tanker operation

All tankers are private or contract carriers. In the 1970s some 34 percent of the world tanker fleet, which aggregates about 200 million dwt, was owned by oil companies; the remaining tonnage belonged to independent shipowners who chartered their vessels to the oil companies. So-called supertankers, which exceed 100,000 dwt, are employed to transport crude petroleum from the oil fields to refineries. The refined products, such as gasoline, kerosene, and lubricating oils, are distributed by smaller tankers, generally less than 30,000 dwt, and by barges.