Transport Guidance for Steel Cargoes
tải về 1.97 Mb. Chế độ xem pdf
|
|
hygroscopic cargo (i.e., a cargo which has its own inherent moisture content – such as rice). Steel is a non-hygroscopic material as it has no inherent moisture. However, steel products are normally transported using timber dunnage, which is a hygroscopic material or may be stowed in holds together with hygroscopic cargoes. American Club: Transport Guidance for Steel Cargoes 64 6.3.2.2 Ship sweat appears as tiny beads of moisture condensing onto the vessel’s metal work. This phenomenon typically occurs on the sides of the hold when the sea temperature is lower than the ambient temperature in the cargo hold, on the undersides of the hatch covers and on the weather deck when the outside air temperature is lower than the ambient temperature in the cargo hold. The result is a reduction of the temperature of the ship’s structures to a value below the “dew point” of the surrounding air. 6.3.2.3 When ship sweat forms on steel structures, the condensation water runs down to the tank top level causing wetting of cargo items in its path. When ship’s sweat forms on hatch covers and the underside of weather deck plating and stiffeners, the water that is formed drips down causing the wetting of the top layer of the cargo stow. 6.3.3 Cargo sweat. Cargo sweat forms under precisely the opposite circumstances than that of ship sweat. Cargo sweat forms on the surface of the cargo when its temperature is below the dew point of the air adjacent to it. 6.3.3.1 An example of cargo sweat. A vessel loads a cargo in cool weather and the cargo is itself cool in temperature. Thereafter, the vessel transits into warmer climates with higher humidity. If an attempt is made to ventilate at that time, then moisture from the warmer humid air introduced into the cargo space condenses onto the relatively colder cargo. 6.3.3.2 Cargo sweat on steel cargoes. Cargo sweat can also affect non-hygroscopic cargoes such as steel. While ship sweat is a more frequent problem and controlled by proper ventilation. Cargo sweat, in contrast, is generally caused by ventilating when it is inappropriate to do so. tải về 1.97 Mb. Chia sẻ với bạn bè của bạn:
|