Nowadays different plants have aging problem, since in many cases the plants are used over their design useful life. But in different cases it is not possible to do a revamping, for economical reason, regulatory constraints, and so on. The aging of the equipment became also a safety problem. Between 1980 and 2006 the Health and Safety Executive estimated that around 28% of the major incidents occurred in the reference period, corresponding to 96 accidents, can be traced back to plant aging.

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... e accidents costed more than 170,000,000 (Horrocks et al., 2010). In these cases a correct maintenance can prolong the plant life, increasing the plant efficiency and maintaining an adequate level of safety. Plant management can choose among different maintenance strategies, whose choice is influenced by different parameters, as: maintenance cost, equipment condition before maintenance, plant trip cost, safety of the operator during the maintenance and during the normal operations. In this paper a multivariable Fuzzy approach is proposed to support the decision-making among different maintenance strategies, through the analysis of the peculiarities of the different strategies, helping the management to weight the pros and cons of the alternatives. This approach is applied to the maintenance of process equipment case study.