超低溫液體供應系統之製程危害辨識與後果分析

Process Hazard Identification and Consequence Analysis for Cryogenic Liquid Supply System

莊浩浰(Hao-Li Chuang) ； 陳俊瑜(Chun-Yu Chen)

《勞工安全衛生研究季刊》 16卷3期 (2008/09) Pp. 276-294

https://doi.org/10.7005/JOSH.200809.0276

摘要

「超低溫液體供應系統」供應各行業不同的製程使用。國內近年來此種設施引發嚴重的意外事故時有所聞，肇因於缺乏完整的風險評估及製程安全管理，使看似簡易的供氣系統，潛藏著高度的風險。本研究以系統化的風險評估程序，運用PDCA管理循環於製程安全管理上，在製程規劃(Planning)階段以本質較安全設計為基礎，再執行(Do)危害評估，辨識重大危害及風險等級，輔以後果分析軟體，驗證(Check)受影響之範圍與結果，進而採取行動(Action)修正原設計或強化安全防護層(Layer of Protection, LOP)，以達到風險永續管理(Risk Sustainable Management)。
危害評估方法，規劃初期以危害與可操作性分析(Hazard and Operability Studies, HazOp)製程危害評估技術，探討超低溫液體供應系統製程中潛在危害，運用本質較安全設計及安全防護層兩大製程危害控制技術，藉此降低操作風險。並利用後果分析軟體(PHAST 6.5)，分別模擬氮氣及氧氣排放所造成氣體擴散對於人員或設備造成的影響，對於排放至大氣中的氮氣容許濃度經公式推導及計算結果為71429 ppm。
研究結果顯示，原始排放設計可能使人員遭受危害氣體之暴露，經採用改變排放管的方向及減少管徑增加流速之方式，再經過模擬結果顯示，已可達到完全避開人員的操作位置，確保風險已有效消除，也驗證了在製程生命週期愈早導入本質較安全設計的概念，對於安全衛生績效、環境影響愈經濟有效。

關鍵字

後果分析 ； 製程安全管理 ； 本質較安全設計 ； 安全防護層 ； PHAST

並列摘要

Cryogenic liquid supply systems are used in various industrial processes, and several facilities in Taiwan have reported serious incidents involving cryogenic systems in the past year. Since cryogenic systems are fairly simple, the incidents were caused primarily by a lack of integrated risk analysis and process safety management.
The purpose of this research is to use a systematic method of hazard assessment to ensure process safety management in the PDCA cycle. Based on Inherently Safer Design (ISD), a hazard assessment was performed to identify major hazards and levels of risk during the planning phase of the project. Consequence analysis software was then used to verify the scope of the hazard, after which the original design must be improved or the Layer of Protection (LOP) consolidated to achieve Risk Continuity Management.
Hazard and Operability studies (HazOp) technology was used to identify the potential hazards of Cryogenic Liquid Supply Systems in the primary stage of the project and aided the ISD and LOP concept in process hazard management. PHAST 6.5 was used to simulate nitrogen and oxygen dispersion for consequence analysis. The release of oxygen or an asphyxiant into air may pose a flammability or asphyxiation hazard respectively. The dispersion programs do not account for the components of air that are present prior to dispersion of the jet. Therefore, the oxygen and asphyxiant mole fractions had to be adjusted and used as inputs to the dispersion programs. The nitrogen concentration of interest was 71429ppm.
The results of the study show that the original vent design could create an asphyxiating/oxygen enriched environment at grade on the platform. The asphyxiating concentration is exceeded on the platform for two of the three weather conditions. Proposed methods to eliminate the possibility of an asphyxiating/oxygen enriched atmosphere on the platform include reducing the vent diameter and changing the direction of the vent. It was demonstrated that these changes would reduce the nitrogen/oxygen concentration on the platform below asphyxiating/oxygen enriched levels. The studies also show that the ISD concept is effective in improving safety performance and environmental protection in the early phases of the life cycle.

並列關鍵字

Consequence Analysis ； Process Safety Management ； Inherently Safer Design ； Layer of Protection ； PHAST

參考文獻

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