Showing papers on "Preventive maintenance published in 1986"

An Algorithm for Preventive Maintenance Policy

Abstract: Simple preventive maintenance (Maintenance type 1P) and preventive replacement (maintenance type 2P) are scheduled in such a way that the system does not drop below a minimum reliability. Failure rate after maintenance type 1P lies between "good as new" and "bad as old". The degree of improvement in failure rate after maintenance type 1P is cailed the improvement factor. A set of curves for the improvement factor as a function of cost for maintenance type 1P and age of the system is proposed. The cost rate for a system is formulated as a ratio of an average cost for a cycle (time between replacements) to an average cycle length. An optimum number of type 1P maintenance actions before type 2P maintenance is obtained by minimizing the cost rate when the failure times are Weibull distributed. The optimum solutions are a function of improvement factors and predetermined upper limit of failure rate.

Modified discrete preventive maintenance policies

Abstract: This article proposes a modified preventive maintenance (PM) policy which may be done only at scheduled times nT (n = 1,2, …): The PM is done at the next such time if and only if the total number of failures exceeds a specified number k. The optimal number k* to minimize the expected cost rate is discussed. Further, four alternative similar PM models are considered, when the system fails due to a certain number of faults, uses, shocks, and unit failures.

The effect of a preventive maintenance program on the failure rate of fixed mechanical equipment

Abstract: THE EFFECT OF A PREVENTIVE MAINTENANCE PROGRAM ON THE FAILURE RATE OF FIXED MECHANICAL EQUIPMENT Edward st. Pierre The premature failure rate of certain types of fixed mechanical equipment, such as air handling units and pumps, in the Sheboygan Area School District was unacceptab­ ly high. This contributed to inflated maintenance and repair costs. The researcher developed, implemented and evaluated the effect of a preventive maintenance (PM) pro­ gram on the failure rate of such equipment. A quasiexperimental, nonequivalent control group research design was used in which the independent variable (IV) was PM and the dependent variable (DV) was the failure rate of fixed mechanical equipment. During the experimental period, November 25, 1985, to February 25, 1986, PM proce­ dures were applied to the fixed mechanical equipment in four school buildings. Four other buildings, sel ected as con­ troIs, did not receive PM. The number of failures of equip­ ment included in the PM program was determined for each of the test and control buildings. Cost data was also main­

Energy savings from increased preventive maintenance on indiana highways

Abstract: In this paper are described the development of trade-off relationships between routine pavement maintenance activities and the application of these relationships in estimating the savings in fuel used in pavement maintenance in Indiana. Two major routine pavement maintenance activities were considered: patching (corrective maintenance) and sealing (preventive maintenance). The results showed that when more sealing was done before winter less patching was required after winter. Different highway classes, pavement types, and geographic locations are taken into consideration. The application example assesses possible cost savings in terms of savings in direct fuel consumption by the maintenance equipment fleet.

Modelling Total Life Cycle Cost

Abstract: In this paper, the concept of terotechnology and the formulation of life cycle cost has been taken from the point of view of the user as against that of the manufacturer, and the stages of design, development of prototypes, manufacture and testing of the machine have not been considered. This is felt appropriate since terotechnology has to date found greater application (and will continue to do so, except for military systems and installations wherein it has possibly found the greatest application) in the case of large capital equipment and machines, for example for process plants, integrated iron and steelworks, power plants etc. The hazard curve provides the bases for the estimation of the time-dependent maintenance cost incurred over the life cycle of an equipment. Accordingly a system study of the hazard rate of power units of a thermal power plant was undertaken and has been presented. Using the modified 'bath-tub' curve obtained from the case study and the Weibull model, an equation of the total life cycle cost has been developed. Thus the model takes into account deterioration of components and system performance over time. The model brings out the efficacy of preventive maintenance action in the form of condition monitoring and shows that the total life cycle can be increased if appropriate preventive maintenance actions are taken in the random failure and wear-out failure regions.

The Effect of Incomplete and Deleterious Periodic Maintenance on Fault-Tolerant Computer Systems

Abstract: Maintenance is a common technique to achieve the reliability requirements of fault-tolerant computer systems. Depending on the system, maintenance may be carried out upon the failure of any one module, at regular intervals, or subject to some other maintenance strategy. Due to human factors, maintenance is not always perfect, contrary to usual assumptions. There are several classes of imperfection that adequately describe maintenance strategies. A system with scheduled shut-down times for maintenance is best described by maintenance action that might be incomplete. On the other hand, a system which has to be diagnosed or maintained on-line is best described by maintenance action that may provoke a system failure; we term this deleterious maintenance. This paper examines these two classes of imperfection and obtains mean time-to-first-failure for each class. The results of three studies on Triple Modular Redundancy (TMR) systems are given for the case of maintenance induced failures in fault-tolerant computer systems. In systems with maintenance-induced failure, an optimum maintenance interval exists. The optimum MTFF is less than the optimum MTFF obtained if perfect maintenance is assumed. This is the limit to which maintenance can be used to improve the performance of the system. To increase MTFF beyond this, spares must be used. When these spares are substituted, the probability of inducing a failure must be much lower than that of maintenance-induced failure. For systems which have to be maintained on-line, it is important not to neglect the case of deleterious maintenance.

New Models for Maintenance of Series and Parallel Systems

Abstract: This paper develops new models for maintenance of multi-component series and parallel systems with inspection, preventive maintenance(pm), and repair; and subject to deterioration with use and stochastic failure. Use of 3-state models makes it possible to consider wear and pm of components. The 3-state model for a component is reduced to an equivalent 2-state model. By combining 2-state models, multicomponent systems are analysed. The error introduced by using equivalent models for the system is below 0.7% for a typical example. A case study of an electrical power system illustrates the application of the technique. Details are available in a separately available Supplement.

Leachate Collection Systems

Abstract: The available experience with the performance of leachate collection systems (LCS) in hazardous waste landfills (HWLFs) is reviewed. Design and operating factors affecting LCS performance, potential problem areas, applicable preventive, and corrective measures and relative R&D needs are identified. Due to the relative newness of properly designed HWLFs, there has been limited operating experience with LCS and opportunity for corrective action at such sites. Design and operation of HWLFs should be aimed at minimizing leachate generation, improving leachate control capability, reducing impact on LCS, and providing preventive maintenance. Case studies of engineered facilities that have now been in service for a number of years can provide the needed hard data for correlating performance with design.

Preventive Maintenance for Roller and Journal Bearings of Induction Motor Based on the Diagnostic Signature Analysis

Abstract: Maintenance preventive des paliers de glissement et des roulements a rouleaux des moteurs a induction. Utilisation d'un diagnostic base sur l'analyse de signature

Reducing Nuclear Plant Cost and Enhancing Safety by Reliability Based Maintenance

Abstract: The nuclear power industry and the government agencies recognize that the growing maturity of nuclear plants, as well as concern for plant outages, necessitates attention to surveillance and maintenance. This paper provides an overview of reliability based maintenance which is available to reduce (optimize) plant costs while maintaining or enhancing plant safety. Categorization of the various types of nuclear plant maintenance is provided as a foundation for maintenance program definition. A technique for maintenance feasibility review is presented, using a decision logic tree to assist the engineering and maintenance staff.

Generic Integrated Maintenance Diagnostics

Abstract: Maintenance Support for a weapon system involves both preventive and corrective maintenance actions. Preventive maintenance is normally associated with mechanical equipment, and requires prognostic maintenance techniques to predict failures before they occur. Corrective maintenance is more closely associated with electronic equipment, and requires diagnostic maintenance techniques to detect and isolate failures after they occur. To pursue a systems approach to weapon system maintenance using both prognostics and diagnostics, the Air Force has initiated a program entitled, ``Generic Integrated Maintenance Diagnostics (GIMADs)''. This paper provides insight into the GIMADS program at Aeronautical Systems Division.

Transit bus maintenance in new york state: issues and analysis

Abstract: Under provisions of a cooperative agreement with the Urban Mass Transportation Administration (UMTA), the New York State Legislative Commission on Critical Transportation Choices conducted a study of transit bus maintenance in the state. Twenty site visits were made and questionnaires were completed and returned by 57 percent of the bus operators. Findings were made relative to spare ratios, mixed fleets, negotiated bidding, maintenance facilities, outdoor storage of vehicles, new mechanic and continuous mechanic training programs, performance measures, management, job aids, driver involvement in maintenance programs, preventive maintenance, record keeping, computer usage, diagnostic techniques, contract management, and parts procurement and inventories. Commission staff developed a series of 27 specific recommendations to (a) improve the effectiveness of bus maintenance practices and (b) preserve the large investment of funds by federal, state, and local governments in buses and bus maintenance facilities. These recommendations are currently under review by UMTA and the final report should be available in published form in the near future.

Evaluation of Microcomputer-Based Operation and Maintenance Management Systems for Army Water/Wastewater Treatment Plant Operation.

Abstract: : Poor data management and inadequate preventive maintenance are considered significant causes for some (DOD) wastewater treatment plants failing to meet their National Pollutant Discharge Elimination System permit requirements. Microcomputer-based operation and maintenance (O&M) management systems have been successfully implemented in private-sector wastewater treatment plants and can provide similar plants at Army installations with improved management of process control parameters, trend analysis to simulate and control processes, automatic report preparation, and better preventive maintenance management. this report provides a detailed evaluation of microcomputer-based O&M management systems for use in Army water/wastewater treatment plant operation. In particular, capabilities of various microcomputer-based process management and maintenance systems were compared to determine how this technology could best be exploited in Army applications. Field demonstrations of microcomputer technologies for sewage treatment plants were performed at Fort Sill, OK, and Fort Meade, MD, and the essentials of an effective preventive maintenance program outlined. Guidance for selection, procurement, and implementation of microcomputer-based O&M management systems at Army water/wastewater treatment plants were then chosen based on the analysis. (Author)

Preventive maintenance system for operating system

Abstract: PURPOSE:To carry out maintenance of an operating system without assistance by setting a storage medium storing a maintenance information relative to all operating systems of the same level, and activating the storing means of the maintenance information. CONSTITUTION:After the storage medium 90 is set at a floppy disc unit 9, a person for maintenance activates a maintenance information storing means 3. The maintenance information storing means 3 accedes to a floppy disc unit 9 and reads a management information 900 in the storage medium 90. Then, making access to a magnetic disc device 10, it reads a maintenance curriculum of a maintenance curriculum storing portion 1001 of a storage medium 100. Comparing the read management information 900 with the maintenance curriculum, and if the management information 900 comes next to the maintenance curriculum, a maintenance information 90i (i=1-n) in the storage medium is read. Then, comparing a condition applied to the maintenance information 90i (i=1-n) with that of the system of a condition storing portion 8, only coinciding maintenance information is written in a maintenance information storing portion 1002.

Cost‐Benefit Analysis of a 1 out of n : G System with Variable Repair and Preventive Maintenance Rates

Abstract: The system studied in this article is a 1 out of n : G system with a single server. A unit is repaired when it fails and is also taken off for preventive maintenance (PM) after it has completed a certain amount of time in operation. A single server attends to both repair and PM of units. All service times are exponentially distributed, but the service rate depends on the type of service (repair or PM) and the number of units waiting for service. Under assumptions of linear revenue and costs, a cost‐benefit analysis of this system is performed. A particular case of three units with time to failure 2‐Erlangian and time to PM constant is taken up for analysis. Numerical results are presented for some values of the system parameters.

Remote maintenance system of facsimile equipment

Abstract: PURPOSE:To execute quickly confirmation of a fault state or preventive maintenance without dispatching a maintenance service personnel to the installed location of a facsimile equipment by providing a loopback test means for a built-in MoDEM in the facsimile equipment and sending back the result of test to a remote maintenance device by an indication of the remote maintenance device CONSTITUTION:The excecution of the MODEM test is indicated from the remote maintenance device 1 to a facsimile equipment 4 via a line 2 and an exchange 3 The facsimile equipment 4 receives a code data indication from the remote maintenenace device 1 and allows a control section 5 to execute a loop test with a decided code to high/medium/low speed MODEMs 6-8 The data of the result of test is transferred to the remote maintenance device 1 via an NCU9 and the line 2

Graphical Techniques for Maintenance Planning.

Abstract: : Items subject to stochastic failure are candidates for preventive maintenance where often an item is replaced or restored to a good-as-new condition. For single component items, the optimal interval for this type of preventive maintenance might be determined via some mathematical model of replacement. Usually, these models require knowledge of the failure distribution as well as the costs of preventive and corrective maintenance. For most problems there is considerable uncertainty as to the appropriateness of a failure model. Bergman and others have espoused graphical techniques for the Age Replacement model which do not require specification of the failure model. This dissertation proposes several graphical techniques for two other replacement models, Block Replacement and one called Blind Replacement.