LNG Shipping Knowledge: A Comprehensive Guide for Ship's Officers
LNG shipping is a specialized sector of the maritime industry that involves the transportation of liquefied natural gas (LNG) from production facilities to import terminals or regasification plants. LNG shipping requires a high level of technical and operational expertise, as well as adherence to strict safety and environmental standards. LNG carriers are designed and equipped to handle the low temperature and high pressure of LNG cargo, which has a boiling point of -162ÂC and a density of about 450 kg/m3.
This article aims to provide an overview of the essential knowledge and skills required for ship's officers serving on LNG carriers, based on the SIGTTO Standards for LNG Shipping Competency. SIGTTO (Society of International Gas Tanker and Terminal Operators) is an international organization that promotes best practices and standards for the safe and efficient operation of gas tankers and terminals. The SIGTTO Standards cover various aspects of LNG shipping, such as physics and chemistry, principles of design, regulations and guidance, hazards and risks, equipment and systems, cargo operations, emergency response, and communication.
The article is divided into three main sections: LNG Fundamental Knowledge and Understanding, LNG Equipment, and LNG Support Systems. Each section covers the key topics and concepts that ship's officers need to know and understand in order to perform their duties effectively and safely on board LNG carriers. The article also provides references to relevant sources of information, such as books, websites, and publications, where readers can find more details and examples.
LNG shipping is a dynamic and challenging field that requires constant learning and updating of knowledge. By following the SIGTTO Standards for LNG Shipping Competency, ship's officers can ensure that they are well-prepared and qualified to handle the complexities and responsibilities of LNG shipping.LNG Fundamental Knowledge and Understanding
In this section, we will cover some of the basic concepts and principles that underlie LNG shipping, such as physics and chemistry, principles of design, regulations and guidance, hazards and risks, environmental impact, risk assessment, individual responsibilities, contingency plans, record keeping, and planning.
Physics and Chemistry
LNG is composed mainly of methane (CH4), the simplest hydrocarbon molecule, with some minor amounts of ethane (C2H6), propane (C3H8), butane (C4H10), nitrogen (N2), carbon dioxide (CO2), and other trace components. The composition of LNG varies depending on the source of natural gas and the liquefaction process. The physical and chemical properties of LNG are influenced by its composition, such as its density, viscosity, calorific value, flammability range, flash point, boiling point, vapor pressure, and expansion ratio.
LNG is a cryogenic liquid, meaning that it has a very low boiling point at atmospheric pressure. LNG boils at -162ÂC (-259ÂF) and has a density of about 450 kg/m3 (28 lb/ft3) at this temperature. LNG is also a clear, colorless, odorless, and non-corrosive liquid that does not dissolve in water. LNG is not explosive or toxic by itself, but it can form flammable mixtures with air when vaporized.
LNG is produced by cooling natural gas to its liquefaction point using various refrigeration cycles. The most common liquefaction processes are based on the use of propane (C3) or mixed refrigerants (MR) as the cooling medium. The liquefaction process reduces the volume of natural gas by about 600 times, making it more economical to transport over long distances. The liquefaction process also removes most of the impurities from natural gas, such as water, hydrogen sulfide (H2S), carbon dioxide (CO2), mercury (Hg), and heavier hydrocarbons.
Principles of Design
LNG carriers are specially designed vessels that can safely and efficiently transport LNG across oceans. LNG carriers have several features that distinguish them from conventional ships, such as:
Cargo containment system: This is the system that holds and isolates the LNG cargo from the rest of the ship. There are different types of cargo containment systems for LNG carriers, such as membrane tanks, spherical tanks, prismatic tanks, and independent tanks. Each type has its own advantages and disadvantages in terms of cost, capacity, safety, and maintenance.
Cargo handling system: This is the system that controls the loading, unloading, transfer, heating, cooling, venting, and reliquefaction of LNG cargo. It consists of various components such as pumps, valves, pipes, heaters, vaporizers, compressors, reliquefaction plants, gas combustion units (GCU), emergency shutdown systems (ESD), etc.
Propulsion system: This is the system that provides power and propulsion for the ship. There are different types of propulsion systems for LNG carriers, such as steam turbines, dual-fuel diesel electric (DFDE), slow-speed diesel (SSD), gas turbine electric (GTE), etc. Each type has its own advantages and disadvantages in terms of fuel efficiency, emissions, reliability, and maintenance.
Navigation system: This is the system that enables the ship to navigate safely and accurately in various sea conditions. It consists of various components such as radar, global positioning system (GPS), automatic identification system (AIS), electronic chart display and information system (ECDIS), gyrocompasses, ec8f644aee