Liquid bulk carriers, also known as tankers, are specialized ships designed to transport large quantities of liquid cargo, such as crude oil, petroleum products, chemicals, and other liquid substances. Unlike container ships that carry packaged goods, these vessels are built specifically for non-packaged, fluid cargo.
Other modes of transportation of liquid bulk cargo include rail tank cars, tanker trucks, and pipelines, depending on the distance, and specific requirements of the cargo
History and Development
The concept of specialized tankers for liquid cargo emerged in the early 1900s.
However, it was not until the 1950s and 1960s that Very Large Crude Carriers (VLCCs) were introduced, revolutionizing the industry by significantly increasing transportation efficiency. The first company to build and use VLCCs was Mitsui O.S.K. Lines (MOL) from Japan, which placed orders for these large vessels to meet the growing demand for oil transportation.
In the 1980s, double-hull designs were adopted following major oil spills, such as the Exxon Valdez incident in 1989. This design provided an extra layer of protection, significantly reducing the risk of environmental disasters.
Technological advancements have continued into the 21st century, with modern tankers now featuring advanced navigation systems, automated safety protocols, and compliance with stringent environmental regulations.
Classification
Liquid bulk carriers are classified based on:
- Properties of the cargo: the physical and chemical properties of the cargo, including potential hazards.
- Size: the dimensions and capacity of the vessel.
This classification is crucial in determining the vessel’s design, construction materials, and safety procedures required for the safe transportation of various types of liquid bulk cargo.
1. Types of liquid bulk carriers based on properties of the cargo
The classification is primarily based on the properties of the cargo, including its potential hazards. Here’s a brief overview of the primary classifications:
- Oil tanker
- LNG Carriers
- LPG Carriers
- Chemical Tankers
- Product Carriers
- Edible Oils and Animal Fats
- Molasses and Liquid Sugar
- Other specialized liquids
1. Oil Tanker
Oil tankers are specialized ships designed to transport crude oil or petroleum products.
Crude tankers move large quantities of unrefined oil from extraction points to refineries, while product tankers transport refined products like gasoline, diesel, and jet fuel to points near consuming markets.
Regarding their design and structure, oil tankers are equipped with specialized tanks capable of carrying up to two million barrels of oil per voyage. These vessels typically contain between 8 to 12 individual tanks, each designed for safe and efficient transport of liquid cargo. Due to safety concerns and stringent international regulations, there has been a significant shift towards constructing double-hulled tankers. This design, featuring two layers of hull plating, aims to minimize the risk of oil spills and environmental pollution in the event of an accident or hull breach.
The global crude oil carrier market has experienced steady growth, with a compound annual growth rate (CAGR) of 3.6% from 2018 to 2024. As of 2024, there are approximately 8,900 oil tankers in operation worldwide, encompassing various types such as VLCCs, Suezmax, Aframax, and smaller vessels. This expansion is primarily driven by rising oil demand, particularly in Asia, and the necessity to replace aging vessels with more efficient models due to stricter environmental regulations.
Major owners of large oil tanker fleets include:
- Teekay Corporation
- A P Moller Maersk
- DS Torm
- Frontline
- MOL Tankship Management
- Overseas Shipholding Group
- Euronav
2. LNG carriers
LNG carriers are specialized ships designed to transport liquefied natural gas (LNG). Inwardly, they are very sophisticated and utilize high technology, resulting in high construction costs. There are two main types of LNG carriers, easily identified by their deck structures. Some feature large spherical tanks, while others have a more streamlined design for the new transportation system known as the “Technigaz System.”
Regarding their design and structure, LNG carriers are equipped with cryogenic tanks that maintain LNG at temperatures as low as -162°C. This allows for the safe and efficient transport of large volumes of natural gas. These vessels can carry between 125,000 to 266,000 cubic meters of LNG.
The global LNG carrier market has experienced robust growth due to the rising demand for natural gas, particularly in Asia and Europe. As of 2024, there are over 700 LNG carriers in operation worldwide. These vessels range in size, with capacities between 125,000 to 266,000 cubic meters. The growth in the LNG carrier fleet is driven by increasing global LNG production and consumption, as well as the expansion of LNG export facilities.
Major owners of large LNG carrier fleets include Teekay LNG Partners, Mitsui O.S.K. Lines (MOL), Nakilat, GasLog, Golar LNG, Höegh LNG, BW Gas.
3. LPG carriers
LPG carriers are specialized ships designed to transport liquefied petroleum gas (LPG). LPG, which consists primarily of propane and butane, is transported in a liquefied state under pressure. These vessels are equipped with pressurized tanks to maintain the LPG in its liquid form during transportation. LPG carriers can be categorized into fully pressurized, semi-pressurized, and fully refrigerated types, based on the pressure and temperature conditions they maintain for cargo.
Types and characteristics:
- Fully pressurized carriers: These are small vessels with spherical tanks designed to transport LPG under high pressure at ambient temperatures. They are typically used for short-distance trade.
- Semi-pressurized/Partly refrigerated carriers: These vessels use both pressure and refrigeration to maintain the LPG in liquid form. They are versatile and can handle different types of LPG and petrochemical gases.
- Fully refrigerated carriers: These are large ships designed to transport LPG at low temperatures and near-atmospheric pressure. They are used for long-distance, large-volume transportation.
The LPG carrier market is expanding due to increased demand for LPG as a clean fuel alternative and its widespread use in residential, commercial, and industrial applications. Key operators in the LPG carrier market include BW LPG, Dorian LPG, and Avance Gas.
4. Chemical Tankers
Chemical tankers are specialized ships designed to transport chemicals in bulk. These vessels are constructed to handle a wide variety of liquid chemicals, each with unique properties and hazards. Chemical tankers are equipped with multiple cargo tanks, allowing them to carry different chemicals simultaneously without risk of contamination.
Types and characteristics:
- Stainless steel tankers: These vessels are used to transport highly corrosive chemicals and are characterized by their stainless steel cargo tanks.
- Coated Tankers: These tankers have epoxy or phenolic coatings on the tank surfaces, allowing them to carry a range of chemicals that are less corrosive.
- Dedicated Chemical Tankers: These ships are built specifically for the transport of chemicals, with advanced safety features and sophisticated cargo handling systems.
The shipping of chemicals in bulk is covered by regulation in SOLAS chapter VII – Carriage of dangerous goods, and MARPOL Annex II – Regulations for control of Pollution by Noxious Liquid Substances. Both conventions require chemical tankers to be designed and constructed to a certain standard as defned in the International Code for Design and Equipment of Ships carrying Dangerous Chemicals in Bulk (IBC Code).
What can go wrong with the chemical tankers?
Chemical tankers face several risks, including:
- Cargo Contamination: Insufficient surface pre-treatment or cleaning can lead to contamination from previous cargoes, causing chemical reactions or degradation of the new cargo
- Corrosion: Highly corrosive chemicals can cause blistering, cracking, and corrosion of tanks if not properly maintained. This risk is mitigated by using stainless steel tanks, but long-term exposure can still cause damage.
- Heat Resistance: Inadequate resistance to high temperatures can result in blistering during loading and unloading processes.
- Water and Seawater Resistance: Exposure to water or seawater can induce hydroscopic stress, leading to cracking and blistering of the tanks.
- Salt and Oxygen Resistance: Areas not properly coated can suffer from osmotic blistering and corrosion under creep damage conditions.
- Mechanical Impact: Lack of resistance to mechanical impacts can result in scratches and abrasions, followed by corrosion.
- Internal Stress/Stress Fatigue: Coatings that lack resistance to internal stress can develop micro, mini, and macro cracking, leading to subsequent corrosion and flaking.
- Operational Errors: Mistakes during loading, unloading, or during the voyage can lead to spills or leaks, posing environmental and safety hazards.
- Fire and Explosion Risks: Many chemicals are flammable or reactive. Any ignition source, such as electrical faults or static discharge, can lead to fires or explosions on board.
The market
The chemical tanker market is driven by the global chemical industry’s growth and the increasing demand for various chemicals used in manufacturing, agriculture, and pharmaceuticals. The market is also influenced by stringent environmental regulations and safety standards.
Major operators:
- Odfjell SE
- Stolt-Nielsen
- Navig8 Chemical Tankers
2. Types of liquid bulk carriers based on the dimensions and capacity of the vessel.
| Class | Dimensions (Length x Beam x Draft) | Capacity (DWT) | Cargo | Description |
|---|---|---|---|---|
| General Purpose Tanker | 150-200m x 20-25m x 10m | 10,000–24,999 | Crude oil, refined products | These are small to medium-sized tankers used primarily for short-distance trade. They are versatile and can navigate through coastal waters and smaller ports. |
| Product Tanker | 150-200m x 25-32m x 12m | 10,000–60,000 | Refined products | Product tankers are designed to carry refined products such as gasoline, diesel, and jet fuel. They often have coated tanks to prevent contamination and corrosion. |
| Medium Range Tanker | 175-225m x 25-32m x 12m | 25,000–44,999 | Crude oil, refined products | Medium Range (MR) tankers are widely used for transporting refined petroleum products and chemicals over moderate distances. |
| Panamax | 200-250m x 32.31m x 12m | 60,000–80,000 | Crude oil, refined products | Panamax tankers are built to fit through the Panama Canal. They offer a balance of size and capacity, making them efficient for various global routes. |
| LR1 (Long Range 1) | 225-250m x 32-42m x 13m | 45,000–79,999 | Crude oil, refined products | LR1 tankers are used for long-haul routes, carrying larger volumes of refined products and crude oil. |
| Aframax | 230-270m x 42m x 14.5m | 80,000–120,000 | Crude oil | Aframax tankers are optimized for maximum efficiency within certain maritime routes, especially where port and canal size restrictions apply. |
| LR2 (Long Range 2) | 250-280m x 42-48m x 15m | 80,000–159,999 | Crude oil, refined products | LR2 tankers are capable of carrying large quantities of crude oil and refined products over long distances. They are often used on international routes. |
| Suezmax | 275-285m x 48m x 17m | 120,000–200,000 | Crude oil | Suezmax tankers are designed to fit through the Suez Canal, maximizing their capacity while adhering to canal restrictions. They are one of the larger classes of tankers before moving to VLCC and ULCC. |
| VLCC (Very Large Crude Carrier) | 320-330m x 60m x 20m | 160,000–319,999 | Crude oil | VLCCs are among the largest tankers used for long-haul routes, primarily for transporting crude oil from the Middle East to Europe, Asia, and North America. They are highly efficient for large-volume transportation. |
| ULCC (Ultra Large Crude Carrier) | 380-415m x 68m x 24m | 320,000–549,999 | Crude oil | ULCCs are the largest tankers in operation, designed for transporting vast quantities of crude oil on the longest international routes. They are highly cost-effective for transporting large volumes but are limited to very few deep-water ports. |
