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

1. Cargo tanks specified in Section 6.1.2 of the COW Manual.
2. During cargo discharge before dry docking.

Regardless of the number of tanks required to be crude oil washed by the MARPOL 73/78 convention, all tanks should be washed by crude oil as far as possible for the purpose of preparation for ballasting and sludge control.

Prohibited Matters Concerning COW:-

1. Crude oil washing shall not be carried out during a ballast passage.
2. Ballast should not be loaded in tanks which were not crude oil washed.
3. Water filled in a tank already crude oil washed but not yet rinsed with water shall be regarded as dirty ballast.

Crude oil Washing at Sea Between Discharge Ports:-