易燃性氣體及蒸氣之防爆危險區域界定探討

Hazardous Area Classification Study for Flammable Gases and Vapors

在易燃性氣體或蒸氣可能存在之危險性場所使用之電氣設備須為防爆型者，但其危險區域範圍大小在國內之應用時，各廠並不一致。本研究之目的在探討適用國內廠商參考之危險區域範圍規劃方法。研究參考美國石油協會、美國國家電工法規、國際電工委員會及石油協會等組織對於危險區域範圍規劃之方法，針對化工製程設備常有之八種主要點洩漏源型態分析比較各種規範所訂之差異性。再對於這些類型之洩漏狀況，以危害分析軟體模擬其可能產生之危害半徑以瞭解規範所訂定之參數意義。防爆區域範圍之設定在國內具規模的廠商雖使用多年，但多為國外廠商所掌控，對其確實原因亦不甚明瞭。因此，有必要驗證以瞭解其原因，做為國內適用性之依據。整體之危險區域範圍規劃與廠房之設計型式會影響氣體或蒸氣之散逸狀況，而影響危險區域範圍之等級和大小。所以研究中將廠房造成之通風型式亦考慮在內。石油協會所訂之方式較有彈性，引用時與製程之條件關聯性較大，使用時較複雜不易管理。使用順應國際潮流之國際電工委員會規範為主軸之訂立方式較為簡明且與現狀差異不大。研究最後將擬訂之方式選用三家知名廠家廠區做區域規劃，與現有廠家之原有規劃比較結果未超出原有範圍，顯示使用上應不致造成困擾。

All electrical apparatus in explosive atmospheres must be explosion proof. However, such practices have not been fully adopted by Taiwan’s industries. To provide a suitable area classification scheme of explosive gas atmosphere, four standards, namely, American Petroleum Institute, National Electrical Code, International Electrotechnical Commission and Institute of Petroleum are studied and compared. Eight different release scenarios of each standard are estimated with dispersion simulation modeling for comparison. Since area classification depends on ventilation conditions, the ventilation factors are considered as well. The Institute of Petroleum standard is recommended for detailed evaluation. The extent set by International Electrotechnical Commission is suitable for preliminary inspection purposes, since it is process parameters independent and size invariant. Processes of three operating facilities were studied by using the proposed area classification schemes to verify their suitability. The results show that there is no conflit between the proposed and existing area classification criteria for explosive atmosphere.