Title of Invention

"A CORNER PIECE MEMBRANE UNIT FOR LIQUID NATURAL GAS STORAGE TANKS".

Abstract

A corner piece membrane unit for LNG storage tanks is disclosed. In an embodiment of this invention, the corner piece membrane unit consists of a horizontal panel part and a vertical panel part integrated into a single membrane unit by an inclined panel part having an inclination angle of 45°. Two outer corrugations axially, parallely and symmetrically extend on the three panel parts at both sides of the membrane unit while being bent at an inclination angle of 45° on the inclined panel part, with both ends of each outer corrugation being respectively positioned on the horizontal and vertical panel parts. A central corrugation axially and centrally extends from each outside end of the horizontal and vertical panel parts toward the inclined panel part until it is partially overlapped with the ends of the two outer corrugations. The above corner piece membrane unit allows an LNG storage tank to safely store cryogenic LNG having a temperature of -162°C while effectively expanding and contracting in response to a liquid pressure of the cryogenic LNG and/or a temperature stress applied from the cryogenic LNG.

Full Text

CORNER PIECE MEMBRANE UNIT FOR LIQUID NATURAL GAS STORAGE TANKS BACKGROUND OF THE INVENTION Field of the Invention The present invention relates, in general, to a corner view membrane unit for LNG (liquid natural gas) storage tanks and, more particularly, to a corner piece membrane unit having an improved structure effectively accomplishing a desired sealing effect at the corners of such an LNG storage tank. Description of the Prior Art As well known to those skilled in the art, it is necessary to provide a plurality of important membrane elements while designing LNG storage tanks. Such important membrane elements include a basic panel membrane unit, a corner piece membrane unit, a cap piece and a connection piece. Of the above elements, the basic panel membrane unit is interiorly installed on the sidewall and bottom of an LNG storage tank, while the corner piece membrane unit smoothly connects the sidewall and the bottom wall of the tank together, thus forming a sealed tank. The cap piece is used for closing the end of a linear corrugate of the basic panel membrane unit. On the other hand, the connection piece. 1 connects curved portions, left on the bottom wall of the tank by a divergence of the linear corrugations of the basic panel membrane units on the bottom wall, to each other. As shown in Figs. 1 and 2, the corner piece membrane unit is necessarily used for connecting the ring joint type basic panel membrane units, interiorly attached on the sidewall and bottom wall of an LNG storage tank, to each other, thus allowing the tank to safely store cryogenic LNG having a temperature of -162°C. Such corner piece membrane units, used for connecting the corners of the tank while forming right angular corners, has to be designed to effectively expand and contract in response to the liquid pressure of the cryogenic LNG and/or the temperature stress applied from the cryogenic LNG while accomplishing a desired sealing effect resisting an LNG leakage from the corners. In an LNG storage tank, the corners having the corner piece membrane units are the portions to which a hydraulic static load is most intensively applied. It is thus necessary to assemble the corner piece membrane units, with reinforcing plates being positioned between the corner piece membrane units and the PC concrete structure so as to accomplish a desired structural strength. However, the conventional corner piece membrane unit of Fig. 1 is formed with a single corrugation being bent at an angle of 90°. Such an acutely bent portion of the corrugation 2 of the corner piece membrane unit may be thus undesirably affected by a stress concentration and may be easily damaged by fatigue load. Fig. 2 is a perspective view of a corner piece membrane unit according to another embodiment of the prior art. In the membrane unit of Fig. 2, two panels are positioned abreast prior to being welded together at their top ends through a buildup welding process, thus being allowed to easily perform a strain behavior in a circumferential direction. However, the wqldinq process complicates the process of producing the corner piece membrane units and may easily result in a structural defect at the welded junctions. Therefore, the corner piece membrane unit of Fig. 2 more easily leaks LNG in comparison with other conventional corner piece membrane units and is less likely to smoothly perform a strain behavior in a vertical direction. SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a corner piece membrane unit for LNG storage tanks, which consists of a horizontal panel part, a vertical panel part and an inclined panel part having an inclination angle of 45° and integrating 3 the horizontal and vertical panel parts into a single membrane unit, with one central corrugation being axially formed at the center of each end portion of the membrane unit and two outer parallel corrugations parallely extending at both sides of the membrane unit while being commonly and partially overlapped with the inside ends of the two central corrugations, thus preventing stress from being concentrated at the end portions of the membrane unit outside the ends of the two outer parallel corrugations. Another object of the present invention is to provide a corner piece membrane unit for LNG storage tanks, which consists of a horizontal panel part, a vertical panel part and an inclined panel part having an inclination angle of 45° and integrating the horizontal and vertical panel parts into a single membrane unit, with one central corrugation being axially formed along the center of the membrane unit and two outer parallel corrugations parallely extending at both sides of the central corrugation while individually having a length shorter than that of the central corrugation, thus preventing stress from being concentrated at the end portions of the membrane unit outside the ends of the two outer parallel corrugations. A further object of the present invention is to provide a corner piece membrane unit for LNG storage tanks, which consists a vertical and horizontal panel parts individually 4 and symmetrically provided with a central corrugation and an arcuate corrugation, with a longitudinal corrugation extending along a right angularly bent junction between the two panel parts, thus allowing each of the three types of corrugations to be somewhat enlarged in radius of curvature or to be reduced in height when a liquid pressure and/or a temperature stress of cryogenic LNG within an LNG storage tank is applied to the corner piece membrane unit. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a perspective view of a corner piece membrane unit for LMG storage tanks according to an embodiment of the prior art; Fig. 2 is a perspective view of a corner piece membrane unit for LNG storage tanks according to another embodiment of the prior art; Fig. 3 is a perspective view of a corner piece membrane unit for LNG storage tanks in accordance with the prim.ary embodiment of the present invention; Fig. 4 is a perspective view of a corner piece membrane 5 unit for LNG storage tanks in accordance with the second embodiment of the present invention; and Fig. 5 is a perspective view of a corner piece membrane unit for LNG storage tanks in accordance with the third embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 3 is a perspective view of a corner piece membrane unit for LNG storage tanks in accordance with the primary embodiment of this invention. As shown in the drawing, the membrane unit according to the primary embodiment consists of a horizontal panel part A1, a vertical panel part A2 and an inclined panel part A3. The inclined panel part A3 has an inclination angle of 45° and integrates the horizontal and vertical panel parts Al and A2 into a single membrane unit. Two outer parallel corrugations 10 parallely and symmetrically extend on the three panel parts Al, A2 and A3 at both sides of the membrane unit while being bent at an inclination angle of 45° on the inclined panel part A3, with both ends 11 of each outer corrugation 10 being respectively positioned on the horizontal and vertical panel parts Al and A2. On the other hand, one central corrugation 12 axially and centrally extends from each outside end of the horizontal and 6 vertical panel parts A1 and A2 toward the inclined panel part A3 until it is partially overlapped with the ends 11 of the two outer corrugations 10. In the above corner piece membrane unit, the two outer corrugations 10 protect the two spaced central corrugations 12, thus allowing the corner piece membrane unit to more effectively expand and contract in response to circumferential strain applied to the membrane unit. In addition, since the corner piece membrane unit of this embodiment is inclined at its corner part at an inclination angle of 45°, it is remarkably improved in operational stability and is more easily and simply installed at the corner within an LNG storage tank in comparison with a conventional corner piece membrane unit bent at an angle of 90°. In the corner piece membrane unit of Fig. 3, the horizontal panel part A1 is brought into contact with the bottom wall of the LNG storage tank, while the vertical panel part A2 comes into contact with the sidewall of the tank. In addition, the two types of corrugations 10 and 12 of the above corner piece membrane unit have the same height. The corrugations 10 and 12 also have a semicircular or polygonal cross-section without affecting the functioning of this invention. Fig. 4 is a perspective view of a corner piece membrane unit for LNG storage tanks in accordance with the second 7 embodiment of this invention. As shown in the drawing, the membrane unit according to the second embodiment consists of a horizontal panel part B1, a vertical panel part B2 and an inclined panel part B3. The inclined panel part B3 has an inclination angle of 45° and integrates the horizontal and vertical panel parts Bl and B2 into a single membrane unit. Two outer parallel corrugations 10' parallely and symmetrically extend on the three panel parts Bl, B2 and B3 at both sides of the membrane unit while being bent at an inclination angle of 45° on the inclined panel part B3, with both ends of each outer corrugation 10' being respectively positioned on the horizontal and vertical panel parts Bl and B2. On the other hand, one central corrugation 12' axially, centrally and continuously extends along a gap between the two outer parallel corrugations 10' from the outside end of the horizontal panel part Bl to the outside end of the vertical panel part B2 while being bent at an inclination angle of 45° on the inclined panel part B3. In the above corner piece membrane unit, the central corrugation 12', which axially, centrally and continuously extends between the outside ends of the horizontal and vertical panel parts Bl and B2, protects the two outer corrugations 10' which do not reach the ends of the horizontal and vertical panel parts Bl and B2. The corner piece membrane 8 unit of the second embodiment effectively performs a desired operational function. That is, the above corner piece membrane unit more effectively expands and contracts in response to circumferential strain applied to the membrane unit. In addition, since the corner piece membrane unit of this embodiment is inclined at its corner part at an inclination angle of .45°, it is remarkably improved in operational stability and is more easily and simply installed at the corner within an LNG storage tank in comparison with a conventional corner piece membrane unit bent at an angle of 90°. In the corner piece membrane unit of Fig. 4, the horizontal panel part Bl is brought into contact with the bottom wall of the LNG storage tank, while the vertical panel part B2 cpmes into contact with the sidewall of the tank. In addition, the two types of corrugations 10' and 12' of the above corner piece membrane unit have the same height. The corrugations 10' and 12' also have a semicircular or polygonal cross-section without affecting the functioning of this invention. Fig. 5 is a perspective view of a corner piece membrane unit for LNG storage tanks in accordance with the third embodiment of this invention. As shown in the drawing, the membrane unit according to the third embodiment consists of a vertical panel part 20 and a horizontal panel part 20'. The 9 vertical panel part 20 is attached to the sidewall of an LNG storage tank. On the other hand, the horizontal panel part 20' is integrated with the vertical panel part 20 into a single membrane unit while meeting each other at an angle of 90° and is attached to the bottom wall of an LNG storage tank. Each of the two panel parts 20 and 20' is provided with an arcuate corrugation 22. A central corrugation 21 linearly extends from the outside end of each panel part 20, 20' toward the middle portion 25a of an associated arcuate corrugation 22. In such a case, a gap is formed between the inside end 23 of each central corrugation 21 and the middle portion 25a of an associated arcuate corrugation 22. A longitudinal corrugation 26 extends along the right-angled junction between the two panel parts 20 and 20'. The above corrugation 26 is corrugated toward the inside corner of the corner piece membrane unit as shown in Fig. 5. In the above corner piece membrane unit, the two panel parts, or the vertical and horizontal panel parts 20 and 20' are individually and symmetrically provided with a central corrugation 21 and an arcuate corrugation 22, with a longitudinal corrugation 2 6 extending along the right anquiariy bent junction between the two panel parts 20 and 20' . The corner piece membrane un i t of the third embediment thus effectively performs a desired operational function. 10 That is, in the corner piece membrane unit of this embodiment, each of the corrugations 21, 22 and 26 may be somewhat enlarged in radius of curvature or may be reduced in height when a liquid pressure and/or a temperature stress of cryogenic LNG within the tank is applied to the corner piece membrane unit. In the above corner piece membrane unit, the longitudinal corrugation 26 is positioned along the corner between the sidewall and bottom wall of the tank. In addition, the central corrugation 21 and the arcuate corrugation of the above corner piece membrane unit have the same height. The three types of corrugations 21, 22 and 26 also have a semicircular or polygonal cross-section without affecting the functioning of this invention. As described above, the present invention provides a corner piece membrane unit for LNG storage tanks. The corner piece membrane unit according to an embodiment of this invention consists of a horizontal panel part and a vertical panel part integrated into a single membrane unit by an inclined panel part having an inclination angle of 45°. Two outer parallel corrugations axially, parallely and symmetrically extend on the three panel parts at both sides of the membrane unit while being bent at an inclination angle of 45° on the inclined panel part. In such a case, both ends of each of the outer parallel corrugations are respectively 11 positioned on the horizontal and vertical panel parts. A central corrugation axially and centrally extends from each outside end of the horizontal and vertical panel parts toward the inclined panel part until it is partially overlapped with the ends of the two outer corrugations. Different from conventional corner piece membrane units, the corner piece membrane unit of this invention allows an LNG storage tank to safely store cryogenic LNG having a temperature of -162°C. The corner piece membrane unit of this invention thus effectively expands and contracts in response to a liquid pressure of the cryogenic LNG and/or a temperature stress applied from the cryogenic LNG while accomplishing a desired sealing effect The corner piece membrane unit o± this invention is also remarkably improved in operational stability and is more easily and simply installed at the corner within an LNG storage tank. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 12 WE CLAIM A corner piece membrane unit for Liquid Nafurai Gas storage tanks having corrugations, characterized in that said corner piece membrane unit for Liquid Natural Gas storage tanks comprising: a horizontal panel part and a vertical panel part integrated into a single membrane unit by an inclined panel part having an inclination angle of 46"; two outer parallel corrugations axialiy, parallely and symmetricaNy extending on said three panel parts at both sides of the membrane unit while being bent at an inclination angle of 45** on the inclined panel part, with both ends of each of the outer parallel corrugations being respectively positioned on the horizontal and vertical panel parts; and a central corrugation axialiy and centrally extending from each outside end of the horizontal and vertical panel parts toward the inclined panel part urrtil it is partially overlapped with the ends of the two outer corrugations. The corner piece membrane unit as claimed in claim 1 wherein said central and outer corrugations have the same height and a semicircular or polygonal cross-section. The corner piece membrane unit as claimed in claim 1, wherein said central corrugation axialiy, centrally and continuously extending along a gap between the two outer parallel corrugations from an outside end of said horizontal panel part to an outside end of said vertical panel part white being bent at an inclination angle of 45** on the inclined panel part. The corner piece membrane unit as claimed in claim 3 wherein said central and outer corrugations have the same height and a semicircular or polygonal cross-section. -13- A comer piece membrane unit for Liquid Natural Gas storage tanics comprising: a vertical panel part and a horizontal panel part integrated into a single membrane unit while meeting each other at an angle of 90°; an arcuate corrugation formed on each of the two panel parts; a central corrugation linearly extending from an outside end of each of said two panel parts toward a middle portion of an associated arcuate corrugation, with a gap being formed between an inside end of the central corrugation and the middle portion of the associated arcuate corrugation; and a longitudinal corrugation extending along a right-angled junction between the two panel parts white being corrugated toward an inside corner of the membrane unit. The corner piece membrane unit as claimed in claim 5, wherein said arcuate corrugation and said central corrugation have the same height, and said arcuate corrugation, said central corrugation and said iongitudinal corrugation have a semicircular or polygonal cross-section. -14- A corner piece membrane unit for LNG storage tanks is disclosed. In an embodiment of this invention, the corner piece membrane unit consists of a horizontal panel part and a vertical panel part integrated into a single membrane unit by an inclined panel part having an inclination angle of 45°. Two outer corrugations axially, parallely and symmetrically extend on the three panel parts at both sides of the membrane unit while being bent at an inclination angle of 45° on the inclined panel part, with both ends of each outer corrugation being respectively positioned on the horizontal and vertical panel parts. A central corrugation axially and centrally extends from each outside end of the horizontal and vertical panel parts toward the inclined panel part until it is partially overlapped with the ends of the two outer corrugations. The above corner piece membrane unit allows an LNG storage tank to safely store cryogenic LNG having a temperature of -162°C while effectively expanding and contracting in response to a liquid pressure of the cryogenic LNG and/or a temperature stress applied from the cryogenic LNG.

Documents:

00930-cal-1999-abstract.pdf

00930-cal-1999-claims.pdf

00930-cal-1999-correspondence.pdf

00930-cal-1999-description(complete).pdf

00930-cal-1999-drawings.pdf

00930-cal-1999-form-1.pdf

00930-cal-1999-form-18.pdf

00930-cal-1999-form-2.pdf

00930-cal-1999-form-26.pdf

00930-cal-1999-form-3.pdf

00930-cal-1999-form-5.pdf

00930-cal-1999-letters patent.pdf

00930-cal-1999-priority document others.pdf