Crude Oil Washing

Crude oil washing (COW) is washing out the residue from the tanks of an oil tanker using the crude oil cargo itself, after the cargo tanks have been emptied. Crude Oil is pumped back and preheated in the slop tanks, then sprayed back via high pressure nozzles in the cargo tanks on to the walls of the tank. Due to the sticky nature of the crude oil, the oil clings to the tank walls, and such oil adds to the cargo 'remaining on board' (the ROB). By COWing the tanks, the amount of ROB is significantly reduced, and with the current high cost of oil, the financial savings are significant, both for the Charterer and the Shipowner. If the cargo ROB is deemed as 'liquid and pumpable' then the Charterers can claim from the owner for any cargo loss for normally between 0.3% up to 0.5%. It replaced the load on top and seawater washing systems, both of which involved discharging oil-contaminated water into the sea. MARPOL 73/78 made this mandatory equipment for oil tankers of 20,000 tons or greater deadweight.

Although COWing is most notable for actual tankers, the current chairman for Hashimoto Technical Service, Hashimoto Akiyoshi applied this methodry in washing refinery plant oil tanks in Japan. Chairman, Hashimoto is currently using this method in the Kyushu Region, Chugoku Region, Tohouku Region in Japan. Because of the logical nature of the technical complexities of COW, crude oil wash is still frowned upon by many who are not able to understand the exact mechanism behind COW; however, it is undeniable that COWing will become the norm not only in saving money for oil companies but moreover for recycling crude oil waste that should not be dumped and neglected.