[Reliability of IM Integrity Management systems: Probability of Detection (POD) and Probability of Sizing (POS)]

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CHAPTER 1: INTRODUCTION

We tend to think that, at first, even informed industry actors' answers would be negative; after all, this was the first answer that came to our minds, too. The reason is that IM is one of those "hot industry issues," especially in refineries, petrochemical plants and process industries in general, where literature and best practices are somewhat overwhelming. All major players are striving to reach IM "best-in-class" practices, and IM is more often than not on the industry's management agenda. On the other hand, though, recent worldwide disastrous events, also in refineries where current best practices are applied, demonstrated that there is room for improvements. Incidents' cause analyses and reports show that improvements are to be found both in the utilized conceptual approaches to IM and in their applications "in the field."

Moreover, IM improvement programs are somehow "heavy and long initiatives" in terms of their impacts on resources and time. So the next question that comes to mind is, "Is there a way to sharply focus and holistically systemize the IM application in a refinery site (or in a process site in general)--an approach that would not sacrifice its long-lasting effectiveness on the verge of efficiency?" This business issue was at the heart of our work that led to the conceptualization of the frameworks, ideas and practical tips reported in this article. In current international practices, equipment IM is usually included as part of a more general maintenance, safety and reliability system, also called the Asset Management System (AMS), that involves a wide variety of refinery activities requiring efforts in terms of money, time and human resources.

Equipment integrity, nonetheless, is somehow a more stringent issue than reliability, especially for aged refineries/petrochemical sites, not only because of its clear economical implications, but also because of wide responsibilities stemming from increasingly stringent legislation and public requirements--responsibilities that will, more and more, require convincing reactions in reasonably short time frames.

Starting from this assumption, we've focused our extensive research and assessment of current industry best practices with the goal of understanding how these issues were tackled. We've found that, while the current industry's best practices do focus on some of the most important IM elements, they still leave "unfocused" some other critical elements that are, in our opinion, necessary not only to sharpen the concept of IM, but also to design and then successfully apply an effective "self-updating" IM system in a complex and running refining site, especially one that is well far along in its life cycle (as most of the European and US refineries are).

Based on these findings, we've strived to develop a "new" approach to IM systems, proposing an innovative methodology, "integrity-only-specific," providing the key points and minimum requirements to develop an IM system or to check the capability of an imported one.

The basic statement of integrity is that a plant's management needs to state, assign and reinforce a maximum accepted risk ...