Managing Reliability of Ethane Crackers using DMR, RBI, and IOWs

Introduction

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 costs. Damage mechanisms associated with Ethane crackers and associated piping and fixed equipment include carburization, creep, erosion, thermal fatigue, sigma phase embrittlement, stress relaxation cracking, oxidation, and general corrosion among others. Factors such as high operating temperatures, coke buildup, 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 fixed equipment and piping component, calculating the risk associated with a potential loss of containment, and clearly defining inspection plans based on the RBI assessment results. 

A well-established integrity operating windows (IOW) program is necessary in order to set boundaries on process parameters related to damage mechanisms and to capture changes in process conditions. This information is critical to the risk calculation by providing real-time notification of changes in 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 article 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.