Preventive Maintenance (PM) is an important activity that uses the systematic inspection, detection, diagnosis and correction before the incipient failures occurrence in order to keep equipment in a satisfactory operational state. The study focused on the processing plant that run continuously under harsh operation conditions based on the relief valves data. This paper developed a model to improve the preventive maintenance performance. The model developed based on availability and maintainability to measure PM performance. The model tested by two scenarios in order to determine the probability of failure at normal operation. The first of scenario was associated with the system failed for corrective maintenance. The second scenario was associated with the system down for preventive maintenance. The findings showed that the model provided information as the most significant characteristic to prolong the life time of equipment / system and improve preventive maintenance performance. Therefore, the study concluded that improvement of preventive maintenance performance for any processing plant has become essential to reduce the probability of failure resulting from corrective maintenance and improve the reliability of system. The model could support for any processing plant in terms of the maintenance cost effectiveness, the production losses and the system sustainability.