Dredging operations are carried on wherever it is necessary to maintain the depth of water in channels, docks, and basins. The spoil is dredged from the bottom and must be removed to dumping grounds some distance out at sea. Some vessels which have hopper space and are self-propelled can take the spoil to the dumping grounds, but as the bucket dredger has no hopper space and is not self-propelled it is move about the port by tugs and transfers the spoil to hopper barges. The suction dredger, also known as a sand-pump or hydraulic dredger, is required when the bottom is particularly soft. A pipe is lowered to the bottom and the spoil, perhaps three-quarters of is water, is drawn up into the hoppers.
Are designed to carry cargo. Some are also designed to carry passengers. Nowadays, most merchant ships are built to carry cargo, but a few still carry passengers. Merchant vessels can operate in the following three basic ways: 1) They can operate as liners. These are employed on regular routes on a fixed timetable. 2) Merchant vessels also operate as tramps. These vessels do not sail on regular routes or keep to fixed timetable, but are employed where there is cargo for them to carry. The traditional tramp cargoes are dry bulk cargoes, but some are designed to carry general cargoes. 3) A large number of merchant ships operate as specialised vessels. These are designed to carry a particular type of cargo. There are several types of specialised vessel. The most common are oil tankers. They are owned by the major oil companies or by independent operators. Two other types of liquid bulk carrier of growing importance are chemical carriers and liquefied natural gas carriers.
TYPES OF SHIPS
On one hand, all cargo ships are divided into two types: dry cargo ships and tankers. On the other hand, cargo ships may be divided into universal ships designed to carry principal different types of cargo and specialized ships designed to carry one type of cargo. Such specialized ships as bulkers, timber-carriers, reefer ships, tankers have long been known. One is cargo-carriers with cargo handling equipment on board for special purposes or routes such as heavy/bulky cargo ships. These ships are also called special-purpose ships. The second trend is Ro-Ro(roll on roll off) ships, in which bow and stern doors and adjustable steel ramps permit vehicles to drive on board and drive off again, requiring only minimum dock-side facilities. The third trend is the container ship. In dependence of the cargo handling method used dry cargo ships may also be divided into: LO-LO (lift-on/lift off), RO-RO (roll on/roll off), FO-FO (float on/float off) e.g. barges. But there are also hybrid vessels where combinations of the above mentioned methods are used, such as LO-LO/RO-RO, RO-RO/FO-FO, and other.
Container ships. The use of containers has continued to increase in recent years. Containerization means the consolidation of goods of single or mixed commodity into a freight container which may be closed or open which, if in conformance to the recommendations of the ISO would be 10, 20, 30, or 40 ft in length. A container is designed to be handled mechanically throughout the transit
Most fishing vessels are designed for one particular kind of fishing. There are trawlers, drifters, seiners, whale-catchers, crabbers sardine luggers, etc. The design of the modern vessel incorporates a high, soft nosed stern? well-flared streamlined bridge and superstructure? a gantry and transom stern. A recently built stern trawler is 73m overall, 12,5m molded breadth, 8m molded depth and is powered by 2,350 h.p. diesel engine which gives a speed of 14,5 knots. The fish room has a capacity of 764 cu. m. and can stow 500 tons of frozen fish.The working deck of a large stern trawler would have an area of 418 sq/ m/ which is clear of all deck fittings, so that a full trawl may be spread out. The stern fishing vessel described here must not be confused with the larger, stern fishing factory vessels which concentrate on filleting and freezing all fish in their various species and packing them in cartons ready for supplying to the customer. The fish are futted in the conventional way on an ordinary side trawler and are frozen whole in blocks ranging in weight from 25 to 45 kg. Cold stowage on board is very compact/ All the blocks are of the same size, labelled by species, and kept stored at 20 degrees F.
GENERAL DESCRIPTION OF A SHIP- a hull.- the bow - the stern midships superstructure holds - forpeak tanks - afterpeak tanks - cranes, winches, derricks angle/ trim list/ heel - load lines - W /winter loading WNA T/ F.
UNIVERSAL VESSELany types of cargoes - deadweight 2,000/ 20,000 Tramp/bulk and timber - to cope with bad weather/ not be too large - Deep tanks/ liquids and dry cargo/ liquids only - hatch /covers/electricity - a half of all ships.
TYPES OF SHIPSall divided into dry cargo/tankers universal/specialized specialized: bulkers, timber-carriers, reefer ships, tankers - heavy/bulky cargo ships/special-purpose ships - Ro-Ro/ bow and stern doors/ steel ramps - container ship - dependence of the cargo handling: LO-LO/ RO-RO/ FO-FO - hybrid vessels/ LO-LO/RO-RO, RO-RO/FO-FO, and other.
MULTI PURPOSE VESSELNowadays universal transformed into multi-purpose vessels - all multi-purpose vessels are adapted to carry standard containers - designed to cope with loads big containers, including refrigerated, trailers ,tracks, explosives and inflammable liquids. For the Arctic. Ventilation. Ramp. Cranes.
CONTAINER SHIP Use containers to increase - Containerizaition means consolidation of goods of single or mixed commodity into a freight containers - ISO would be 10,20,30,or 40ft in length by 8ft wide and 9ft high - Cellular type - roll on/roll of container ships - short service Damage, pilferage, insurance is minimum.
RO -RO designed to carry all sorts of rolled vehicles and motor cars by driving them on/of the ship - Loading may be effected through the stern bow doors or side ports. - The types of access hydraulically operated, access ramps, internal ramps, lifts, bulkhead doors. - advantages: 1) independence of port facilities 2)quick door - to door service; 3)faster cargo handling rate; 4)the risk of damage or pilferage is reduced. disadvantage of Ro-Ro ships: 1)considerable amount of cargo volume is occupied by vehicles or trailers; 2)considerable space below the lower deck cannot be used for trailers.
BARGE CARRYING VESSELS.Idea to keep cargo in the same package all the way and not to reload it.Difference between a container and barge: much bigger and can float LASH-lighter aboard ship and SEA BEE barge. difference: LASH ship is a lift-up and lift over type using a 500 tons gantry crane, while the SEA BEE ships float barge on elevator of 2000 t. capacity using rolled system for stowage. Advantages:1)Rapid loading/discharging 2)Can anchor and discharging dont using berth 3)Long life in 2,5 times more than container 4)Simpler organization . Disadvantages:1)distribution is limited by draught 2)ice on waterways can restrict barge transport 3)LASH type is more expensive than the equivalent container ship.