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Reliability and Maintainability Symposium, 1999. Proceedings. Annual

Date 18-21 Jan. 1999

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Displaying Results 1 - 25 of 72
  • 1999 Annual Reliability and Maintainbility Symposium [front matter]

    Page(s): i - x
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  • Annual Reliability and Maintainability. Symposium. 1999 Proceedings (Cat. No.99CH36283)

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  • Author index

    Page(s): xvii - xviii
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  • PANEL: Advisory Board - What Are The Successful Companies Doing?

    Page(s): 219 - 223
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  • Author index

    Page(s): cx
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  • Investigation of reliability of hydraulic-robots for hazardous environments using analytic redundancy

    Page(s): 122 - 128
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    The Rosie mobile worksystem is a robot that is on the cutting edge of hazardous environment robotics. It is a heavy-duty hydraulic robot designed for nuclear reactor decontamination and dismantlement. The robot consists of a wheeled platform containing a central hydraulic power supply powered by an electric tether, four independently steerable wheels, and a heavy-duty crane/manipulator. The hydraulic wheel actuator subsystem has been determined to be a vital component of the mobile platform through reliability analysis. Our research into analyzing this robot's reliability through the technique of analytical redundancy (AR) will help provide the Department of Energy (DOE) with a more complete and effective set of tests for monitoring and diagnostics of the Rosie system. In this paper, we discuss the derivation through AR of a suite of model based tests for the default sensor package for one of Rosie's wheel actuators. AR allows us to exploit the sensor information of the sensors values and the system model to derive tests of the consistency of the sensor data. Some of these tests are comparison of the actual system response to control inputs to predicted response indicated by the model, the other tests uncovered by the AR analysis reflect higher order state interdependencies. These tests and their use in monitoring and diagnostics for Rosie are detailed and examined in depth. This work is also an interesting example of the application of model based techniques for an important class of practical systems View full abstract»

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  • Reliability management and engineering in a commercial computer environment

    Page(s): 323 - 329
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    The TandemTM Division of Compaq Computers has developed a highly effective reliability program for the commercial computer industry. The program diligently applies reliability principles throughout the design, manufacture and field use of our products. Our process establishes reliability goals that, in turn, drive change and improved product reliability. We have enhanced not only the reliability of the assemblies that we design, but also the reliability of those purchased from outside suppliers. We have developed an effective field reliability data collection and analysis process that allows us to measure the increase in reliability and identify potential future problems. We have impacted the design by providing analyses that optimize cost while achieving the high system availability that our customers expect. The evidence of the effectiveness of our efforts comes through the field data that shows decreased failure rates and sustained high levels of customer satisfaction View full abstract»

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  • Reducing human performance-related risk with REHMS-DTM

    Page(s): 288 - 292
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    The Reliable Human-Machine System Developer (REHMS-D) can be used to reduce product and process risk by designing for reliable human performance. REHMS-D can be applied to a wide variety of large systems, including those for transportation, medicine, utilities and defense. REHMS-D also can be applied to commercial products, business processes, information systems and manufacturing processes. REHMS-D is a trademark of KPL Systems View full abstract»

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  • System reliability modeling considering the dependence of component environmental influences

    Page(s): 214 - 218
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    A system reliability modeling procedure is described and demonstrated to accommodate the case when component failure times are statistically correlated because of the shared environmental exposure of components within a system. When component failure times are correlated, independence assumptions are not valid, and thus, many common reliability modeling practices are inappropriate. If component reliability is influenced by environmental exposure, then the components within a system are likely to have correlated time-to-failures because all components within a system are influenced similarly by the system-level environmental stress profile. This scenario is often overlooked when failure data is analyzed for a homogeneous population of parts that have experienced nonhomogeneous usage profiles. The model presented here is based on proportional hazards models for component reliability and discretized approximation of the joint probability density function for system environmental stress variables. The discretization approach is mathematically convenient, accurate and offers several pragmatic advantages over alternative computation approaches. A hypothetical three-component series system is analyzed, and the results are compared to two common approximations: (1) component independence assumption and (2) use of environmental stress average values. The results indicate that the described approach is convenient and has the potential to be scaled-up to large problems View full abstract»

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  • The effect of failure-distribution specification-errors on maintenance costs

    Page(s): 69 - 77
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    This paper examines the problem of determining and evaluating optimal fixed-length inspection intervals for a single machine that operates continuously subject to nonobvious, random failures. Good-as-new repairs are performed when the machine is found to be failed. Both the fixed-interval inspection and replacement times are instantaneous. Two possible single parameter failure time distributions are used in this investigation: exponential and 2-Erlang. The focus of this paper, however, is on the consequences of mis-specifying the form of the failure distribution or the parameter value(s) of the failure distribution. Robustness analysis indicates that long run expected cost per unit time is extremely robust to moderate errors in the specification of the expected time to failure (cost increases of less than 0.6% for ±20% error in expected failure time), when the form of the failure distribution is correct. Conversely, accurately specifying the mean time between failures, but incorrectly specifying the form of the failure distribution, results in significant increases in long run expected cost per unit time. Mistaking an exponential for a 2-Erlang, or vice versa, can result in cost increases of over 20% for reasonable values of cost parameters View full abstract»

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  • A new method for obtaining the TTT plot for a censored sample

    Page(s): 112 - 117
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    For a censored sample where withdrawns or suspensions are present, Kaplan-Meier-estimation (KME) method, also called product-limit-estimation (PLE) method, and piecewise-exponential-estimation (PEXE) method, have been typically used to estimate both the survivor function (or cdf) and the total time on test (TTT) statistic at each observed failure time. This paper presents a new method, called mean-order-number (MON) method, for estimating TTT statistics and TTT plot for a censored sample. This method is illustrated using Dodson's example as quoted by numerous authors. A comparison is made among MON, KME, and PEXE. It turns out that MON method is not only easy to use but its results are consistent with KME and PEXE as well View full abstract»

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  • Chemical-process design and maintenance optimization under uncertainty: a simultaneous approach

    Page(s): 78 - 83
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    Research work has emphasized the importance of reliability and maintenance in chemical process operation and the benefits from achieving high process availability levels by optimizing the trade-offs between maintenance costs and plant production volumes. This has motivated the need for the development of contemporary techniques and tools for availability assessment of process systems, which go beyond traditional practices, by focussing on the interactions of reliability and maintenance optimization with the detailed process operation and its dynamic, continuously changing environment. Furthermore, at the design stage of chemical plants, operability considerations accounting for the plant's life cycle, such as flexibility, reliability and maintainability are not typically included. The main reason for this is that there is a lack of an integrated design framework enabling process engineers to look at the various operability factors in conjuction with cost in a systematic and quantified way during process design development. This work presents theoretical and computational developments aiming at the integration of maintenance optimization in optimal life-cycle process design and development under uncertainty. In particular, the impact of uncertainty upon determining the optimal balance between maintenance costs and benefits as well as the interactions of process design and maintainability in the presence of uncertainty are clearly shown and quantified View full abstract»

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  • The ProphetTM risk management tool set

    Page(s): 426 - 431
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    Raytheon has developed a powerful risk management tool set, named ProphetTM, which has proven highly successful in managing several programs, and is now being deployed throughout Raytheon. This paper describes ProphetTM features, the processes it supports, and the concepts behind them. Features include user-friendly input screens, roll-up risk factors, automated risk reduction charts, expected cost impact analysis, assessment history and rationale tracking, process productivity aides, tailorability features to suit a broad assortment of programs, integration with master planning and scheduling, tracking of technical performance measures, and risk metrics for technical trade studies View full abstract»

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  • Disturbance analysis using a system bond-graph model

    Page(s): 358 - 364
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    Conventional failure effect analysis depends on the expert's judgement and experience, which may lead to an erroneous result. To solve this problem, this paper proposes a failure effect analysis using bond-graphs, which represent the system behavior in a unified way from the viewpoint of energy flow. The system state equations obtained from a system bond-graph represent the system behavior in the time space domain, and process variables can be obtained in functional forms of state variables and input variables. Qualitative evaluation of deviations caused by a component failure or external disturbance can be analyzed using a tree graph expression of the system state equations. Not only final deviations remaining under the component failure condition, but also initial transient deviations just after the failure occurrence can be obtained by propagating steady state conditions or assumed deviations along the tree graph. An illustrative example of a water flow control system shows the details of the proposed method View full abstract»

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  • Assuring COTS products for reliability and safety critical systems

    Page(s): 317 - 322
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    The increasing use of (commercial off the shelf) COTS components, including both hardware and software, in today's new systems is a reality. Cycle time reductions and development economies make this so. Since COTS products have been matured through field operations, they offer potential reliability advantages. Along with the COTS advantages there are some unknowns about COTS that pose a risk to the developer. This paper documents these reliability risks and exposures associated with COTS deployment. Most of the risk is in requirements' deficiencies, interface discrepancies, and intolerance to off-nominal input conditions. These risks aren't substantially different from those found in developmental products, but they may have greater effect View full abstract»

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  • A quantitative assessment of the application of software reliability to reusable code

    Page(s): 165 - 170
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    With the increasing utilization of reusable software, there is a definite need for software reliability analysis during the early phases of the software development life cycle. Software defects that are unobserved in one environments can manifest themselves in another, resulting in failure. If software reliability metrics are utilized in the early phases of the software development life cycle, they can identify potential problems that may be encountered when software is reused in another environment, and the cost of implementing such modifications is minimal. The benefits of such analysis is the prevention of catastrophic failures that result from the activation of unaccounted faults that are exposed when a given code is used in applications beyond its original intended environment View full abstract»

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  • Medical diagnostic device reliability improvement and prediction tools-lessons learned

    Page(s): 29 - 31
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    To be successful in the medical diagnostic industry, companies must strive to be the most cost competitive supplier. Abbott Laboratories has traditionally been diligent in pursuing several avenues for cost reduction including raw material supplier contracting, outsourcing, as well as direct labor reduction through design for manufacturability, inventory and scrap reduction. Today, Abbott focuses increased attention on reliability improvements as a means to cost efficiencies. While traditional methods of cost improvement are never seen by the final customer, reliability improvements result in a more satisfied customer. Abbott has used lessons learned from past product development to create in-house reliability engineering tools. These tools help predict reliability of development products; but more importantly, they help Abbott build reliability into the product View full abstract»

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  • Modeling reliability growth late in development

    Page(s): 201 - 207
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    Reliability is often overlooked during early developmental testing when the focus is on improving system performance. As a result, rapid reliability growth programs are frequently initiated late in development, just before the system enters production. The widely-used AMSAA reliability growth model is difficult to apply on such programs because it is a cumulative function of test time and the number of failures observed; therefore, it usually projects that an excessive amount of testing is required to overcome a period of low reliability, even at high growth rates. This paper formulates an alternative model for projecting reliability growth late in development that does not suffer from this problem. The model also provides a framework for reliability growth on system acquisition programs that utilize short development cycles, such as spiral development. An example application of the model on the AWACS RSIP reliability growth program is presented and discussed View full abstract»

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  • Practical treatment-methods for adaptive components in the fault-tree analysis

    Page(s): 97 - 104
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    In this paper, the dependability analysis of functionally reconfigurable logic is discussed. Such logic can change its function if a failure has occurred and it has been detected. Based on the fault tree technique, several methods are illustrated and investigated, namely the macro-models, the Markov chains, and the multi-static models, which provide the treatment of the system components with adaptive properties. This paper also proposes a multi-state based procedure well fitted to the re-configuration. Closed formulas are applied in this procedure, as they ensure simpler and faster analysis for a class of systems than other procedures View full abstract»

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  • A comprehensive review of hard-disk drive reliability

    Page(s): 403 - 409
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    A shorter development cycle (i.e. 12-18 months on average), a shorter life cycle in the field (i.e. 2-3 years on average); as well as higher reliability requirements (i.e. a specified minimum MTTF of 400,000 hours), all present new challenges to the hard-disk drive manufacturer. In order to meet and exceed the ever-increasing customer expectations, a systematic approach needs to be taken beginning with the early design state, through pre-production and mass production, and finally through to field operation. This paper presents Quantum's current effort in achieving this goal View full abstract»

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  • Risk mitigation of reliability-critical items

    Page(s): 283 - 287
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    During the development of new and complex electronic products, the developer identifies high-risk components by listing those components that could generate project risk based on past experience, also adding those new components with limited history. These critical items are key to product performance and, therefore, are an area of major concern during product development. Critical items are issues not totally understood by the program's development staff, even though these individuals will be specifying and designing these items into the end product. The applications for which critical items are used can have major effects on the reliability of the critical items as well as on the products that incorporate them. Critical items are normally purchased from specialty suppliers, who design and manufacture them to a procurement specification. Critical items are classified as program risks and constitute a subset of a program's total risk area that must be managed. Critical items are considered to be risk items because they are unique to the program (custom-designed), can embody new technologies or processes, can be state of the art (pushing the envelope of knowledge and understanding), can have higher failure rates than other components, can be life-limited, and can jeopardize safety. Critical items have enough technical and programmatic uncertainties within themselves that must be mitigated and managed by the program development staff, without adding critical item design application issues resulting from product design decisions. This paper describes a current effort that focuses on solutions for these issues View full abstract»

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  • Improving availability and cost performance for complex systems with preventive maintenance

    Page(s): 383 - 388
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    This paper investigates improving system limiting availability and expected system cost rate for a complex system through age replacement preventive maintenance (PM). This study defines the complex system as a classic bridge reliability structure consisting of five independent subsystems. A competing risk model is used for each subsystem's unique life distribution. This model includes two independent modes of failure for each subsystem. They assume the expected system failure repair time and PM action time are known or may be estimated. System-level age replacement PM models are developed for both system limiting availability and expected system cost rate. Often, both availability and cost performance are critical system characteristics. A methodology is presented that allows tradeoffs between availability and cost to be evaluated. The paper demonstrates the methodology for a specific example. The maintenance strategy assumes that failed subsystems are maintained according to their failure mode and working components are preventively maintained. This strategy applies whether failure maintenance or PM action is required. This strategy is selected, since, in terms of maintenance service, it lies between the extremes of pure system-level maintenance and independent subsystem-level maintenance. Limitations of the system-level maintenance strategy are identified View full abstract»

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  • Software reliability cases: the bridge between hardware, software and system safety and reliability

    Page(s): 396 - 402
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    High integrity/high consequence systems must be safe and reliable; hence it is only logical that both software safety and software reliability cases should be developed. Risk assessments in safety cases evaluate the severity of the consequences of a hazard and the likelihood of it occurring. The likelihood is directly related to system and software reliability predictions. Software reliability cases, as promoted by SAE JA 1002 and 1003, provide a practical approach to bridge the gap between hardware reliability, software reliability, and system safety and reliability by using a common methodology and information structure. They also facilitate early insight into whether or not a project is on track for meeting stated safety and reliability goals, while facilitating an informed assessment by regulatory and/or contractual authorities View full abstract»

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  • A modified FMEA tool for use in identifying and addressing common cause failure risks in industry

    Page(s): 19 - 24
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    The nature of common cause failures (CCFs) is explored in the context of existing analytical techniques. Failure modes and effects analysis (FMEA) is described as a means for accomplishing early risk assessment in the context of an existing analysis framework. Cause and coupling factor taxonomies are refined to fit the FMEA methodology. This modification allows consideration of CCF risks. Blending this methodology with the standard FMEA process enables a seamless prioritization of single failure and CCF risks for further studies and actions. An example is provided to illustrate the use of this new tool View full abstract»

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  • KB3: computer program for automatic generation of fault trees

    Page(s): 389 - 395
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    KB3, formerly named EXPRESS, is a knowledge based-workbench that assists in building reliability models. At EDF, KB3 is used for the safety studies of nuclear power plants. It is founded on knowledge bases describing generic classes of components, with their behaviour and failure modes. This description results of a generic functional analysis (FA) and a failure mode and effect analysis (FMEA) of the systems and is written in a dedicated language, called FIGARO, developed at EDF. Using these classes of components, the user can describe the studied system in a graphical system editor and generate fault trees for different missions of the system. He can also add specific knowledge about the system. Thus, he can be released from the limits of the generic knowledge base. KB3 may be linked with different codes for the quantification of the generated fault trees View full abstract»

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