论了硬度法测定总渗氮层和有效渗氮层深度由于界限硬度值要求不同,导致引入的标准不确定度分量不同,并对每个标准不确定度分量进行了评定。结果表明:在相同试验条件和方法下,硬度法测定总渗氮层深度结果测量不确定度明显小于硬度法测定有效渗氮层深度结果测量不确定度。其原因在于试验测定结果重复性引入的标准不确定度分量是硬度法测定总渗氮层深度结果测量不确定度主要来源;而硬度法测定有效渗氮层深度结果测量不确定度主要来源却是由计算模型中插入的界限硬度值引入的。另外,采用硬度法测定深度,应注意硬度计工作台移动的分度值和垂直度偏差对测量结果的影响。     

硬度法测定渗氮层深度结果的测量不确定评定及分析

主要以综合评定法对硬度法测定渗氮层深度结果的测量不确定度来源进行了分析,分别讨论了硬度法测定总渗氮层和有效渗氮层深度由于界限硬度值要求不同,导致引入的标准不确定度分量不同,并对每个标准不确定度分量进行了评定。结果表明：在相同试验条件和方法下,硬度法测定总渗氮层深度结果测量不确定度明显小于硬度法测定有效渗氮层深度结果测量不确定度。其原因在于试验测定结果重复性引入的标准不确定度分量是硬度法测定总渗氮层深度结果测量不确定度主要来源;而硬度法测定有效渗氮层深度结果测量不确定度主要来源却是由计算模型中插入的界限硬度值引入的。另外,采用硬度法测定深度,应注意硬度计工作台移动的分度值和垂直度偏差对测量结果的影响。     

随机荷载作用下参数不确定结构的疲劳损伤估计

基于改进区间分析和频域疲劳计算方法,对参数不确定结构在平稳高斯荷载作用下的疲劳损伤进行研究,提出完全混合和简化计算两种方法。采用区间变量模型定义结构的不确定参数,功率谱密度描述外荷载的随机性;利用有理级数显式表示结构区间频响函数及在平稳高斯荷载作用下不确定结构的应力响应区间。通过数值方法验证疲劳损伤期望率关于不确定参数的单调性后,将应力响应中不确定参数的界限完全组合提出完全混合方法,准确估计参数不确定结构的疲劳损伤期望率区间;简化计算方法则将不确定参数的界限适当组合,由显式表达式近似计算结构的疲劳损伤期望率区间。算例表明,两种方法均具有较高计算精度,且大幅减少计算量。     

特征灵敏度分析中参数μ的选择问题

本文指出，对于重特征值λ０，即使在是对称阵的假设下，含μ的灵敏度方程的解也与μ无关；由数值计算稳定性所确定的μ值界限，需要知道异于λ０的特征值的信息，这与非模态展开法的策略有所背离。     

Optimal maintenance models with minimal repair, periodic overhaul and complete renewal

This paper investigates the maintenance decision situation in which three actions, minimal repair, periodic overhaul and complete renewal, may be applied to the system under consideration. A new mathematical model is proposed to describe system improvement due to the maintenance action of an overhaul that differs from the virtual age approach by considering a direct reduction on the system's failure rate. Based on this improvement model, two cost models for determining the optimal overhaul interval and the number of overhauls in a renewal cycle, that minimize the expected unit-time cost or the total discounted cost, are established. Existence conditions of optimal solutions are obtained and special cases of the two cost models are discussed.     

RELIABILITY ANALYSIS AND MAINTENANCE POLICY OF RADIATORS FOR A LARGE FLEET OF BUSES

Parts in an engineering system are subject to deterioration caused by friction, impact, metal fatigue, etc. which occur when the system is in operation, and also due to ageing of its plastic and rubber parts and rusting of metal parts. In order to ensure that a system functions properly, it is important to perform maintenance which rectifies the faults in its parts as time passes. In this paper the authors use Weibull analysis to investigate the failure pattern of radiators in the cooling system of different bus types in a large public transportation company, and work out from a costing point of view that regular preventive maintenance is not recommended but overhaul of the radiators should be done once in several years when the bus undergoes a major overhaul. In this analysis, the renewal function of the Weibull distribution has to be computed. A table for the renewal function has been computed as well. The manpower requirement for the maintenance of radiators for the bus fleet is also investigated. © 1997 John Wiley & Sons, Ltd.     

Die Zerstörungsfreie Prüfung der Hubbänder der OTTO-HAHN-Brennelement-Wechselmaschine nach einem speziellen Ultraschallverfahren

The Guarantee of Quality for the Steel Hoops of the Refueling Machine of the Nuclear Ship OTTO HAHN by Way of a Special Procedure with Ultrasonic The basic overhaul and renewal of the refueling machine constructed 1965–1967 for the reactor system of the nuclear ship OTTO HAHN required among other things the replacement of the lifting hoops which are necessary for raising the fuel elements and guiding the gripping device. These steel hoops are the critical components of the refueling machine. Therefore the quality assurance of the material was articularly specified. On way of ensuring this guarantee of quality is to carry out tests involving the use of ultrasonic equipment as desired and applied here. The process is explained and its application with the results obtained is described.     

论述变电设备状态检修体系研究

对状态检修的维修技术应用研究、管理保障体系、状态检修标准化体系、状态检修指标评价体系、设备状态监视以及维修辅助决策平台研究和开发等各项内容,提出了分析及解决策略。     

Proportional Intensity Models Robustness with Overhaul Intervals

The class of semi‐parametric proportional intensity (PI) models applies to recurrent failure event modeling for a repairable system with explanatory variables (covariates). Certain repairable systems (e.g. aircraft and electrical power generating plants) experience a substantial period of downtime due to performing maintenance (i.e. major overhaul) at scheduled intervals or following a major failure. Other systems (e.g. emergency power units) experience extended periods of non‐operating dormancy. These discontinuities in observation time have potential effects on the accuracy of estimation for covariate effects, particularly where calendar time is the life metric. This paper examines the robustness of two PI methods (Prentice–Williams–Peterson gap time (PWP‐GT) and Andersen–Gill (AG)) as a function of the overhaul or dormancy duration. The PWP‐GT model proves to perform well for sample size of 60 (30 per level of a class covariate), constant or moderately decreasing/increasing rate of occurrence of failures, and relative overhaul (dormancy) durations less than half of the immediately preceding interval between failures. The AG model performs consistently well for a small sample size of 20 (10 per level of a class covariate) for homogeneous Poisson processes, regardless of the relative overhaul (dormancy) duration. Copyright © 2005 John Wiley & Sons, Ltd.     

Production and quality control policies for deteriorating manufacturing system

In this paper, a novel model for a deteriorating manufacturing system is analysed, considering repairs and overhauls of random durations. The machine manufactures one product and the model is further complicated because the quality of the parts’ produced deteriorates according to the wear of the machine and human interventions. When a breakdown occurs, either a repair or an overhaul is performed. The machine is restored to as-good-as-new conditions if the overhaul is selected, and conversely, its condition deteriorates following repairs. Multiple operational states are considered to define an ageing process. The decision variables of the model are the production rate and the repair/overhaul switching strategy. This paper provides new insights to this research area by considering the simultaneous production and repair/overhaul control policy under the effect of deteriorations. The optimal decision policy minimises the total incurred cost comprising the inventory, backlog, repair and overhaul costs over an infinite planning horizon. Our paper differs from other research projects in its consideration of the machine’s history, defined by the number of repairs and multiple operational states. A numerical example is given to illustrate the proposed approach and a sensitivity analysis has been conducted to confirm the structure of the obtained control policies.     

改进操作以缩短制氧机排液及启动时间

在马钢 35 0 0 0m3 /h制氧机 2 0 0 2年大修期间 ,改进操作 ,返送液体 ,缩短制氧机排液及启动时间 ,以缩短工期 ,提前出氧 ,提高经济效益。     

A method for defence product major overhaul analysis focusing on interfaces redesign and extended life supportability

Due to high acquisition costs of new units, defence products can be subjected to life extension processes, sometimes not previously planned during their life cycle. These processes are characterised by widespread maintenance tasks and they can be denominated as major overhauls. The main objective of this paper is to propose a methodology to aid the major overhaul technical management. In general, the major overhaul defines the scope of maintenance and modernisation. Main problems about maintenance are managed by risk-based decision-making for determination of replacement rules and quantities of spares. The need for redesign of parts that interacts with the upgraded subsystems is evaluated by design structure matrix and a HAZOP-based analysis aiming at achieving product performance requirements. The proposed method is a support tool to the major overhaul manager, not replacing technical methodologies that are specific to each branch of the overhauled product. The proposed method was applied to a major overhaul project of an armoured personnel carrier. The results enabled a better characterisation of detailed design, analysing risks in the context of maintenance and modernisation aiming at controlling modernised product life cycle.     

Optimal periodic replacement for a deteriorating production system with inspection and minimal repair

Here we discuss an inspection policy model for a deteriorating production system with minimal repair. A minimal repair is resorted to as and when the system is found to be in a failed state during an inspection unless it is apre-set overhaul/replacement time in which case the system is overhauled or replaced. Using a dynamic programming formulation, and assuming that the cost of minimal repair is a non-decreasing function of age, we arrive at the optimal inspection time that maximizes the profit per unit time for a given overhaul/replacement time. The procedure is then extended to determine the optimal periodic overhaul/replacement time and the corresponding optimal number of inspections and their schedule.     

南钢RIK80-4型空压机大修总结

因为级间冷却器和密封器的材质先天不足,南钢RIK80-4型空压机存在运行效率低、故障率高的问题。简介空压机大修前的运行状态和检修情况,阐述大修过程和达到的效果,最后对空压机运行和选材方面提出了建议。