What are Tanker Ships?

Vessels that facilitate the supplying of mass quantities of liquefied freight are referenced as tanker vessels. Such liquefied freight can include both rock oil excavated from the underwater reservoirs and all other types of liquid freight like alcoholic beverages, hydrogen-based organic compounds, chemicals and even juices. They also carry liquefied gaseous substances.

As mentioned earlier, the vessels designed for a particular purpose of transporting liquefied goods (such as crude oil; Petroleum; LNG; LPG; wine; bitumen etc.) in bulk are termed as tanker ships or tanker vessels or more commonly as TANKERS.

Currently, due to advancement in technology, a large number of tankers for the transportation of liquefied freights came into existence.

These tankers are equipped with modern technologies and available in many different sizes and capacities. This size variation ranges from small self-propelled barges to ultra large crude carriers. Out of the total merchant ships in the world, about 30% are tankers.

Different kinds of tanker ships are utilised to provide the appropriate transportation facilitation for these myriad types of liquefied freight. Some of the longest vessels in the world today are tanker ships.

The construction and the technical structuring of tanker ships are stipulated by the IMO (International Maritime Organisation). These stipulations have been amended periodically so as to ensure that the underlying safety aspects of the transportation of such volatile elements are met without any compromises.

Tanker size and classes: The size of tankers is measured in DWT i.e. Dead Weight Tons and as per their size they are classified as follows:

Seawaymax, Panamax, Aframax, Suezmax, VLCC (Very large crude carrier) and ULCC (ultra large crude carrier).

Tanker product and classes: Tankers can transport any liquefied material in bulk based on the material they carry, they are classified as follows:

Asphalt/Bitumen Carriers; Bunker Tankers; Crude Oil Tankers; LNG/LPG Tankers; Product Tankers; Chemical Tankers; Other Tankers; etc.

Famous tankers:

TI Class Tankers

Biggest oil tankers in the world (now scrapped)

Tanker Vessels: An Elucidation

As specified earlier, different variances of liquefied freight necessitate the use of different kinds of tanker vessels. Tanker ships are mainly classified on the basis of the type of cargo and size of the vessel. Some of the most commonly used tankers are:

  • Crude Oil tanker
  • Chemical tanker
  • Product tanker
  • Gas tanker

Crude Oil Tankers

 Tanker vessels that are used for oil transportation through marine channels are referred to as oil tanker ships. The terminology of ‘oil tankers’ too by itself is a big domain and covers not just crude oil tankers but also those vessels that are used in the transiting of distilled and processed rock oil.

Vessels that help in the transportation of such distilled rock oil in the form of gasoline, petrol and all petroleum-based organic compounds, from their distilling units to the necessary dispersion centres are referred to as product tankers.

Dead weight tonnage (DWT) determines the maximum capacitance of oil tanker ships. The classification of these tanker ships, therefore, is directly proportional to their DWTs /size.

History Of Tankers:

In late 1861, Elizabeth Watts sailed a vessel carrying 224 tons of petroleum to England. It was the first cargo-carrying liquefied material. The tanker industry was set up in about 1886 and had developed specialized vessels to transport oil across the world. The 2700-ton GLUCKAUF of Britain was the world’s first true oil tanker which had separate tanks for the oil built into its hull. It was the first ship to have oil compartments in which oil can be directly pumped, whereas earlier oil had been shipped in drums or barrels. The Glukauf is the tanker whose design is somewhat that we follow till date.

Americans invented the tank steamship to carry oil in bulk; an enterprising Yankee demonstrated this fact. He stated that oil can be pumped directly through the pipeline to the steamship, and it can safely be transported across the oceans. This will reduce the cost of multiple barrels as in one tanker more quantity of oil can be transported.

But till 1950, after 90 years of tanker industry being set in, it still makes the vessels to carry oil only instead of other liquefied freights.

The significant achievement of that time was their fleet of 16000 DWT size, which is still in use. After the middle of the 20th century, tankers carrying all type of liquids and with larger sizes (VLCCs and ULCCs) came into existence.

In 1990, double hull designs became more popular.

Other innovations of the 21st century, not worked for modification in tankers instead worked for safety of their voyage. Standards were set by IMO (International Maritime Organisation) to carry out a safer design of tanker ships.

Classification of Tankers

Based on the above principle, the tanker ships are mainly classified into:

  • Suezmax
  • Panamax
  • Aframax
  • Very Large Crude Carrier (VLCC)
  • Handymax
  • Capesize
  • Ultra Large Crude Carrier (ULCC)
  • Handy

ULCCs or Ultra Large Crude Carriers are the biggest oil tanker vessels in operation presently with DWTs ranging to a maximum of about five-hundred and fifty thousand tonnes.

The second biggest crude and product tanker vessel types in operation are the VLCCs or Very Large Crude Carriers. These vessels’ variances have a maximum DWT of slightly over three-hundred thousand tonnes.

Find out more about VLCC and ULCC Vessels

Crude oil tankers and product tankers are also classified on the basis of the important international water conduits in which they can gain easy entryway. These vessels include:

The tanker vessels that are built to suitably pass through the Panama and Suez Canals are referred to as Panamax and Suezmax vessels. The former vessels have DWTs up to eighty thousand tonnes while the latter ships have DWTs ranging to about two-hundred thousand tonnes. After both the canals where underwent expansion, higher capacity tankers have been built to pass through them. These vessels are known as Post-Panamax and Post-Suezmax vessels.

Aframax tanker ships have DWTs up to slightly over 1, 00,000 tonnes and these tanker types can gain entryway to almost all harbour facilities across the world.

Find out more about Panamax and Aframax Tankers

Read here for an extensive classification of tanker ships

Gas tankers are specially built tankers which are used to carry liquefied natural gas (LNG) and liquefied petroleum gas (LPG).

Operational Procedure

The tanker operation should be well planned and documented carefully before actual execution. Each and every person present on the tanker and terminal should be familiar with details of plan and plan should be modified before execution, after proper consultations and record the changes formally.

Following are the operations which are executed on tanker ship transportation:

1. Setting of Lines and Valves
2. Pressure Valve Operations
3. Proper handling of generated pressure surges
4. Proper checking of Butterfly and Non-Return (Check) Valves
5. Loading Procedures
6. Discharging Procedures
7. Pipeline and Hose Clearing after all Cargo Operations

Loading Operation 

First of all, the loading order is issued by the owner/operator or charger of the tanker vessel. Leakage of hose couplings should be checked before loading. Tank lids are closed, and tank riser is placed in the loading position.

Lower the ullage meter to its lowest position. Shut the suction and discharge valves. Connect the terminal lines and manifold of the ship through hoses.

After adequately checking the ship for all pre-loading operations, ship indicates the terminal that it is safe to open the loading valves now and start loading.

Actual loading operations is listed as:

1. Loading should be started slowly to ensure that all connections are oil tight, and there is no static accumulation. Supervise the pump room, if the oil is flowing over boards through sea-chests, ask for immediate shutdown. Take the samples of oil being loaded, for checking its temperature.

2. After all checking, the speed of loading of oil may be increased to its maximum allowable rate.

3. Regular supervision should be ensured of the moorings, emergency, towing wire, etc. and the loading speed should not exceed the maximum allowable rate. The tank valve is closed as soon as the ullage reached its calculated level.

4. The speed must be minimized near the end of loading, so the chances of overtopping or overflow will be diminished.

5. Firstly close the shore valve and then close the manifold valves. Tank valves should be closed at last. In the drip tray hoses and loading arms are emptied after closing all the valves, before disconnecting the hoses with the manifold. Blind flanges are inserted in manifold valves after disconnecting loading arms from them and close all the main and cross over valves.

Discharging Operation 

1. Ship or terminal representative or cargo inspector should take the details of the ullage, density, and temperature of the freight loaded. This will help the receiver to calculate the quantity of cargo before discharge.

2. Then connect the hoses to the tank and open the tank ventilators. Free the pump room from gas and open the necessary valves.

3. Throughout the discharge procedure keep going the ventilators of the pump room. Open the necessary cargo lines along with the terminal valves. Start the inert gas and let the pumps stand by until the discharging is about to start.

4. Open the short gate valve and ship manifold valves, and start discharging. Safety measures and precautions to be taken during discharging are same as in case of loading operations.

5. When discharging starts liquid level is at its highest value, at that time discharging speed can be increased. But when the liquid level is low, lower the discharge speed to the minimum allowable draining rate.

6. If a grumbling sound can be noticed from the tank outside, it implies that the tank is nearly dry. The drain wing should be familiar with the location of all the suction valves of the tanker. After draining the tanker completely, tank dips are taken in the presence of a terminal inspector.

7. Remove all the connection and drain the hoses and loading arms completely.

Tanker vessels are indispensable in the maritime domain. The utility of these vessels has become even more applicable and viable in the ever-growing nature of maritime liquefied cargo transportation, thanks to the technological advancements that have been made in the structural and constructional facets of these vessel types.

Tanker Market Study

Throughout the year 2018, a mixed freight rate market (a combination of highs and lows) was faced by tanker owners. Also, the trading conditions had become more and more challenging due to the oversupply of tonnage and also spot earnings are less than operational expenses. Time charter equivalent was averaged maximum to just over $11,000/day during the 1st nine months of the year for TD3C (a VLCC trading between the Middle East and China).

But, after autumn there came an impressive increase in loadings due to stronger demand from Asian refiners for the Middle East and Atlantic Basin.

This results in increased TCE of TD3C to about $50,000/day in the fourth quarter of the year only. The highest number of tankers were demolished in the year 2018 than in the past 15 years.
On a positive side, the expectations are increasing in long haul trade out of America and also to meet the increasing demand in the preparation of IMO2020.

Future Of Tankers

2018 was a bittersweet year for the tankers. But, IMO2020 oil demands can improve the conditions of tankers. Fleet growth is expected to attain a centre stage in 2019.

Future of tankers depend on the future of oil demand, and so, it is policy driven. In the Middle East as the capacities of refineries are increasing and a number of emerging strategic petroleum reserves in the US, China and India increases the tanker market and its trading lanes and result in an increased expectation of prospering future of tanker industry.

You may also like to read – What Are Coaster Vessels?

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 


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