The Maintenance Concept Adjustment and Design method primarily developed primarily for the maritime industry and for ships, with the aim of analysing and modelling technical systems from a maintenance point of view. The system was developed with the aim of analysing and optimizing maintenance and spare parts requirements and minimizing life cycle costs. In this study, several changes to the method are presented in order to make it more user-friendly. The first proposed change is the modification of the failure analysis method; instead of the Weibull process, the Power Law Process is introduced. The proposed change, which will simplify the failure analysis, was subjected to several suitability tests, the first being the Akaike Information Criterion test. The test showed that the Power Law Process model fits the analysed data better than the Weibull model. Next, the applicability was tested by comparing the results obtained with the Power Law Process analysis with previously published data using the Weibull method. After establishing the validity of the proposed changes, the functionality is tested on a new maintenance and spare parts optimization model, which is an extension of the model used in the Maintenance Concept Adjustment and Design method. In addition to simplifying the process, a further simplification is sought, namely the use of the brute force method to solve the optimization of maintenance and spare parts. The verification of the optimization results was carried out using Brent’s optimization method and the Limited memory Broyden–Fletcher–Goldfarb–Shanno method with Boundaries. Both methods confirmed the optimization results. Finally, the optimization results were verified using the Weibull model for failure data, which confirmed the validity of the proposal to modify the Maintenance Concept Adjustment and Design method in the failure data analysis and optimization method segment. Furthermore, this thesis deals with an additional modification of inventory policy in the maritime industry due to current laws and regulations, which has never been applied before. By introducing a safety critical spare parts minimum, a new safety barrier is created to prevent the consequences of a spare parts shortage. This new minimum is included in the optimization model and tested to see how this change affects maintenance and spare parts management. Initially, this will lead to additional costs for the company and increase the safety of the ship. Further analysis has shown that the cost of these spare parts is easily compensated by the avoidance of costs that may arise from the lack of spare parts.