Gas
Material, Processing and Power Technologies
Development and Construction of Large capacity Full containment LNG tank
Engineering Dept.
Concept of Full Containment LNG TankbFeatures of Full Containment LNG tankbStructure of Full containment LNG tankbOur world leading technologies for large-capacity Full containment LNG tankbLatest developed technologies
Our large-capacity Full Containment LNG storage tank has high safety together with effective use of the site area and significant cost-reduction which is achieved by advantage of scale.
Concept of Full Containment LNG Tank
Full containment LNG tank has high safety which is realized by comprising two independent tanks, i.e., a double-walled metal tank and a prestressed concrete wall.
¦What is PC?
PC is an abbreviation of Prestressed Concrete. Prestressing force along the wall provides the resistant force against the tensile force generated by liquid pressure in case of LNG leakage.
Features of Full Containment LNG tank
- High safety (Reinforced secondary container)
The outer PC wall is a secondary container which is designed to contain leaked LNG and limit the hazard area in case of the leakage from the inner tank, which contribute to the high safety. - Efficient land use (Realizing large capacity)
No dike space is required which enable to increase the tank size by fully utilizing the site area.
For example, the site area for our 180,000 m3 Full containment tank is the same for a conventional 75,000 m3 double-walled metal tank. This means the LNG storage capacity per land area has significantly increased by 2.5 times. - Economic advantage (Streamlined design structure)
Full containment LNG tank has streamlined design structure which leads to economic advantage, i.e., a common foundation both for the inner tank and the outer tank, a steel liner integrated with PC outer tank rather than self-standing , and so on.
Structure of Full containment LNG tank
- Inner tank
The inner tank which directly contains LNG is designed to cope with severe earthquake conditions. It consists of a flat-bottom, cylindrical and free-standing wall, and a dome roof. 9% nickel steel is used as the material which has excellent strength and toughness at cryogenic temperature. - Insulation
The space between inner and outer tank of shell and roof is filled with granular perlite to suppress boil-off gas and purged with nitrogen gas in order to prevent the perlite from dampening. There is also a bottom insulation which has sufficient compressive strength to support the inner tank. - Outer roof and Steel liner
Steel liner is placed on the internal surface of the PC wall and on bottom slab which seals the nitrogen gas. The outer tank roof supported at the top of the PC wall forms a double dome structure together with the inner tank roof. - PC outer wall
Prestressed Concrete (PC) is used for the outer tank, where compressing force is applied along circumferential and vertical directions by prestressing steels which work as opposing force against liquid pressure in case of LNG leakage. - Cold resistance relief (PUF)
Poly-urethane form (PUF), a cold resistance relief material, is set up inside the PC wall to relieve thermal stress in case of LNG leakage. - Base slab
Base slab is made of reinforced concrete, and is supported by steel pipe piles driven into the bearing stratum. - Bottom heater
Bottom heating system is provided in the base slab in order to prevent the ground from freezing. Brine is used for the heating medium.
Our world leading technologies for large-capacity Full containment LNG tank
- The Japanfs first and the World largest(180,000 m3, at that time) Full containment LNG tank
Aiming at efficient use of site area and construction cost reduction, we have been developed full containment LNG tank as a new-type and larger yet safe and reliable tank. In 1993, we constructed 140,000 m3 tank as the Japan’s first full containment LNG tank and the world largest (at that time). Furthermore, In 2000, the world largest (at that time) full containment tank with 180,000 m3 capacity was successfully constructed. - Streamlined design structure which enables reduction in construction cost and period
Further reduction in construction cost and period has become possible by the latest technologies for design and construction based on our R&D and a number of experiences in construction and operation.
Latest developed technologies
We continue developing new technologies to increase Full containment LNG tank advantages.
- Development of new material: 7% Ni-TMCP steel
9% Ni (Nickel) steel has been used for about 40 years for inner tank. For further cost reduction, we have been investing the possibility of 7% Ni-TMCP (Thermo Mechanical Control Process) steel, where the reduction of Ni, a rare metal, content can be achieved. This technology is already established and will be commercially available soon. - Increasing capacity (above 200,000 m3) and reducing cost
As the design safety factor for LNG tank was revised in 2008 in Japan, we have been investigating the possibility of further larger capacity (to above 200,000 m3) and cost reduction based on our experiences without compromising the reliability.
