![]() Choosing 2/3 of LEL as a guide arrives at the following maximum amounts of toluene:įor other solvents, the corresponding amounts can be calculated based on the fact that one gram molecule (=as many The amount of solvent should be of such small quantities that forming explosive mixtures in the tank isĪvoided. The certain extent on the tank walls and dissolves minute amounts of cargo residues, which after draining the tank canīe washed off using water with/without cleaning agents added. The water is then heated using the heating coils, and the solvent vaporizes. The method will only beĮffective for removal of the very last traces of a previous cargo.įill the tank with water to just above the heating coils and add a non-water-soluble solvent, usually toluene or It can also be done as a final cleaning process, after washing with a cleaning chemical. The process should preferably be carried out with the tank inerted. It is wise to pump slowly to notĮxceed I m/s in the filling pipe. Regards static electricity charges in the interface between the two liquids. There have been advanced warnings that this floatation method, although frequently used, might involve hazards as The filling and draining can be done with a level change of 0, 5 - 2, 0 m/h depending on the degree of Transferred to the next tank, and the process repeated (with the same water used again to minimize solvent losses). After filling, the water is slowly drained again until the tank is empty. Then the tank is slowly filled with water, thereby lifting the toluene The tank is first filled to a level of 0, 4 - 0, 8 m from the bottom with a strong non-water-soluble solvent, which isĪlso reasonably cheap. The method is then very effective, but it is less effective ifĬargo residues on the tank walls are of any considerable thickness. Only be used after first washing with cleaning chemicals. "upgraded" to methanol standard via two-three intermediate cargoes of aromatics ). Lubrication oil additives, and before loading hydrocarbon-sensitive products such as methanol. Remember to keep the hatch lid slightly open to eliminateĮxcess pressure during steaming or sub-pressure after steaming is finished!įor the final cleaning to achieve a high degree of cleanliness after heavier hydrocarbons such as lubrication oils, After steaming with a cleaning chemical, steaming is continuedįor a while. ![]() The tank should first have been steamed thoroughly. The cleaning chemical is added to an ejector in a similar operation, which draws it into the steam when steaming the Operator must use protective oilskins, goggles, and preferably a breathing mask too. The cleaning chemical is sprayed directly onto the tank bulkheads using a high-pressure (portable) pump and a long lance, which the operator can direct all round the tank. The cleaning chemical can be applied undiluted directly onto the tank walls Remember cross-overs and risers to deck!įig: Chemical tanker tank cleaning method using chemical agent Incorporate major parts of the piping system in the cleaning circuit. The recirculation method can be used with all types of cleaning chemicals. It refers in particular to recirculation washing. There are indications that contaminated washing water may cause incendive static electricity sparks. Washing should only be carried out because the tank atmosphere is well below LEL (lower explosive limit).Ĭheck during washing! Washing should be carried out under the inert gas atmosphere if cargo vapor concentration isĪbove LEL. ![]() Another cargo pump or stripping pumpĭrains the water back to the containment tank where the cargo residues can be removed by carefully drawing out the A cargo pump may serve as a washing pump withĭelivery to the washing line on deck, and then to the washing machines. The water may be further heated using heating coils. Gives a better utilization of the cleaning chemical a mixture of 5 - 50 tons of hot water with the recommendedĪmount of cleaning chemical is made in a cargo tank, a slop tank, a cofferdam, or a special tank for the purpose. Rinsing being sea or freshwater, depending on the product to be loaded. ![]() 1-2 hours of washing is usually to be recommended. High, and its full cleaning effect is not always utilized. The direct addition of cleaning chemicals to the washing water is quite common, but chemical consumption tends to be ![]() Method is more cumbersome in the latter case. But the dosage becomes less accurate, and the Sometimes, the cleaning chemical is added to the washing water pump's suction side, thus eliminating the need for a dosage pump. The cleaning chemical is injected into the washing water utilizing a dosage pump, usually air-driven, through aįitting attached to the deck's washing pipe. It is summarized below practical tank cleaning methods for various chemical cargo.Ĭleaning agent added directly to the washing water ![]()
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