Search

The author gives examples of where, on a recent large production project with an extremely tight client startup schedule, the use of proper inspection and testing procedures ensured the project's successful startup ahead of the client's schedule. The factory inspection and witness tests that should be performed on electrical equipment are discussed, and field testing and checkout of equipment are considered. Cases of the problems uncovered are highlighted to show the user the types of problems that can be uncovered by proper specifications for inspection and testing of certain electrical equipment. It is concluded that discovering equipment defects at the earliest stage can improve project schedule performance markedly, and that proper timing of on-site testing can ensure contractor performance as well as detect damage or errors in installation. >

ISBN: 0818608676; An original BIST (built-in self-test) scheme is proposed to cover some shortcomings of self-checking circuits and to ensure all tests needed for integrated circuits. In the BIST scheme, self-checking techniques and built-in self-test techniques are combined in an original way and take advantage one from the other. This results in a unified BIST scheme (UBIST), allowing a high fault coverage for all tests needed for integrated circuits, e.g. offline test (design verification, manufacturing test, and maintenance test) and online concurrent error detection.

As software maintenance requirements continue to grow, conflicting with demands for new development, managers must continually evaluate the cost effectiveness of various maintenance strategies. He shows that one can measure and use a significant benefit from maintenance-the reduction in failure risk-to evaluate maintenance strategies. The ability to measure the differential risk of failure in modules within a system can be used to design high-risk-first maintenance strategies and to motivate the effort. Moreover, maintenance's impact on failure risk can demonstrate whether it is advantageous to fix errors as soon as they are found or perform scheduled maintenance in the future. Failure risk assessments can also be used to measure the effectiveness of perfective maintenance strategies. Not only can this type of maintenance be justified, but alternative strategies can be compared to determine which will minimize failure risk. >

This chapter reviews fundamental requirements of effective preventive/predictive maintenance, which includes procedure and discipline. Discipline is a major problem in many organizations. Careful inspection, which can be done without “tearing down” the machine, saves both technician time and exposure of the equipment to possible damage. Human senses are able to detect large differences but are generally not sensitive to small changes. Accelerometers, eddy-current proximity sensors, and velocity seismic transducers enable the techniques of motion, position, and expansion analysis to be increasingly applied to large numbers of rotating equipment. Motors, turbines, compressors, jet engines, and generators can use vibration analysis. The spectrometric oil analysis process is useful for any mechanical moving device that uses oil for lubrication. Information for developing lubrication specifications can come from four main sources—equipment manufacturers, lubricant vendors, other equipment users, and individual experience. Calibration is a special form of preventive maintenance whose objective is to keep measurement and control instruments within specified limits. A “standard” must be used to calibrate the equipment. Standards are derived from parameters established by the National Bureau of Standards (NBS). Planning is the heart of good inspection and preventive maintenance. A formal record is desirable for every inspection and preventive maintenance job.

This presentation discusses the application of emerging virtual modeling and software design methodologies to practical use in engineering test development, manufacturing test and field maintenance testing. Object oriented design methodologies are being adapted to the automated test process for complex electronic components, printed wiring assemblies, electronic and avionics subassemblies and aircraft/weapon systems and subsystems. This paper describes engineering tools based on these processes that are being developed and used on both defense and commercial programs in an attempt to reduce program and product life cycle costs. >

Automatic routine execution (REx) testing of telecommunications switching equipment is often performed to improve system reliability, and to check the operational status of communications equipment. For duplex equipment REx testing, at a minimum, periodically checks the inactive unit for problems. If problems are found, then repairs can be made before service is impacted. In addition to this clear benefit, there are also costs associated with testing. Equipment that is being extensively tested may not be in-service, and the testing itself can lead to two types of incorrect conclusions, conclusions that lead to either unnecessary repairs, or to a dangerous misperception that the equipment is working properly. The first type of incorrect conclusion is a false positive. The second is a false negative. Since there are both costs and benefits associated with REx testing, it is natural to conclude that REx tests should be run neither too frequently nor too infrequently. In this paper we develop a detailed reliability model of a generic duplex peripheral module. The term generic is used, since the intent is to provide a useful methodology with some results that are independent of specific equipment, provided by various manufacturers. The model shows that picking the correct REx testing frequency results in significant savings in downtime. The impact on system outages as a function of REx testing frequency is shown for a number of cases.

The ATS concept developed for test of all electronics in the Swedish multi-role combat aircraft JAS 39 Gripen, has been successfully delivered to the Swedish Air Force. All major requirements originally set up, has been fulfilled-although not necessarily in the way it was planned some 10 years ago. C/ATLAS has been used for analog test in combination with VETO for dynamic digital test. Coordination of production test and maintenance test of all Swedish built electronics in the Gripen has been achieved. That was one of the most important goals to reduce the overall project cost. To fully implement COTS was another of the major cost reduction items. The JAS-ATE was designed to be modular, flexible and cost effective-which is what was achieved.

Increasing installation of transmission facilities underground has led utilities to place greater emphasis on the qualification, acceptance and maintenance testing of high voltage cables. In particular, there is an urgent need for more searching probes of latent defects than are presently furnished by high voltage (AC or DC) withstand testing. As an alternative to this type of test, partial discharge (PD) testing can provide information on the existence of those latent defects known to cause premature in-service failure of high voltage cables. However, in order to realize the benefits of PD testing, the measurement system must be sufficiently sensitive, which implies for field testing, a high noise rejection capability. The present work addresses these key issues in designing a credible PD test for transmission class cables. The major noise sources are identified and methods to counter them are described. >

In recent years conventional DC testing of installed insulation has begun to lose favor. The authors present a novel technique that overcomes all previous objections to DC testing and many of the disadvantages, such as size and weight, of the already identified alternatives. The power supply, called a pulsed resonant power supply, produces line frequency output with no DC content. There is no switching involved; hence the supply is readily adaptable for partial discharge and power factor measurements. With its many attributes, the pulsed resonant power supply is well suited for maintenance testing of large rotating machines. >

The author reports on the design, material characteristics, and test results obtained under the US Air Force's advanced aircraft avionics packaging technologies (AAAPT) program, whose charter is to investigate new designs and technologies for reliable packaging, interconnection, and thermal management. Under this program, AT&T Bell Laboratories has completed the preliminary testing of and is evaluating a number of promising materials and technologies, including conformal encapsulation, liquid flow-through cooling, and a cyanate ester backplane. A fifty-two module system incorporating these and other technologies has undergone preliminary cooling efficiency, shock, sine and random vibration, and maintenance testing. One of the primary objectives was to evaluate the interaction compatibility of new materials and designs with other components in the system. >

The authors present a new scheme, the Berkeley FAULT system, for managing information concerning equipment maintenance and repair activities. The solution to the problems is designed with four goals in mind. First, the system must help facility management keep track of equipment maintenance events as they occur. Secondly, the system should help maintenance technicians conduct offline equipment maintenance by reviewing previous maintenance cases. Thirdly, the system must be usable and maintainable by equipment operators, maintenance technicians, and facility managers without need of assistance from expert programmers. Fourthly, the system should cooperate with automated diagnostic systems by maintaining failure histories of equipment in the facility and by providing a mechanism that allows a diagnostic system to schedule necessary maintenance tasks automatically. >

A working system of preventive and predictive maintenance referred to as the standard maintenance procedure (SMP) program, is discussed. The system consists of a series of dynamically linked programs, each of which plays an important role in the effectiveness of the maintenance program. The system applies to both electrical and/or mechanical maintenance and provides the process of equipment inspection. The delay reporting system, product quality information, maintenance inspection program, equipment shift report system, and failure analysis and corrective action of the SMP program are described. >

This paper presents a new set of on-line partial discharge (PD) monitoring system for large power transformer. Four sets of 500 kV power transformers can be monitored automatically at the same time, and then fault warning and localization are made by software. Various methods are used to reject interference in order to increase the monitoring sensitivity of PD. The on-line calibration technique, the pulse injection through capacitive tapping, is applied for measurement of apparent discharge. The earthing fault of transformer was found while the system commissioning. Now this system has been in operation steadily for more than two years. As one of main prevision maintenance testing item, on-line PD monitoring systems are paid more attention by engineers both in China and abroad. Up to now, some on-line systems had already been put in operation in Canada, Japan and China. They have already got many good results and accumulating a lot of good experiences. On base of summarizing forefather's works, a new type of JFY-2 on-line PD monitoring system for large power transformer has been developed by Jilin electric power research institute joint with Tsinghua university.

The sophistication and complexity of avionic, and other, prime systems has been growing at a pace that has not been matched by commensurate improvements in test technology. The result is NFF (no fault found) and other test effectiveness deficiencies that will soon, if they have not already, reach crisis levels. This pending crisis is all the more serious because it tends to be hidden by a variety of technical, administrative and commercial factors that often mask the real problems, and that sometimes even hinder the measures needed to correct them. Corrective action requires recognition of the true nature of test effectiveness deficiencies, the paradigms and processes with which they are associated, and the changes required to keep pace with modern prime system technology, maintenance requirements and safety objectives.

The most difficult and time-consuming portion of test program development is the diagnostic element. Because of this difficulty, diagnostics are often foregone in the production/maintenance test environment This results in a rework pile of test items that usually become scrapped because manual troubleshooting is too labor-intensive and available technician time is too scarce. A solution to this dilemma is to implement diagnostics in the production/maintenance test environment using a simplified approach: model-based diagnostic reasoning. This paper will describe how to use model-based diagnostics to uncouple the diagnostic logic from the test logic. It will describe how design and test data can be merged to form a Diagnostic Knowledge Base (DKB) The Diagnostician, a commercial off the shelf (COTS) software tool, works with the DKB as part of the test program. The Diagnostician provides the model-based reasoning at runtime. This will allow the unit under test (UUT) design changes to be easily implemented into the diagnostic test program without extensive software changes. By having a different DKB for each revision level, diagnostics can be performed by keying on the revision of the UUT with the same test program.

Step-stress testing has a number of worthwhile applications for the analysis of the projected life for components and occasionally systems. These include the common situations of testing when only a small number of systems are available, when extremely long or specialized test equipment are required, when limited environmental chamber capability and/or test fixtures are involved, and lastly when very expensive support equipment is a test limit. Step-stress testing has had limited applicability in the past. This has been due to improperly described degradation or accumulative fatigue, poor control of the test samples and difficulty with the analysis of the failure data. A tight series of step-stress ground rules are proposed in this paper to solve or mitigate these and other common accelerated test problems. This paper also presents methods to improve the analysis of the step-stress test. While these methods are approximate, they lend themselves to analysis on a computer by standard hand techniques. Additionally, the ground rules presented suggest that wider limits may be taken for running a step stress test than has been suggested in the past. These ground rules aid the analysis by helping limit the range of results. The step intervals need not be of the same length nor stress steps uniform in size.

The "caused by" condition for any electrical fault can be determined by a thorough and carefully executed analysis. As soon as new equipment is installed, a process of normal deterioration begins. Electrical equipment failure, not attributed to misapplication, transient overvoltage or heavily loaded joints and connections usually involves deterioration of enclosure and degradation of insulation. Experience shows that electrical equipment lasts longer when covered by a preventive maintenance program. Proper performance of electrical equipment is often directly dependent on the maintenance being performed. An effective electrical preventive and predictive maintenance program requires knowledge of the possible causes of electrical equipment malfunctions or failures. A key factor in developing and implementing an electrical preventive and predictive maintenance program is the communication of the need of such an activity by the electrical personnel involved. Proper communication skills must be used during the investigation of an electrical failure in order to find the actual cause of the fault. The sources of information on why the equipment faulted is obtained by analyzing the equipment condition and/or interviewing the personnel involved at the time of the fault. The investigation needs to be thorough and detailed so the roof cause of the incident is found and corrective actions can be taken to prevent it from happening again. Technologists must communicate the problems and identify corrective actions to the owners of the equipment that had the problems so the owners can understand the actions they need to take and the implications of any changes on operability and longevity.

Maintenance testing of machine insulation using high-voltage dc is a widely accepted practice in the electric utility industry. Variations in measured current versus applied potential have proven useful in diagnosing certain insulation defects and modes of deterioration. A number of different methods are typically used for high-voltage dc testing. For example, the test voltage may be applied as a series of either uniform or graded steps. Alternatively, a linearly increasing ramped voltage may be used. This paper will describe the principles of de testing, with an emphasis on the measured stator insulation current response versus voltage. Advantages and disadvantages of the various voltage application methods will be outlined. Field measurements will be presented to demonstrate the superiority of the ramped dc test technique over the conventional stepped methods.

Diagnostics for the 21st century will be driven to provide improved combat availability of vehicles and reduced life-cycle maintenance costs; all within the confines of a two level or less maintenance system. The Diagnostics of tomorrow must be designed to be relevant, practical and productive. This paper will briefly address some of the current problems of today's maintenance environment, suggest a roadmap for an effective maintenance system of tomorrow, and provide guidance on an implementation plan. We will address in particular the diagnostic architectures of combat vehicles, viable maintenance practices and concepts, and the applicability of existing and future Test Maintenance and Diagnostic Equipment (TMDE).

Confirmation of avionics field failures by a depot maintenance organization is often performed on Automatic Test Equipment (ATE) which is designed to certify a module as "fit to fly". When the ATE does not confirm the failure, the field failure is generally regarded to have been an intermittent event. For any application, these are a major cost driver, and for safety-critical applications, intermittent events are intolerable. As part of the depot maintenance plan to assure a reliable repair operation, an Environmental Stress Screening (ESS) process is employed to detect and eliminate latent defects induced by the repair operation. The time available during this process allows the application of test and monitoring equipment designed specifically to detect and identify intermittent failures.

To detect the incipient faults of electrical equipment effectively and reduce the loss when faults occur, a prototype of condition monitoring system has been developed. This system integrates the on-line and off-line diagnosis technology to monitor the condition of electrical equipment. Through the analysis of history data, electrical test data and on-line data, it can also make decisions for the maintenance of electrical equipment. The system consists four parts: ANN-based condition assessor; ANN based fault classifier; intelligent prediction and maintenance decision support system; and knowledge based expert system. Test results show that this system has a high diagnosis accuracy and can make useful maintenance decisions.

With the great advancement of sensor and information technology, the semiconductor equipment data is now available to process engineers in real time. However the volume of data collected and quickly accumulated is often so large that the data is rarely analyzed and put to use effectively. In this paper, we propose an integrated approach that utilizes multivariate statistical techniques to combine various equipment data items into a single equipment health index. We then use this index to determine appropriate time points for equipment preventive maintenance (PM).

The premise of this paper is that there is a great need of integrating the activities associated with operational test and evaluation, maintenance testing, and training to enhance the effects of these activities and reduce the costs associated with them. It is expected that significant program activities improvements and cost savings could be made by leveraging technologies and program activities into an integrated, cohesive set of activities. This paper, however, does not address the management or bureaucratic issues associated with such a concept, but rather the technology and information/data that could be formally integrated in order to gain significant cost and schedule savings, while resulting in a better product to the soldier/user in the field. This paper addresses four specific areas of overlap where significant opportunities lie: (1) Design for testing and diagnostics/prognostics; (2) Maintainability considerations; (3) Applications of maintenance tests to system test and evaluation; and, (4) System Battle Damage Assessment and repair training.

This chapter discusses several equipment designs used for maintenance. There are two types of maintenance—preventive maintenance and breakdown (corrective) maintenance. Preventive maintenance aims at maintaining equipment in good condition so as to obviate the need for breakdown maintenance. Breakdown (corrective) maintenance is performed after the equipment has malfunctioned. Maintenance of machines and systems involves a number of operations that can extend time and cost if not properly designed for the capacities and limitations of the maintenance personnel. The steps involved in a maintenance task include (1) detecting the fault(s), (2) isolating the fault(s), (3) accessing the part(s), (4) dissembling the machine, (5) removing and repairing the part(s), (6) replacing the part(s), (7) reassembling the machine, and (8) testing and checking to verify successful repair. The primary objective of all aspects of maintenance, including equipment design, is to ensure that the system performs its intended function, at any time.

This chapter describes the guidelines for equipment design for maintenance. These guidelines can be used to determine equipment design parameters so that maintenance tasks may be simplified and performed more efficiently. Certain data are necessary to determine the effectiveness of maintenance operations and, hence, indirectly determine the effectiveness of equipment design. For example, excessive time taken to reach a failed unit may indicate that the arrangement and placement of components need improvement, that the maintenance tools used may not be compatible with the particular machine (component) design, or that the technician is lacking in skills. These data provide valuable parameters for evaluating the effectiveness of maintenance, system performance, or equipment performance. Problems can be recognized when the data for the above performance parameters or indexes show any undesirable deviation from expected values, assuming normal, or ideal conditions. Several aspects of human–equipment interaction in maintenance work must be considered when trying to find solutions to problems arising from improper equipment design. These aspects include visual access, physical access, physical mobility, technician strength, muscular and physiological endurance of the operators, cognitive and decision making demands, education and training, and industrial safety.

One way to define the difference between reliability and maintainability is that while reliability is the probability that a failure will not occur in a particular time, maintainability is the probability that required maintenance will be successfully completed in a given time period. Maintainability is a design characteristic that affects accuracy, ease, and time requirements of maintenance actions. Reliability and maintainability are important measures of the effectiveness of systems or products. It may be measured by combining factors, such as frequency of maintenance, maintenance costs, elapsed maintenance or repair times, and labor hours. These measures make possible the quantitative assessment of product maintainability. The primary purpose of maintainability measures is to influence design and subsequently produce a more cost-effective and maintainable end product. The measures used in maintainability analysis include mean time to repair (MTTR), mean active preventive maintenance time, and mean active corrective maintenance time, maximum corrective maintenance time, and mean maintenance downtime. MTTR measures the elapsed time required to perform a given maintenance activity and is subsequently used to calculate system availability and downtime. The objective of a preventive maintenance program is to postpone the point at which the equipment or any of its components wears out or breaks down. A carefully planned preventive maintenance program can help to reduce the equipment's downtime and improve its performance.

Human factors engineering applies knowledge about human capabilities, strength, and size to equipment design. Failure to effectively consider such factors can lead to serious maintainability and maintenance problems. The performance of military equipment during the war proved that equipment is only as good as the people operating and maintaining it. For the equipment to perform at its maximum capacity, the operating and maintenance personnel must also perform effectively. However, these personnel may fail to do so because of inadequate attention to human factors during equipment design or poor training. Human factors play an important role in both equipment reliability and equipment maintainability, but to a different degree. Reliability deals with those inherent characteristics of the equipment that promote either failure or long life. Maintainability has to do with the servicing, diagnostic, inspection, and repairability characteristics of the equipment. Maintainability is more dependent on the action of the operating and maintenance personnel, and to a greater extent involves the interactions between people and machines. Therefore, it depends more on human factors than reliability. Failure to consider human factors carefully during equipment design can lead to increased maintenance problems and reduced effectiveness and readiness.

TWRS [Tank Waste Remediation System] Controlled Baseline Database, formally known as the Performance Measurement Control System, is used to track and monitor TWRS project management baseline information. This document contains the maintenance testing approach for software testing of the TCBD system once SCR/PRs are implemented.

Distance relays have provided reliable and secure protection for AC electrified railway circuits. This paper examines microprocessor distance relays which offer the flexibility of shaped impedance characteristics, for increased fault arc resistance coverage and load avoidance. Microprocessor relays offer applications flexibility through many ancillary features. In addition, each distance relay can include comprehensive self-monitoring, with any factor affecting availability communicated to the operator. Such failures would traditionally have remained unnoticed until inception of a fault, or until maintenance testing. Simple function testing can now replace comprehensive periodic testing. Traction circuit measurements can be polled on demand, either locally, or remotely via serial communications. Measurements are also appended to fault records, allowing fault diagnosis, and the establishment of condition-based maintenance regimes for circuit breakers.

Quality control is the key to effective competition in the international market The dominance of the consumer electronics, steel, and automotive industries by Japan is largely attributed to the manufacture by Japanese firms of products of consistent quality. An actual difference in cost effectiveness will result when manufacturable designs are produced in tightly controlled processes.

The authors reply to a discussion (published in this issue) of their paper with the aforementioned title, published in this journal (Volume 6, Number 1, January 2001). The authors acknowledge that their statement that carbon monoxide and hydrocarbon emission are highest during vehicle idling is misleading, but is not central to the thrust of findings of their paper. They do dispute that that nearly all of the variance in their statistical models can be explained by the levels of other pollutants, which are included as independent variables. Instead, they claim that their model predicts emissions of a pollutant from a vehicle based solely on the vehicle's parameters and that no knowledge of the emissions of other pollutants is needed.

Downtime of rotating equipment in large petrochemical plants often led to serious or even disastrous safety and environmental accidents, which generally stem from inadequate maintenance or incapability of failure prediction. In order to allocate maintenance resources rationally and improve the reliability, availability and safety of equipment, a kind of risk- and condition-based maintenance decision-making and task optimizing system for rotating equipment in large petrochemical plants is established in this paper. Using real-time database, web service and service-oriented architecture (SOA), a risk- and condition-based maintenance decision-making system architecture is developed to provide a unified data structure and man–machine interface, which integrates reliability-centered maintenance (RCM), condition monitoring system (CMS) and manufacturing executive system (MES) together. Risk assessment and condition monitoring technology is applied to form maintenance decision making, such as to determine the priority maintenance level, to optimize maintenance content, and to determine the right maintenance time. Based on the decision-making system, the risk rank and degradation trend of failure characteristics are used to support the decision making and to optimize maintenance tasks. The result of an engineering case shows that the maintenance decision-making based on the risk assessment and condition monitoring can lower the operational risk while enhancing the reliability, availability and safety.

ISBN: 0818654406; First presents a self-checking implementation for RAMs. Then, the unified BIST technique is applied to this scheme. It merges self-checking and BIST techniques and allows a high fault coverage for all tests needed for integrated circuits, e.g. off-line test (manufacturing and maintenance test) and periodic as well as concurrent on-line testing. In order to preserve the RAM contents for periodic on-line testing the authors employ a transparent BIST implementation.

A plant`s maintenance program is the principal vehicle through which age-related degradation is managed. From 1988 to 1991, the NRC evaluated the maintenance program of every nuclear power plant in the United States. Forty-four out of a total of 67 of the reports issued on these in-depth team inspections were reviewed for insights into the strengths and weaknesses of the programs as related to the need to understand and manage the effects of aging on nuclear plant systems, structures, and components. Relevant information was extracted from these inspection reports and sorted into several categories, including Specific Aging Insights, Preventive Maintenance, Predictive Maintenance and Condition Monitoring, Post Maintenance Testing, Failure Trending, Root Cause Analysis and Usage of Probabilistic Risk Assessment in the Maintenance Process. Specific examples of inspection and monitoring techniques successfully used by utilities to detect degradation due to aging have been identified. The information also was sorted according to systems and components, including: Auxiliary Feedwater, Main Feedwater, High Pressure Injection for both BWRs and PWRs, Service Water, Instrument Air, and Emergency Diesel Generator Air Start Systems, and Emergency Diesel Generators Air Start Systems, emergency diesel generators, electrical components such as switchgear, breakers, relays, and motor control centers, motor operatedmore » valves and check valves. This information was compared to insights gained from the Nuclear Plant Aging Research (NPAR) Program. Attributes of plant maintenance programs where the NRC inspectors felt that improvement was needed to properly address the aging issue also are discussed.« less

This Site Maintenance Plan has been developed for Pacific Northwest Laboratory`s (PNL) Nonnuclear Facilities. It is based on requirements specified by US Department of Energy (DOE) Order 4330.4A, Chapter I, Change No. 4. The objective of this maintenance plan is to provide baseline information for compliance to the DOE Order 4330.4A, to identify needed improvements, and to document the planned maintenance budget for Fiscal Year (FY) 1993 and to estimate maintenance budgets for FY 1994 and FY 1995 for all PNL facilities. Using the results of the self-assessment, PNL has selected 12 of the 36 elements of the Maintenance Program defined by DOE Order 4330.4A, Chapter I, for improvement. The elements selected for improvement are: Facility Condition Inspections; Work Request (Order) System; Formal Job Planning and Estimating; Work Performance (Time) Standards; Priority System; Maintenance Procedures and Other Work-Related Documents; Scheduling System; Post Maintenance Testing; Backlog Work Control; Equipment Repair History and Vendor Information; Work Sampling; and Identification and Control. Based upon a graded approach and current funding, those elements considered most important have been selected as goals for earliest compliance. Commitment dates for these elements have been established for compliance. The remaining elements of noncompliance will be targeted for implementationmore » during later budget periods.« less

Although each maintenance task performed on an item of equipment may enhance its reliability, neither preventive nor overhaul maintenance can return the equipment to good‐as‐new condition. Applying the concept of maintenance improvement factors to both types of maintenance, mathematical models are developed that are used to generate preventive and overhaul maintenance schedules. Examples are provided to demonstrate the sensitivity of the schedules to model parameters.

ISBN: 081869064X; An improved self-checking solution for the sequencing part of the MC 68000 microprocessor is presented. Compared with previous self-checking schemes for this microprocessor, the present scheme makes its possible to reduce the overhead and simplifies the implementation of both functional circuits, and checkers. The unified BIST (built-in self-test) method is applied to this scheme. This method uses a merging of self-checking and BIST techniques and allows a high fault coverage for all tests needed for integrated circuits, e.g., offline test (design verification, manufacturing, and maintenance test) and online concurrent error detection. An area overhead of about 27% is required, which is quite satisfactory in comparison with previous results.

The author argues that the original paper (C.J. O'Donnell, see ibid., vol. 33, no. 5, p. 1367-9, 1997) can provide some useful insight for the user and specifier of these products, but argues that it is important to keep in mind some of the limitations on the data as collected. As was determined at the discussion following the presentation of the paper, he states how the paper covers only tests which were performed on low voltage power circuit breakers as covered by ANSI Standard C37.16 and does not include any data from testing of low voltage molded case circuit breakers. Thus, he believes the title of the report should be corrected to reflect the actual type of breakers included and the applicable standard. He also lists other areas in the report which he believes should be strongly considered when evaluating the validity or reliability of the data presented.

Summary The present study assessed the effects of self-instructional training on learning-disabled children's perceptual deficits. Twenty-nine children (M age = 9.70 years) were assigned randomly to a control (n = 10), an attention-placebo control (n = 9), and self-instruction group (n = 10). Analyses of covariance (with the pretest score as the covariate) yielded significant treatment effects at post- and maintenance testing, although there was no evidence whatsoever of any generalization to academic performance of classroom behavior. Analyses of the frequency of overt self-verbalizations at post- and maintenance testing further suggested the efficacy of self-instructions for direct treatment effects. Finally, the importance of S characteristics in self-regulation programs was emphasized: Children with an internal locus of control orientation tended to use overt self-verbalizations most frequently.

This paper presents the results of a review of maintenance methods that may be considered for condition monitoring of equipment in a nuclear power plant. Some of these methods are presently being used on instruments and equipment whose performance is governed by the plant technical specifications. Other methods are being used to monitor the condition of heavy power production equipment in the plant. From a survey of eight utilities which have or will soon have operating generating stations it was found that eM was not being used on light equipment or environmentally qualified equipment. An exception is the monitoring of drift in pressure transmitters by some utilities. An explanation for the lack of widespread use of condition monitoring (CM) is the uncertainty over the cost effectiveness and reliability of the test methods to yield unambiguous information. A purpose of CM is to optimize the preventive maintenance program by adjusting the tests performed and the schedule to the unique requirements of the equipment. By showing the changing condition of the equipment with time, CM may also be able to predict when certain criteria will be reached in the future. CM programs to demonstrate the ability of certain tests to show a correlation between degradation and the measured parameter and to establish criteria for judging the condition of the equipment could help remove some of the ambiguity that now exists.

This paper considers a two-unit (identical) parallel system with facilities of preventive maintenance, inspection and two types of repair, type I and type II. These two types of repair facilities have a considerable difference in their costs. Both the units of the system can fail simultaneously due to some common-cause or they can fail one by one. The time of failure of a unit and system, the commencement of maintenance and inspection are assumed to be constant while repair and maintenance times are arbitrarily distributed. Various measures of system effectiveness are evaluated using regenerative point technique.

Automatic test equipment for 100 percent incoming inspection of electronic devices is inexpensive enough and effective enough today that sample testing no longer makes sense for most quality-control organizations. Although component manufacturers normally perform 100 percent inspection--at least in the early stages of manufacture--there are a great many ways in which errors can be passed along to the user. As a result, incoming digital integrated circuits (IC's) may have error rates as high as 5 percent and, for linear ICes, rejection rates may be up to 10 percent. Nor do acceptable quality levels (AQL's) provide a positive assurance of the quality of a lot, as is pointed out in an appendix. Break even is basically the point at which the cost of testing meets the cost of not testing. It is often expressed as the number of units that must be tested per year to justify a piece of automatic test equipment. Both the cost of testing and the cost of not testing can be calculated quite easily once the various factors to be used are considered.