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

• Mixture of different grades of oil should be avoided.
• Where the tank is washed by a two-stage method, top and bottom, the top wash shall be carried out with the same grade of oil to avoid contamination but a bottom wash with a different grade of oil may be possible if unavoidable, with approval of the cargo consignee.
• If a different grade of oil is used as wash oil with the agreement of the cargo consignee, it will be advantageous to use crude oil with less sediments.

2) Check the necessity for flushing with fresh crude oil, and if necessary, such quantity.

Tank to be Crude Oil Washed :- Cargo tanks necessary to be washed are as follows: