US 3272375 A
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Description (OCR text may contain errors)
p 3, 1966 A. H. HOLCOMBE ETAL 3,272,375
APPARATUS FOR GRYOGENIC LIQUID STORAGE CONTAINERS 5 Sheets-Sheet 1 Original Filed June 29, 1961 INVENTORS 4451 4/1/059 #04 60MB;
5774/1/49 P. Kat/r Sept. 13, 1966 A. H. HOLCOMBE ETAL 3,272,375
APPARATUS FOR CRYOGENIC LIQUID STORAGE CONTAINERS Original Filed June 29. 1961 5 Sheets-Sheet 2 INVENTORS 445144051? 4! 40469/149! 5779/1446) 4. Ava
p 13, 1956 A. H. HOLCOMBE ETAL 3,272,375
APPARATUS FOR CRYOGENIC LIQUID STORAGE CONTAINERS Original Filed June 29, 1961 5 Sheets-Sheet 5 INVENTORS 445%4/1 05? IOACUIVBE srawuy a? n aa/ United States Patent 3,272,375 APPARATUS FOR CRYOGENIC LIQUID STORAGE CONTAINERS Alexander H. Holcombe, Clarence, and Stanley R. Koch,
Tonawanda, N.Y., assignors to Union Carbide Corporation, a corporation of New York Continuation of application Ser. No. 120,584, June 29, 1961. This application Mar. 3, 1965, Ser. No. 445,297 9 Claims. (Cl. 220-15) This is a continuation of application Serial No. 120,584 filed June 29, 1961.
This invention relates to cryogenic liquid storage apparatus and particularly to mobile, thermally-insulated cryogenic liquid storage containers.
The present day, conventional method of storing cryogenic liquids comprises storing such liquids in doublewalled, vacuum-insulated storage containers. As the desired volume of liquid tobe stored in one body is increased, the problem of supporting the inner product liquid vessel within the protective outer shell becomes more and more acute. The strength of the inner vessel support structure depends in part upon the size and number of the members thereof and, for relatively large storage containers, the conduction of atmospheric heat through the support structure into the product liquid may become a sizable proportion of the total atmospheric heat in-leak therein. This problem is particularly troublesome in connection With mobile storage containers of the size employed in highway trailers and railway tank cars. Not only must the static weight of the inner vessel be supported, but provision must be made for forces experienced by the inner vessel because of accelerations, decelerations, and shocks due to bumps which the moving container undergoes. These forces necessitate employing stronger and hence larger support structures.
Heat inleak through the support structure may be compensated to a certain extent by employing more efficient insulation between the inner vessel and the outer shell. However, when the transported liquid has a very low atmospheric pressure boiling temperature, such as liquid hydrogen or helium, the problem created by heat inleak through the support structure becomes extremely critical and connot be countered sufficiently by merely increasing the efliciency of the insulation. Means must be found to restrict this heat inleak through the support structure in order to minimize the loss of storage liquid by excessive evaporation thereof.
It is, therefore, a primary object of this invention to provide a support structure for the inner vessel of a cryogenic liquid storage container which contributes to the total ambient heat leakage into the inner vessel to a much smaller degree than conventional inner vessel support structures.
This and other objects and advantages of the present invention will become apparent from the following detailed description thereof together with the accompanying drawings in which:
FIGS. 1, 3, 5 are partial, horizontal, sectional views of three storage containers illustrating the principles and novel features of this invention.
FIGS. 2, 4, 6 are end sectional views of the invention illustrated in FIGS. 1, 3, 5 respectively.
FIG. 7 is a partial, horizontal, sectional view of a storage container illustrating another embodiment of this invention.
In general, the inner vessel support structure of this invention comprises a plurality of re-entrant tubes each having first and second ends which are respectively gas tightly sealed and joined to the lower and upper portions of the wall of the inner vessel. The latter has openings within the space bounded by at least one end of each reentrant tube thereby providing gas communication between the interiors of the re-entrant tubes and the insulation space. A plurality of load rods, one end of each being joined to the outer shell of the storage container, extend into respective re-entrant tubes and are joined by their other ends to the walls of such re-entrant tubes. The reentrant tubes and the respective load rods are preferably employed in cylindrical containers wherein they are positioned in transverse planes relative to the longitudinal axis of the container with at least one such load rod-re-entrant tube combination being positioned in each of the aforementioned transverse planes.
The load rods are positioned to cooperatively support the inner vessel from either the lower portion or the upper portion of the outer shell. To cooperatively support the inner vessel in this manner, the load rods are assembled in substantially unstressed relation so as to take loading in either tension or compression. Whether the load rods cooperatively support the inner vessel from the upper portion or the lower portion of the outer shell, substantially the only stress experienced by the load rods will be that exerted by the static weight of the inner vessel and its contents plus any dynamic forces resulting from movement of the container. Because the load rods must absorb both tensile and compressive stresses, it is essential that they be assembled in unstressed relation. That is, the load rods cannot be prestressed, for example by tightening connecting end nuts so as to maintain the load rods in a constant state of tension as is done in typical prior art containers where force-opposed load rods are used.
It is preferred that the re-entrant tubes and the respective load rods be inclined from the horizontal at an angle based upon the resultant of the transverse forces acting upon the inner vessel, and preferably disposed at right angles to the longitudinal axis of the storage container. For example, if the force exerted by the dead weight of the inner vessel equals the horizontal transverse force which the inner vessel would experience during transportation, two load rods, connected to the inner walls of the respective re-entrant tubes, could be located in each transverse plane and at right angles to one another, each being equidistant from the vertical axis of the container. Such an arrangement is shown in FIGS. 1 and 2, which will be described in detail subsequently.
The inner vessel support structure is best adapted for employment in horizontally positioned cylindrical storage containers and will be described herein in conjunction with such a container. It should be understood, however, that other container configurations are also suitable, such as, for example, spherical and oval-shaped containers, and that this invention is not limited to employment only in cylindrical containers.
Furthermore, the low heat leak characteristics of this inner vessel support structure are most useful in containers storing such cryogenic liquids as liquid hydrogen, neon, and helium. Consequently, the insulation space is preferably substantially completely filled with highly eflicient insulation such as the opacified type and evacuated to a low positive pressure below about microns of mercury absolute. Of course, other liquids may be stored in containers employing this support structure and other insulation such as powder-in-vacuum and straight vacuum may be used in conjunction therewith. But, inasmuch as this invention is most useful when employed in liquid hydro gen, neon, and helium service, Where highly efiicient insulations are required, it will be described in conjunction therein.
FIGS. 1 and 2 illustrate one embodiment of the inner vessel support structure which suspends an inner vessel 10 from outer shell 12. Insulation space 14 between outer shell 12 and inner vessel 10 is preferably substantially completely filled with opacified insulation.
The term opacified insulation as used herein refers to a two-component insulating system comprising a low heat conductive radiation permeable material and a radi ant heat impervious material which is capable of reducing the passage of infrared rays without significantly increasing the thermal conductivity of the insulating system.
As more fully described and claimed in copending US. application Serial No. 597,947, filed July 16, 1956, in the name of L. C. Matsch, now U. S. Patent 3,007,596, the low heat conductive material may be fibrous insulation which may be produced in sheet form. Examples of such a material include a filamentary glass material such as glass wool and fiber glass, preferably having fiber diameter less than about 50 microns. Also such fibrous materials preferably have a fiber orientation substantially perpendicular to the direction of heat flow across the insulation space. The spaced radiation-impervious barriers may comprise either a metal, metal oxide, or metalcoated material, such as aluminum-coated plastic film or other radiation reflective or radiation adsorptive material or a suitable combination thereof. Radiation reflective material comprising thin metal foils are preferably suited in the practice of the present invention. For example, reflective sheets of aluminum foil having a thickness between 0.2 mm. and 0.002 mm. may be employed. When fiber sheets are used as the low-conductive material, they may additionally serve as a support means for the relatively fragile radiation-impervious sheets. For example, it is preferred that an aluminum foil-fiber sheet insulation be spirally wrapped around inner vessel 10 with one end of the insulation wrapping in contact with inner vessel 10 and the other end nearest outer shell 12 or in actual contact therewith.
It will be appreciated that other forms of opacified insulation may be used. For example, the radiation impervious barriers may be incorporated directly into the low heat conductive material as described and claimed in US. Patent No. 2,967,152 issued in the name of L. C. Matsch et al. Such opacified powder-vacuum type insulation might comprise, for example, equal parts by weight copper flakes and finely divided silica. The latter material has a very low solid conductivity value but is quite transparent to radiation. The copper flakes serve to markedly reduce the radiant heat inleak.
Even though the previously described preferred opacified insulation is more effective than straight vacuum insulation at higher internal pressure (poorer vacuum), its effective thermal insulation life is extended if the pressure can be maintained at or below a desired level such as, for example, below about 100 microns of mercury absolute. A gas removing material such as an adsorbent may be used in insulation space 14 to remove by adsorption any gas entering through the joints of the cryogenic container. In particular, crystalline zeolitic molecular sieves having pores of at least about Angstrom units in size, as disclosed in US. Patent No. 2,900,800 issued in the name of P. E. Loveday, may be employed as the adsorbent in accordance with the teachings therein since this material has extremely high adsorptive capacity at the temperature and pressure conditions existing in insulation space 14 and is chemically inert toward any gases which might leak into such insulation space. The adsorbent material may be provided within insulation space 14, for example, by intermixing the same with the insulation or by placing it in the inner vessel support structure in a manner to be described subsequently.
The inner vessel support structure shown in FIGS. 1 and 2 comprises two inclined re-entrant vessel tubes 16 and 18 located in a plane transverse to the longitudinal axis of storage container 20. Each re-entrant tube extends radially through inner vessel and joins the other at their intersection at the center of the aforementioned transverse plane. At the respective re-entrant tube first ends 22 and 24, the same are preferably joined gas tightly to inner vessel 10 by means such as welding. The second ends of the re-entrant tubes, at 26 and 28 respectively, are joined gas tightly in openings in the wall of inner vessel 10 thereby providing gas communication between the interiors thereof and insulation space 14.
In thisembodiment, load rods 30 and 32 extend from outer shell anchoring means 27 and 29 wherein they are connected to such means, through insulation space 14 and the interiors of their respective re-entrant tubes to the center of the aforementioned transverse plane. At the center each load rod is attached to connecting member 34 which may be fixedly or rotatably positioned therein by, for example, being respectively welded or pinned to the walls of the intersecting re-entrant tubes. The load rods are secured to outer shell anchoring means 27 and 29 and to inner connecting member 34 by suitable methods known to those in the art. For example, the load rods might be threaded at each end and screwed to connecting member 34 and by adjusting nuts to the respective outer shell joining means.
By joining the load rods at the longitudinal axis of storage container 20, or even by passing them through the center of the adjacent transverse planes Without joining the load rodsas in FIGS. 3-6, the inner vessel 10, when subjected to transverse forces, may tend to rotate about the storage container longitudinal axis due to the dynamic eifect of its liquid contents. In order to counteract this tendency, anti-rotation stops 36 and 38 are placed within the respective re-entrant tubes 16 and 18 near the second ends thereof. These anti-rotation stops are preferably constructed from a low heat conductive material such as a thermosetting phenolic resin of annular shape, such as a disk with a central opening. The load rod extends through the opening in the disk and when the inner vessel 10 begins to rotate, the anti-rotation stops prevent the load rods from moving into cont-act with the re-entrant tubes thereby preventing the rotation of inner vessel 10 sufficient to effect a substantial increase in the heat inleak.
Re-entrant tubes 16 and 18, in the embodiment of FIGS. 1 and 2, could be extended just past the storage container longitudinal axis and then terminated. However, by extending them radially to the opposite side of inner vessel 10, they provide added rigidity to inner vessel 10 in the transverse direction. Furthermore, by placing a screen or similar gas permeable material across the first ends 22 and 24 of re-entrant tubes 16 and 18, the aforementioned adsorbent material could be placed within these first portions of the tubes. Inasmuch as the adsorbent material placed therein would be at all times in thermal contact with the liquid storing portion of inner vessel 10, the adsorbent would be conditioned to operate most efliciently.
The inclination of the re-entrant tubes and the load rods therein from the horizontal is based upon the resultant of the transverse forces applied to the inner vessel. In most instances, positioning the re-entrant tubes equidistant from the vertical axis of the transverse plane and at right angles to one another will be satisfactory. Of course, more than one transverse plane containing an inner vessel support structure is necessary to provide adequate inner vessel support. The number and spacing of such planes involves design considerations, but, in most cases, two such planes located near the outer ends of the container will ordinarily provide adequate support-even for storage containers of the size of highway trailers or railroad tank cars.
By suspending inner vessel 10 from outer shell 12 as shown in FIGS. 1 and 2, load rods 30 and 32 are normally in tension. When the storage container experiences an upward force, for example, from passing over a bump in the roadway, load rods 30 and 32 may be momentarily loaded in compression. To balance the compressive and tensile strengths of the load rods, it is preferable that they be tubular shaped rather than being solid rods, so as to provide adequate stiflness Without excessively increasing the heat transfer therethrough due to cross-sectional area of metal. Since these load rods are capable of absorbing both tensile and compressive forces, they each do the work of two inasmuch as ordinarily it would be design practice to provide one set of load rods to handle the dead weight load of an inner vessel and to provide another set to handle the upward forces on the inner vessel caused by going over bumps and so forth. The latter case might be visualized by picturing four load rods, similar to load rods 30 and 32 of FIG. 2, extending radially outward from connecting means 34 at equi-spaced angles and each load rod being pre-stressed in tension. This is a typical prior art method of supporting an inner vessel and the superiority of the present invention is plainly evident. Especially in liquid hydrogen and helium storage, where ambient heat leak is a serious problem, the advantages of the present invention are self-evident inasmuch as the number of possible heat leak paths is reduced to half that of the above example of prior art support structures.
FIGS. 3 and 4 show an alternative inner vessel support structure for suspending an inner vessel 110 from the upper portion of outer shell 112. This support structure difiers from that depicted in FIGS. 1 and 2 in that load rods 130 and 132 extend to the lower or first ends of re-entrant tubes 116 and 118 and are connected thereto. Accordingly, each re-entrant tube is positioned in a transverse plane adjacent and parallel to the plane of the other re-entrant tube such that the re-entrant tubes do not touch but are in close adjacency. The inner vessel support structure of FIGS. 3 and 4 has the advantage over that depicted in FIGS. 1 and 2 in that the heat leak path is considerably extended, thereby even further restricting the influx of ambient heat to the inner vessel.
The support structure of FIGS. 5 and 6 is similar to that shown in FIGS. 3 and 4, except that the support structure is inverted, and inner vessel 210 is supported on the bottom portion of outer shell 212. Because load rods 230 and 232 are normally compressed when supporting inner vessel 210 from below, it is preferable to construct them with a larger section modulus than the load rods normally stressed in tension (FIGS. 1-4), as the downward design loads are usually somewhat greater than the upward design loads. This may be accomplished by providing tubular shaped load rods having a larger diameter than those load rods employed in the support structure shown in FIGS. 1-4.
The inner vessels of the mobile storage containers depicted in FIGS. 1-6 are prone to longitudinal movement caused by acceleration and deceleration of the storage container, inasmuch as the preferred inner vessel support structures depicted therein do not completely restrict such movement. FIG. 7 illustrates a preferred method of counteracting the tendency of the inner vessel to move axially longitudinally under the above-mentioned conditions. A re-entrant tube-load rod support structure, similar in many respects to those shown in FIGS. 1-6, is provided and shown herein located at one end of the storage container and positioned either in line with the longitudinal axis or parallel to the longitudinal axis thereof. The load rod is preferably constructed to prevent relative longitudinal movement of the inner vessel whether such be forward or backward. Alternately, the load rod may be inclined to the horizontal and also more than one may be employed to support the inner vessel longitudinally. The length to which this inner vessel end support structure extends int-o the inner vessel depends on the length of the heat leak path required to maintain the heat influx along this path below a pre-determined value, as well as the amount of metal cross section needed to accomplish the desired column strength.
It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention. For example,
if the transversely positioned inner vessel support structures depicted in FIGS. l-6 were also inclined with respect to the longitudinal axis of the storage container, the longitudinal support structure of FIG. 7 could be eliminated.
What is claimed is:
1. In combination with a double-walled cryogenic liquid storage container having a horizontally disposed longitudinal axis, an inner liquid product holding vessel, an outer shell surrounding the inner vessel and spaced'to form an insulation space therebetween, and means for filling, discharging, and venting said inner vessel, the improvement which comprises inner vessel support means for the sole support of said inner vessel from said outer shell consisting of a plurality of inner vessel re-entrant tubes positioned in transverse planes substantially perpendicular to the longitudinal axis of the container, each extending radially through the longitudinal axis of said inner vessel and having a first end and a second end each gas tightly sealed from the interior of said inner vessel and joined to the walls of said inner vessel, said first end being joined to the lower portion of the wall of said inner vessel and said second end being joined to the upper portion of the wall of said inner vessel such that the interior of each re-entrant tube is in gas communication with the insulation space; and a plurality of transversely positioned load rods, each extending into one of the re-entrant tubes through the said first end of such tube and having one end connected to said outer shell and the other end connected to an inner wall of such corresponding re-entrant tube.
2. The apparatus according to claim .1 wherein the load rods are connected to the second end portion of said re-entrant tubes.
3. In combination with a double-walled cryogenic liquid storage container having a horizontally disposed longitudinal axis, an inner liquid product holding vessel, an outer shell surrounding the inner vessel and spaced to form an insulation space therebetween, and means for filling, discharging, and venting said inner vessel, the improvement which comprises inner vessel support means for the sole support of said inner vessel from said outer shell consisting of a plurality of inner vessel re-entrant tubes positioned in transverse planes substantially perpendicular to the longitudinal axis of the container, each extending radially through the longitudinal axis of said inner vessel and having a first end and a second end each gas tightly sealed from the interior of said inner vessel and joined to the walls of said inner vessel, said first end being joined to the lower portion of the wall of said inner vessel and second end being joined to an opening positioned in the upper portion of the wall of said inner vessel such that the interior of each re-entrant tube is in gas communication with said insulation space; and a plurality of transversely positioned load rods each extending into one of the reentrant tubes through the second end of such tube and having one end connected to the upper portion of said outer shell and the other end connected to the inner wall of such corresponding re-entrant tube.
4. The apparatus according to claim 3 wherein the load rods are connected to said re-entrant tubes at the longitudinal axis of said container.
5. The apparatus according to claim 3 wherein the load rods are connected to the second end portion of said reentrant tubes.
6. The apparatus according to claim 3 wherein the plurality of re-entrant tubes are paired, the re-entrant tubes of each pair being in a common transverse plane and gas tightly joined such that the interiors of the joined re-entrant tubes are sealed from the interior of the inner vessel; and the load rods corresponding to each of the paired re-entrant tubes are connected to each other at the longitudinal axis of the container.
7. The apparatus according to claim 1 having a low heat conductive anti-rotation stop associated with each load rod and the re-entrant tube into which such load rod extends, such stop being proximate to and spaced apart from its associated load rod and proximate to the first end of its associated Ie-entrant tube.
8. The apparatus according to claim 3 having a low heat conductive anti-rotation stop associated with each load rod and re-entrant tube into which such load rod extends, such stop being proximate to and spaced apart from its associated load rod and proximate to the second end of its associated re-entrant tube.
9. In combination with a double-walled cryogenic liquid storage container having a horizontally disposed longitudinal axis, an inner liquid product holding vessel, an outer shell surrounding the inner vessel and spaced to form an insulation space therebetween, and means for filling, discharging, and venting said inner vessel, the improvement which comprises inner vessel support means for the sole support of said inner vessel from said outer shell consisting of a plurality of inner vessel re-entrant tubes positioned in transverse planes substantially perpendicular to the longitudinal axis of the container, each tube extending radially through the longitudinal axis of said inner vessel and having a first end and a second end each bei-ng respectively gas tightly sealed and joined to the lower and upper portions of the Wall of said inner vessel; openings in the Wall of said inner vessel Within the space bounded by at least one end of each re-entrant tube there- References Cited by the Examiner UNITED STATES PATENTS 1,522,886 1/ 1925 Heylandt.
2,229,081 1/1941 Hanson et al. 220-75 X 2,256,673 9/ 1941 Hanson et a1 22075 2,528,780 11/1950 Preston 220-15 X 2,587,204 2/1952 Patch et a1 22015 X 2,940,631 6/ 1960 Keeping 22914 2,986,01 1 5/1961' Murphy 229--15 X 3,080,086 3/1963 James 22915 3,132,762 5/1964 Gabarro et al 220-45 3,154,212 10/1964 1 Brush 220--15 LOUIS G. MANCENE, Primary Examiner.
THERON E. CONDON, Examiner.
J. R. GARRETT, R. A. JENSEN, Assistant Examiners.