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Tank dismantling procedure

Apr 12, 2018



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    Hiroshi Nishigami

    Maki Yamashita

    Shunsuke Ohnishi

    Nobuhiro Wadama

    Osaka Gas Co., Ltd

    Hiroto Yamaoka

    Tatsuo Tsuji, Yu Murakami

    IHI Corporation

    Takehiro Inoue

    Naoki Saito

    Motohiro Okushima

    Nippon Steel & Sumitomo Metal Co., Ltd

    KEYWORDS: aboveground LNG storage tank, aging research, dismantling method]


    In 2011, Osaka Gas commenced the dismantlement of two aboveground LNG storage tanks with a storage

    capacity of 45,000 m3 each at the Senboku 1 terminal. The said LNG storage tanks had been in commercial

    operation for approximately 40 years, and were the first to be dismantled in Japan. Concurrent with the

    dismantlement of the said LNG storage tanks, Osaka Gas also began the research on the deterioration due to

    their aging. Aging evaluation of the said LNG storage tanks will contribute to the LNG industry by not only

    potentially increasing its lifetime, but by improving its functions and safety as well. In this paper, the method of

    dismantling and the research results with regard to the aging for the two types of LNG storage tanks,

    respectively made of 9% Nickel steel and Aluminum alloy are reported. The contents of the research will be of

    the following criteria: (1) Mechanical properties of 9%Ni steel and Aluminum alloy (2) Thickness of steel pipe

    piles (3) Deterioration of instrument devices (4) Deterioration of insulation materials. After dismantling of the

    said LNG storage tanks, Osaka Gas decided to construct a large scale LNG storage tank applying newly

    developed 7% Ni-TMCP steel for its inner tank. The storage capacity of the new LNG storage tank will be

    230,000m3, and is scheduled to be completed by November, 2015. The present state of the construction of the

    innovative LNG storage tank will be reported in this paper as well.


    In 1972, IHI Corporation (IHI) built three LNG storage tanks

    with capacities of 45,000m3in Osaka Gas Co., Ltd (Osaka Gas)

    Senboku I Terminal. Since then, the tanks, which were of the

    single containment type with double steel walls, had been

    successfully operated without any trouble for 40 years. However,

    the conventional LNG storage tanks were getting more

    inefficient in the use of receiving terminal because of its lower

    dike in comparison with the state-of-the-art full-containment

    LNG storage tanks. (Figure1)

    Figure 1. One of the demolished

    LNG storage tanks

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    To keep up with the increasing demand for LNG and for effective practical use, Osaka Gas started to demolish

    the two conventional LNG storage tanks in 2011, and now a large LNG storage tank of 230,000m3has been

    under construction since September 2012.

    Demolition of old LNG storage tanks was executed with paying sufficient attention to the safety in consideration

    of the influences on the other facilities in operation and neighboring companies. Then, Osaka Gas investigated

    the demolished LNG inner tanks material and its thermal insulation material jointly with IHI as the constructor

    and Nippon Steel & Sumitomo Metal Co., LTD (NSSMC) as the supplier of tanks steel products. Moreover, we

    examined the steel pipe piles and the instrumentation devices from Osaka Gass own point of view. This paper

    describes the study on dismantling method of LNG storage tanks, the results of the investigations, and also

    reports on the new material used for the LNG storage tank under construction.

    Investigation items:

    1) Base metal mechanical properties (chemical composition / macro-micro structure / tensile strength /

    Charpy absorbed energy / retained austenite)

    2) Weld metal mechanical properties (chemical composition / macro-micro structure / tensile strength /Charpy absorbed energy)

    3) Fracture toughness properties (CTOD test / duplex ESSO test / wide plate test)

    4) Corrosion of foundation piles (steel pipe piles)

    5) Deterioration of concrete

    6) Deterioration of instrumentation devices

    7) Deterioration of thermal insulation material


    2.1 Specification of the tanks

    Table 2.1 and Figure 2.1 show the specifications of the two demolished tanks.

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    Table 2.1 Specification of the tanks

    1 Internal liquid LNG

    2 Capacity 45,000KL

    3 Type single containment type with double steel walls


    Dimensions inner tank outer tank

    Diameter 44,600mm 46,400mm

    Height 28,820mm 31,850mm

    Roof radius 35,700mm 36,600mm

    5 Design temp. -162 ambient temp.

    6 Design pressure 0.12kg/cm2 50mmH2O

    7 Main material 9%Ni steel(Al alloy) carbon steel

    8 Insulation perlite & perlite concrete

    9 Thickness of insulation

    tank shell & roof; 900mm

    tank bottom ;1,100mm

    10 Foundation slabreinforced concrete

    diameter :44,600mm thickness ;800mm

    11 Dike

    reinforced concrete

    height :4,000mm(3,000mm from the ground)

    thickness ; 1,400mm

    12 Earthquake historyground surface acceleration;


    13 Commercial operation Feb.1972.

    Note; ( ) shows Al alloy tank

    Figure 2.1 Configuration of the demolished LNG storage tank

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    2.2 Dismantling procedure

    The LNG tanks were demolished through the following procedure in Figure 2.2.

    Step 2 Perlite extraction from the annular space Step 4 Removal of the outer tank roof

    Step 6 Removal of the outer tank shell plate Step 7 Removal of the inner tank shell plate

    Figure 2.2. Dismantling procedure

    (1) Since the tank structure changes at every step during the tank dismantling, the dismantling steps should

    be observed by FEM analysis, ABAQUS. Figure2.3 shows some examples of the results by the analysis.

    (2) The tanks were dismantled by 150 tons cranes.

    (3) Perlite was removed by a new extraction machine.

    (4) Some samples for the study were taken before the tank dismantling.

    1. Setting of entering road into the dike

    2. Perlite extraction from the annular space

    3. Removal of the pipe, pipe frame etc.

    4. Removal of the outer tank roof

    5. Removal of the inner tank roof

    6. Removal of the outer tank shell plate

    7. Removal of the inner tank shell plate

    8. Removal of the outer tank bottom plate

    & bottom insulation

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    Figure 2.3. The examples ofthe strain diagram


    3.1 Visual inspection

    3.1.1 Inner tank

    K11 tank (9% Ni steel) and K31 tank (AL alloy) were found to be in good condition. No damages and buckling

    were detected due to the Hanshin Awaji Great Earthquake in 1995. There was no influence on the soundness

    of the tank. There was no damage to the instrumentation devices (level gauge, thermometer) installed in the


    3.1.2 Outer tank(a) Manhole for perlite filling

    Some corrosion was found at the blind flange of perlite manhole. The doubling plate and the root of the

    manhole were also corroded.

    (b) Outer tank roof plate and shell plate

    Some corrosion was seen at the welding seam. It is estimated that the repair painting had not been done


    (c) Roof walkway

    Corrosion was seen just right under the protecting seal due to the deterioration of it. In addition, corrosion was

    found at checker plate of walkway.

    (d) Anchor bolt

    Some anchor bolts especially under the pipe rack were corroded. After removing a weather seal, the surface of

    several bolts were corroded and decreased its thickness.

    (e) Inner tank anchor strap

    As a result of the investigation, the conspicuous deterioration, damage, deformation and corrosion were not

    seen. The reason of these phenomena was that the annular space had been filled with nitrogen since the time

    of the construction.

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    3.2.1 Base Metal of Inner Tank

    Table 3.1 shows sampling parts and investigation items of each tank. Details are given as follows.

    Table 3.1. Sampling Parts and Tests (Base Metal)

    Tank Sampling Part




    Tensile TestCharpy

    Impact TestCTOD Test






    1st Course - - -

    13th Course - - -

    Annular Plate - - - -

    Bottom Plate - - - -



    1st Course

    13th Course - -

    Annular Plate - - - -

    Bottom Plate - - - -

    (a) Chemical Compositions of Base Metal

    Chemical analyses were carried out on representative samples taken from the 1st and 13th shell courses andannular bottom plate of each tank. Table 3.2 shows the results of K31 tank (made by aluminum alloy), and

    Table 3.3 shows that of K11 tank (made by 9%Ni steel).

    Table 3.2. Chemical Composition (A5083 Base Metal)


    PartSi Fe Cu Mn Mg Zn Cr Ti B

    Shell Plate

    1st Course0.08 0.10 0.01 0.67 4.51

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    (b) Tensile Properties

    Tensile tests were carried out by using specimens: a full thickness specimen in accordance with JIS Z 2201

    No.1A. The tests were performed in both the L an

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