In the maritime expanse, the term “oil tanker” conjures visions of colossal vessels that traverse the world’s oceans, seamlessly linking oil-rich regions to energy-hungry markets. An oil tanker is a maritime behemoth, meticulously engineered to transport the lifeblood of modern economies – crude oil – across vast distances. Ranging from smaller coastal vessels to mammoth supertankers, these maritime giants play an indispensable role in the global energy landscape.
Oil tankers are liquid cargo ships that transport bulk petroleum and refined oil products. They refer to ships built or designed to carry bulk oil (crude oil or petroleum products) mainly in their loading places, including oil and bulk dual-purpose ships, as well as any chemical liquid cargo ships that carry all or part of bulk cargo oil and comply with the provisions of Annex II of the 73/78 Pollution Convention.
Oil Tanker Size
The size of tankers is measured in DWT, i.e. Dead Weight Tons, and as per size, they are classified as follows:
- Seawaymax
- Panamax
- Aframax
- Suezmax
- VLCC (Very large crude carrier)
- ULCC (Ultra-large crude carrier)
Oil tankers are divided into crude oil tankers and refined oil tankers. The tonnage of oil tankers ranges from hundreds of tons to hundreds of thousands of tons. The tonnage of ships carrying crude oil is larger. The tonnage of very large crude oil carriers (VLCCs) is 200,000-300,000 tons, and the tonnage of ultra-large crude oil carriers (ULCCs) is more than 300,000 tons. Oil tankers are the largest type of ships.
Characteristics of Oil Tankers
The characteristics of oil tankers are that the requirements for fire and explosion prevention are particularly high, so the fire-fighting equipment is relatively complete. In order to reduce solar radiation and control the temperature in the cabin, the outer shell is often painted in light colors. The ship is equipped with deck watering equipment for summer and steam heating oil equipment for winter. Oil tankers are all stern-engine type ships with small freeboards and are easy to get on the waves. There is usually a bridge for crew members to walk on the deck. There is no large cargo hatch on the deck of the oil tanker. In order to clear the tank, only the personnel hatch is opened, which also serves as an expansion well. In the past, oil tankers were mostly single-hulled structures. With the increasing attention paid to marine pollution by humans, oil tankers are required to be double-hulled.
In addition to transporting petroleum and its products, oil tankers can also transport fish oil, vegetable oil and other oils. Oil tankers are stern-engine type and single-deck. The cargo oil tank is divided into several independent compartments by longitudinal and transverse bulkheads to increase strength, reduce the influence of free liquid surface on stability, and facilitate the transportation of different types of oil. Isolation empty tanks are required at the front and rear ends of the cargo oil tank. The cargo oil loading and unloading equipment consists of a pipe system and a cargo oil pump. The cargo oil pump cabin is located between the engine room and the cargo oil area.
Oil tankers carrying crude oil, heavy diesel and residual oil are also equipped with heating devices to prevent the oil in the cabin from solidifying due to temperature drops. Oil tankers should have certain cooling, fire detection, fire prevention, and fire extinguishing facilities and systems according to the volatility and flammability of the oil types they carry. The International Maritime Organization requires crude oil tankers with a deadweight of more than 20,000 tons to be equipped with inert gas devices to ensure that the oxygen content in the cargo oil tank is less than 8% under any conditions to prevent explosions.
In terms of pollution prevention, crude oil tankers with a deadweight of more than 20,000 tons are required to use crude oil to wash the tanks, and like finished oil tankers with a deadweight of more than 30,000 tons, they are required to have dedicated ballast water tanks. The cargo oil tanks are no longer used as ballast tanks to prevent the discharge of ballast water containing residual oil from polluting the ocean. In addition, regulations have been made on the protection area of the cargo oil tanks to limit the contact range between the cargo oil tanks and the outside world, so new ship types with double bottoms and double hulls have emerged.