Crude oil washing
Encyclopedia
Crude oil washing 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(1). 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.
on their empty trips. High pressure, hot, seawater
jets were used to clean the tanks and the mixture of seawater and residue called slops discharged into the sea, as was the oil-contaminated ballast water. The 1954 OILPOL Convention attempted to reduce the harm by prohibiting such discharges within 50 miles (80.5 km) of most land and 100 miles (160.9 km) of certain particularly sensitive areas.
Crude oil washing equipment became mandatory for new tankers of 20,000 tons or more deadweight
with the 1978 Protocol to the 1973 MARPOL Convention. Revised specifications for the equipment were introduced in 1999.
Modern tankers also use segregated ballast tanks and these remove the problem of discharge of ballast water.
Oil tanker
An oil tanker, also known as a petroleum tanker, is a merchant ship designed for the bulk transport of oil. There are two basic types of oil tankers: the crude tanker and the product tanker. Crude tankers move large quantities of unrefined crude oil from its point of extraction to refineries...
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(1). 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.
Seawater washing
Originally oil tankers used one set of tanks for cargo and about one third of the same tanks were for water ballastSailing ballast
Ballast is used in sailboats to provide moment to resist the lateral forces on the sail. Insufficiently ballasted boats will tend to tip, or heel, excessively in high winds. Too much heel may result in the boat capsizing. If a sailing vessel should need to voyage without cargo then ballast of...
on their empty trips. High pressure, hot, seawater
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...
jets were used to clean the tanks and the mixture of seawater and residue called slops discharged into the sea, as was the oil-contaminated ballast water. The 1954 OILPOL Convention attempted to reduce the harm by prohibiting such discharges within 50 miles (80.5 km) of most land and 100 miles (160.9 km) of certain particularly sensitive areas.
Load on top
The discharges from seawater washing were still considered a problem and during the 1960s the load on top approach began to be adopted. The mixture of cleaning water and residue was pumped into a slop tank and allowed to separate into oil and water during the journey. The water portion was then discharged, leaving only crude oil in the slop tank. This was pumped into the main tanks and the new cargo loaded on top of it, recovering as much as 800 tons of oil which was formerly discarded.Crude oil washing
Even with load on top there is still some oil in the discharged water from the slop tank. Starting in the 1970s, equipment capable of using crude oil itself for washing began to replace the water-based washing, leading to the current technique of crude oil washing. This reduces the remaining deliberate discharge of oil-contaminated water and increases the amount of cargo discharged, providing a further benefit to the cargo owner.Crude oil washing equipment became mandatory for new tankers of 20,000 tons or more deadweight
Deadweight
Deadweight may refer to:* Deadweight loss, an economics concept* Deadweight tonnage, a ship's carrying capacity with crew and supplies* "Deadweight" , a song on Beck's 1997 album A Life Less Ordinary...
with the 1978 Protocol to the 1973 MARPOL Convention. Revised specifications for the equipment were introduced in 1999.
Modern tankers also use segregated ballast tanks and these remove the problem of discharge of ballast water.