Reducing costs of repairable spare parts supply systems via dynamic scheduling

We study a system consisting of one repair shop and one stockpoint, where spare parts of repairables are kept on stock to serve an installed base of systems. Part requests are met from stock if possible, and backordered otherwise. Our objective is to determine initial stock levels and a policy for scheduling repair jobs such that holding and backorder cost are minimized. We propose two dynamic scheduling rules, compare their performance with the static priority rule, and show that even when stock levels and static priorities have been optimized simultaneously, dynamic scheduling rules often reduce total cost by more than 10%

Economic Instruments and Induced Innovation: The Case of End-of-Life Vehicles European Policies

The paper addresses the dynamic-incentive effect of environmental policy instruments when innovation is uncertain and occurs in very complex industrial subsystems. The case of end-of-life vehicles (ELVs) is considered focusing predominantly on the effects of the European Directive adopted in 2000 which stipulated economic instruments as free take-back, and on the voluntary agreements in place in many EU countries. The ELV case study is an example of a framework where policy-making faces an intrinsic dynamic and systemic environment. Coherent sequences of single innovations taking place in both upstream (car making) and downstream (car recycling/recovery) of the ELV system can give rise to different “innovation paths”, in accordance with cost-benefit considerations, technological options and capabilities associated to the different industrial actors involved. The impact of economic instruments on innovation paths, in particular free take-back, is considered. Deficiencies or difficulties concerning the transmission of incentives between different industries can prevent the creation of new recycling/recovery/reuse markets, giving rise to other less preferable and unexpected outcomes. The implication for policy is a need for an integrated policy approach, as enforceable VAs, in order to create a shared interindustry interest for innovation and to reduce the possible adverse effects which economic instruments exert on innovation through cost benefit impacts on key industrial and waste-related agents involved in the ELV management system. These advantages should be taken into account vis à vis the emergence of Integrated Product Policy (IPP) as a leading concept of EU environmental policy and the associated shift from "extended producer responsibility" to "extended product responsibility".ELV, Induced innovation, Dynamic efficiency, Economic instruments, Recycling

A Roadmap for Acquisition of Legacy Parts Through an On-demand Solution Aimed at the Energy Sector on the Norwegian Continental Shelf - A Case Implementation

\section{Abstract} Equinor has initiated a Field Life Extension (FLX) project to prolong the end-life operational capabilities of their installations by innovative methods, including Stafjord A. One of these innovative methods is to implement an on-demand solution for re-supplying the installation with spare parts manufactured through alternative methods, such as additive manufacturing (AM) and rapid casting. However, due to the age of specific components, the documentation for design, material specification, and manufacturing may be missing, i.e., legacy parts. The main aim of this thesis is to map the path from notification of a potential failure of a legacy part to the installation of a near-identical part. The life extension implies that mechanical equipment, such as valve bodies for the fire deluge systems must maintain their integrity throughout the expanded life cycle. Unfortunately, this component has exceeded its life expectancy by twice. Hence, increased degradation and risk for potential accidents introduce the need for acquiring new valve bodies. A literature review investigated the challenges and requirements for implementing the on-demand solution for legacy parts. Standards and manufacturing methods have been studied and compared. An Analytical Hierarchy Process was used to analyze the input from experts within AM and rapid casting. Finally, a case review processed the valve body through the Reverse Engineering Process (REP) activities. A roadmap is proposed based on regulations governing the manufacturing of mechanical components used on the Norwegian Continental Shelf (NCS). Furthermore, requirements for implementing the on-demand solution for legacy parts are described, including a proposition for an explicit criticality assessment for metal AM. A recommendation for operational part-monitoring and identification linked with a digital warehouse of the corresponding part is made to finalize the proposed roadmap for acquiring legacy parts on the NCS. The Analytical hierarchy process (AHP) reveals that rapid casting outperforms metal AM for valve body manufacturing. In addition, metal AM and rapid casting are benchmarked regarding realistic cost and lead time procurement limitations. The results include the AHP output and indicate that the cost of ordering the valve body favour rapid casting, but the lead time for metal AM is lower than rapid casting. The total cost for metal AM per part is nearly equal to the cost of the initial requested batch of 26 valve bodies produced by rapid casting

Dynamic demand fulfillment in spare parts networks with multiple customer classes

We study real-time demand fulfillment for networks consisting of multiple local warehouses, where spare parts of expensive technical systems are kept on stock for customers with di??erent service contracts. Each service contract specifies a maximum response time in case of a failure and hourly penalty costs for contract violations. Part requests can be fulfilled from multiple local warehouses via a regular delivery, or from an external source with ample capacity via an expensive emergency delivery. The objective is to minimize delivery cost and penalty cost by smartly allocating items from the available network stock to arriving part requests. We propose a dynamic allocation rule that belongs to the class of one-step lookahead policies. To approximate the optimal relative cost, we develop an iterative calculation scheme that estimates the expected total cost over an infinite time horizon, assuming that future demands are fulfilled according to a simple static allocation rule. In a series of numerical experiments, we compare our dynamic allocation rule with the optimal allocation rule, and a simple but widely used static allocation rule. We show that the dynamic allocation rule has a small optimality gap and that it achieves an average cost reduction of 7.9% compared to the static allocation rule on a large test bed containing problem instances of real-life size