Fredy Kristjanpoller

Introducing buffer inventories in the RBD analysis of process production systems

Abstract The throughput analysis is an important issue for the design and operations management of process production lines. The throughput of a line depends on the availability and nominal throughput of its machines. Further on, it is influenced by the accumulation process of production material stocked into buffers along the line; hence, the buffer inventory level is also a relevant variable that has to be considered when assessing the throughput of the line. The present paper is particularly concerned with using such an assessment for supporting maintenance decisions. The buffer inventory level should provide the proper isolation time before the buffer becomes empty, so that, during this time, a maintenance intervention can be carried on at a failed machine upward, without causing a propagation of the effect of the failure in the machines downward (the so called ‘material starvation’). Alike, it should guarantee the proper isolation time before reaching the complete utilisation of the buffer capacity, so that also during this time a maintenance intervention is possible at a failed machine downward without causing a propagation of the effect of the failure in the machines upward (the so called ‘blocking of production’). This strategy is particularly interesting in the process industry where the capital cost of equipment is high and the holding cost of material is low. Hence, the isolation times before reaching ‘material starvation’ or ‘blocking of production’ have to be properly studied in order to make an accurate analysis of their effect on the throughput of the line. The present paper provides a model to this end, derived by extending the well known Reliability Block Diagram (RBD) method, currently used in the normal duties of a maintenance engineer. The usual RBD availability analysis is integrated by a state space analysis through which isolation times can be analysed. Besides, an empirical study – the case of a production line taken out from the mining industry – is carried on in order to demonstrate the use of the integrated tool in practice.

Stochastic model of reliability for use in the evaluation of the economic impact of a failure using life cycle cost analysis. Case studies on the rail freight and oil industries

This paper aims to investigate the technical and economic factors related to failure costs (non-reliability costs) within the life cycle cost analysis (LCCA) of a production asset. Life cycle costing is a well-established method for the evaluation of alternative asset options. It is a structured approach that addresses all the elements of this cost and can be used to produce a spend profile for an asset over its anticipated life-span. The results of an LCCA are used to assist management in the decision-making process when there is a choice of options. The main costs can be classified as the capital expenditure incurred when the asset is purchased, and the operating expenditure incurred during the asset’s life. This paper explores different aspects related to the failure costs within the LCCA, and describes the most important aspects of the stochastic model: a non-homogeneous Poisson process. This model is used to estimate the frequency of failures and their impact which can cause various failures in the total costs of a production asset. This paper also contains a case study for the rail freight industry (Chile) and the oil industry (Petronox, Venezuela) where the proposed model and concepts are applied, and respectively compared in terms of results. Finally, the presented model provides maintenance managers with a decision tool that optimizes the LCCA of an asset and increases the efficiency of the decision-making process related to the control of failures.

Integrated system reliability and productive capacity analysis of a production line. A case study for a Chilean mining process

The analysis of a production line requires the consideration of its reliability and productive capacity since they have a direct influence on the expected levels of performance. These factors have an intrinsic stochastic behaviour which must be accounted for in the analysis. This paper proposes an integrated approach based on Monte Carlo simulation which is tested on a case study concerning the production line of a private mining company located in northern Chile. Specifically, the primary, secondary, and tertiary crushing processes are analysed in detail. Actual maintenance and operation data for 16 months of operation are considered in the case study. A tailored simulation model is developed that is able to jointly estimate the reliability and productivity of the process. The integration of these two aspects allows situations in which equipment becomes unavailable to be identified and this can improve business continuity and process productivity.

Expected impact quantification–based reliability assessment methodology for Chilean copper smelting process: A case study

Currently, a lack of interpretation tools and methodologies hinders the ability to assess the performance of a single piece of equipment or a total system. Therefore, a reliability, availability, and maintainability analysis must be combined with a quantitative reliability impact analysis to interpret the actual performance and identify bottlenecks and improvement opportunities. This article proposes a novel methodology that uses reliability, availability, and maintainability analysis to quantify the expected impact. The strengths of the failure expected impact methodology include its ability to systematically and quantitatively assess the expected impact in terms of reliability, availability, and maintainability indicators and the logical configuration of subsystems and individual equipment, which show the direct effects of each element on the total system. This proposed analysis complements plant modeling and analysis. Determining the operational effectiveness impact, as the final result of the computation process, enables the quantitative and unequivocal prioritization of the system elements by assessing the associated loss as a “production loss” regarding its unavailability and effect on the system process. The Chilean copper smelting process study provides useful results for developing a hierarchization that enables an analysis of improvement actions that are aligned with the best opportunities.

Propuesta de un modelo de gestión de mantenimiento y sus principales herramientas de apoyo

Este articulo presenta un modelo para la gestion integral del mantenimiento, teniendo en consideracion la caracteristica de mejora continua en el tiempo. A modo de introduccion y contextualizacion, se explica la importancia que tiene la alineacion de objetivos a todo nivel organizacional para lograr la integracion y correcta gestion de la unidad de mantenimiento. El modelo a presentar se compone de siete principales etapas, las cuales deben desarrollarse progresivamente segun el escenario actual de la organizacion, haciendo enfasis en la gestion y optimizacion sostenida en el tiempo de procesos asociados a la planificacion, programacion y ejecucion del mantenimiento. Adicionalmente, el modelo presentado complementa herramientas de apoyo para el desarrollo e implementacion de las etapas, y caracteristicas operacionales reales, las cuales podrian afectar el desempeno de la unidad de mantenimiento. Finalmente, se presentan algunas consideraciones generales y respectivas conclusiones.

Reliability Assessment Methodology for Massive Manufacturing Using Multi-Function Equipment

Experience reveals that reliability varies depending on the characteristics of operation. The manufacturing process based on multifunction equipment gives a usual case of variation in operating conditions. This work presents a methodology for the reliability analysis of multifunction processes, using the RCM approach, and a modification of the Universal Generating Function (UGF) under a massive manufacturing context. The result is a characterization of reliability, for each piece of equipment and for the production system. The methodology is applied in a workshop of a textile industry, where there is prior evidence that the failure behavior varies according to the type of function executed by multifunction machines.

Design of Performance Indicators Based on Effective Time and Throughput Variability. Case Study in Mining Industry

The following paper proposes a method on how to analyze productive systems to achieve performance indicators that allows to know the state of the system. In particular, the objective of the paper is to analyze performance indicators that allow to understand the state of the production line in systems that present variability conditions in the performance of their equipment, and in their operational conditions that will not allow direct calculation of the effective time. It is proposed to begin with the utilization of a methodology to increase the understanding of the system, which will generate a conceptual model that will concentrate the required knowledge through a logic structure that will ease the subsequent analysis. Then, a step by step process is proposed to define the system, its performance indicators of interest, and the most efficient and effective way to obtain those, considering the existing restrictions. Finally, system and subsystem level indicators will be obtained, which will be a representation of the real state of the process, by representing the effective times, and variable throughput. All of the above will be applied in a case study in the mining industry from Chile.

Reliability assessment based on energy consumption as a failure rate factor

The present study defines a methodology to analyze the relationship between the failure rate of any component and the factors that can influence it, in order to link time independent operating variables to the reliability study. Characterizing the failure rate using these variables is especially useful for changing time operational contexts. To do this, a study of traditional and modern methods of analysis, together with the assumptions that must be fulfill for its implementation and the methodology for testing the assumptions is performed. Specifically, the methodology proposed in this paper is used to develop a complete study of the influence of the energy consumption of a component, at the rate of engine failure. As can be inferred, there is a relationship between energy consumption and the rate of failure; the practical experience reveals that companies frequently use the energy expenditure variable, but documented studies that corroborate their decision are not found in the literature.

A Support System for Selecting the Most Suitable Spare Parts Strategy

This paper reports an algorithm to create a decision support system for the most suitable spare parts strategy. It is developed based on risk and cost analysis. The algorithm decision support system makers includes information about the possible scenarios in the maintenance field; moreover, this information is useful to support future strategies, helping to decide the number of the spare parts necessary to increase at the maximum process/equipment availability rate. In this task, the algorithm is based on risk analysis considering two main aspects. The first, related to success and failure probabilities is estimated through Poisson distribution; the second one is related to the expected total cost, considering: storage costs, capital tie-up costs, repair costs, purchase order costs (normal and emergency), opportunity costs, and others.

Career Employability Development Through a Specialized Asset Management’s Degree: An Exploratory Analysis for a Chilean Program

Asset Management as a growing discipline is being incorporated into the Chilean Industry, especially into the mining Industry; however, there is a need to provide the necessary skills and knowledge regarding these new positions. In that regard, since 2005 we have successfully incorporated a master’s program scheme entitled Master of Asset Management (MGA, currently in its 9th offering). Up to date, more than 300 postgraduate students from different industries have attended this MGA, becoming the leading program in Latin America. In the training field we have developed a Diploma on Asset Management (DGA—140 h). With the present study, we have analysed the students’ profiles to identify the industry distribution and, at the same time, to measure the extent to which the skilled labour (graduates) have moved between different job positions and/or companies, be it as a horizontal mobility (does not result in a change in the worker’s grading or status) or a vertical mobility (if it does). Additionally, we regularly test the influence of the market-value and scholastic and social dimensions of the human capital on the alumni. The scope is mainly the Chilean industry.