US 3613932 A
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United States Patent  Inventor Katsuro Yamamoto Tokyo, Japan [211 App]. No. 29,139  Filed Apr. 16, 1970  Patented Oct. 19, 1971  Assignee Bridgestone Liquefied Gas Company Limited Tokyo, Japan  Priority May 1, 1969  Japan [31 1 44/33395  LOW-TEMPERATURE LIQUEFIED GAS STORAGE EQUIPMENT 5 Claims, 6 Drawing Figs.
 U.S. Cl 220/9 LG,
1 14/74 A  Int. Cl B65d 25/18  Field of Search ..220/9 LG, 9 F; 114/74 A; 62/45  References Cited UNITED STATES PATENTS 3,309,418 6/1962 Versluis 220/9 LG X 3,085,708 4/1963 Dosker 220/9 LG 3, 1 o,7i i961 *smare'igzrzm..;..;1 526/511; 3,272,373 9/1966 Alleaume et al 220/9 LG FORElGN PATENTS 191,538 9/1964 Sweden 220/9 LG Primary Examiner-Joseph R. Leclair Assistant Examiner-James R. Garrett Attorneys-Robert E. Burns and Emmanuel J. Lobato ABSTRACT: A storage tank and tanker for storage of lowtemperature liquids such as liquefied gases. The tank is constructed as an inner container or vessel made of flexible metallic material supported or contained in an outer vessel or tank provided with a thermal insulation lining. The inner tank has its walls joined by elongated areas of jointure which are arcuate in cross section defining rounded edges of the tanks. The corners of the inner tank each have a configuration of a portion of a sphere and the arcuate areas of jointure join the corners to the walls merging therewith smoothly. The outer tank is rigid and has a lining interiorly thereof made of a rigid thermal insulation material provided with four recesses in the lining of the bottom of the tank. The recesses are spanned by the bottom of the inner tank when it is free of a cold liquid and when it is loaded or filled the four comers are received in tion of the inner tank without concentration of stresses,
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LOW-TEMPERATURE LIQUEFIED GAS STORAGE EQUIPMENT This invention relates to storage tanks for low-temperature liquids obtained by liquefaction of gases such as methane, oxygen, ammonia, etc. that are gaseous at ordinary temperatures, and more particularly to a low-temperature liquefied gas storage and transport tanker.
Customarily, liquid gas storage tanks have an inner vessel made of a thin metallic film constructed to allow deformation movement of the inner vessel that arises due to changes of temperature and load. However, each edge section of the inner vessel, for example cylindrical section or arcuate section where two side walls of the inner vessel meet together or a hemispherical corner where two side walls and a bottom wall meet together, each has considerably high rigidity. Furthermore, not only the radii of curvature of the cylindrical section at the edges and spherical surfaces at the corners but also other plane parts contract when undergoing a change from a no-load condition at ordinary temperature to the no-load condition at low temperature (the condition when an introduction of a low-temperature liquefied gas has begun). Therefore, the walls of the inner vessel are forced by the action of internal pressure to undergo a complicated deformation when the inner vessel continues to undergo the subsequent change of a loaded condition at low temperature (the condition when the inner vessel is filled with a low-temperature liquefied gas).
However, the radii of curvature of the parts at the four corners of the inner vessel which have the configuration of a portion of a sphere cannot change to a great extent because of their high rigidity. And, in addition, the edges of the inner vessel, though stretched out to increase their radii of curvature, show a high resistance in a longitudinal direction. Therefore, the vertical rounded edges, particularly those at the four corners of the inner vessel, together with the lower corners offer a resistance, as if they were columns, so that free deformation of other surfaces of the inner vessel is prevented and results in a stress concentration or, conversely, buckling on these rounded edges themselves.
An object of this invention is to solve the above problems inherent in the conventional storage tanks and to provide a low-temperature liquefied gas storage tank that can avoid damage due to concentration of stresses by making the wall of the inner vessel have a natural deformation under a loaded condition at low temperatures.
Therefore, a feature of the storage tank according to this invention is that it consists of a flexible inner vessel made of a low temperature resisting metallic material comprising twodimensionally curved or rounded edges, three-dimensionally curved solid angle corners and sidewalls or surfaces connected to them and a rigid outer vessel that is outside the inner vessel. The outer vessel has a heat insulating layer of a compressive strength, which has four spaced recesses to accommodate the corners at the bottom of the inner vessel when in a loaded condition at low temperature.
In the above-mentioned storage container according to this invention, the whole flexible inner vessel, which is supported by the heat insulating layer or lining of the outer vessel, can be deformed naturally without causing stress concentration at such parts as its cylindrical or rounded edges, etc., since the three-dimensionally curved solid angle corners at its bottom fit into the recesses formed in the heat insulating layer. The corners are received in the recesses when the inner vessel undergoes a change from an expanded condition, under no-load at ordinary temperature, to a deformed condition under load at low temperature, a contracted condition under no-load at low temperature.
For a better understanding of this invention, reference will be made to the accompanying drawings relative to an embodiment of this invention applied to a tanker for transportation of low temperature liquefied. gas in which:
FIG. I is a fragmentary horizontal sectional view of a part of a tanker provided with a compartment accordingto the invention;
FIG. 2 is a fragmentary enlarged sectional view taken along a section line Il--Il of FIG. 1;
FIG. 3 is a fragmentary enlarged sectional view along a section line III--IIl of FIG. 1;
FIG. 4 is a perspective drawing of an inner vessel forming a part of the storage container according to the invention;
FIG. 5 is a fragmentary enlarged section view of a part A of FIG. 2; and
FIG. 6 is a fragmentary elevation view of a sidewall of the inner vessel of FIG. 4.
While the invention will be described as applied to a tanker, to those skilled in the art-it is apparent that the invention is applicable to a storage tank for storing liquefied gases. The invention will be described as a tank or compartment of a tanker.
Referring more particularly to the drawings, as shown in FIGS. 1 and 2, a hull 1 of a tanker is provided with an inner vessel 3 made of such a low temperature resistant material as nickel steel or stainless steel thin plates and is installed within the double hull 1 that serves as a rigid outer vessel. A heat insulating layer 2, made for example of a material having a compression resisting property such as a hard foamed polyurethane, lines the bull or outer vessel or tank and is placed between the inner vessel 3 and the double hull 1.
The inner vessel 3, as shown in FIG. 4, consists of almost flat surfaces or sidewalls 3a, cylindrical or arcuate elongated portions or areas defining edges 3b and comers 3c. The thickness of the inner vessel is such that it maintains its flexibility as a whole.
As illustrated in FIG. 1, the heat insulating layer 2 supports the inner vessel 3 and has four recesses 2a at the four corners thereof to accommodate the corresponding solid angle corners 3c at the bottom of the inner vessel in the loaded condition at a low temperature. The surface of every recess 20, as shown in FIG. 3, merges smoothly with the surface of the heat insulating layer 2 that supports other parts of the bottom wall of the inner vessel 3. The recesses 2a are defined by surfaces converging in a direction toward the respective corner of the outer hull or tank to define an area of maximum depth of each recess. The outer or outboard boundaries of the recesses are defined by rounded surfaces which are inboard and spaced from the lining of the bulkheads of the hull, it being understood that these bulkheads are equivalent to the sidewalls of a tank. These rounded surfaces merge smoothly with a rounded surface defining the area of maximum depth of each recess.
At about the center of a top plate of the inner vessel is fitted a gastight lower flange of a rigid access trunk 5 reinforced with brackets 4, and the upper and lower flanges of the same rigid trunk 5 are also firmly fitted and secured to the double hull 1 serving as the outer vessel through supports 6 and 7 made of a heat insulating material. Between the hull l and the trunk Sis disposed a heat insulating annulus 8 to form a construction that prevents the coldness within the inner vessel from exerting a direct influence upon the hull.
Entry of the cargo and gas pipes, etc. entering into the inner vessel 3 is all made through the trunk 5 whose opening is closed with a gastight cover, not illustrated, which is pierced by such pipes.
As seen from a sectional view along the section line II--ll in FIG. I, that is, a sectional view across the edge of the inner vessel 3, the vessel originally in a no-load condition at ordinary temperature is shown by a solid line in FIG. 2. When the introduction of a low-temperature liquefied gas starts, the inner vessel 3 undergoes thermal contraction centering around the part fitted with the trunk 5, and gets deformed into the low temperature no-load condition shown by dot-dash line 3'. As the introduction of a low temperature liquefied gas continues, the internal pressure stretches the inner tank edges along a dotted line 3" indicative of loaded condition at low temperature, then the bottom of the inner vessel, with an exception of the solid angle corners, becomes supported by the hull l, and the compression resistant heat insulating layer 2, as a result of the descending of the sidewall of the inner vessel.
As to this point, more detailed explanation will be given in connection with FIG. 5. Point a on the sidewall of the inner vessel 3 in the no-load condition at ordinary temperature moves to point a in the no-load condition at low temperature, and further to point a", through the stretching of the edges, in the loaded condition at low temperature. This means that the sidewall of the inner vessel descends from point a to point a" by a length of b, which brings the cylindrical or rounded edge 3b at the bottom of the inner vessel close to the heat insulating layer 2. On the other hand, however, no such descending of the sidewall as mentioned above takes place in the hemispherical corner 30 where the internal pressure exerted on the wall cannot produce any extensive stretching because of considerably high rigidity. Therefore, the sidewall as a whole descends in such a manner, as shown in FIG. 6.
Now, assume that a horizontal line cd is drawn on the sidewall in the no-load condition at ordinary temperature. The greater part of this horizontal line corresponding to the edge 3b descends by a length or distance of b to form a horizontal line ef. But, at points and d, it hardly descends and remains in the original position, since the comer 30 does not stretch as described above. Thus, the horizontal line ca is forced to assume a form of a curve cefd. However, as the fiat sidewall cannot undergo such a deformation, while remaining flat, there will occur some bucklings near two points e and f or on the cylindrical edges extending vertically from the solid angle corner 3c. This invention can avoid the occurrence of such a phenomenon, thus enabling the inner vessel to undergo a deformation without strain.
As seen in a sectional view along a section line Ill-Ill in FIG. 1, that is, a sectional view across the solid angle corner at the bottom of the inner vessel 3, the inner vessel originally in the no-load condition at ordinary temperature shown by a solid line in FIG. 3 undergoes thermal contraction and gets deformed in the no-load condition at low temperature shown by the dot-dash line 3'. As more low temperature liquefied gas is filled in, although the solid angle corners 3'0 cannot be stretched out extensively even under the internal pressure because of their considerably high rigidity and the edges lying above show a strong resistance in the vertical direction, each solid angle comer 3's moves downwardly to 3"c, as shown by a dotted line, with the descending of the sidewall and fits into a corresponding recess 2a formed in the heat insulating layer 2. This enables the whole wall of the inner vessel to have a natural deformation movement, sufficiently preventing the concentration of stresses as well as the occurrence of bucklings particularly on the edges.
As described above, the flexible inner vessel of the low temperature liquefied gas storage tank or container according to the invention can be deformed naturally even in the loaded condition at low temperature and supported in a very rational manner by the rigid outer vessel through the compression resistant heat insulating layer.
What I claim and desire to secure by letters patent is:
l. A storage container for storage of a low-temperature liquid such as a low-temperature liquefied gas comprising, an inner vessel of flexible metallic material having four sidewalls, at least four lower comers each having a configuration of a portion of a sphere and elongated areas of jointure joining the adjacent vertical edges of the four sidewalls and the edges of a bottom to the lower edges of the sidewalls, said areas of jointure each having an arcuate cross section and each defining an arcuate edge of said container merging smoothly with respective ones of said lower four comers, outer support means supporting the bottom and sidewalls of said inner vessel in a loaded condition, said outer support means being defined by an outer vessel having an inner surface defining a bottom having four recesses in the vicinity of the four bottom comers of said outer vessel spanned by the bottom of said inner vessel in a nonloaded condition and disposed to receive respective lower corners of said inner vessel in a loaded condition with said inner vessel containing a low-temperature liquid contracting the inner vessel, said recesses each increasing in depth in a direction outwardly toward a corresponding corner of the outer vessel and each defined by surfaces converging toward comers of said outer vessel, and each recess having rounded outermost side surfaces converging smoothly with a rounded surface at an area of greatest depth of each recess.
2. A storage container for a low-temperature liquid according to claim 1, in which said inner vessel comprises a top having an access trunk providing access to the interior of the inner vessel.
3. A storage container for a low-temperature liquid according to claim 1, in which said outer vessel is provided with an insulating inner lining, and in which said recesses are defined by said inner lining.
4. A storage container for a low-temperature liquid according to claim 1, in which said inner vessel comprises a tank having a top provided with a trunk, and in which said outer vessel comprises an outer tank having a thermal insulation lining defining said recesses.
5. A storage container for storage of a low-temperature liquid according to claim 1, in which said thennal insulation comprises a rigid foamed polyurethane.