Cryogenic fluid storage tank

Abstract

A Liquid Natural Storage (LNG) tank comprising an outer mechanical support structure (20) providing a closed space housing a membrane wall of the cryogenic tank is disclosed. Spacer elements (21) is supporting a membrane wall constituted by a mixture of steel plates, steel rods, wooden beams and plywood plates.

Claims

1. A Liquid Natural Gas (LNG) storage tank comprising an outer mechanical support structure providing a closed space housing a membrane wall of a cryogenic tank, wherein the membrane wall is constituted by at least the following constructional elements in order from the inner surface side of the outer mechanical support structure toward the interior storage space of the LNG storage tank: a spacer element connected in one end to the inner surface of the mechanical support structure; a first plywood wall; a single plated corrugated steel membrane supported by the first plywood wall; a second plywood wall; and a double plated membrane supported by the second plywood wall comprising a first corrugated steel plate welded to a second corrugated steel plate; wherein the corrugations on the first corrugated steel plate is sideways displaced relative to the second steel plate, thereby a pattern of distributed bubbles is arranged over the surface of the double plated membrane; wherein the a steel rod integrated with the spacer element is connected to the double plated membrane in one end while the other end of the steel rod is attached to a nut accessible via an opening on a side face of the spacer element.

2. The storage tank according to claim 1, wherein the steel rod of the spacer element is guided through an adapted hole in joining plate, wherein the joining plate is welded to the single plated membrane on all sides around the steel rod of the spacer element.

3. The storage tank according to claim 1, wherein corrugations on the surface of the single plated membrane is fitted into adapted cutouts on the surface of the first plywood plate.

4. The storage tank according to claim 1, wherein a plurality of adjacent located plywood plates are connected together via tongue and groove connections.

5. The storage tank according to claim 1, wherein the double plated membrane is replaced by a single plated corrugated steel membrane.

6. The storage tank according to claim 1, wherein the single plated membrane supported by the first plywood plate is omitted.

7. The storage tank according to claim 6, wherein the double plated membrane is replaced by a three-layer membrane comprising three connected corrugated steel plates.

8. The storage tank according to claim 1, wherein a shock absorber is arranged between the steel membrane facing towards the inner space of the tank and a connected spacer element.

9. The storage tank according to claim 1, wherein ball joints are connected at least in one end of a spacer element.

10. The storage tank according to claim 1, wherein a hinge is arranged between a spacer element and an inner wall of the mechanical support structure.

Description

DESCRIPTION OF THE FIGURES

(1) The cryogenic storage tank according to the present invention will now be described in more detail with reference to the accompanying figures. The attached figures illustrate an example of embodiment of the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

(2) FIG. 1 illustrate an example of embodiment of the present invention.

(3) FIG. 2 illustrate another example of embodiment of the present invention.

(4) FIG. 3 illustrate another example of embodiment of the present invention.

(5) FIG. 4 illustrate another example of embodiment of the present invention.

(6) FIG. 5 illustrate another example of embodiment of the present invention.

(7) FIG. 6 illustrate another example of embodiment of the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

(8) Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms “comprising” or “comprises” do not exclude other possible elements or steps. Further, the mentioning of references such as “a” or “an” etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

(9) The present invention uses combinations of materials comprising for example steel plates in membranes and wooden beams in respective support structures as well as plywood plates that also constitute parts of respective membranes.

(10) FIG. 1 illustrates an example of embodiment of the present invention of a cryogenic tank wall wherein an inner double plated membrane 10 is supported by a plywood wall 11. FIG. 1 illustrates a section of the cryogenic wall. The illustrated wall section will stretch around the whole circumference of a cryogenic tank defining a sealed cryogenic tank.

(11) The double plated membrane 10 comprises a first and second corrugated steel plate 10a, 10b. The corrugation pattern can be viewed as distributed bubbles over the surface of the membrane formed by indents on the first and second steel plate facing each other.

(12) The indents on the first steel plate 10a is displaced horizontally relative to the indents of the second steel plate 10b. Then a “top” of the first steel plate 10a is located above a “valley” on the second steel plate 10b. Thereby, a repeated pattern of closed spaces is arranged in between the two steel plates.

(13) The first steel plate 10a and the second steel plate 10b is welded to each other at respective welding points 15. The first steel plate 10a can be welded to further first steel plate adjacent to the first steel plate 10a. Likewise can the second steel plate 10b be welded to a further adjacent second steel plate. Then a double plated corrugated membrane can be made as indicated by the reference numeral 14.

(14) In the example of embodiment illustrated in FIG. 1, there is also a further single plated steel membrane 13 supported by a further plywood wall 23. Corrugations 12 is arranged spaced apart on the single plated membrane 13. Space for the corrugation is arranged as an indent 12 on the surface of the supporting plywood plate 23 supporting the single plated membrane 13.

(15) The single plated membrane is constituted by a plurality of single steel plates welded together as illustrated by the reference numeral 22. A joining cover 22 is welded across the joint between the respective adjacent steel plates. A space for the cover is arranged inside the plywood plate 11 supporting the double plated membrane 10.

(16) Further plywood plates via tongue and grooves join the plywood plate 23.

(17) Respective sections of the tank wall is attached to spacer elements 21 providing a space between the tank wall and an outer mechanical support structure 20. The outer mechanical support structure can be a ship hull or a concrete wall of a land based tank assembly. Other outer support structures can be container walls and similar objects.

(18) A coupling element 19 is welded to the side of the double plated membrane facing towards the plywood wall 11. A spacer element 21 is attached to the coupling element, for example by a threaded coupling 18. The spacer element is further guided through the single plated membrane 13 and the plywood wall 23, and is connected to the outer mechanical support structure 20 via a hinged connection for example. The spacer element 21 is guided through the single plated membrane 13, wherein a joining cover 17 is welded to the single plated membrane 11 surface on all sides around the spacer element 21. The spacer element 21 pass through an adapted hole in the joining cover 17 and may be welded to the joining cover 17.

(19) The spacer element 21 is a hybrid design comprising a steel bolt being connected to the coupling element 19 attached to the inner double plated membrane 10. At an opposite end closer to the mechanical support structure 20, the steel bolt is integrated inside a wooden beam for example. A nut 19 is arranged inside an accessible cavity in the wooden beam 21. When the nut 19 is tightened, the whole wall assembly is tightened together between the joining cover 17 and the coupling element 19 providing a leakage proof cryogenic tank wall.

(20) FIG. 2 illustrates another example of embodiment of the present invention. The difference between this example of embodiment compared to the example illustrated in FIG. 1, is that the double plated membrane 10 is replaced by a single plated corrugated steel membrane 10c. The other details with respect to the spacer element etc. are the same. The single plated membrane 13 supported by the plywood plate 23 is also present.

(21) FIG. 3 illustrate a further example of embodiment of the present invention comprising only a double plated corrugated membrane 10 as disclosed in the example illustrated in FIG. 1. In this example of embodiment, the single plated membrane 13 is removed. Consequently, only the plywood wall 23 is present in this example of embodiment. The spacer element etc. is the same as in the other examples of embodiment of the present invention.

(22) FIG. 4 illustrates another example of embodiment wherein the double plated corrugated membrane 10 in the example illustrated FIG. 3 is replaced by a three plated membrane 10d comprising three joined corrugated membrane plates. When viewed in order from the inside of the tank, the first and second corrugated steel plate is arranged as in the example of embodiment disclosed in FIGS. 1 and 3. A first corrugated steel plate is displaced horizontally relative to a second corrugated steel plate defining “bubbles” as discussed above. A third corrugated steel plate is attached to the second steel plate also displaced horizontally relative to the first and second corrugated steel plate. Then there is a double set of “bubbles”, one set of bubbles constituted in between the first and second corrugated steel plate, and a second set of “bubbles” in between the second and third corrugated steel plate.

(23) FIG. 5 illustrate another example of embodiment according to the present invention. As an example, a same configuration as disclosed in FIG. 1 is used. In addition, FIG. 5 disclose the use of a shock absorber 51 in the coupling element 19 and the steel bolt of the hybrid spacer element 21. The shock absorber is of a magnetic/electrical type. A property of such shock absorbers is that when a shaft moves in and out of the shock absorber, the magnetic forces used to provide dampening of the shaft vary with the change of magnetic flux. When the movement is slow, there is minimal absorption in the shock absorber. When the movement is quick the absorber works. Another type of shock absorbers that can be used is based on a magneto rheological fluid, wherein the amount of absorption can be controlled or regulated.

(24) When the cryogenic tank is at room temperature, i.e. there is no cryogenic fluid inside the tank and the membrane 10 will rest onto the plywood wall 11. When cryogenic fluid is filled inside the tank, the steel material of the membrane 10 will start to shrink. For example, if the tank has the shape of a cylinder, the diameter of the tank shrinks. The absolute amount of displacement of the walls is dependent on the actual size of the tank. Large tanks will have a larger absolute value of reduction in the diameter for example than a smaller tank. However, the movement is rather slow and the shaft of the absorber will follow the connected membrane movement inwards. If there is, a sudden slushing inside the tank the impact on the inner membrane will be taken up by the absorber. The impact force will be guided passed the other membranes and plywood panels into the outer mechanical support structure 20, for example, a ship hull. It also important to note that if for example a large wave hits the side of the ship hull, the shock absorber will minimize the transfer of forces onto the membranes and walls of the tank.

(25) FIG. 6 illustrate another example of embodiment of the present invention, The example illustrate the use of a ball joint 60 located between a spacer element 21 and the mechanical support structure 20. A same ball joint can be arranged closer or adjacent to the tank wall. The effect is that when the structure twist or move due to for example waves hitting a ship hull the transfer of the twisting forces to the spacer elements will be minimized thereby the integrity of the tank will be better protected.

(26) An aspect of the present invention is that the strength of a LNG storage tank according to the present invention is controllable and achievable by the following features: The steel quality 304 provides a softness and steel quality that enables stretching off steel plates within known limits without the steel plates to be teared apart. The mechanical movements of steel plates due to thermal expansion and contractions are mitigated by corrugation elements provided on the respective steel plate surfaces of the membrane elements. The mechanical integrity of membrane elements can further be enhanced by increasing the number of fastening bolts attaching respective membrane elements to the wooden wall elements, to the spacer element or directly to the mechanical support structure. The area of the membrane surface between bolts are still enabled to mitigate thermal induced stress in the steel plates by corrugations in the surrounding of the respective fastening bolts. The wooden elements of the design is capable of withstanding twisting and stretching of the walls of the tank. The transfer of forces between the inner double plated membrane, the wooden wall elements and the mechanical support structure is controllable, and especially any transfer of forces between the wooden wall elements and inner double plated membrane elements can be eliminated, or at least be reduced significantly. Use of shock absorbers in spacer elements connected to an outer mechanical support structure. Use ball joints in spacer elements between the tank wall and an outer mechanical support structure.