Explain various advantages and disadvantages of C.O.W and how often is it carried out?

1. In any case, crude oil washing shall be finished before departure from the final discharge port.
2. In the case of two or more discharge ports, it is possible to carry out crude oil washing at sea between such discharge ports.
3. In this case, washed tanks shall be left empty, ready for a dry inspection at the next discharge port, prior to sailing.
4. This inspection is to be conducted by sounding several parts of the tank bottom, etc. when the tank is empty.
5. Crude oil washing between discharge ports may minimize any potential delays whilst discharging operation
6. The same safety and pollution precautions shall be taken as in port.

Method of Crude Oil Washing:-

➢ Cleaning Methods:-

1) Multi-Stage System: While cargo oil is still in a tank, the upper part above the oil surface is washed (top wash) and the bottom is washed (bottom wash) by stripping tank washing after the tank has been emptied.

As one version of this method, when tank washing is divided into two stages, namely top and bottom, it is called a two-stage method.