Preparation of Cargo Tanks for Loading/Unloading of Liquid Natural Gas

Ukapljeni prirodni plin (LNG) spada u grupu fosilnih goriva, te se uglavnom sastoji od metana. Metan mora biti ohlađen na -161.7 °C kako bi postao ukapljen, te kao takav zauzima 600 manje volumena nego u plinovitom stanju. LNG plin može uzrokovati potencijalne opasnosti pri izljevu poput eksplozije, ozebline na koži, oštećenje oplate zbog smrzavanja i sliĉno. Brodovi za prijevoz LNG-a morem primjenjuju metodu potpuno hlađenog prijevoza LNG tereta, što se izvršava uz pomoć razliĉitih izvedbi spremnika koji ispunjaju uvjete sigurnog transporta. Ovi spremnici dijele se na samonosive (sferiĉni i prizmatiĉni) i membranske (TechnigazMark III, GT 96 i GTT CS1).Kako bi se posada broda uspješno riješila opasnosti zahtjeva se pravilno izvršavanje predradnji u spremnicima tereta. Redoslijed predradnji nakon dokovanja te prije ukrcaja je: inspekcija, sušenje, inertiranje, izbacivanje inertnog plina i hlađenje spremnika. Redoslijed predradnji nakon iskrcaja, te prije dokovanja je: uklanjanje preostalih tekućina, grijanje, inertiranje i prozraĉivanje spremnika tereta. U ovome radu razmotreni su sigurnosni rizici s kojima se suoĉava posada broda za prijevoz ukapljenog prirodnog plina, konstrukcijska rješenja spremnika za prihvat takvog specifiĉnog tereta, te naposljetku predradnje za ukrcaj i iskrcaj ukapljenog prirodnog plina.Liquefied natural gas (LNG) belongs to the group of fossil fuels, it mainly consists of methane. Methane must be cooled to -161.7 °C to become liquefied, as such it occupies 600 less volume than in the vapour state. LNG gas can cause potential spill hazards such as explosions, frostbite on the skin, damage to the form work due to freezing, etc. LNG ships apply the method of fully refrigerated transport of LNG cargo, which is carried out with the help of different designs of tanks that meet the requirements of safe transport. These tanks are divided into self-supporting (spherical and prismatic) and membrane (TechnigazMark III, GT 96, and GTT CS1). For the ship's crew to successfully avoid potential hazards, the pre-work in the cargo tanks must be performed correctly. The order of pre-work after docking and before loading is inspection, drying, inerting, inert gas ejection, and cooling of the tank. The order of pre-work after unloading, and before docking is the removal of stagnant liquids, heating, inertia, and ventilation of cargo tanks. This paper discusses the safety risks faced by the crew of a ship for the transport of liquefied natural gas, the design solutions of tanks for receiving such a specific cargo, and finally the preliminary work for the loading and unloading of liquefied natural gas