Managing Reliability of Ethane Crackers Using Dmr, RBI, and Iows

Ethane crackers are subject to severe operating conditions that pose reliability issues and require high maintenance which can have a significant impact on the operational and maintenance cost. Damage mechanisms associated with Ethane crackers and associated piping and fixed equipment include corrosion, creep, carburization, thermal fatigue, stress relaxation cracking, sigma phase embrittlement, and oxidation, among others. Factors such as high operating temperatures, decoking practices, unexpected shutdowns, and operational breaches can induce or enhance the severity of the damage mechanisms and reduce equipment life. Therefore special attention is needed to avoid unexpected catastrophic failures while optimizing equipment performance.

Risk Based Inspection (RBI) methodology incorporating a damage mechanism review (DMR) can be used to manage the assets in Ethane crackers and reduce the risk of loss of containment by identifying the damage mechanisms that are expected to occur in each piece of fixed equipment and piping, calculating the risk associated with a potential loss of containment, and clearly defining inspection plans based on the RBI assessment results.

Since day to day changes in process conditions are not fed back into the risk calculation of RBI software, a well-designed and implemented integrity operating windows (IOW) program is required to incorporate these changes by providing real time notification of key process parameters that can accelerate degradation and increase risk.

Process data provided by the process engineer is key information that is used when assigning damage mechanisms and developing IOW parameters. This presentation discusses the use of the DMR, RBI, and IOW programs to manage reliability in Ethane crackers. It will also touch upon the role that Process Engineers have in the reliability process.