英國石油Texas City煉油廠蒸氣雲爆炸事故後，英國石油公司延聘貝克專案小組進行事故調查和分析，並提出十項改善建議事項，其中最具關鍵的就是製程安全主動式與被動式績效指標，因此，製程安全績效指標的設計與應用，近幾年已成為許多專家學者研究的重點，本研究深入探討HSE、CCPS、OECD和CEFIC等機構制定的製程安全績效指標設計原則和理念。
本研究以防護層洋蔥模式為依據，探討CCPS第三類參數虛驚事件和其他被動式參數不足之處，CCPS定義的第三類參數包括未超過化學品洩漏量恕限的製程安全事件，以及啟動安全系統如製程偏離、啟動安全儀控系統或釋壓裝置等，主要針對防護層洋蔥模式外層的緊急應變、實體防護、排放系統和安全儀控系統，設計製程安全虛驚事件參數，雖然曾提製程偏離，但對於靠防護層洋蔥模式內層的基本程序控制系統以及警報和操作人員介入，所設計的製程安全虛驚事件參數考量尚不周全，因此，本研究針對基本程序控制系統以及警報和操作人員介入兩道防護層深入探討，並以CCPS製程安全參數設計原則和理念設計績效指標，希望能彌補CCPS製程安全虛驚事件參數的缺失。

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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