鍋爐產生的蒸汽是石化工廠主要的動力來源，以供應廠區各製程使用。現今的鍋爐雖已採用自動化控制且設置多重安全連鎖裝置，但是鍋爐造成的意外事故仍然頻傳。究其原因，主要是未依照規定實施設備維護保養及人員違規操作。蒸汽鍋爐工場主要區域有：(1) 鍋爐區(包含：重油區、飼水區、加藥區)、(2) 脫硝區及(3) 脫硫區。本研究以某公司的蒸汽鍋爐工場為對象，利用初步危害分析 (PHA) 及危害樹分析 (HTA) 等兩種風險分析技術藉以發現蒸汽鍋爐工場危害特性並比較兩種分析技術的差異性，並嘗試將嚴重度導入 HTA 中，以顯示危害事件的事故原因及由事故原因所對應的相對危害等級。結果顯示，PHA僅能簡單分析對製程主要影響及其預防措施； HTA較能明確且立即顯現製程的重大危害、程序偏離、根本原因及其應採取的矯正與預防措施。另外，將嚴重度導入危害樹分析後則具有下列特色：(1) 以整個製程的危害思維進行風險分析；(2) 導入嚴重度、可能性及風險等級的觀念，並以顏色區域顯現事故發生時的危害情境；(3) 明確顯現預防事故發生的對策，如製程偏離對應矯正措施，根本原因對應預防措施。 The steam generated from steam boiler is the main source of power to support petrochemical plants operations. Even equipped with automatic control system and multiple safety interlocks to the boiler, unfortunately, boiler accidents still occur frequently. Violations to the specified equipment maintenance schedules and procedures are the main reasons for accidents to occur. In addition, the operator errors are also known to contribute to the accidents. There are three main areas in the stream boiler plant: (1) boiler area (consists of heavy oil area, feeding water area, and the reagent area), (2) denitrification and (3) desulfurization.
In this thesis, we selected a boiler plant of an unnamed company as our study object. By using the techniques of PHA and HTA, we intended to find the potential risks of the boiler and to compare the accuracy of these two techniques on the identification of the hazards. We also tried to incorporate the effect of the severity to the HTA to demonstrate the root causes of the accidents and the corresponding degree of severity of the accidents. Results show that PHA can only find common hazards to influence the process. However, HTA can promptly and clearly provide significant clues to the potential hazards of a process, deviation from intended design, and root causes. Thus, HTA offers better recommendations to prevent accidents from occurring. We also find that by incorporating the severity of accidents into HTA analysis, we found some characteristics as follow: (1) the entire process, instead of its individual sections of the process, is considered when the risk analysis is conducted, (2) the degree of the accident occurrence can be categorized by different colors representing the degree of severity, (3) we can clearly picture the severity and the actions to prevent the accidents from happening; such as to control the deviation of process to happen or to the occurrence to happen by improving the process at design stage or after process had been implemented.
