Types of Ships Cargo ships are classified into various types on the basis of purpose, size, type of cargo etc. The economic factor is of prime importance in designing a merchant ship. Every owner wants maximum return on their investment which means a ship‟s construction not only depends on the current economic necessities but the factor of future adaptability also plays a part. 1. Container Ships As the name suggests, a vessel structured specifically to hold huge quantities of cargo compacted in different types of containers is referred to as a container vessel (ship). The process of sending cargo in special containers is known as containerization. One of the most potent methods of hauling goods is done by Container Ships. These ships have made it feasible to transfer towering quantities of cargo at a time and have changed the global trade efficaciously. Container ships are the cargo ships which carry most seagoing non-bulk cargoes. In today‟s world, container vessels carry around 90% of the world‟s non-bulk cargoes. One of the main ways of carrying ready goods worldwide is through Container Vessels. These containers are of a 1
standardised size so that they can be easily transferred to various modes of transport. Anything can be carried on a Containership. Because of the increasing demand in the market, increasing cargo-carrying capacity, increasing operating efficiency and improvement in environmental processes and operation of a container vessel in liner service, the container vessels have become bigger and bigger continuously. The container carrying capacity of container ships today has increased more than 1200% as compared to 1968. They have become more technologically advanced and fuel-efficient by the time. Container vessels can be classified in many ways: 1.1 Handling Modes a. LoLo Container Ships Lift-on/Load-off vessels are the Geared container vessel, which can load and discharge the cargoes itself using the ship‟s own crane. They have the capability to operate without port cranes and can do the cargo operations unassisted. b. ROCON Container Ships ROCONs are ro-ro vessels which also carry containers. The arrangements are such that the containers may be loaded on the deck or there is separate hold specifically for loading containers. 1.2 Ship Sizes a. Panamax Panamax size vessels were first introduced in 1980. These vessels were of around 4000-5000 TEUs. Their dimension was such that they could pass the Panama Canal. They were limited to the max length of 294.1m, Breadth of 32.3m and max draught of 12m, which was par in comparison to the dimensions of the canal. b. Post- Panamax A new transportation net was introduced by APL without using the Panama Canal. This created the „Post-Panamax‟ type. Introduction of Regina Mærsk in 1996 created a new development in the container ship market with an official capacity of 6400 TEU. Post-Panamax‟s development was climactic. In the present world, they occupy nearly 30% of the world‟s fleet. These size of vessels were subversive introducing new ideas and methods in the container shipping market. Concept of cellular container vessels was introduced. Wherein the cell guides ran from the bottom of the hold to some tiers above the deck. This n reduced the running cost of ship owners as no lashing materials were used to secure the 2
containers but also improved the speed of loading and discharging and reduced container shifting. c. Suezmax Suezmax max size vessels were introduced in relation to Suez canal. These vessels have nearly the same size as that of the Suez canal. Suezmax vessels have a carrying capacity of around 12000 TEUs, with Breadth about 50-57 m and draught in between 14.4m-16.4m. d. Post-Suezmax These are Ultra large container vessels with a carrying capacity of 18000 TEU with a breadth of 60m 21m max draught. These vessels are known as Post Suezmax as their dimensions are too big for the vessel to pass the Suez canal. e. Post – Malacamax This size emulates the maximum permissible draught of 21m of Malacca Strait. For this size of the vessel to enter the Ports, the port authorities will have to be ready. Presently only two ports in the world is ready to accept this size of vessel i.e., Singapore & Rotterdam. 1.3 Service Range a. Feeder Ship These ships are used for short routes. Basically, the voyages are not longer than 500nm and they trade in the coastal areas only. The Capacity of such vessels does not exceed 1500TEU. b. Mother Ship These are the vessels which are on international trade. The size of these vessels is much bigger than feeders. 2. Bulk Carrier Ships Bulk carriers are a type of ship which transports cargoes (generally dry cargo) in bulk quantities. The cargo transported in such ships is loose cargo i.e. without any specific packaging to it and generally contains items like food grains, ores and coals and even cement. Some other forms of dry cargo are: Tramps: A boat or ship engaged in the tramp trade is one which does not have a fixed schedule or published ports of call. Cargo Liners: An ocean liner is a ship designed to transport passengers from point A to point B. The classic example of such a voyage would be a transatlantic crossing from Europe to America. 3
Bulk carriers can be classified in many ways: 2.1 Types of Bulk Carriers by Design a. Basic Bulk Carrier / Conventional Bulkers A conventional bulker is a vessel that is built with hatchways. Alongside, the vessel is also equipped with cranes and transporters to facilitate ease in the loading and unloading processes. These vessels enjoy much better tractability in terms of their cargo loads and their navigational routes. These bulk carriers have holds capped by hatch covers. The number of holds depends on the size of the vessel. They range from 5 for 35000-ton vessels to 9 for 250,000-ton vessels. They use their own cranes to load and discharge the cargoes especially in ports where there are no shore-cranes available. These bulk carriers are constructed in such a way that they can carry multiple numbers of cargoes and can travel anywhere in the world. These vessels were the first ones to be added in the modernized fleet. b. Combined Bulk Carriers These types of bulk carriers have special design and are quite expensive in comparison to other types of Bulk Carriers. The vessels have greater flexibility in order to carry Ore bulk and even oil as Cargo. These vessels could be easily identified as the deck area has both pipelines and Pontoons. These types of bulk carriers have special design and are quite expensive in comparison to other types of Bulk Carriers. The vessels have greater flexibility in order to carry Ore bulk and even oil as Cargo. These vessels could be easily identified as the deck area has both pipelines and Pontoons. 4
c. Gearless Bulk Carrier Bulkers that are unequipped with cranes and conveyor facilities are gearless bulkers. Huge in size, these bulk carriers make port only on those ports of call which provide conveyor and crane facilities to discharge their bulk loads. And since only a few ports offer such facilities, there automatically comes a cap on the number of port calls made by a gearless bulk carrier. These are the bulkers which have no cranes or even conveyors of their own. Because of the above reason, these bulk carriers are unable to carry out operations were shore assistance is not provided. These bulkers are big in size and can only go alongside the largest and avant- garde ports. These bulk carriers are very cost effective as there is no expense on installation, maintenance and operation of the Cranes/Gears. 5
d. Self Dischargers These type of bulkers have Self-discharging/Loading facilities on board in the form of Conveyors or Cranes. These vessels can operate in any inaccessible waterway as they do not require any shore-based system to carry out operations. These bulk carriers have the capability to discharge directly on the quay, a barge, a warehouse or hoppers. This application was introduced basically for deep sea trade in view of the adequacy of the bulk handling facilities around the world. In these bulk carriers, hold terminates above the Double bottom tank top, setting up a series of hoppers which are hydraulically operated. e. Bulker Lakers The bulk carrier ships that ply in the American Great Lakes are called as the lakers. Recognisable on account of their distinct constructional style, these vessels enjoy better operational longevity. These types of bulk carriers were embossed specifically for trading in Great Lakes. You can easily identify it as these bulkers have accommodation in forwarding which helps them to transit the locks easily. These vessels are exposed to very less corrosion damage and have a very long lifespan as they trade only in the fresh water. The largest Laker is of 300m in length, with a width of 32m and a maximum draught of 15m. These Lakers were initialed called as boats but classified as vessels later on. f. BIBO or “Bulk-In, Bags Out” Acronym for Bulk-In, Bags Out; these kinds of bulkers streamline the loaded bulk cargo in the vessel by sacking the same into smaller quantities. Since the process 6
occurs simultaneously, while the cargo is loaded onto the ship, these vessels command unique respect amongst the other existing vessel kinds. This is a very special type of bulker, where the cargo is loaded as bulk but are equipped with equipment to bag those bulk cargo and discharge them in bags. The port stay of these vessels is very short in their destinations as the time taken to discharge bagged cargo is very less. g. Open Hatch Bulk Carrier/Forest Product Carriers These types of bulk carriers don‟t have upper & lower wing tanks. In place of the wing tanks, they have linear sides which help them to accommodate forestry products. As the name says, these vessels have an open hatch to directly load the cargo and discharge. These vessels are geared with moving or fixed gantries, which assists them to load and discharge the cargoes. 2.2 Major Category of Bulk Carriers As Per Size a. Mini Bulk Carrier Dead weight tonnage of these vessels is less than 10,000. They have less than 5 Cargo Holds. They typically carry minor or general cargoes. b. Small Bulk Carrier Dead weight tonnage of these vessels is between 10,000 to 25,000. They have less than 5 holds. They carry minor bulk or steel products in general. c. Handy Size Carriers Dead weight tonnage of these vessels is between 25,000 to 40,000. They usually have 5 holds. They carry minor bulk or steel products in general. d. Handymax Carriers Dead weight tonnage of these vessels is between 40,000 to 60,000. They usually have 5 holds. In general, they carry Minor Bulk, Steel products, Coal and Grains. e. Panamax Carriers Dead weight tonnage of these vessels is between 60,000 to 100,000. It usually has 7 cargo holds. They generally carry Bauxite, coal, grain, Ore, Phosphate etc. These vessels have a maximum breadth of 32.2m. This size of bulkers was introduced to pass through the Panama Canal. 7
f. Post-Panamax Bulk Carrier Dead weight tonnage of these vessels is between 80,000 to 120,000. They usually have 9 cargo holds. These vessels have more breadth than the Panamax and were designed for the bulkers to transit through the New locks of Panama Canal. Image Credits: @canaldepanama – Twitter g. Capesize Bulk Carrier Dead weight tonnage of these vessels is between 100,000 to 200,000. They usually have 9 cargo holds. These vessels travel from Asia to Europe without entering the Suez Canal. They are completely gearless with no cranes or derricks and completely rely onshore facilities for loading and discharging. h. VLBC (Very Large Bulk Carriers) Dead weight tonnage of these vessels is over 200,000. They usually have 9 cargo holds or more. They are completely gearless with no cranes or derricks and completely rely onshore facilities for loading and discharging. 2.3 Category of Bulk Carriers under Size as Per Region a. Karsarmax Bulker These Bulkers were designed to berth specifically at the Port of Kamsar (Republic of New Guinea). Max allowable length overall is 229 m and are larger than the Panamax. b. Newcastlemax Bulker This size of bulkers referred to the largest vessels which can enter Port of Newcastle, Australia. This size of vessels has a maximum Beam of 50m and length of 300m. 8
c. Setouchmax Bulker This size of vessels was designed for vessels to navigate in Setouchi Sea, Japan. They were restricted to 203,000 DWT(Dead Weight Tonnage) d. Seawaymax Bulker This size of the vessel is referred to the vessels which can pass through the Locks of the St. Lawrence Seaway (Great Lake, Canada). Their length was restricted to 226m and draught of 7.92 m. e. Malaccamax Bulker This size of the vessel is referred to vessels which could pass through Strait of Malacca. The maximum allowable LOA is of 330m, the draught of 20m and DWT of 300,000. f. Dunkirkmax Bulker These bulkers were designed to trade in the eastern Harbour lock in the Port of Dunkirk(France) The Maximum allowable beam is of 45 m / LOA of 289 m and 175,000DWT. 3. Tanker Ships Tanker ships are specialised vessels for carrying a large amount of liquid cargo. Tankers are further sub-divided into different types on the basis of the cargo they carry. Tanker Turning in Gibraltar – Credits: Depositphotos 9
Tankers can be classified into: 3.1 Tankers on Basis of Type 3.1.1 Oil Tankers Oil tankers, as their name suggests, carry oil and it‟s by-products. Oil tanker, however, is a generic terminology and includes not only crude oil but also petrol, gasoline, kerosene and paraffin. An Oil Tanker is designed to carry Petroleum products in bulk. These vessels carry a wide range of products ranging from Crude oil to Refined products. Their size is measured in tons or DWT. Its size ranges from 55,000 DWT to VLCC‟s of over 300,000 DWT. Most of these Oil tankers are owned and operated by commercial oil importers or exporters and even by governments. Due to their immense size, they have become quite cheaper to transport petroleum products from one place to another. Literally, for a typical Oil tanker, it costs around 2-4 cents per Gallon only. Oil tankers are further sub-divided into two main types: product tankers and crude tankers: – Product tankers are used to transport the above-mentioned petroleum- based chemicals Product Tankers are used to carry refined oil (various grades) to the point near the engrossing market. They are smaller in size as compared to the Crude oil tankers. The tanks here are coated with epoxy that is used to protect the cargo and also helps in tank cleaning. – Crude tankers are specifically used to transport crude oil from the excavation site to the crude oil refining industrial plant These tankers move a large quantity of unrefined crude oil from its elicitation point to the oil refineries, where they are refined and various grades are products are extracted and distributed later on. These vessels are much larger in size than the other variants of oil tankers. For example, moving crude oil from oil ell of Pointe Noire, Congo to the refineries in the coast of the United States. 10
3.1.2 Gas Tankers Tankers which are specially designed to carry Gas in bulk are called Gas tankers. They are specially designed to carry different forms of gasses. Technically these types of vessels are more on the cutting edge than any other type of vessels such as Bulkers, Containers and Other variety of Tankers. They are mostly built in the shipyards of Korea or Japan. As per the type of cargo carried and the carriage predicament, these can be classified into five categories as named below: a. Fully Pressurised Ships These types of Tankers are the cinch type of gas carrier compared to all of its other varieties. Cargo herein is carried in the ambient temperature. They have “C type” of tanks which are made in Carbon steel with an emblematic design pressure of 18barg. There are no thermal insulations or any other plants. The cargo can be directly transferred by the pumps or compressor of their own. These types of the vessel usually are smaller in size as because of the design pressure, the tanks are extremely heavy. b. Semi-Pressurised Ships These are very similar to fully pressurised ships in term of the tanks construction and structure, but they are designed to carry gas at a maximum working pressure of 5-7 bars. It can be used to transport a wide variety of gas cargo in bulk and can be usually seen in the busy coastal areas around the Mediterranean and Northern Europe. Due to its cargo handling flexibility, semi pressurised gas tankers are most popular among the operators and owners. c. Ethylene Ships This variant of Gas carriers are built for unambiguous trades but also have arrangements to carry LPG‟s or Chemical Gases. Their cargo carrying capacity is between 1000-12000 m3. They too have Type C pressure tanks. The Thermal insulation and liquefaction are fitted on this variant of gas tankers. d. Fully Refrigerated LPG Ships These tankers carry Liquified gases at low temperature and atmospheric pressure. They have a very significant prismatic shaped cargo tanks made up of 3.5% nickel steel, which allows them to carry cargo at a temperature as lower as -48°C. e. LNG Carrier 11
The LNG Carriers are those tanker ships that are used to cargo LNG or Liquefied Natural Gas. These types of tankers require careful and delicate handling owing to the precariousness of the material they carry. Statistically speaking, there are around 193 LNG tankers that are currently under operation. LNG carrier Gaselys LNG(Liquified Natural Gas) Carriers are specifically designed to trade a high volume of LNG. These ships have a cargo carrying capacity between 125000 m3 to 135,000 m3. Their average life span could be somewhere between 20-25 years. LNG is carried at its boiling point, which is -162°C. In the years, there has been a lot of development in the containment system of LNG Vessels. These carriers are fitted with independent cargo tanks or with membrane tanks. 3.1.3 Chemical Tankers Chemical tankers are those cargo tankers which transport chemicals in various forms. Chemical tankers are specifically designed in order to maintain the consistency of the chemicals they carry aboard them. These tanker ships are applied with coatings of certain substances that help in the easy identification of the chemicals that need to be transported. Chemical tankers are tankers that are used to transport various liquid chemicals. Each Chemical Tankers transport the same kind of chemicals. They range from 5000 DWT to 12
35000DWT in size. The size is very smaller of these vessels as compared to the Oil tankers due to the specialized nature of the cargo and the size restriction of the Ports and shore facilities. It consists of various tanks which are coated with specialized coatings such as Phenolic epoxy or stainless steel or zinc paint. Type of coating of their tanks determines the suitable cargo the chemical which can be carried. Customarily Chemical Tankers can be classified into 3 categories as per their type: TYPE 1 Products which possess very serious environmental and safety hazards which require maximum preventive measures to prevent any leakage of cargo comes under Type 1 Chemical Tanker. TYPE 2 Chemical products with markedly severe environmental and safety hazards which require significant preventive measures to forestall any escape of such cargo can be classified as Type 2 Chemical Tankers. TYPE 3 Chemical tankers which transport products with amply severe environmental and safety hazards which require a moderate degree of containment in a damaged condition can be referred to as Type 3 Chemical Tankers. Most of these chemical Tankers are IMO Type 2 or Type 3 since the volume of IMO Type 1 cargo is limited. 3.1.4 Slurry Tankers Slurry refers to all those materials that do not disperse or dissolve in water – otherwise regarded as waste materials. The slurry is used as a fertiliser and the slurry tankers help to haul slurry to areas where they can be put to productive use. This type of vessel is used to carry frittered products where it will be economically useful, in general, is a by-product of refinery products which is very aromatic and forms a very small portion of the global fuel market. These types of vessels are not ideal for shipping any other chemical products other than slurry itself. 13
3.1.5 Hydrogen Tankers: As the name suggests, hydrogen tankers are cargo tankers used for the shipping and transportation of liquefied hydrogen gas. These tankers are specifically designed to carry Liquified hydrogen gas in bulk. They can‟t be used to carry any other purpose. Kawasaki heavy industry was the first to design a Hydrogen Tanker. 3.1.6 Juice Tankers As the name suggests, these tankers were specifically designed for the carriage of juices. Juice tankers or more specifically orange juice tankers which are used for the cargo carrying of orange juice in mass quantities. They either carry concentrated or fresh orange juice, originating from Brazil to the other parts of the world. One of the biggest juice tankers is the Brazilian tanker, Carlos Fischer. However, other fruit juices carriers are also available. These tankers have refrigeration, temperature controller and preservation plants, which helps them to keep the juice fresh at all times. 3.1.7 Wine Tankers Transporting wine has become quite simpler and feasible in contemporary times as sleek tankers have come up which are used specifically to carry wine to their intended destinations. These tankers are used in carrying wine from the place of production to their different destination. Wine tankers are for transporting already produced wine from one country to another country for packaging. 3.1.8 ITB (Integrated Tug Barges) In this type of vessel, the stern is jagged into a special type of tugs which can easily be connected to the barge, establishing it as a single unit. ITBs are prominently used in the eastern coast of the United States. These tankers are mainly tugs attached to barges leading to the formation of a single cargo carrying unit. The carrying capacity of ITB‟s is are not higher as a product or crude carrier but that capacity is enough for meeting the market demand. A number of barges can be connected to a single tug to increase the carrying capacity. 14
3.1.9 Tankers as Per Construction of Hull a. Single Hull Tankers Single Hull Tankers have only 1 outer layer which is watertight and this layer runs throughout the structure of the vessel. This construction of the vessel has a greater threat to the marine environment. Single hull tankers are also more stable as compared to the Double hull tankers. A major problem of leaking ballast pipes are also considered as a danger in these kinds of vessels as the threat of contamination of the cargo is always present since the ballast pipes pass through the Cargo tanks of the vessel. b. Double Hull Tankers As the name defines, the double hull tankers have a double layer of watertight protection which runs throughout the length of the vessel. Both the inner and outer layers are present on the bottom as well as on the side of the vessel. Here the gap between both the hulls is used as ballast tanks for maintaining the vessels stability. Though Double hull tankers possess less threat to the marine environment in case of accidents and are more snug, these vessels are not as stable as the single hull. The reason is that it increases the centre of gravity and reduces the metacentric height. 3.2 Tankers on the Basis of Size 15
4. Roll-on Roll-Off Ships RoRo or Roll on Roll off ship is a special type of vessel which is used for the transportation of automobile vehicles. Also known as car carriers, these vessels have special inclines (ramps) constructed so as to make the loading and the unlading of vehicles and cargo easier and more convenient. The inclines of a RoRo vessel are connected to the entrance either in the front (bow) or at the back (aft) of the vessel or at both. Vehicular traffic can thus pass through these doors without any complexity. Alongside transporting vehicular traffic between riverside harbours, these vessels have also become increasingly helpful in transiting vehicles across ports spread across seas. Over the years, several technological advancements have taken place in these car carrier vessels and resultantly, there have emerged into various types of RoRo ships. 16
Types of Roll on/Roll off Vessels 4.1 Pure Car Carrier (PCC) and Pure Car and Truck Carrier (PCTC) RoRo Ships A PCC (Pure Car Carrier) is a kind of RoRo ship which transports only cars; whereas a PCTC (Pure Car and Truck Carrier) transports not only cars, but also trucks and other variations of four-wheeled vehicles. These kinds of vessels are quite large and quite conspicuous while on water along with being quite sturdy. They are mainly used in the delivering of newer vehicles to their required exporting destination. 4.2 Container Vessel + Ro Ro (ConRo) Ship RoRo vessels that combine the features of both a traditional container vessel and a RoRo ship are referred to as the ConRo. Such vessels‟ interiors are distributed in such a way that both their loads are evenly distributed and balanced. The maximum load that is transited by these vessels is between 20,000 to over 50,000 dead weight tonnes (DWT). 4.3 General Cargo + Ro Ro Ship (GenRo) Ships A normal cargo carrying vessel equipped with the RoRo facility is termed as the GenRo. Slightly compacter and smaller as compared to the previous two categorisations, the GenRo is capable of carrying loads with approximate DWTs between 2,000 to almost 30,000. 4.4 RoPax RoPax is the reference given to a car carrying vehicle that also provides for voyagers‟ living aboard the vessel. RoPax though is mainly used as a technical term, and these vessels are commonly called as ferries that transport vehicles and passengers across river docks. 17
4.5 Complete RoRo Ships A Complete RoRo vessel is a kind of car carrier that is constructed with inclines both on its insides as well as on the outside. Vessels of these kinds don‟t have any hatchways, and are used mainly in the high seas. They are self-contained and are capable of lading anywhere between 2,000 to around 40,000 dead weight tonnes. 5. Passenger Ships Passenger ships, as the name suggests, are mainly used for transiting passengers. The passenger ships are broadly categorised in two classes namely: Ferry and Cruise Ships. Apart from this distinction, there have been specified numerous types of passenger ships. Each of the vessel types can be elaborated as follows: Ferries – Vessels used for transiting passengers (and vehicles) on short-distance routes are called ferries. 5.1 Ferry Ships Ferry ships are those vessels which are used to transit voyagers on short-natured water travel routes. Ferry ships can be dual in nature that is, either they can be vessels are only used for the purposes of transporting passengers or they can be ships that can also carry the vehicular load along with the intake of voyagers. These ships go for their voyage on a regular schedule and have fixed fares. Ferries are also referred to as water taxis or water buses. These are the ships which sail on the same route with many intermittent stops. These ships serve the same purpose as the public transport on road or rail do. So, ferries are the smaller ships used for smaller distance voyages or rather as public transport. 18
The transportation cost through ferries is much lowered as compared to bridges and tunnels. In some regions, ferries provide long distance services, Mediterranean Sea ferry service is the best example of long route ferry service. Ferry ships that are used for transporting not only passengers but also the vehicular loads, and loading and unloading to the ship is carried out through Roll-off/ Roll on systems are termed as Ro-Ro ferries. There are many different types of ferries that are in existence today. The name by which each ferry is known is unique and is named so because of its major characteristic or feature. Some of the main types of ferries can be listed as follows: a. Catamarans: Catamarans are a famous ferry type. They generally are operated as passenger boats and are exceedingly popular wherever they are used. Speed is the major USP of a catamaran and for this reason alone a catamaran ride is favourite among people – young and old alike. One of the most famous catamaran services are operated in the UK by the shipping company Stena Line. b. Channel Ferries: In simple terms, channel ferries are ferries that cross the English Channel as their routine voyage. Channel ferries as a means of transportation were introduced in the early 19th century because of the difficulties posed to ships in the treacherous English Channel waters in both England as well as France. The Channel ferries were small and speedier thus making them a very trustworthy transportation vessel in the English Channel. In today‟s times, there are many variants of Channel ferries that undertake journey not just between England and France but via the English Channel to other parts of Europe as well. c. Car Ferries: Car ferries are basically cargo ferries that help carry cars and other automobile vehicles. Car ferries have two different interpretations. In the United States, car ferries are used to ferry railway carts or cars. These railway cars are loaded into the ferry with the help of tracks that can be attached and detached at will. These attachable and detachable adjustments are also called as Roll-On/Roll- Off ramps. These ramps form the car ferry type in the United Kingdom. d. Roll-On/Roll-Off Ferries: These ferries are also known as Ro-Ro ferries. They are a very useful ferry type especially when it comes to cargo hauling in the form of other vehicles. This type of ferry is mainly used in the United Kingdom. There are also certain other ferries that use such Ro-Ro ramps for boarding of vehicles in addition to the ferrying of passengers. Such ferries are called as cruise ferries. e. Double-Ended Ferries: The front and the back portion of this type of ferry – known as the prow and the stern – can be alternated. In simple terms, it can be said that while making a journey to a particular port, the prow and the stern remain as the parts mentioned; while the ferry makes a return journey, the prow gets converted into the stern and vice versa. 19
5.2 Cruise Ships Large vessels equipped with all luxury and necessary amenities, used for transportation and destination vacations are referred to as Cruise Ships or generally cruises. These vessels are opted for long distance travel and bring the opportunity of international trade to the country. The cruise ship offers a vacation full of fun and amusement. It provides a new and totally different vacation spot with a new experience for the vacationers. Being totally different from the usual vacation, a cruise offers swimming, jogging. Cruise ships are the most famous type of merchant‟s vessels which are used for transiting of passengers from one country to another for recreational trips. These ships are also used for recreational activities, a media of social gathering and for country tourism due to availability of in-house guides and experts facility. Only design and amenities are not the thing, safety should be a major concern. Cruise vacations and cruise transportation are more favoured than other modes due to less cost and safer, calm, pleasant and pollution free environment. Cruise ships are further subdivided on the basis of size into: 1. Large cruise ships: Large cruise ships are the ships with larger voyager carrying capacities. 2. Small Cruise ships: Small cruise are the ships with smaller voyager carrying capacities. 3. Liners: These are the special sort of large cruises, equipped with best facilities. These look more or less like floating cities. 4. Special Cruise ships: These are the ships which are designed for a special destination. For example cruise ships for visiting Antarctica region. Though presently cruise vessels are used for recreational transiting of passengers, these vessels were preceded by voyager vessels that aided in the transporting of voyagers for commercial purposes internationally. 5.3 Special Cruise Ships Cruise ships built for visiting specific regions of the world are termed as special cruise ships. For e.g. cruise ships visiting Polar Regions (Arctic and Antarctic) are called polar cruise ships. They are specially designed and built to face the tough environment of such extreme climatic regions. Passenger ships, both of the ferry ships and the cruise ships variances, have become extremely popular in contemporary times. Providing a sense of novelty amongst the likes of road, rail and aerial travelling options, passenger‟s vessels help people to re-associate 20
6. Offshore Vessels Offshore vessels mainly help in oil exploration and construction jobs at sea. Offshore vessels are of several types. Some of the main ones are: Supply Ship: Vessels that supply to offshore rigs Pipe Layers: Vessels engages in laying pipes and cables Crane Barges or floating cranes: A crane vessel, crane ship or floating crane is a ship with a crane specialized in lifting heavy loads Semi-submersible Drill Rigs: These are Mobile Offshore Drilling Units to make stable platforms for drilling oil and gas Drill Ships: A drillship is a merchant vessel designed for use in exploratory offshore drilling of new oil and gas wells or for scientific drilling purposes Accommodation Barges: Could be a stand-alone floating hotel or can include accommodation as well as space for Cargo Production Platforms: To extract and process oil and natural gas, or to temporarily store product until it can be brought to shore for refining and marketing Floating Storage Unit (FSU) – Floating vessel mainly used for storage of oil and by- products. Floating Production and Storage Unit (FPSO): A floating production storage and the offloading unit is a floating vessel used by the offshore oil and gas industry for the production and processing of hydrocarbons, and for the storage of oil Anchor handling vessels – These are used for offshore construction and installation operations. Diving vessels – Are vessels used by divers for diving in the ocean for underwater jobs. 21
7. Fishing Vessels Ships or boats used for recreational or commercial fishing at sea are called fishing vessels. Fishing vessels are mainly classified into two types – trawlers and non-trawling vessels. Trawlers, Purse Seiners: A fishing trawler, also known as a dragger, is a commercial fishing vessel designed to operate fishing trawls. Trawling is a method of fishing that involves actively dragging or pulling a trawl through the water behind one or more trawlers. A purse seine is a large wall of netting deployed around an entire area or school of fish. The seine has floats along the top line with a lead line threaded through rings along the bottom. Once a school of fish is located, a skiff encircles the school with the net. Factory Ships: A factory ship, also known as a fish processing vessel, is a large ocean- going vessel with extensive on-board facilities for processing and freezing caught fish or whales 8. Speciality Vessels Speciality vessels are constructed and used for specific purposes. Tugs: A tug (tugboat) is a boat or ship that manoeuvres vessels by pushing or towing them. Tenders – A boat or a larger ship used to service or support other boats or ships, generally by transporting people and/or supplies is called a tender vessel. Pilot Crafts – Pilot crafts are used for the transportation of harbour pilots. Cable Layers – Cable laying vessels help in laying cables on to the sea bed. 22
Research Vessels – They are special types of vessels used for carrying out a variety of researches at sea. Some of the most common types of research vessels are – seismic vessels, hydrographic vessels, oceanographic vessels, polar vessels etc. Salvage Vessels – Salvage vessels are vessels engaged in salvage operation; recovery of lost property at sea. Lightships: A lightvessel, or lightship, is a ship which acts as a lighthouse. They are used in waters that are too deep or otherwise unsuitable for lighthouse construction. Barge Carriers: A barge is a flat-bottomed boat, built mainly for river and canal transport of heavy goods. Timber Carriers: Vessels that carry timber Livestock Carriers: Vessels that carry livestock/animals Ice breaker ships: They are used for cutting ice deposits in extremely cold climate conditions to make waters navigational. 9. High-Speed Craft High-speed crafts are a special type of technologically advanced high-performance (typically high speed) marine vehicles. Though most of these technologies are not used in commercial vessels, a few have been successfully implemented and tested in conventional merchant vessels of small scale. Some of the main types of high-speed crafts are: Multihulls including wave piercers Small waterplane area, twin-hull (SWATH) Surface effect ship (SES) and Hovercraft Hydrofoil Wing in Ground Craft (WIG) 10. Dredgers Dredging is an excavation activity usually carried out underwater, in shallow seas or freshwater areas with the purpose of gathering up bottom sediments and widening 23
Dredgers are vessels with excavation tools used for removing sand and other types of deposits from the seabed. Dredgers are used for several purposes such as making shallow coastal areas navigational, deep-sea mining etc. Dredgers are mainly classified into two types: 1. Mechanical dredgers These are available in a variety of forms, but each has the same working principle of “hand-packing”. These are equipped with a grab or a bucket, which is driven on the loose bed sediments, then material get filled in the bucket and the bucket is then raised to transport it to the requisite disposal site. Some common mechanical dredgers are briefed as follows: a. Bucket Dredgers These are the oldest type of mechanical dredgers. These are fixed on anchors so considered as stationary dredgers but can be moved along the semi-arcs while dredging, with the help of winches. An endless chain of buckets is provided in bucket dredgers, these buckets scrap off and fill the loose dredged material in them and after being completely filled, these buckets can be emptied into barges by turning the bucket upside down over the barges. b. Bucket Ladder Dredgers These kind of dredgers are just modification of conventional bucket dredgers, the series of buckets used in these dredgers are mounted on a wheel which mechanically picks up the sediments. They are more efficient and can be used to rip out even powerful and hard corals. The only limitations of these dredgers are their low production, the requirement of more anchor lines and high level of noise, which made them obsolete these days. Bucket Ladder Dredgers 24
They can be used for a wide variety of materials including soft rock material and are powerful enough to rip out the corals as well. But because of their low production, high level of noise and the need for anchor lines, their use has hugely diminished in recent times. c. Grab Dredgers Grab Dredgers (or Clamshells) are also stationary dredgers fastened either on anchors or on spud-poles. The cutting tool, of these dredgers, is a grab which consists of wire operated two half-shells. These half-shells after filling dredged material in them, load the material in barges. Grab is mounted either on a dragline or hydraulic excavator. These can be of different types such as (top) open grab, (top) closed grabs and watertight grabs. Grab dredgers can be of different capacity ranging between 1.0 and 20 m³ whereas the capacity of grab hopper draggers ranges from 100 to about 2,500 m³. Their capacity largely depends upon the crane power. Grabs are efficient in removing material in corners of dock and basins and also these make excavation closer to quay walls easier. Grab Dredgers A revolving crane, fitted with a grab, placed on a hopper vessel or pontoon is known as a grab dredger. As the name suggests, it picks up the sediments at the seabed with a clam grabbing motion and discharges the contents. Often used for excavating bay mud it also is useful to pick up clays and loose sand. d. Backhoe Dredgers These are also referred to as Dipper dredger and are somewhat similar to onshore excavators. These are used for harbour maintenance and shallow dredging. These 25
are hydraulically driven excavators and consist of a half-open shell or a digging bucket which is capable of digging across a wide range of materials. The shell or bucket is moved toward the machine and when filled, emptied in barges. Bucket capacity ranges between 0.5 and 13 m³. Care should be taken while dropping this heavy and rigid bucket as it can cause damage to canal lining or quay walls. Backhoe Dredgers Like some onshore excavators, Backhoe dredgers have a digging bucket attached to it which digs through a wide range of materials and when it is excavated it‟s brought out and placed on the onboard barges. Although they have few limitations where deep dredging is concerned but with some recent modern dredgers, deeper excavation is made quite easy. 2. Hydraulic Dredgers The key feature of hydraulic dredgers is that the material dredged by these type of dredgers is in suspension form and raised through the pumping system and fed to outlet pipes. These are most suitable for dislodging fine materials because it is easier to hold fine materials in the suspension than heavy gravels. Gravels and other powerful material can also be removed through hydraulic dredger by using greater power pumps. Some common hydraulic dredgers are as under: 26
a. Suction Dredgers These are generally employed to remove sand or silt deposits from the seabed. They have a vertical suction pipe, which is pushed vertically inside the sand deposit and dredged material is sucked with or without water jet. The dredged material is laden into barges or can directly to the reclamation area. These suction dredgers can be of two types viz. profile or plain suction Dredgers and Cutting Suction Dredgers. Rest of the working and design of cutter suction dredger is similar to the plain suction dredger but has the only difference that cutter suction dredger is equipped with a cutting tool which may be swinging arc. Cutter suction Dredgers CSD, as they are normally called, have a cutter head at the suction inlet which helps to loosen the earth and take it to the suction mouth. Used for hard surfaces like rock, CSDs suck up the dredged soil with the help of a wear-resistant pump and then discharge it through a pipeline or a barge. b. Trailing Suction Hopper Dredger A Trailing Suction Hopper Dredger is a self-driven dredging vessel. It consists of hoppers or trailers with bottom gates or valves. The material is loaded in hopper hydraulically when this hopper or trailer is filled, the bottom valves or gates are closed and the hopper is raised up with cranes or winches. This dredger is most commonly used in open water: rivers, canals, estuaries and the open sea dredging. Suitable mostly for harbour maintenance and pipe trenching, a hopper dredger is a self-propelling vessel that holds its load in a large onboard hold knows as the hopper. They can carry the load over large distances and can empty it by opening the bottom doors or by pumping the load offshore. Hopper dredges mostly dredge the soft non- 27
rock soils and because of their high production rates can carry out land reclamation projects easily. Trailing Suction Hopper Dredger c. Water Injection Dredger It is a self-driven dredger which excavates sediments with strong water jets. Strong water jet converts the sediments into suspension, as this suspension is heavier than water, it is carried away by water currents and gravity and disposed-off at a specific site. This type of dredger is generally used to dredge mud or fine sand bottoms and are more commonly used for harbour maintenance. Water Injection Dredger 28
Often used for environmentally sensitive projects, water injection dredgers work by fluidizing the material by pumping water into the bed material. Once it is fluidized it is either moved by a second burst of water or is carried away by the natural current. 3. Other types of dredger: These are the dredgers which don‟t fall in the category of hydraulic and mechanical dredgers but are designed for a specific purpose. All these other types of dredgers are operable in shallow waterways such as narrow canals, industrial lagoons and reservoirs. They include: a. Jet-lift dredgers and Air-lift dredgers Jet-lift dredgers work on the principle of Venturi effect. A high-speed stream is injected, which in turn pushes the adjacent water along with the bed material, into a delivery pipe. Air-lift dredgers are similar to jet-lift dredgers with the only difference that high- pressure air is used as the medium for inducing water or material and dispose off through suction pipe. These jet-lift dredgers, as well as air-lift dredgers, cannot be used for powerful and hard material. b. Augur suction dredgers These dredgers work on the outline of mechanical cutter suction dredgers, except that these dredgers are equipped with a rotating Archimedean screw for cutting, which is placed perpendicular to the suction pipe. The augur like screw rotates and removes material, after removal the material is served to the centrally placed suction pipe. This dredging method is employed where the material is to be dredged in precise vertical as well as horizontal dimensions. c. Reclamation Dredger This type of dredger is generally used for reclamation purpose. These are also referred to as barge unloading dredgers. d. Pneumatic dredgers These work on the same principle as a vacuum does. They consist of a chamber with high vacuum pressure inside and the chamber is suspended with the help of a crane. Bed material is pumped in the inlet chamber through vacuum pressure and the chamber is lifted up through crane and emptied at the requisite site. These type of dredgers are opted only for easily flowing material. 29
e. Amphibious dredgers These are a result of great technical advancement as these are capable of working in both submerged as well as in raised condition. These are equipped with grabs, buckets or a shovel installation to carry out the dredging. f. Plough or bed leveler It is a special type of dredger which has a long cutting blade or bars fixed with a boat. As the dredger move over the bed, it scrapes off the bed level to the requisite depth. It is used for short length direct dredging, as it simply scraps the dredged material with a blade to a certain distance. 30
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