Analysis of Reliability, Maintenance and Risk Based Inspection of Pressure Safety Valves

The present study focused on doing a survey about the current state of the art of applying the RBI (Risk Based Inspection) methodology on pressure safety valves (PSVs) in the process industry, as well as, analyzing the reliability of applying the Weibull distribution according to standard API RP 581 and determining an optimum inspection interval of PSVs. From the maintenance reports data of two companies (a petrochemical and oil company), it was possible to analyze the reliability and determine the Weibull parameters (shape parameter and life characteristic) of the PSVs and also to determine the failure probability of the PSV as described in the API RP 581. In addition, the optimal inspection intervals for PSVs were also calculated. Introduction There is a general question in the oil and gas industry, as well as, in the chemical industry: how long should the pressure safety valve (PSV) be allowed to operate before being inspected and tested? This question has not been seen as a serious problem so far, but with the recent global financial crisis and some accidents, many companies dealing with PSVs have come to realize the need to reduce spending by eradicating unnecessary inspections and tests, while maintaining the integrity of the PSV. The need for inspection and maintenance is due to several factors such as the degradation of wear or corrosion, low reliability of components, human errors, legislative or external factors, (e.g.) aggressive or temporal environments. In these actions, mostly based on time, many resources are spent, whether human or material.