Condition Based Maintenance optimization for a service plant Filippo De Carlo*, Maria Antonietta Arleo**, Mario Tucci*, Orlando Borgia * *Department of Industrial Engineering, University of Florence, viale Morgagni, 40, 50100 Firenze – Italy (filippo.decarlo@unifi.it, mario.tucci@unifi.it, orlando.borgia@unifi.it) ** Department of Management, Economics and Industrial Engineering, Politecnico di Milano, via Lambruschini, 4, 20156, Milano – Italy (mariaantonietta.arleo@polimi.it) Purpose The increasing availability required to industrial plants and the limited budgets often existing to assure it, require a careful formulation of maintenance optimization models. This need is primary for process plants, for which minimization of stops and maximization of their availability, are essential for ensuring targeted production and, therefore, profitability. In this context, the choice of the maintenance strategy is hence fundamental, depending on the system features and then on the effectiveness of the strategy. To evaluate the maintenance activities expected costs, it is necessary to implement appropriate technical and economic models, in order to represent the different types of maintenance types adopted. The aim of this study is to evaluate the technical and economic feasibility of condition based maintenance techniques for a service facility of a process plants. Design/methodology/approach For this aim, the study was done for a HVAC system of a pharmaceutical laboratory. Three different kinds of maintenance strategies (corrective, time based and condition based) were considered, referring to three important equipment of the laboratory. For each system, the evaluation of the average cost of each maintenance strategy was done, so as to identify the most affordable one. Finally, we considered the cost-effectiveness of the implementation of a reliability continuous monitoring system, through the installation of an up-to-date supervision structure. Originality/value The paper offers an example of an economic model for the maintenance of a HVAC service system, presenting an original evaluation of continuous monitoring economics. Moreover, in this study, the newest monitoring technologies were considered, up to date and improved from the latest studies. This paper is directed to facility service and process plant managers. Keywords: CBM, HVAC system, maintenance optimization models. 1. Introduction HVAC (Heating, Ventilation and Air Conditioning) systems are usually designed to ensure thermal comfort conditions (temperature, ventilation and humidity) inside a public building or an industrial plant. These systems become critical when they are organically incorporated into more complex process plants, in which it is necessary to have well-specified air requirements needed by the production cycle. In the chemical and pharmaceutical industry, there are many examples of companies in which the HVAC systems are playing an enabling role for the productivity of the department in which they are inserted. These industries, in fact, have, some laboratories in which tricky production phases take place. The laboratories require the retention of stringent internal environmental conditions and the careful control of ventilation, to prevent the proliferation of bacteria, viruses and other harmful microorganisms. A lot of laboratories areas must keep sterility conditions, which is achieved also thanks to the correct operation of the thermal ventilation plant and to the moisture control. For chemical and pharmaceutical companies, moreover, the exact control of the temperature and humidity conditions is an important parameter for the certification of the production process. In such companies, therefore, it is essential to ensure high values of availability for service facilities, including HVAC systems, in order to minimize the costs of plant downtime that would result from a failure of such systems. In these kinds of industries, in fact, faults of air conditioning systems can cause stopping of the work process and even throwing away some of the produced goods[1]. In addition, any stops would involve considerable time of non-production related to the restoration of optimal temperature and humidity conditions. Such reversals may be definitely costly and complex for the company, especially for the need to "rehabilitate" the production process. For all these reasons, the proper maintenance of an HVAC system is critical both when it would become uncertified for the production process, both in different contexts, such as in the case of commercial buildings, in which thermal comfort is economically significant. XVIII Summer School "Francesco Turco" - Industrial Mechanical Plants 309