Development and Construction of large-capacity Full containment LNG tank
Large-capacity full containment LNG tanks which is originally developed by Osaka Gas offer a high level of safety as well as a substantial cost reduction achieved through efficient use of premises and economies of scale from capacity increases.
The highly safe full containment LNG tank comprises an inner tank made of 9 % nickel steel and a prestresssed concrete outer tank.
The outer tank concrete is induced compressive strength in advance, hence the outer tank by pre-stressed resists tensile force resulting from liquid pressure generated in the event of an LNG leak.
- 1. High level of safety with reinforced secondary container
A highly safe LNG tank consists of inner made of 9% nickel steel and Prestressed concrete outer tank.
- 2. Efficient land use as well as Realization of increasing capacity
Elimination of the need for a space between the LNG tank and dike results in an increased land use efficiency, requiring no land area expansion when increasing the tank size.
For example, Osaka Gas has a 180,000 m3 full containment LNG tank, built on a site with the same area as that of a conventional 75,000 m3 double-walled metal LNG tank. This is a remarkable 2.5-fold improvement in land use efficiency.
- 3. Cost effectiveness with streamlined structure
The inner tank and the outer tank share the base.
- 1. Inner tank
LNG is stored in the inner tank, which is an earthquake resisting flat-bottom, cylindrical, vertical tank provided with a dome roof. The inner tank is made of 9% nickel steel, which exhibits excellent strength and toughness at a cryogenic temperature of −160℃.
- 2. Insulation
LNG evaporation is retarded by insulation, which is granular perlite filling the anular space. Nitrogen gas is sealed into the space for moisture prevention. Insulation with sufficient strength is placed on the bottom to support the inner tank.
- 3. Outer tank roof and liner
The side steel liner and bottom steel liner are affixed on the outer tank and base slabs respectively in order to hold the insulation and seals nitrogen gas. The domed outer tank roof is supported at the top of the outer tank.
- 4. Prestressed concrete outer tank
The outer tank is made of pre-stressed concrete. Pre-stressing steel placed along circumferential and vertical directions apply a compressing force to the concrete. This design is intended to make the structure liquid-tight in the event of an LNG leak resulting in the application of liquid pressure to the outer tank.
- 5. Cold resistance relief (PUF)
The outer tank has a polyurethane foam (PUF) material on its inner surfaces. This PUF material works as a cold resistance relief material in the event of an LNG leak from the inner tank.
- 6. Base slab
The base slab, made of reinforced concrete, is supported by steel pipe piles driven into the bearing stratum.
- 7. Bottom heater
The tank bottom is maintained at a predetermined temperature by a brine heater placed in the base slab to prevent the ground from freezing.
Osaka Gas's world-leading technology for large-capacity full containment LNG tank
- 1. Japan's first Full Containment LNG tank, world's largest (180,000 m3) (at time of construction)
Osaka Gas has developed the Full Containment LNG tank as a safe and reliable tank that features a novel structure, while aiming to increase LNG tank capacity with efficient land use and construction cost reduction in mind. In 1993, we constructed Japan's first Full Containment LNG tank with 140,000 m3 capacity, which was the world's largest (at that time).
In 2000, Osaka Gas constructed another Full Containment LNG tank with additionally increased capacity of 180,000 m3 (the world's largest at that time).
- 2. Streamlined technology for reductions in construction cost and period
Osaka Gas acquired Full Containment LNG tank technology through the development, construction and operation. Using this know-how as a basis, we have achieved further reductions in Full Containment LNG tank construction cost and period by introducing and/or developing the latest design and construction technologies.
Additional development/commercialization of novel technologies
Osaka Gas continues developing and commercializing novel technologies to promote evolution of the Full Containment LNG tank technology.
- 1. Development and commercialization of new material 7% nickel TMCP steel
9% nickel steel has been used for some 40 years as inner tank material of LNG tanks. To reduce the nickel content for material cost reductions and to conserve important resources on the earth, since nickel is a rare metal, Osaka Gas has developed as a novel material 7% nickel TMCP steel. This steel is made through a computer controlled advanced process known as Thermo Mechanical Control Process (TMCP). Use of the 7% nickel TMCP steel has been approved by the government for use in Osaka Gas's LNG tanks.
- 2. Further efforts for increasing tank capacity (to 230,000 m3) and reducing construction cost and period
Based on the Osaka Gas's knowledge and experience regarding LNG tanks, we have been studying the possibilities of increasing tank capacity (to 230,000 m3) as well as reducing construction cost and period without compromising safety.