(54bj) Critical Equipment: A Matter of Priorities

Many companies in the process industries use equipment criticality assessments as a vital tool to assist in setting priorities and optimizing maintenance strategies. The goal is to deliver high performance and availability in a cost-effective way. But what does the ‘critical equipment’ designation actually mean? And in practical terms, how should it be used? In the manufacturing industry, criticality is usually understood in terms of the magnitude of the consequences that would result from an equipment failure. Two fundamental approaches inform such designations: the risk-based approach and the consequence-based approach. Each offers strengths and weaknesses, which are relevant to determining their most appropriate application in varying contexts.

More nuanced than a simple reflection of a company’s tolerance for risk, the basis of a criticality designation is important to document, as it will influence a series of future decisions regarding the design, maintenance, and modification of equipment. Informed by DuPont’s own experiences as a plant operator, this paper first outlines the broad elements that distinguish the risk-based and consequence-based approaches to equipment criticality. It then proceeds to explore how the nature of the consequences of failure in different scenarios—in particular, whether they are linked to business or environment, health, and safety (HSE) outcomes—should play a role in the process of equipment assessment and the actions that follow.

The paper argues that the risk-based approach is best for prioritizing where to perform costly reliability studies, as well as when and how to invest in spare parts and redundancy. In contrast, the strength of the consequence-based approach lies in determining maintenance strategy, as well as setting priorities for maintenance tasks designed to prevent events with high consequences of failure.

When such consequences are HSE-related, the paper suggests that it is essential that maintenance strategies are formulated to prevent failure, and that HSE-critical maintenance tasks are treated with high priority, avoiding deferrals without proper scrutiny and risk assessment.