Method for Achieving Fired Equipment Risk Analysis Consistency

In 2010, LyondellBasell senior management requested an assessment of all fired equipment used in North America.  This assessment relied on industry standards as guidance to evaluate the fired equipment design, maintenance and operation.  As a result of this work, management moved forward with recommendations to modernize the fired equipment design and operation.

One spinoff from this work was an effort to look at how process hazard analyses (PHA) for various manufacturing units evaluated the hazard scenarios of fired equipment as well as how safeguards were applied to prevent incidents.  A total of 15 PHAs, using the layer of protection analysis (LOPA) methodology, covering 50 pieces of fired equipment were audited for completeness and consistency.  The study was conducted by first developing a guideline of hazard scenarios that should be considered along with typical initiating events and independent protection layer (IPL) credits that were applied.  The 15 PHAs were then compared to this guideline.

The study found that for similar scenarios in the PHAs the categorization of the consequences varied even for equipment of similar size and service.  The initiating event frequency for the various scenarios also showed some variability.  While most PHAs effectively addressed the major scenarios, there were some PHAs which did not consider particular scenarios.  However, in most of these cases existing IPLs did adequately address the hazards.  It was also found that credits (risk reduction factors) assigned to IPLs were generally similar with little variance.  The reason for this is that the company provides good guidance on the application of credits for IPLs.  The guideline developed for this study is not only applicable as an auditing tool but can provide direction for future PHAs to use in determining what scenarios to consider, what consequence and initiating event frequency to use, and what IPLs may apply.