| dc.description.abstract | A vapor cloud explosion at British Petroleum’s Texas City refinery proved, once again, the devastating impact of major accident involving large quantities of chemicals. Reports from the Chemical Safety Board and Hazard Investigation on the accident and BP US Refineries Independent Safety Review Panel recommended closer monitoring of process safety data. Despite the comprehensiveness of Process Safety Management, most of chemical and petrochemical companies are not required to report to competent authorities or to reveal to the general public on incidents causing spills, fires, explosions or injuries. Leading and lagging process safety performance indicators become the focus of trade associations, individual companies, government agencies, and academics since 2007.
Development of process safety performance indicators was first proposed by Health and Safety Executive of the UK in late 2006. Both leading and lagging performance indicators are derived from the intended functions or effectiveness of risk control systems. Center for Chemical Process Safety of the American Institute of Chemical Engineers proposed the use of leading and lagging metrics to measure the effectiveness or failure of process safety management. The lagging metrics are defined as process safety incident, other incidents, near miss and unsafe behaviors or insufficient operating discipline. In addition to process safety incident, annual total incident rate and incident severity rate are included as well. CCPS views mechanical integrity, action items follow-up, management of change, and employee training and competency as leading metrics. The European counterpart of American Chemistry Council, the European Chemical Industry Council, has a similar set of leading and lagging indicators. Process safety performance indicators of CCPS, HSE, CEFIC, and OECD guidance for safety performance indicators are analyzed in this study.
In-depth analysis reveals the fact that CCPS performance metrics are mostly derived from the fundamental principle of protection layers. These metrics cover the basic functions of safety instrumented systems, relief devices, and physical protection of post-release. By definition, the lines of defense against chemical process incidents also include basic process control systems and critical alarms and operator intervention. In addition, process control and alarm management precede other protection layers. Hence objective of this study is to design a set of lagging process safety performance indicators capable of evaluating the effectiveness of process control systems and alarm management to supplement the ones proposed by CCPS.
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