Proposal of a System based on Fuzzy Logic for Selection of Safety Valves maintenance interval

The processing industries have specific characteristics that require greater reliability of their equipment, among which is the operation with high pressures. To prevent these pressures from reaching higher values than specified, a situation also known as overpressure, control devices are used, with safety valves being the most common. These valves must have a preventive maintenance plan, whose maximum intervals in Brazil are defined by the regulatory standard NR-13. However, the operational history and technical data provide support for the definition of the ideal intervals for each valve, and the in charge professionals are responsible for this analysis. This work aimed at creating a systematic method for defining these intervals, based on the procedure adopted in the company and the knowledge of the specialist professionals, using the Fuzzy inference system. The proposed method uses more specific criteria for each type of failure, allowing to determine each consequence of this failure in the different valves. In addition, the use of fuzzy variables allowed to eliminate the gaps between the classifications existing in the current methodology.