The Types of Ships
Liners and Tramps
Vessels that have been designed to transport cargo or/and passengers are called merchant ships. They may be classified as liners or tramps.
A liner carries cargoes between two fixed destinations.
Her sailing schedule has been pre-arranged – she has a fixed homeport, port of destination and port(s) of call, and fixed ETA’s and ETD’s (Estimated Times of Arrival and Estimated Times of Departure). A liner-vessel is allowed to carry up to 12 passengers.
Freighters that carry cargoes according to schedules that are not fixed are called tramps.
Homeports, ports of destination, ports of call, ETA’s and ETD’s differ with every voyage.
A tramp is not allowed to carry any passengers.
Merchant ships may carry general cargoes, bulk cargoes, refrigerated cargoes, heavy cargoes, timber, and many many more.
General Cargo Ships
General cargo is cargo that has been packed in crates, boxes or bags, or cargo coming in pieces (unpacked cargo items).
Cargo is loaded and discharged by the vessel’s own derricks or by shore based cranes.
The conventional general cargo ship has several tweendecks.
Bulk cargo is unpacked cargo of one commodity.
Dry bulk cargo, such as grain, ore, fertilizers, etc. is carried in specially designed vessels with holds that have been divided into compartments by longitudinal and transverse separations, so that the ship’s stability will not be affected by a full cargo.
Dry bulk cargo is loaded and discharged by cranes with grabs or by pumps.
Liquid cargoes such as crude oil, petroleum, edible oils, etc. are carried in tankers, for example in Very Large crude Carriers (VLCC’s), chemical tankers, such as Liquefied Petroleum Gas (сжиженный углеводородный газ) tankers (LPG carriers) or Liquefied Natural Gas tankers (LNG carriers).
Product tankers are small tankers that carry different sorts of oils.
For safety reasons tankers must be fitted with double bottom. These spaces also provide storage for fuel, lubricating oil and waters.
Cargo that has been containerized is carried by container ships.
Containers are most often measured in Twenty Feet Equivalent Units (TEU’s) and are stowed in a cellular arrangement in Rows, Bays and Tiers.
The rows run abeam, or athwartship; the bays run fore to aft and the tiers are horizontal layers. The three-figure code on each container refers to this stowage system. Thus, each container can easily be found.
Container ships are sometimes equipped with their own gantry cranes that load and discharge the containers. Container ships may carry general cargoes, liquid cargoes or refrigerated cargoes.
Roll-on/Roll-off ships (RO/RO ships)
On a Ro/Ro ship cargo is rolled on and rolled off by lorries (грузовики) or trailers (тягачи).
The great advantage of this system is that no cargo handling equipment is required.
The loaded vehicles are driven aboard via ramps through special stern and bow doors and are properly secured for the passage. Upon arrival in the port of discharge, the vehicles are released and driven ashore to their destinations.
A coaster carries cargo along the coast or on sea voyages. Trans-Atlantic voyages are quite common.
A coaster is of limited length and tonnage.
Her engine room is situated aft. Often there are no tweendecks and the cargo spaces have no obstacles, so that a variety of cargo can be handled.
Refrigerated-cargo vessels (Reefers)
Refrigerated-cargo vessels are ships that carry perishable cargoes, such as meat or fruit. These cargoes require cooling and must be stored in spaces that have precise temperature-and humidity controls during the voyage.
Reefers, as these ships are also called, are equipped with refrigerating plants.