The proposed paper presents: the description and the analysis of an Analytic Network Process Model for the evaluation and the management of maintenance projects in engineering plant field. The study was made in Ansaldo Energia (AEN), Italian company active in the energy sector, one of the world's major power plant producers. The test cases are three power plants belonging to three important Service customers. Three service contracts that respectively represent, from an HSE (Health Safety Environment) point of view, the "as was", the "as is" and the "to be" are presented and discussed aiming to demonstrate that HSE could be improved in a systematic way. These three examples are characterized by an increase in HSE preventive activities more than the simple actions required to be compliant with HSE laws and rules. The complex of the HSE measures, known in Ansaldo as "HSE package", are generally proposed in service contracts with the aim of improving the overall Customer Satisfaction that, recently, is strictly connected with HSE. Due to a rising general awareness of HSE, many general contractors are facing the complex trade-off among HSE performances improvement and other project KPI (Key Performance Indicator) related to cost saving, making this business even harder than expected. Finally this paper tries to answer these research questions: Is the HSE project with more preventive actions effectively the best project to be implemented by Ansaldo? How much does an improvement of Customer Satisfaction and HSE cost to the company in terms of time and effort?