This study identifies the concepts of reliability, cost of downtime, cost of spare parts, and procurement lead time as the four key moderators of spare parts availability. These concepts are used to establish a model to manage spare parts inventories. Reliability was assessed in terms of developing failure predictions for major component categories. Cost of downtime was evaluated by identifying various methods for determining costs associated with downtime. Cost of spare parts was examined to find correlations with economic indicators. These correlations were used to predict future price movements. Yearly changes in lead time were identified and correlated with economic indexes to develop movement predictability.

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Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Effective management of spare parts inventory is essential to companies because it influences inventory costs and asset utilization. The vast and diverse portfolio of spare parts, intermittent demand patterns and contradicting objectives between departments are examples of some of the factors that complicate Spare Parts Management (SPM). Managers of spare parts are faced with trade-off decisions between risk and cost on a daily basis. These decisions include, amongst many, determining appropriate stock levels and order frequencies. Despite the importance of SPM, decisions are however often made intuitively in practice with little factual support, and the decision-making process is commonly constrained within departmental silos. Even though there is a large body of academic knowledge on this topic, practical applications of spare parts inventory solutions lag behind theoretical studies. The majority of studies in literature focus on single components of SPM, such as demand forecasting and parts classification, whereas fewer studies consider the decision-making process itself. This study proposes a decision-making framework for spare parts inventory management. The framework is based on a wide-ranging literature review that focuses on capturing the essence of Spare Parts Management (SPM), but also acknowledges the interconnectedness of the problem. Therefore, core inventory management principles, as well as closely related topics such as Supply Chain Management (SCM) and Physical Asset Management (PAM), are studied in the context of spare parts. The broad scope of the literature study leads to a holistic approach to the problem and prevents sub-optimization. The proposed framework condenses principles from various fields of study (SCM, PAM, Classification and Inventory Management) into a stepwise methodology presented as a decision-making framework. The objective of the framework is to provide managers with a structured process, based on factual information, to enable better decision-making in the field. Furthermore, the framework aims to capture the fundamentals of SPM in a simplistic manner to ease the adoption of the framework in practice. A case study is conducted in the South African mining industry to validate the framework. The case study demonstrates that the framework is practical, provides structured guidance, and assists managers to make trade-off decisions in managing spare parts inventory. / AFRIKAANSE OPSOMMING: Effektiewe voorraadbestuur van onderdele is belangrik vir maatskappye omdat dit voorraadkoste en die benutting van bates beïnvloed. Die bestuur van onderdele is ’n komplekse probleem. Ondermeer is die portefeulje van onderdele items breed en divers, die vraagpatrone sporadies en word die voorraadvlakke geaffekteer deur kontrasterende doelwitte tussen verskillende departemente. Bestuurders van onderdele word daagliks gekonfronteer met besluite rakende risiko’s en kostes, soos om toepaslike voorraadvlakke te bepaal en om te besluit wanneer om bestellings te plaas. Hierdie besluite word dikwels intuïtief geneem met min feitelike ondersteuning en insette in die besluitnemingsproses word gereeld beperk tot sekere departemente. Ten spyte van die geweldige akademiese belang in die onderwerp, is daar min suksesvolle praktiese toepassings. Die meerderheid van studies in die literatuur fokus op spesifieke elemente van onderdele bestuur, soos vooruitskatting en klassifisering van parte, terwyl minder op die besluitnemingsproses konsentreer. Hierdie studie stel ’n besluitnemingsraamwerk vir die bestuur van onderdele voorraad voor. Die raamwerk is gegrond op ’n deeglike literatuurstudie wat die essensie van onderdele bestuur ondersoek, maar ook die interverbondenheid van die probleem in ag neem. Voorraadbestuurbeginsels en verwante onderwerpe soos Voorsieningskettingbestuur en Fisiese Batebestuur word dus bespreek. Die breë omvang van die literatuurstudie lei tot ’n holistiese benadering wat sub-optimering van die probleem voorkom. Die voorgestelde raamwerk som beginsels uit verskillende relevante studievelde op in ’n stapsgewyse metode wat voorgestel word as ’n besluitnemingsraamwerk. Die doel van die raamwerk is om bestuurders te voorsien met ’n gestruktureerde proses, gebaseer op feitelike inligting, om besluitneming in die veld te verbeter. Verder poog die raamwerk om die fundamentele konsepte in voorraadbestuur vas te vang in ’n eenvoudige manier sodat die raamwerk maklik geïmplementeer kan word in die praktyk. Die voorgestelde raamwerk is gevalideer deur middel van ’n gevallestudie in die Suid-Afrikaanse mynbedryf. Die gevallestudie toon dat die voorgestelde raamwerk prakties is, die besluitnemingsproses op ’n gestruktureerde wyse lei, en bestuurders help om beter, ingeligte besluite te neem.

Syfte– Syftet med denna studie var att finna ett klassificeringsverktyg som kan underlätta beslutsfattande vid reservdelsuppläggning. För att besvara syftet formuleradestre frågeställningar;   Vilket analysverktyg kan användas för att systematiskt klassificera reservdelar i olika    grupper? Hur kan de klassificerade grupperna nyttjas vid reservdelsuppläggning?  Hur kan efterfrågan prognostiseras för de olika klassificerade grupperna med hänsyn till servicenivå? Metod– Studien bedrevs deduktivt genom teoribyggande, med både en empiriskt fallstudie och analytisk konceptuell inriktning. De metoder som studien använts sig av är; litteraturstudier, intervjuer och insamling från dokumentstudien. Litteraturstudien har varit inom områdena; reservdelsklassificering och prognostisering.  Resultat– Studiens resultat är att det krävs en multiklassificeringsmodell för att systematiskt klassificera reservdelar på grund av den komplexa naturen av reservdelshanteringen. Klassificeringsmodellen kan sedan utnyttjas till flera ändamål. De användningsområden som studien funnit är; hjälp vid bestämning av servicenivå, hjälp med val av prognostiseringsmetod för reservdelsgrupperna samt att finna reservdelar som har en skiftande efterfrågetrend.    Implikationer– Klassificeringsmodellen ämnar sig till att underlätta företags reservdelsuppläggning. Med hjälp av modellen ska fallföretaget lättare kunna ta beslut så som vilken servicenivå och prognosmetod som kan användas för deras reservdelar. Begränsningar–  Den här studiens begränsning är att bara ett fallföretag studerades på grund av tidsbegränsningen. Detta medförde att modellen som anpassades blev företagsspecifik och rekommenderas att valideras på andra företag.  Nyckelord– Klassificering, Reservdelsklassificering, Beslutstöd, Prognostisering, Reservdelsprognostisering, Servicenivå / Purpose–The purpose of this study was to find a classification tool that can ease the decision-making process of spare parts planning and forecasting. To accomplish this, three research questions were formulated; Which analysis tools can be used for a systematic classification of spare parts into different groups? How can the classified groups be used when planning and forecasting spare parts? How can the forecasting be done for the different classified groupsconsidering thecustomer service level?  Method– The study was deductively through theory-building, with both an empirical case study and analytical conceptual approach. The methods used were; litterateur research, interviews and collection of secondary data. The litterateur research has been conducted in the areas; spare parts classification and forecasting.  Findings– The finding of this study was that a multi criteria method is needed for a systematic classification of spare parts, because of the complex nature of spare part handling. The classification model can then be used for multiple tasks. The tasks that this study found were; help in deciding the customer service level, help in choosing forecast method for the different spare part groups and finding the spare parts that have shifted in demand trend. Implications– The classification model intends to ease companies spare parts planning and forecasting process. With help from the model the case company should have a more effective process now in choosing which customer service level and forecasting method to use for their spare part.   Limitations– This studies limitation was that only one case company was studied because of time constraints. This makes the modified model very company specific and needs to be further validated on other companies.  Keywords– Classification, Spare parts classification, Decision support, Forecasting, Spare parts forecasting, customer service level

High availability of a system can be achieved by performing timely replacement of degraded or failed components. To this end, spare parts are expected to be available and reordered when needed. It is not uncommon that spare parts may deteriorate on the shelf because of their physical characteristics and/or the imperfect storage and transportation conditions. Such phenomena will affect the reliability of spare parts and the availability of the system. In this dissertation, we first focus on a system with single critical operating component and one unit of deteriorating spare part. For such a system, to ensure the system availability and cost efficiency, making a joint decision on component replacement and reordering time is of vital importance. In particular, we study both failure-switching and preventive-switching strategies, where cumulative damage is considered for the spare part switching from its in-stock to operating conditions. To determine the corresponding optimal component replacement and reordering policies, the long-run average costs are minimized under a fixed lead time. It is expected that the work will benefit quite a few industry sectors, such as mining, oil and gas, and defense, where the operation of systems heavily relies on capital-intensive components. To advance the research a step further, we have relaxed the system with only a single operating component to a more complex system with multiple components. In addition, we have eliminated the limitations on the order quantity and inventory capacity. To capture the on-shelf part deterioration, a two-phase deteriorating process is adopted, for which the first phase is from the spare's new arrival to the identification of its degradation, and the second phase is the period thereafter but before the unit fails. Based on the parts' degradation states, we introduce two different replacement strategies for the spare consumption, i.e., the Degraded-First strategy and the New-First strategy. Because of the random nature of component failures and on-shelf deterioration, stochastic cost models for both DF and NF strategies are derived. With the objective of cost reduction through coordinating the inventory and maintenance policies, an enumeration algorithm with stochastic dynamic programming is employed for finding the joint optimal solution over a finite time horizon. Numerical experiments are conducted to study the impacts of these two strategies on the operation costs, and the analysis of key parameters that affect the optimal solutions is also carried out in the numerical study. The joint policies of our interest focus on both replacement and reordering of spare parts, which are more realistic and complex than those policies handling maintenance and spare parts inventory control separately. In particular: When the maintenance planning and inventory control strategy are jointly optimized, we consider the spare parts inventory experiencing on-shelf deterioration, which has not been well studied in the related literature. When dealing with a system carrying only one spare part, the impact of on-shelf deterioration of the spare part on its remaining operational lifetime is explicitly dealt with and described by the Cumulative Exposure (CE) model. For the extended model for a multi-component system, we make an early attempt to adopt a two-phase process to take into account on-shelf degradation of parts. The issues in the degradation-level-based ordering of spare parts in the multi-component system are also discussed. Several integrated cost models are developed in both systems and are used to determine the optimal replacement and reordering decisions with the objective of minimizing the expected long-run cost rate over an infinite/finite horizon.

This thesis examines the spare parts mission scaling problem within the land environment of the Canadian Forces. A revision was done to the recently proposed Land Automated Scaling System, thus providing a readily implementable version of this model. This revised model determines the kit of spare parts for a first or second line unit to carry in order to maximize the operational availability of the deployed weapons systems, subject to a volume constraint. Bayesian methods and actual part demand data are used to revise the demand distribution to more accurately reflect the distribution of the number of parts required during a mission, taking into account the environmental conditions and usage mode of the equipment. The model is easy to use, requiring readily available and easily accessible input data. In addition, it can be operated on a Base minicomputer, thus allowing it to be used by the ordinance engineering and supply officers at the unit/formation level to produce and revise their parts scales as their situation requires.

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science in Engineering. Johannesburg, November 1994. / Inventories are produced, used (e.g. for raw materials, supplies, spare parts, and So forth) or distributed by every organisation. Moreover, inventories represent a major investment from the perspectives of both individual firms and entire national economies. In addition, enormous costs are incurred in the planning, scheduling, control and actual carrying out of replenlshment-Iprocuretnentl related activities. Interest in the subject of inventory management is constantly increasing, yet Silver and Petarsonlll (P(eface) found that "although invi ,~ory management ha.l been studied in considerable depth from a theoretical perspective, yet, those of us who, throuah consulting work, come into. clos>!)contact with mananerlal decision procedures in this arer are repeatedly surprised to find how limited, and ad hoc, many of the existing decision systems actually are. The rate at which theory has been developed has far outstripped the rate at which decision practices of firms have been successft,Jlly upgraded. A major g~o has existed between the theoretical solutions, on the one hand, and the real world problems, on the other". Inventory control is the science-based art of ensuring that lust enough inventory (or stockl is held by an organisation to meet both its internal and external demand commitments economically. There can be disadvantages in holding either too much 01 too little inventory. Therefore, inventory control is primarily concerned with obtaining the correct inventory with compromise between these two extremes. The control and maintenance of inventories is a problem common to all enterprises in any sector of a given economy. The primary aim of this study is to identify What the inventory policy of a company shoull;I be to Secure a reduction in inventory-related costs while maintaining a high level of customer service. Lewis(2) defines two bMlt:~ tvpes of inventory policy. Those in which decisions concerning replenishment are based on the lellel of inventory held, are known as "fixed-order quantity models" or "re-order level policies" and those in which such declslons arc made on a time basis are known as "fixed-time period models" or "re-order cycle policies". According to Nadder(3) (7I 11) the basic distinction between fixed-order quantity models and fixed-tlme period models is that the former are "event-triggered" while the latter are "time-triggered". That is, a fixed-order quantity model initiates an order when the "event" of reaching a specified re-order level occurs. This event may take place at any time, depending on the demand for the items considered. In contrast, the fixed-time period model is limited to placing orders at the end of a predetermined time period; hence, the passage of time alone "triggers" the model. In this thesis, we shall discuss both classical inventory models and heuristic models. We shall also conduct an investigation into the factors affecting high levels of inventory ~ mainly lead times (supplier and internal lea' times) in relation to spare 9arts in the heavv-dutv truck and bus industry. The thesis also suggests guidelines for controlling stock or these types of commodities in a practical environment. This will be done by either researching the existing inventory models or developing new inventory models or a combination of both, the intention being not to look for absolute optimisation, but rather to achieve significant improvements over current operations. / GR 2016

Detta examensarbete har utförts som en del av civilingenjörsprogrammet i maskinteknik vid Karlstads Universitet i samarbete med Valmet. För Valmet är försäljning av reservdelar är en vital del av deras totala affär. I avsikt att stärka konkurrenskraften mot kunder i framförallt lågkostnadsländer vill Valmet erbjuda mer kostnadseffektiva lösningar genom att utveckla konstruktionen på befintliga reservdelar. Målet med examensarbetet var därför att ta fram ett systematiskt arbetssätt för produktutveckling av kostnadseffektiva reservdelar och validera det genom implementering på en befintlig produkt i Valmets reservdelssortiment.   Underlaget till det framtagna arbetssättet samlades in genom att utföra en litteraturstudie, en nulägesanalys på Valmet och en intervju på ett företag som är framgångsrikt inom eftermarknad. Arbetssättet syntetiserades som en process med stöttande riktlinjer genom att utgå från Valmets befintliga utvecklingsprocess och integrera teoretiska modeller, principer och verktyg ur vetenskaplig litteratur. Arbetssättet testades sedan på lutmunstycken för sodapannor.   Grunden för det framtagna arbetssättet bestod av en kombination av Value Management och Design to Cost. Fokus i arbetssättet ligger vid att utveckla en reservdel som återställer systemet till sitt normala arbetstillstånd, för ett pris som kunden är beredd att betala, och som balanserar tillförlighet med tillgänglighet så att den totala kostnaden för kunden minimeras.   Genom att implementera det framtagna arbetssättet på lutmunstycken för sodapannor kunde ett förslag på en lösning med 66 % lägre pris och med 50 % lägre total kostnad för kunden tas fram. Implementeringen visade att arbetssättet praktiskt kan användas på enklare reservdelar men att det behöver testas på komplexa produkter av ett tvärfunktionellt team innan det används av Valmet.  Arbetssättet stärker Valmets förutsättningar för att erbjuda ett mer kostnadseffektiv reservdelsortiment.

The purpose of this thesis was to develop methodologies and procedures for the construction and use of CAD part families. This project uses the software CADDS5 created by Computervision, Inc., and its "Family of Parts" module. This software allows the creation of an entire family of similar parts using a single parametric master model and a text file containing the necessary parameters for each member of the family. CADDS5 users at Raytheon were surveyed to determine how they use standard parts, what types of standard parts are used, and typical modeling strategies. A set of criteria were developed to determine which groups of parts would be good candidates to be used as test cases. Four test cases were used to develop the methodology or procedure for the creation of families of parts. In addition, efficient use of these part families required the development of a set of search engines to allow the users to find parts more easily, and a parts server to generate new family members. The Family of Parts software in CADDS5 serves as a starting point for the creation of a usable library of standard parts. However, it has a poor user interface and has no system for part management and database administration. This thesis has made up for several of these shortcomings, and has created the core of a working library that can be easily used by all of the designers without requiring detailed knowledge of the details behind the implementation. The methodology developed during this project provides the necessary information for designers to create the majority of standard parts in use at Raytheon. For those who want to expand the library, it has provided useful information that will help them create high-quality parts that will work well with this system.

Made available in DSpace on 2016-04-28T20:19:11Z (GMT). No. of bitstreams: 1 2007-Alexandre Jose Ramos Valentim.pdf: 673243 bytes, checksum: d13a838d7af8a461dfb971477d4a2bcd (MD5) Previous issue date: 2007-06-22 / This paper work was focused on the inventory management of spare parts. This theme is very relevant to the academic means due to the little national research and literature about it. The main goal of this research is analyzing the use of the inventory management of spare parts hybrid model in a company in the steel field. In order to do that, it was carried out a critical review of the literature available, reviewing the fundamental concepts of the inventory management, such as stock techniques and approaches (Economical Order Quantity, Reorder Point, ABC, Just-in-Time and MRP), as well as the calculations needed to reorder the stocks, in addition to other specific issues and main indicators in the spare parts management. The methodology adopted was the field research, which allowed a major deepening into the issues of the research. The company studied was selected due to the importance of its inventory management techniques related to its maintenance activities in the company s field of work. Presented the productive flow and the supply of the company, detailing the processes related to the inventory management of spare parts, including the functioning of the computing systems, as well as the calculi that support the activities, and the analysis of the research results. In the critical analysis of the results, it was made a confrontation with the theories presented and improvements were suggested in the model of the strategic management of the company, with the goal of reducing the values in stock and improving the users service. / Este trabalho foi realizado com foco na gest?o de estoques de pe?as sobressalentes, sendo esse tema bastante relevante para o meio acad?mico devido a pouca pesquisa e literatura nacional a respeito. O objetivo principal desta pesquisa ? a an?lise do uso do modelo h?brido de gest?o de estoque de pe?as sobressalentes em uma empresa do setor sider?rgico. Para isso foi realizada uma revis?o cr?tica da literatura dispon?vel, sendo revistos os conceitos fundamentais para gest?o de estoques, como t?cnicas e abordagens de estoque (Lote Econ?mico de Compra, Ponto de Ressuprimento, ABC, Just-in-time e MRP), bem como os c?lculos necess?rios para reabastecer estoques, al?m das quest?es mais espec?ficas para a gest?o de pe?as sobressalentes e principais indicadores. Como metodologia, optouse pela utiliza??o da pesquisa de campo, que permitiu um maior aprofundamento das quest?es da pesquisa. A empresa escolhida foi selecionada pela import?ncia das t?cnicas de gest?o de estoques para suas atividades de manuten??o dentro do setor de atua??o. Apresentado o fluxo produtivo e de abastecimento da empresa, com detalhamento dos processos relacionados a gest?o de estoque de sobressalentes, incluindo o funcionamento dos sistemas informatizados e os c?lculos que apoiam as atividades, e a an?lise dos resultados da pesquisa. Na an?lise cr?tica dos resultados foi realizada uma confronta??o com as teorias apresentadas e sugeridas melhorias no modelo de gest?o estrat?gica da empresa, com o objetivo de diminui??o dos valores imobilizados em estoque e melhora dos n?veis de atendimento aos usu?rios.