Tanker

A tanker is ship that is designed to transport liquids in bulk. Tankers, like other ship types, are today highly specialized and exists in number of varieties and sizes. From small self propelled barges up to ULCC (ultra large crude carrier). An example of what Tankers are designed to carry is: crude oil, Petroleum, liquefied natural gas, liquefied petroleum gas, Bitumen, molasses, wine and chemicals (i.e. ammonia, chlorine). The tanker segment represents about 30% of the worlds total merchant fleet.

Tanker size and classes

Petroleum tankers are categorized into the following classed that determines theirs size in DWT (Dead Weight Tons).

Seawaymax:DWT 10 000 – 60 000

Panamax: DWT 60 000 – 80 000

Aframax:DWT 80 000 – 120 000

Suezmax: DWT 120 000 – 200 000

VLCC (very large crude carrier): DWT 200 000 – 315 000

ULCC (ultra large crude carrier): DWT 315 000 – 520 000

Tanker Design and Types

Design

The design of Tanker ship is similar to a Bulker with the exception that the cargo holds have been replaced with tanks. Machinery either two our four stroke engines depending on size and design of the vessel. In most cases HFO (heavy fuel oil) is used as fuel for propulsion but in some cases (like on LNGs) natural gas is used instead of HFO. Design speed of the vessels is normally between 10 – 18 knots. For on- and offloading of the vessel tankers are equipped with a cargo pump system that is closely monitored due to risk of fire.

Asphalt/Bitumen Carriers

Are ships that specially designed to carry asphalt/bitumen products. Characteristics of those ship is that they are designed with “floating tanks” which means that the tanks are allowed to expand due to high temperature of the product they carry, up to 260°C. Tanks are sometimes insulated to minimize heat losses. Size of a bitumen carrier is in the smaller segment (<10 000 DWT) typically between 1 000 – 6 000 DWT.

Bunker Tanker

Is a ship designed to supply fuel to ships offshore. Bunker tanker are smaller vessels from 100 – 5 000 dwt and the design is the sames as product tankers.

Crude Oil Tanker

Crude oil tankers are dedicated to transport crude oil from offshore oil plants (oil platforms) or oil fields to refineries. Ships in this category falls belongs to the real “giants of the sea” and the worlds largest ships could be found among crude oil tankers.

LNG/LPG

Gas carriers are ships that are specially designed to transport gas. This ship type is considered to be more technically advanced than Bulker and Tankers. Most ships of this type are built at yards in Korea or Japan as they have the experience and proven track record. Oil price and the resent environmental debate has increased demand for LNG. Not only as source of energy for land based installation but also as fuel for ships due its environmental advantages. However there are still some challenges in infrastructure around LNG.

LNG Carrier

Is a ship that designed to transport Liquefied Natural Gas (LNG). In order to keep the natural gas liquefied the gas has to be cooled held in the tanks at -162°C. The liquefied gas is in some designs kept in sphere shaped tanks that are carefully insulated to avoid heating up and “boil-off” of the LNG. It also gives the ship a very characteristic look. No insulation is perfect and according to WGI (World Gas Intelligence), on a typical voyage an estimate of 0.1% – 0.25% of the cargo converts to gas each day, depending on the efficiency of the insulation and the roughness of the voyage. Some LNG carriers are designed to use the “boil-off” from the cargo tanks as fuel for propulsion and are equipped with dual fuel engines.

LPG Carrier

This ship type is specially designed to transport petroleum gas like propane, butane, propylene and butylene.

CNG Carrier

Is a ship that is designed to transport Compressed Natural Gas.

Product Tankers

Ship designed for transporting refined products from the refineries such as gasoline, diesel oil and aviation fuel. Product tankers are available from small tanker barges up sizes of 170 000 DWT and is the most common tanker type.

Chemical Tanker

Ship that is designed to transport different kinds of chemicals but are also able to transport the same products as the Product Tanker. A chemical tanker is in most cases more advanced than the Product Tanker when comes to the cargo handling system as have to avoid mixing of the products it is transporting.

Other Tanker

Apart from whats been described above there a number of specialized tankers like Wine tanker, Fruit Juice Tanker, Water Tanker, Sulphur Tankers and Storage Tanker.

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