Introduction
The application of risk-based inspection (RBI) to heat exchanger bundles presents several challenges related to effectiveness and feasibility. The user’s typical approaches vary from run-to-failure and/or turnaround calendar-based. These practices have proven to be ineffective for minimizing the impact on business interruption.
On the other hand, provided the large population of bundles and tubes to evaluate, the accuracy of available NDT methods on a small sample of the exchanger bundles can be poor. Inspection using NDT on a large percent of bundles is often not cost-effective when compared to bundle replacement.
The method discussed herein was developed based on API RP 581’s (API’s RBI Methodology) approach for metal loss, combined with statistical treatment of the NDT result/data using Extreme Value Analysis. This allowed us to optimize the scope of NDT during turnarounds, while improving the reliability of bundles. In addition, a better focus on process-related corrosion issues was achieved.
Starting in 2013 and focused on specific cases, this approach was applied to more than 1600 bundles at 10 sites in three years. Today it is fully implemented at most of our refineries and petrochemical facilities.
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