US3115983A

US3115983A - Support system for cryogenic liquid storage tank

Info

Publication number: US3115983A
Application number: US857664A
Authority: US
Inventors: Ivan L Wissmiller
Original assignee: Chicago Bridge and Iron Co
Current assignee: Chicago Bridge and Iron Co
Priority date: 1959-12-07
Filing date: 1959-12-07
Publication date: 1963-12-31
Anticipated expiration: 1980-12-31
Also published as: BE597851A; GB910224A; BR6024558D0; NL257928A; NL123988C

Description

Dec. 31, 1963 1. L. WISSMILLER 3,115,983

SUPPORT SYSTEM FOR CRYOGENIC LIQUID STORAGE TANK Filed Dec. '7, 1959 2 Sheets-Sheet 1 INVENTOR. Ivan L. Wissmil/er Merriam, Smith 8 Marshall A T TOR/VE Y5 Dec. 31, 1963 1. WISSMILLER ,1

SUPPORT SYSTEM FOR CRYOGENIC LIQUID STORAGE TANK Filed Dec. 7, 1959 2 Sheets-Sheet 2 INVENTOR. Ivan L. Wissmi/ler Merriam, Smith 8 Marshall A T T OR/VE Y8 United States Patent 3,115,983 7 SUPPORT SYSTEM FOR CRYOGENIC LIQUID STGRAGE TANK Ivan L. Wissmiller, Chicago,'lll., assignor to Chicago Bridge & Iron Company, Chicago, 111., a corporation of Illinois i I Filed Dec. 7, 1959, Ser. No. 857,664 11 Claims. (Cl. 220-) This invention relates to a multi-walled tank for the storage of liquefied, normally gaseous materials. It particularly relates to an improved supporting system for the inner vessel or vessels of a multi-wall storage tank employed especially as a low temperature storage facility.

In designing a mu-lti-wall tank for the storage of liquefied, normally gaseous materials or so called cryogenic liquids one of the problems that confronts the designer has to do with the properties of the materials which must be used in the vessel which contains the cryogenic liquid. Carbon steels are to be avoided in those portions of the tank where low temperatures are encountered. Carbon steels can be employed in services where temperatures of above F. occur but at lower temperatures it is not advisable to use such steels. This permits the use of carbon steels in the Outer shell construction; however, different materials of construction must be used for fabricating the vessels exposed to the extremely low temperatures which do not become embrittled at low temperatures. The use of a variety of construction materials complicates the design of support structures for suspending the inner vessels within the outer vessels in spaced relationship each to the other. For example, in a cryogenic storage tank for extremely low temperature service, such as for liquid oxygen service, one of the most usual and most satisfactory materials for the construction of the inner storage vessel is aluminum. It is quite difiicult, and sometimes impossible, to weld aluminum to other more conventional materials. As a consequence one of the most effective means for connecting components of the tank together cannot be used. Moreover, differences in coefiicients of thermal expansion make it diflicult to provide bolted mechanical connections.

In addition, it is desirable to limit the possible paths of heat transfer into the inner vessel by making the support structures for the inner vessel as small and as light as practicable. Various suspension means such as chains, straps, or other supporting devices have been employed in multi-wall tank construction to minimize any temperature gradient from the inner storage vessels to the outside atmosphere. Factors which afiect the rate of heat transfer through the support structure include the length of the metallic path between the ambient temperature at the outer vessel wall and the point of connection of the supporting structure to the inner vessel, the cross sectional area of the support, and the coefiicient of thermal conductivity of the support structure.

According to the present invention there is provided a support means for suspending the inner storage vessel or vessels within the outer shell of a multi-wall type storage tank especially adapted for the storage of cryogenic liquids, which comprises a system of tension bars, cables or the like extending from the inner vessel to points of attachment at or about the outer shell. The tension members are attached to the inner vessel so as effectively to eliminate any substantial bending moment which otherwise might be induced and also to eliminate the necessity for welding or bolting [the tension support members to the inner vessel.

FIGURE 1 is an elevation view of a multi-wall spherical cryogenic tank with the outer vessel wall partially cut away;

FIGURE 2 is afragmentary enlarged view taken in the plane 22 of FIGURE 1;

FIGURE 3 is an enlarged partial sectional view of an alternative embodiment showing adjustable connecting means for the support system;

FIGURE 4 is a View taken in the plane 44 of FIG- URE 3;

FIGURE 5 is a view of another alternative embodiment of securing the support to inner shell connection; and

FIGURE 6 is a cross-sectional side view along line 66 of the embodiment shown in FIGURE 5.

In the specific embodiment illustrated in FIGURE 1 there is shown a multi-wall tank having an outer spherical shell 10 supported by a plurality of columns 11 extending from a suitable foundation 12 to points of attachment about the equator of the outer vessel It}. A circular reinforcing memberp13 encircles the outer vessel It) at the level of the connections of the support structure hereinafter described, which in this case is at the equator, to provide a stiffening of the outer shell in the area of such attachment. A plurality of support base members 14 for attachment of the several vessel supports, for convenience referred to as gusset plates, is attached to the reinforcing member 13 by Welding or other means. Support base members 14 are spaced around the reinforcing member 13 in pairs as shown in FIGURE 2. The terminal ends of a tension bar or cable 15 employed in holding the inner vessel 16 in substantially rigid, spaced relationship within the outer shell 10 are attached by suitable means respectively to the two support base members 14 which comprise a pair. The tension member 15 is bent around a semicircular pad plate 17 suitably attached as by welding to the wall of inner spherical vessel 16. Retaining lugs 18 employed to retain the tension bar or cable 15 on the peripheral face of pad plate 17 are attached to pad 17 by suitable means, such as by bolts, screws or welding. if deemed desirable or necessary, stiffening bars 19 can be attached to the wall of vessel 16 and the pad 17 to provide additional stiffness and shear strength for transferring the loads from the vessel 16 to the pad 17 for transmittal to the tension bars or cables 15. Suitable piping for filling, emptying and venting; manholes and other conventional tank fittings normally used are not shown for simplicity.

The construction is shown in greater detail in FIGURE 2, in which the various parts have been assigned the same reference numerals as in FIGURE 1.

In the embodiment shown in FIGURES 1 and 2, the semi-circular pad 17 is constructed of the same material as is used for the inner vessel 16, or a similar material which can be readily secured by welding to the wall of inner vessel 16 and which Will have substantially the same coefiicient of expansion as the material employed in the construction of the inner vessel 16 in order that the two parts may readily be attached together by welding and further that they will have the same coefficient of thermal expansion, thus minimizing shear stresses occurring across the joints upon diiferential cooling or heating of the parts. Similarly, the stifiening bars 19 are made of the same material. The tension member 15, on the other hand, can be of a dissimilar material having either greater strength or a lower coeflicient of thermal conductivity than the material of which the inner vessel 16 and pad 17 are made. Since the tension member 15 is not integrally attached to any portion of the inner vessel 16 or the pad 17, no welding or thermal problems arise. The tension member 15 is merely bent about the curved portion of pad 17 and held in place by lugs *18, remaining free to adjust to differentials in thermal movement or to strain caused by tensioning.

It is obvious that variations in this arrangement can be made without departure from the source of this invention. For example in place of lugs 13 as shown in FIGURES l and 2 a flange which could be an integral part of the pad 17 or a separate part suitably attached to pad 17 will serve the same purpose. In addition, while the two ends of the tension member are shown as converging toward each other, they may as well be parallel or divergent. Either converging or diverging ends are preferred in order to afford a greater degree of lateral stability to the support of the inner vessel. Similarly, while pairs of support base members 14 are shown, it is obvious that a single support base member of suitable dimensions can be utilized.

The tension member 15 shown in FIGURES 1 and 2 can consist of a suitably shaped rigid bar, or flexible support such as a chain or wire rope or cable of high strength material having ductility at the low operating service temperature. The material of construction employed for fabricating the tension member preferably should have a lower coefficient of thermal conductivity than the wall of the inner storage vessel. If a rigid bar is used it is preferably secured to the support base members 14 by Welding. Such a construction, however, does not permit subsequent adjustment of the support structure which may be desired. Moreover, it is impracticable to use this type of connection where a high strength flexible chain or cable is employed instead of a tension bar. Generally 3 to 8 tension members can be used to support the inner storage vessel. Additional supports can be used if needed.

FIGURES 3 and 4 show a different embodiment of a portion of the invention in which a high strength cable having the requisite low temperature characteristics is used as the tension member 15. In this illustrative embodiment a wire rope bridge socket is interposed between the support base pad eye 31 and the flexible tension member 15 such as a wire rope or cable or chain. The socket has threaded ends 32 which are engageable by nuts 33 to position collar 34 thus affording an adjustability not inherent in the construction shown in FIGURES l and 2. Duplicate systems can be used for securing each terminal end of the flexible tension member or only one end can be made adjustable. One of the advantages of using wire rope or cable is that the wire, being cold drawn, is of higher strength than a hot rolled bar of the same material. In addition, the twisted strands of wire rope afford a longer and more tortuous heat transfer path than an equivalent length of bar material of the same cross sectional area and therefore has a lower coeflicient of thermal conductivity.

The selection of the size and shape of the pad 17 depends upon such factors as the amount of shear to be transmitted through the attachment between the pad and the inner vessel 16, the stiffness of the inner vessel 16 and the bending moment resulting from the eccentricity of loading caused by the fact that the axis of the tension member 15 is spaced a slight distance outwardly from the neutral axis of the material from which vessel 16 is constructed. While a semi-circular shape for the pad 17 is shown, any pad having a smoothly curved edge in contact with the tension member 15 may also be effectively utilized. In selecting the shape of the pad it is desirable to eliminate points of local stress concentration and a generally curved pad is therefore preferred while sharp corners are to be avoided.

The pad is located on the wall of the inner vessel substantially at the point of tangency with the longitudinal axis of the tension member. Accordingly the position will depend upon the location of the support base member. It is preferred that the support base members be located adjacent the horizontal equator of the outer vessel; however, they can be installed in other angularly displaced positions relative to the horizontal equator.

It is obvious that the method of connecting the tension member 15 to the inner vessel 16 by means of the pad 17 results in a greatly reduced bending moment when compared with conventional methods of attachment and in particular when compared with conventional methods of attachment of dissimilar materials which are not capable of being welded together.

Where there are likely to be significant dimensional changes in the tension member 15, or where it is anticipated that substantial adjustments may be necessary from time to time in the total length of the tension member 15, an alternate means for securing a flexible tension member 15 to the inner vessel 16 can be used as is shown in FIGURES 5 and 6. In this construction the tension member passes around a sheave, that is attached to the support pad 17 welded to the wall of the inner vessel 16 to minimize the effect of frictional forces resisting desired movement in the tension member 15. Pad 50 comprises a baseplate member 51 welded to the wall of vessel 16. An upright leg 52 is fastened to plate 51 and is provided with an opening 53 through which one end of link 54 is connected. The other end of link 54- connects with the eye 55 of pulley block 56 which has a sheave 57 around which is passed flexible tension member 15.

In constructing a cryogenic storage tank, materials are selected for the inner vessel and for that portion of the inner vessel support which will have to operate at low service temperatures which do not become embrittled at the service temperatures. The outer shell on the other hand, and its support structure need not be made of the more expensive low temperature service material because they will operate at approximately ambient temperature and a mild carbon steel is therefore suitable. Materials which are suitable for the inner vessel and support structure include aluminum, stainless steel of the 300 series, and certain nickel steel alloys such as Il /2% nickel, and 9% nickel.

The storage tanks of this invention are useful as low temperature storage facilities having capacities of 500 to 25,000 barrels; however, they can be used for storage in capacities outside this range. The storage vessels can be designed to withstand superatmospheric pressure, although this is not necessary if the temperature of the stored cryogenic liquid is at or about its boiling point. The space between the outer shell and the inner storage vessel can be insulated by any suitable means, as, for example, by placing therein granular fibrous or solid insulation, by evacuation of substantially all air from this space, or by a combination of these.

In the foregoing description reference has been made to a rnultiwall tank and an outer shell, and it should be understood that, since the outer wall or shell is designed primarily to act as a vapor barrier to prevent the accumulation and condensation of water vapor in the insulating space, the outer wall or shell need be of substantial independent strength. For example, if a rigid type of insulation material is employed in the insulation space the outer vessel wall may consist merely of a layer of vapor impervious material, such as a metal sheet or foil, attached to the outer surface of the insulating material. By employing this type of construction it is necessary to provide an elevated structure to which the support base members can be secured. A suitable structure could consist of horizontally placed, circular or polygonal reinforcing member positioned in an elevated position by a plurality of peripherally spaced columns. The support base members could be secured to the reinforcing ring and the inner vessel supported therefrom employing the suspension system of this invention.

The foregoing detailed description and illustrative examples have been given for the purpose of explaining the invention and no undue limitations in the claims which follow should be implied there-from.

What is claimed is:

l. A support system for a cryogenic liquid storage tank comprising an elevated structure spaced apart from the cryogenic liquid storage vessel, said structure having sufficient strength to support the weight of said vessel and its contents, suspension members attached to said structure and depending generally downwardly and inwardly therefrom and secured to said vessel to support it in an elevated position, and relatively thin pad plate members shaped to conform to the shape of a portion of the surface of said vessel and secured to the exterior surface of said vessel below the horizontal equator of said vessel to be in substantially surface to surface contact therewith, each of said suspension members comprising an open-loop metallic tension member having its terminal ends secured to said structure, the bight of said loop engaging said relatively thin pad plate member at a point substantially tangential to said storage vessel.

2. A support system in accordance with claim 1 in which said pad plate members are fabricated from the same material of construction as utilized in the construction of said vessel.

3. A support system in accordance with claim 1 in which tension members have a lower coefiicient of thermal conductivity than the wall of the cryogenic liquid containing vessel.

4. A support system for a cryogenic liquid storage vessel comprising an elevated structure spaced apart from the cryogenic liquid storage vessel, said structure having sufiicient strength to support the weight of said vessel and its contents, suspension members attached to said structure and depending generally downwardly and inwardly therefrom and secured to said vessel to support it in an elevated position, and relatively thin pad plate members shaped to conform to the shape of a portion of the surface of said vessel and secured to the exterior surface of said vessel below the horizontal equator of said vessel to be in substantially surface to surface contact therewith, each of said suspension members comprising an openloop metallic tension member having its terminal ends secured to said structure, the bight of said loop engaging said relatively thin pad plate member at a point substantially tangential to said storage vessel, the bight of said loop being contiguous to said storage vessel.

5. A support system for a cryogenic liquid storage vessel comprising an elevated structure spaced apart from the cryogenic liquid storage vessel, said structure having sufiicient strength to support the weight of said vessel and its contents, suspension members attached to said stru ture and depending generally downwardly and inwardly therefrom and secured to said vessel to support it in an elevated position, and relatively thin pad plate members shaped to conform to the shape of a portion of the surface of said vessel and secured to the exterior surface of said vessel below the horizontal equator of said vessel to be in substantially surface to surface contact therewith, each of said suspension members comprising an openloop metallic tension member extending tangentially from said storage vessel and having its terminal ends secured to said structure, said pad plate lying in peripheral, frictional engagement in the bight of said loop and having a lug for retaining the tension members in position whereby the weight of said vessel and its contents is trwsmitted through said pad members to said tension members.

6. A support system for a cryogenic liquid storage vessel comprising an elevated structure spaced apart from the cryogenic liquid storage vessel, said structure having sufficient strength to support the weight of said vessel and its contents, suspension members attached to said structure and depending generally downwardly and inwardly therefrom and secured to said vessel to support it in an elevated position, and relatively thin pad plate members shaped to conform to the shape of a portion of the surface of said vessel and secured to the exterior surface of said vessel below the horizontal equator of said vessel to be in substantially surface to surface contact therewith, each of said suspension members comprising a flexible, metal multi-wire cable, open-loop tension member having its terminal ends secured to said structure, the bight of said loop engaging said relatively thin pad plate member at a point substantially tangential to said storage vessel.

7. A support structure in accordance with claim 6 in which at least one of the terminal ends of said tension members is adjustably secured to said structure.

8. A support system for a cryogenic liquid storage tank comprising an outer shell, a plurality of tubular columns secured to the wall of said shell and supporting said outer shell, an inner storage vessel suspended within said shell and insulated therefrom, suspension members attached to said outer shell and depending generally downwardly and inwardly therefrom and secured to said vessel to support it in spaced relationship within said shell, and relatively thin pad plate members shaped to conform to the shape of a portion of the surface of said vessel and secured to the exterior surface of said vessel below the horizontal equator of said vessel to be in substantially surface to surface contact therewith, each of said suspension members comprising an open-loop metallic tension member having its terminal ends secured to said shell, the bight of said loop engaging said relatively thin pad plate member at a point substantially tangential to said storage vessel, the bight of said loop being contiguous to said storage vessel.

9. A support system for a cryogenic liquid storage tank comprising an outer shell, a plurality of tubular columns secured to the Wall of said shell and supporting said outer shell, an inner storage vessel suspended within said shell and insulated therefrom, a compression ring member circumscribing said outer shell and integrated with the wall of said shell and the tubular supports therefor, suspension members attached to said shell and said ring and depending generally downwardly and inwardly therefrom and secured to said vessel to support it in spaced relationship within said shell, and relatively thin pad plate members shaped to conform to the shape of a portion of the surface of said vessel and secured to the exterior surface of said vessel below the horizontal equator of said vessel to be in substantially surface to surface contact therewith, each of said suspension members comprising an open-loop metallic tension member having its terminal ends secured to said shell and said ring, the bight of said loop engaging the underside of said relatively thin pad plate member at a point substantially tangential to said storage vessel, the bight of said loop being contiguous to said storage vessel.

10. A support system for a cryogenic liquid storage tank comprising a spherical outer shell, tubular supports secured to the wall of said shell about its periphery and supporting said shell, a spherical, inner storage vessel suspended within said shell and insulated therefrom, a compression ring member circumscribing said outer shell and integrated with the wall of said shell and the tubular supports therefor, suspension members attached to said shell and said ring and depending generally downwardly and inwardly therefrom and secured to said vessel to support it in a suspended relationship within said shell, and relatively thin pad plate members shaped to conform to the shape of a portion of the surface of said vessel and secured to the exterior surface of said vessel below the horizontal equator of said vessel to be in substantially surface to surface contact therewith, each of said suspension members comprising an open-loop metallic tension member having its terminal ends secured to said shell and said ring, the bight of said loop engaging said relatively thin pad plate member at a point substantially tangential to said storage vessel, the bight of said loop being contiguous to said storage vessel.

11. A support system for a cryogenic liquid storage tank comprising an elevated structure spaced apart from the cryogenic liquid storage vessel, said structure having sufficient strength to support the weight of said vessel (I and its contents, suspension members attached to said structure and depending generally downwardly and inwardly therefrom and secured to said vessel to support it in an elevated position, relatively thin pad plate members shaped to conform to the shape of a portion of the surface of said vessel and secured to the exterior surface of said vessel below the horizontal equator of said vessel to be in substantially surface to surface contact therewith, each of said suspension members cornprising an open-loop metallic tension member having its terminal ends secured to said structure, the bight of said loop engaging said relatively thin pad plate member at a point substantially tangential to said storage vessel, and means for retaining the bight 0f the loop in engagement with said relatively thin pad plate member.

References Cited in the file of this patent UNITED STATES PATENTS 883,479 Place Mar. 31, 1908 2,842,427 Kinzel May 26, 1936 2,924,351 Hawk et a1. Feb. 9, 1960

Claims

1. A SUPPORT SYSTEM FOR A CRYOGENIC LIQUID STORAGE TANK COMPRISING AN ELEVATED STRUCTURE SPACED APART FROM THE CRYOGENIC LIQUID STORAGE VESSEL, SAID STRUCTURE HAVING SUFFICIENT STRENGTH TO SUPPORT THE WEIGHT OF SAID VESSEL AND ITS CONTENTS, SUSPENSION MEMBERS ATTACHED TO SAID STRUCTURE AND DEPENDING GENERALLY DOWNWARDLY AND INWARDLY THEREFROM AND SECURED TO SAID VESSEL TO SUPPORT IT IN AN ELEVATED POSITION, AND RELATIVELY THIN PAD PLATE MEMBERS SHAPED TO CONFORM TO THE SHAPE OF A PORTION OF THE SURFACE OF SAID VESSEL AND SECURED TO THE EXTERIOR SURFACE OF SAID VESSEL BELOW THE HORIZONTAL EQUATOR OF SAID VESSEL TO BE IN SUBSTANTIALLY SURFACE TO SURFACE CONTACT THEREWITH, EACH OF SAID SUSPENSION MEMBERS COMPRISING AN OPEN-LOOP METALLIC TENSION MEMBER HAVING ITS TERMINAL ENDS SECURED TO SAID STRUCTURE, THE BIGHT OF SAID LOOP ENGAGING SAID RELATIVELY THIN PAD PLATE MEMBER AT A POINT SUBSTANTIALLY TANGENTIAL TO SAID STORAGE VESSEL.