Maintenance Models

O. Elizalde, J.M. Asua and J.R. Leiza, Monitoring of emulsion polymerization reactors by Raman spectroscopy Calibration model maintenance, Appl. Spectrosc., 59, 1280-1285 (2005). 

Performance of PLS regression models to predict benzene and total aromatics by GC methods were equally robust. Model maintenance was minimal and the spectrometer operated within validation limits for periods of over a year. 

Occasionally attempts to justify a process analyzer are made on the basis that it will reduce the number of grab samples that need to be taken from the process to be analyzed, and therefore reduce the sample load on the QC lab. This is not usually a good justification for an on-line analyzer for two reasons (1) The reduction in lab analyses rarely offsets the cost of analyzer installation and operation (2) An on-line analyzer relies on high quality lab data for calibration, validation, and long-term model maintenance, so the reference method can never be eliminated entirely. 

Model maintenance and archival along the lifecycle of process design must be supported. The model repository ROME [24] provides functionality for model management and archival. ROME accesses proprietary modeling tools in order to extract information about the models being maintained. ROME stores only metadata about the models being archived and can therefore easily reference models in a variety of representations, open-form or closed-form as well as declarative or procedural models. 

A number of capabilities should be provided by an integrated and shared MBMS of a DSS (Barbosa and Herko 1980 Liang 1985) construction, model maintenance, model storage, model manipulation, and model access (Applegate et al. 1986). These involve control, flexibility, feedback, interface, redundancy reduction, and increased consistency ... 

In de Smidt-Destombes et al. (2004) the tradeoff between repair capacity and spare part inventory control is investigated for a single k out of N system under condition based maintenance i.e. when the number of defect components exceeds some previously defined limit, maintenance is initiated. They propose exact and approximate methods to analyze the system availability. Continuing along these lines, de Smidt-Destombes et al. (2007) considerM identical k out of N systems under block replacement. For each system all defect components are replaced every fixed time interval. Two methods are proposed to analyze the system availability as a function of the number of spare parts stocked and the block replacement interval. The main difference between these studies and our contribution is that in our contribution we focus on applying a cost structure, while their focus is on estimating up-time. Furthermore, we consider multiple different systems, while de Smidt-Destombes et al. (2004, 2007) focus on either just one system, or on multiple identical systems. Finally, in our model maintenance is immediately initiated when equipment fails. 

In the second phase, questions of dealing with the long-term issues of having an analyzer need to be evaluated. This is a very complex metric, which can include variables such as staffing those is responsible for day-to-day operation and the per year running cost of having such an analyzer. Running costs themselves include a need to define hardware consumables, process downtime for hardware maintenance, technician time, and the process model maintenance cost. 

Christer A.H., Wang W., Baker R. and Sharp J., (1995) Modelling Maintenance Practice of Production Plant Using Delay-Time Concept , IMA Journal of Mathematical Application in Business and Industry, Vol. 6, pp. 67-84. 

The benefits of flaw visualization tools applications are supported by strength maintenance software, based on computer modelling and realizing assessment procedure. 

Biological Antioxidant Models. Tea extracts, tea polyphenol fractions, and purified catechins have all been shown to be effective antioxidants in biologically-based model systems. A balance between oxidants and antioxidants is critical for maintenance of homeostasis. Imbalances between free radicals and antioxidants may be caused by an increased production of free radicals or decreased effectiveness of the antioxidants within the reaction system. These imbalances can be caused by the radicals overwhelming the antioxidants within the system, or by an excess of antioxidants leading to a prooxidant functionaHty (105—118). When antioxidant defense systems are consistently overwhelmed by oxidative reactions, significant damage can... 

A group of computers becomes a network when intercomputer communication is estabhshed. Prior to the 1980s, all system suppliers used proprietaiy protocols to network their systems. Ad hoc approaches were sometimes used to connect third-pai ty equipment, which was not cost-effective in system maintenance, upgrade, and expansion. The recent introduction of standardized protocols has led to a decrease in initial capital cost. Most current DCS network protocol designs are based on the ISO-OSI seven-laver model. 

Adequate support from the facility staff is absolutely essential. The facility staff must help the analysis team gather pertinent documents (e.g., PSilDs, procedures, software descriptions, material inventories, meteorological data, population data) and must describe current operating and maintenance practices. The facility staff must then critique the logic model(s) and calculation(s) to ensure that the assumptions are correct and that the results seem reasonable. The facility staff should also be involved in developing any recommendations to reduce risk so they will fully understand the rationale behind all proposed improvements and can help ensure that the proposed improvements are feasible. Table 12 summarizes the types of facility resources and personnel needed for a typical QRA. 

The confluence of sharply rising Operations and Maintenance (O M) costs. NRC requested Individual Plant Examinations (IPEs) and increased personal computer capabilities gave rise to the R R Workstation. Its uses and maintains-current PSA models and databases for individual plants to perform O M planning and scheduling, and uses the PSA in IPE models to identify plant design, procedure and operational vulnerabilities. The Risk and Reliability Workstation Alliance was organized by EPRI to support the R R Workshop in order to achieve O M cost reduction, plant productivity and safety enhancement through risk-based, user-friendly, windowed software louls (Table 3.6 8). The Alliance, initiated in 1992, includes 25 U.S. utilities and four international partners from Spain, France, Korea, and Mexico. SAIC is the prime contractor for the R R Workstation, with participation of five other PSA vendors. 

MAPPS Maintenance Personnel Performance Simulation model NUREG/CR-3fi26. I984... 

MAPPS (NUREG/CR-3634) is a task-oriented, computer-based model for simulating actual processes in maintenance activities. It includes environmental,... 

The MSF model (NUREG/CR-3837) is used principally to determine the level of dependence between safety systems introduced by maintenance, testing, and calibration activities. It is a mathematical model which modifies the independent failure probability of any single component by considering that a component with which it is redundant has already failed. This allows the conditional failure probabilities of redundant components to be calculated to determine the overall system failure probability. Documentation requirements are given in Table 4.5-6. 

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