![]() ![]() and since clay slurry is INSOLUBLE in water and HEAVY, just filling up the cofferdam will NOT do.Ĭrystallizing cargoes like phosphoric acid and caustic soda are also abrasive. There are certain cargoes which will harden inside the cofferdam and hence cannot be purged with air, before loading the next cargo.Īlso some of these cargoes may be "ABRASIVE" ( like clay slurry ) and destroy the ceramic sleeve on which the cargo seal abuts. you must NOT load cargo in a tank whose pump's cofferdam is clogged. Sulphuric aacid sloshing in rolling during loaded passage, can destroy all the butterfly valves at the manifold, on both sides.Ĭofferdam prevents cargo from entering the hydraulic system- and also hydraulic oil from entering the cargo tank.Ĭonversely both hyd oil and cargo are expected to ingress in the cofferdam in small quantities-as this space is also a INDICATOR which tells you if the cargo or oil seal requires renewal, due to wear. But on the other hand after completion of loading your manifold cross pipes of aft tanks will be full of cargo. This makes sure that after dischg all your cargo goes ashore by gravity. On modern Chemical tankers, superstrip piping is avoided by raising the aft tank delivery pipes upwards, so that cargo flows towards manifold by gravity -due to a sloping pipeline. Air cannot skim on top of cargo in a very small diameter pipeline. So air is blown inboard of a shut manifold valve, to force the cargo to flow downhill, to the aft tank stack, and then the cargo is ushered into a small diameter superstip pipeline ( this could be portable -if fixed piggy back superstrip pipelines are not fitted for all aft tanks ), which takes the cargo outboard of the shut manifold valve, ashore. ![]() You cant blow cargo in a large dia pipeline uphill against gravity, ( aft of manifold with trim by stern ) from tank till manifold, as air will skim on top of cargo inside the pipeline. Superstrip of cargo pipelines, must be done on a chemical tanker after dischg to comply with Marpol ROB min quantity.Īlso - in case of inconvenient cargoes like Sulphuric acid, Luboils and high MP cargoes, after completion of loading.īasically you shove cargo from inboard side of the shut manifold valve, to outboard shore side. ![]()
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