(104f) Normalization of Process Safety Metrics

AICHE Spring 2012 Meeting

Mengtian Wang, Ray A. Mentzer and M.SamMannan, Mary Kay O'Connor Process Safety Center, Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX

Currently, industry commonly measures safety performance by using lost time injury rates or other personnel safety parameters. For instance, OSHA’s Lost Time Injury Rate (LTIR), Total Recordable Injury Rate (TRIR) or similar metrics for personnel safety are broadly used in industrial sectors. Unfortunately, process safety measurements have not been emphasized as much. Process safety deals with fires, explosions and toxic releases. The BP Texas City refinery explosion is one of several catastrophic accidents where management overlooked the importance of process safety while focusing on personnel safety. Despite advances in process safety metrics, there is still disagreement on whether current safety metrics sufficiently measure process safety.

Safety metrics measure the effectiveness of a facility’s safety program. Leading and lagging indicators can be used as tools to improve existing and future performance. The UK HSE developed a Step-By-Step Guide to Developing Process Safety Performance Indicators to help safety managers or professionals track performance indicators within the organization to assure that major hazard risks are controlled. Moreover, the API Recommended Practice 754 identifies leading and lagging indicators in the refining and petrochemical industries for driving improvements to reduce the risk of major hazards. The CCPS Guidelines for Process Safety Metrics uses the total employee and contractor work hours as a normalization factor. Finding an improved normalization factor for process safety indicators, which is more representative of the process than personnel hours is the goal of this research.

The normalization of incident rates is one of the benchmark methods to compare the safety performance either within or outside a process plant. While LTIR or TRIR use the total work hours as the normalization factor, is this the best denominator for process safety indicators? To address the issue, industry is trying to find more consistent, broad, and unbiased criteria for tracking process safety. However, total work hours is still widely used and accepted, so any proposed alternative must be based on available data. Motivated by that perspective, this research aims at exploring options to evaluate the severity of process safety incidents and comparison with existing metrics. Therefore, the objective of this paper is to present how the new normalization factors can be integrated to assess process safety. Potential denominators will be tested and verified via several chemical incident databases to decide their feasibility and credibility.

Key Word: Process Safety Metrics, Process Safety Indicators, Denominator for Process Safety, Normalization of Incident Rates