2.2 Special Vessels
Beyond cargo giants and passenger liners there are many types of specialized vessels, each crucial for specific maritime tasks. This chapter explores their characteristics and equipment.
Cable Layers:
Main Characteristics: Cable laying ships are designed to lay and bury communication and power cables under the sea bed. They feature massive cable storage holds and deployment equipment capable of handling immense cable weights and lengths.
Sophisticated positioning systems and dynamic positioning technology are crucial to maintain the vessel's position during deployment.
Equipment: Key equipment onboard includes:
Cable Storage Carousels: These giant spools hold kilometers of cable, ensuring smooth and controlled unwinding during deployment.
Laying Tensioners: These maintain constant tension on the cable as it's payed out, preventing damage during the process.
Plows or Trenchers: Depending on the seabed conditions, cable layers may deploy plows or trenchers to bury the cable beneath the seabed.
Survey Vessels: Mapping the Ocean Floor
Main Characteristics: Survey vessels are equipped with advanced technology to map the underwater topography, identify potential hazards, and gather valuable data for various purposes. They come in various sizes, from smaller vessels for coastal surveys to sophisticated deep-sea research vessels.
Specificities: The specific equipment onboard a survey vessel depends on the intended purpose. However, some common features include:
Multibeam Echo Sounders (MBES): This technology creates detailed 3D images of the seabed, providing precise bathymetric data.
Subsea Positioning Systems: These systems allow for accurate positioning of the vessel and any deployed survey equipment on the seabed.
Sampling Equipment: Survey vessels may be equipped with winches and specialized tools to collect sediment or water samples for further analysis.
Main Characteristics: Dredgers are specialized vessels designed to excavate and remove underwater sediments. They come in various configurations, with different methods for extracting materials, including suction dredging, mechanical dredging, and bucket dredging.
Specificities: The type of dredger and its specific equipment depend on the intended purpose and the type of material being dredged. However, some common features include:
Dredge Pumps: These powerful pumps are at the heart of a dredger's operation, sucking up or cutting through sediment and transporting it to a designated location.
Discharge Pipes: Dredged materials are pumped ashore or to another vessel through long discharge pipes.
Positioning Systems: Similar to survey vessels, dredgers require precise positioning to ensure accurate excavation and avoid damaging underwater infrastructure.
Main Characteristics: Salvage tugs are powerful vessels specifically designed for emergency response and rescue operations at sea. They boast robust towing capabilities, advanced firefighting equipment, and the ability to operate in challenging weather conditions.
Specificities: Salvage tugs require a high degree of maneuverability and the ability to tow disabled vessels safely to port.
Equipment: Key equipment onboard a salvage tug includes:
High-capacity Towing Winches: These winches allow them to tow large vessels through rough seas.
Firefighting Equipment: Salvage tugs are often equipped with powerful pumps and firefighting monitors to combat onboard fires on distressed vessels.
Specialized Salvage Gear: This may include equipment for divers, pollution control measures, and tools for securing damaged vessels.
Offshore Support Vessels:
Main Characteristics: Offshore support vessels (OSVs) are a diverse group of vessels that provide critical support for offshore oil and gas exploration and production activities. They can include platform supply vessels, anchor handling tugs, and crew transfer vessels.
Specificities: The specific purpose of an OSV determines its equipment and capabilities. However, some common features include:
Tugs:
A tug is a vessel that assists other vessels with entering and leaving the port or harbor or assisting with a salvage operation. There are sea-going tugs and harbour tugs, but in both cases their engines must be capable of developing enormous power.
Main Characteristics:
Manoeuvrability : The largest and most powerful tugs are often fitted with Controllable Pitch Propellers (CPP) that have adjustable blades. Manoeuvrability will be enhanced even more by bow thrusters and stern thrusters.
Power : The main feature of tugs are often their high power, expressed as bollard pull in tons, the largest ones reaching 200 tons.
Towing : These tugs are linked to the towed vessel by a towing line, a strong wire rope stowed on a special winch in the tug and that can be up to 2,000 m long. A short weaker cable, called pennant, is inserted between the main line and the ship to be towed, so that this pennant will break in case of overloading, thus saving the main line.
Characteristics:
Reinforced Hull: Icebreakers feature a specially strengthened hull design, often incorporating angled or rounded shapes, to withstand the immense pressure of breaking through ice floes.
High-Powered Engines: Powerful propulsion systems are crucial for pushing through thick ice. Many icebreakers utilize diesel-electric engines for efficient power generation.
Water Ballast Systems: These systems allow icebreakers to adjust their weight and draft, optimizing their ability to ride over ice or break through it.
Equipment:
Bow Thruster: A powerful thruster located at the bow of the vessel assists in maneuvering and maintaining position in icy waters.
Ice Ram: This specially reinforced structure at the bow is designed to break through ice floes. The shape of the ram varies depending on the icebreaking method (crushing, pushing under, or riding up).
Firefighting and Rescue Equipment: Icebreakers often operate in remote and harsh environments, making onboard firefighting and rescue capabilities essential.
Heavy Lift Ships:
Characteristics:
Massive Cranes: The defining feature of a heavy lift ship is its colossal cranes, capable of lifting and transporting incredibly heavy and oversized cargo. These cranes can have lifting capacities exceeding thousands of tons.
Strengthened Decks: The decks of heavy lift ships are specially reinforced to accommodate the immense weight of the cargo being transported.
Ballast Water Systems: Similar to icebreakers, ballast water systems are crucial for maintaining stability during loading and unloading operations, which can significantly affect the vessel's center of gravity.
Equipment:
Motion Compensation Systems: These advanced systems help stabilize the ship and the cargo during lifting operations, mitigating the effects of wave motions.
Ballast Control Systems: Sophisticated systems precisely manage the ballast water to ensure optimal stability throughout the loading and unloading process.
Specialized Cargo Handling Equipment: Depending on the cargo type, heavy lift ships may be equipped with additional gear like spreader beams, lifting yokes, and self-propelled modular transporters (SPMTs) for maneuvering heavy cargo on deck.