Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering Transport Technology / Logistic Engineering
M.A. Schroten Het ontwerp van een generiek simulatiemodel voor een reservedelenhuishouding. Masters thesis, Report 93.3.LT.4298, Transport Technology, Logistic Engineering.
At the Royal Dutch Navy sparepart stock, a distinction is made between stocks on board and stocks ashore. In these stocks there are two types of spare parts: repairables and consumables. The repairable items make a circular course through the inventory system.
Usualy two analytical models are used to define the stocklevels ashore and on board. The performance indicator for the stocks ashore is the service level, while the availability of the installations for which the stocks are held indicates the performance of the on-board-stocks. An integral view over both stocks could bring the performance of the total stock to a higher level.
It appears that the the situation at the Navy is not unique. Because of this, the idea of a model that can evaluate situations equivalent of the sitation at the Navy becomes attractive. In this model the processes at the installations and the processes in the inventory system should be separated. A new situation arises from this separation in which service units replace the onbourd stocks. These service units are able to give service on serveral locations. With a small stock they travel from site to site to replace parts that have failed. Every service unit has its own service area. An example for such a situation is a company that takes care of maintenance of copiers. The service units depend on a central depot for their supply.
It is hard to find an analytical solution for the integral view. Therefore a simulation model is made. The goal of this model is to evaluate propositions for the stocklevels at the service units and the central depot wich are generated by separate analytical models. Besides that, experiments can be done with stocklevels, failure rates and the repair process of the broken parts.
The first step of the design of the simulation model leads to a conceptual model. This model bases the object oriented design of the simulation model. This model is implemented into FEL-GLOW, a model which generates the stocklevel propositions for the Royal Dutch Navy. The most important conclusion of the experiments with stock levels, is that the stock should be concentrated at the service units. High performance of the central depot is not necessary. Besides that, reduction of the repair time at the repair depot will cause reduction of the amount of parts needed in stock.
Reports on Logistic Engineering (in Dutch)
