2.1 Merchant Tankers
Merchant tankers are cargo ships specifically designed to transport bulk liquids over long distances. They play a critical role in the global economy by carrying essential products such as crude oil, refined petroleum products (gasoline, diesel), and other liquids like chemicals and liquefied natural gas (LNG). This chapter will provide an overview of merchant tankers, including their various types, characteristics, specificities and equipment.
Main Types:
Crude Oil Tankers:
VLCC (Very Large Crude Carrier): 200,000 – 300,000 DWT, workhorses of oil transportation, often single-hull due to construction limitations.
ULCC (Ultra Large Crude Carrier): Exceed 300,000 DWT, rare due to size restrictions of some canals and ports, typically double-hull for safety.
Aframax: 80,000 – 120,000 DWT, medium-sized, efficient for medium-distance routes.
Suezmax: 120,000 – 200,000 DWT, designed to navigate Suez Canal, often double-hull.
Product Tankers:
MR (Medium Range): 25,000 – 50,000 DWT, versatile for diverse refined products, frequent port calls.
LR (Long Range): 50,000 – 80,000 DWT, longer voyages compared to MR tankers, complex cargo handling systems.
Handysize: 10,000 – 35,000 DWT, smaller size for regional product distribution, coastal operations.
Liquefied Gas Carriers (LPG Carriers):
LPG Tankers: Transport liquefied petroleum gas (LPG) like propane and butane at moderate pressure, often featuring spherical or semi-spherical tanks.
VLGC (Very Large Gas Carrier): Over 80,000 DWT, largest LPG carriers, typically double-hull.
Refrigerated LPG Carriers: Utilize refrigeration systems for additional pressure control and wider product range.
Liquefied Natural Gas Carriers (LNG Carriers):
LNG Tankers: Transport liquefied natural gas (LNG) at cryogenic temperatures (-162°C) in double-hull, highly insulated tanks with containment systems.
LNG-FPSO (Floating Production, Storage and Offloading): Combine LNG production, storage, and offloading capabilities, used in offshore fields.
Small-Scale LNG Carriers: Emerging market for transporting smaller LNG volumes to regional markets.
Chemical Tankers:
IMO Product Tankers: Designed for specific IMO (International Maritime Organization) chemical categories, with varying tank materials and configurations.
Parcel Tankers: Divided into multiple smaller tanks for carrying different compatible chemicals simultaneously.
Heated Tankers: Equipped with heating systems for temperature-sensitive chemicals.
Characteristics:
Size: Expands beyond DWT to consider length, beam (width), and draft (depth) for canal and port compatibility.
Cargo Capacity: DWT is crucial, but cargo density also impacts volume transported (e.g., LNG is lighter than crude oil).
Hull Design: Double-hull becoming increasingly mandatory for environmental and safety reasons.
Segregation of Cargo: Tanks can be coated with different materials, have separate ventilation systems, and employ inert gas purging for safety.
Cargo Handling: Loading/unloading rates, cargo heating/cooling requirements, and vapor recovery systems vary based on cargo type.
Specificities:
Crude Oil Tankers: Long voyages necessitate efficient fuel consumption and navigational autonomy. Ballast water management systems crucial for stability during return journeys without cargo.
Product Tankers: Complex cargo handling due to diverse products and frequent port calls requires efficient cargo segregation and cleaning procedures.
LPG/LNG Carriers: Specialized cargo containment systems, safety protocols for cryogenic temperatures, and regasification facilities at receiving terminals are essential.
Chemical Tankers: Wide variety of tank materials, designs, and safety measures depending on specific chemical properties and potential hazards.
Equipment:
Navigation and Communication: Advanced systems like Electronic Chart Display and Information Systems (ECDIS) and Automatic Identification System (AIS) for enhanced safety and efficiency.
Loading/Unloading Systems: Cargo pumps, pipelines, valves, vapor recovery units, and inert gas systems tailored to specific cargo types and safety requirements.
Safety Equipment: Firefighting systems, lifeboats, life rafts, pollution prevention equipment, and gas detection systems, complying with stringent international regulations.
Cargo Monitoring: Sensors and gauges for real-time tracking of cargo levels, temperature, pressure, and potential leaks.