WHAT
IS COW?
Crude oil washing (COW) is a system
whereby oil tanks on a tanker are cleaned out between voyages not with water,
but with crude oil - the cargo itself
The solvent action of the crude oil makes the cleaning process far more effective than when water is used.
The system helps prevent pollution of the seas from operational measures.
MARPOL Annex I Regulation 13 (6) requires every new crude oil tanker of 20,000 tons dead weight and above to be fitted with a cargo tank cleaning system using crude oil washing.
WHY
COW?
•Previously, oil tanks on crude oil tanker
were cleaned by water but this method of cleaning increased marine pollution and required bigger slop tanks to store left over residue
and oil water mixture.
•In order to prevent this problem, a better non pollutant way was introduced where in oil carg of the tank itself was used to clean the cargo tanks.
•When oil cargo is sprayed with pressure on tank walls and surfaces, the sediments sticking to the tank dissolves and converts into useful cargo which can be pumped out to the shore tanks.
•This system virtually eliminates the requirement of slop tanks on ships and almost all cargo can be transferred to the shore.
•In order to prevent this problem, a better non pollutant way was introduced where in oil carg of the tank itself was used to clean the cargo tanks.
•When oil cargo is sprayed with pressure on tank walls and surfaces, the sediments sticking to the tank dissolves and converts into useful cargo which can be pumped out to the shore tanks.
•This system virtually eliminates the requirement of slop tanks on ships and almost all cargo can be transferred to the shore.
•Maintaining a pressure of at least 10 bar assists this process.
Before
starting the operation
•confirm all pre arrival checks are
performed.
•The complete COW operation to be
discussed with ship and shore staff.
•Signal and Emergency signs to be
discussed to stop the operation between
shore and ship staff.
•Inert Gas plant to be working and oxygen
content must be less than 5 %.
•Fixed Oxygen analyser to be checked and
calibrated for proper functioning.
•Portable oxygen analyser should be made
available and checked for proper
functioning.
When
the operation is under process
•The inert gas values to be frequently
checked- Tank pressure and O2 value.
•A responsible person to be always present
on deck.
•All deck lines and valves must be
frequently checked for any leakages.
•Trim should be sufficient to assist the
bottom washing of tanks.
The level of holding tanks to be
continuously monitored to avoid overflow.
When
the Operation is finished
•Drain tank wash line off crude oil
•Shut all the valves in the line used for
the operation
•Stop and drain all the machines involved
in the operation
•Drain all the cargo pumps after the
operation is finished
Suspending
Crude Oil Washing
Suspend
COW operations immediately if:
•The oxygen content of Inert Gas being
supplied exceeds 8% by Volume.
•Any indication of cargo oil leakage or
malfunction in the COW system.
•COW operation is not carried out in
accordance with the COW operation plan, or if communication between the CCR and
main deck is lost.
•If the required necessary safety
precautions as described and covered above cannot be followed.
•If terminal instruct to do so
