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Why robust cargo containment system is a must for FLNG


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Why robust cargo containment system is a must for FLNG

  1. 1. Why robust cargo containment system is a must for FLNG Running a successful FLNG project entails a whole host of factors that include determining risks and preparing mitigating strategies to reduce, if not, totally avoid those risks. IQPC’s Darwin Jayson Mariano recently spoke to Okada Tetsuo, Structural Engineering General Manager at Japan Marine United Corporation (JMU), a leading company in the shipbuilding industry, to get some insights with regard to this issue. The discussion also touched on interesting technologies in FLNG as well as Asia’s role in the future development of the industry. What are the most common risks associated with FLNG projects? Pls share some details. There are varieties of risks associated with the operation of FLNG projects, but what we see as most important from the point of view of engineering on cargo containment system are the risks in association with cargo liquid sloshing and collision by other ships. Sloshing is, as you know, is a phenomenon where the fluid movement in the tank resonates with the ship motion and creates an impact force between the free surface of the fluid and the tank structure. This is a very dangerous phenomenon, and to date, many damages due to sloshing have been reported for LNG membrane cargo containment systems, but what was most devastating may be the explosion and fire accident of onshore oil tanks, caused by the Tokachi-oki Earthquake that hit northern Japan in 2003. In that case, large-amplitude long-period ground motion of the earthquake generated severe sloshing of oil in the tank, and then caused the sinking of floating roofs and fires. In case of LNG carriers, such dangerous situation can be controlled to some extent by limiting the liquid filling level to nearly full or nearly empty, prohibiting intermediate level. However, in case of FLNG operation, intermediate liquid level is inevitable, thus sloshing is more important than for LNG carriers. It is known that as long as the resonance can be avoided, the liquid motion in the tank can be well controlled, and that small
  2. 2. “ tanks have small natural period of the internal liquid, sufficiently apart from that of ship motion. I consider that it is essential to apply sufficiently small tanks both in longitudinal and athwartship direction, or to divide the tank by swash bulkhead internally so that each compartment is small enough. This is a very natural engineering solution, conventional and established way against sloshing in marine field so far, applied to almost all ships carrying bulk liquids including oil tankers. Another risk associated with FLNG operation is collision by other ships. In the worst case, it may lead to the flooding of hold space. Subsequent to such an undesirable event, it is quite important to avoid secondary disaster, such as total loss of LNG, fires, cryogenic brittle fracture of the hull structure, and so on. Key words to realize this would be sufficiently robust cargo containment system and emergency cargo transfer. Knowing these risks, what other risk mitigation strategies do you employ? How effective are they in your opinion? I have almost answered this question in the previous question, but I would like to stress that as long as IHI-SPB cargo containment system is employed, it can effectively avoid sloshing problems by arrangement of internal structures, and the cargo tank structures can be designed robust enough to withstand external loads from cargo hold flooding, giving chance for the LNG in the flooded compartment to be safely transferred into other tanks. What we see as most important from the point of view of engineering on cargo containment system are the risks associated with cargo liquid sloshing and collision by other ships. What interesting technologies or innovations do you see lately in the FLNG field? How will it affect the industry? One of the areas that I am interested in is the fabrication technology of aluminum structures. In recent years, many research and development activities and even investments to actual construction lines are observed, including friction stir welding and many varieties of welding robots. I think that these activities and investments will contribute to supply more costeffective aluminum tanks of better quality. What are the yet to be explored opportunities in the FLNG sector? As you know, LNG is becoming more and more important, because of worldwide trend to reduce emission and keep environment, skyrocketing of energy prices, and so on, leading to development of smaller, deep water and far offshore gas field, which did not pay to the investment formerly. Development of FLNG capable of efficient operation in many varieties of harsh environment will open new opportunities. ” What role will Asia be playing in the future development of the industry? Asia is now one of the most active areas in the world in various aspects such as LNG consumption, engineering and construction of FLNG projects and gas production. Asian demand for LNG will double within a decade. To absorb such strong demand, faster development of FLNG is expected, and Asian countries will be able to contribute to this supply, using engineering and construction capability in Japan, Korea and China. Learn more about the latest progress from ongoing and upcoming floating LNG projects at the 10th Annual FLNG Asia Pacific Summit | 2526 June 2013 | Singapore To find out more, visit