|
An inerting system decreases the probability of combustion of flammable materials stored in a confined space, especially a fuel tank, by maintaining a chemically non-reactive or "inert" gas, such as nitrogen, in such a space. "Inerted" fuel tanks may be used on land, or aboard ships〔("Layout of I.G. Plant on Ships" ), Lamar Stonecypher, editor. (Bright Hub Engineering ), 2009-07-12.〕 or aircraft. Three elements are required to initiate and sustain combustion: an ignition source (heat), fuel and oxygen. Combustion may be prevented by reducing any one of these three elements. If the presence of an ignition source can not be prevented within a fuel tank, then the tank may be made inert by: # reducing the oxygen concentration of the ullage—the space above a liquid fuel—to below that capable of combustion (the combustion threshold); # reducing the fuel concentration of the ullage to below the "lower explosive limit" (LEL), the minimum concentration capable combustion; or # increasing the fuel concentration to above the "upper explosive limit" (UEL), the maximum concentration capable of combustion. At present, flammable vapors in fuel tanks are rendered inert by replacing the air in the tank with an inert gas, such as nitrogen, nitrogen enriched air, steam or carbon dioxide. This reduces the oxygen concentration of the ullage to below the combustion threshold. Alternate methods based on reducing the ullage fuel-air ratio to below the LFL or increasing the fuel-air ratio to above the UFL have also been proposed. ==Oil tankers== Oil tankers fill the empty space above the oil cargo with inert gas to prevent fire or explosion of hydrocarbon vapors. Oil vapors cannot burn in air with less than 11% oxygen content. The inert gas may be supplied by cooling and scrubbing the flue gas produced by the ship's boilers. Where diesel engines are used, the exhaust gas may not have a low enough oxygen content so fuel-burning inert gas generators may be installed. One-way valves are installed in process piping to the tanker spaces to prevent volatile hydrocarbon vapors or mist from entering other equipment. 〔Bruce, George J. Eyres, David J. (2012). ''Ship Construction (7th Edition)''. Elsevier. 978-0-08-097239-8 page 234 〕 Inert gas systems have been required on oil tankers since the SOLAS regulations of 1974. The International Maritime Organization (IMO) publishes technical standard IMO-860 describing the requirements for inert gas systems. Other types of cargo such as bulk chemicals may also be carried in inerted tanks, but the inerting gas must be compatible with the chemicals used. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Inerting system」の詳細全文を読む スポンサード リンク
|