Types of gas carriers and vacancies
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Sometimes, in order to find out whether a vacancy is suitable for a seafarer, you have to search the Internet for a long time for information about the specifics of working on a ship of a particular class. To speed up this process a little, we figure out which types of gas carriers most often receive vacancies, and whether there are any significant differences between them.
Features of transportation of liquefied gas
It is not so important where the primary process of gas liquefaction takes place - right at the place of production or in the port terminal, it enters the ship already in a liquid aggregate state. Gas loading, one of the most critical operations, involves the entire team, each at its own level. A certificate of completion of training in loading operations is required for anyone who is going to apply for a job on a ship of this class without experience. Gas is liquefied in two ways: pressure or low temperature, and some ships use both. Cargo tanks inside the hull, the so-called tanks are designed to maintain the required temperature and pressure level inside. For the transportation of petroleum gases, as a rule, additional protection is used - the second layer of the outer shell.
Types of gas tankers
Tankers for the transportation of liquefied gas are divided according to the type of storage:
- pressure type (Fully pressurized gas carrier) - without refrigeration unit, gas is liquefied by pressure
- semi-refrigerated or semi-pressure type (Semi-refrigerated gas carrier) - refrigeration units maintain the temperature in the cargo tank from 0 ° С to -89 ° С, and the pressure - at the level of 4-6 bar
- refrigerator type (gases are liquefied by temperature, not pressure)
The latter type is the most common and includes ultra-modern VLEC tankers (Very Large Ethane Carrier), LPG carriers, which transport petroleum products, and LNG carriers, which are mainly designed to transport methane.
Types of tanks
Storage systems on tankers also have their own typology: built-in and independent. The first are an integral part of the ship's hull. If the thermal liquefaction method is used for transportation, then a membrane is often added to the inside of such a tank - this helps maintain the pressure level slightly above atmospheric without additional equipment. The membrane tank is the most popular, more than 75% of all gas carriers are equipped with it.
The second type - independent or supplementary, have three subtypes (A, B, C). Type A - prismatic containers that are attached to the body in only one place and require additional shielding in case of leakage. Type B - similar to its predecessor, but the safety requirements for it are much higher. Tanks of this type are made of more durable materials, for this reason they only require partial insulation. The latter, type C, are steel cylinders into which gas is pumped under pressure. They are used in pressure vessels.
Engine types
It is also important to know the type of propulsion system that propels the vessel. Such information will tell a lot to those who are looking for a job at sea as a mechanic. Now in operation - the following engines:
- marine steam turbines - 65% of all ships are equipped with them
- dual fuel diesel engines (DFDE) - installed on 20% of gas carriers
- low-speed diesel engines (SSD) - 12%
- three-fuel diesel engines (TFDE) - it accounts for only 3%
Lifetime
But the main thing that is interesting to every seaman who decides to link his life with a tanker is its service life. True, ships that have been sailing for more than ten years are rare, there are no more than 25% of the total number of gas carriers. To work on them, you need less certificates and real technical knowledge, however, the level of safety is lower here.