US3842775A

US3842775A - Tank for storing fluids on a ship or the like and tie down means therefor

Info

Publication number: US3842775A
Application number: US00291373A
Authority: US
Inventors: N Edwards; M Petro; J Guilhem; P Jean
Original assignee: Pittsburgh Des Moines Steel Co
Current assignee: PITTSBURGH-DES MOINES Corp
Priority date: 1972-09-22
Filing date: 1972-09-22
Publication date: 1974-10-22
Anticipated expiration: 1991-10-22

Abstract

A tank for storing fluids, including a closed bottom and a side wall, a tank support in an inner bottom portion of a ship or the like, and unique tie down means fixed to and depending from said tank and fixed to said tank support to hold said tank and resist forces on the tank tending to move the tank relative to the support.

Description

United States Patent 1191 Edwards et al.

TANK FOR STORING FLUIDS ON A SHIP OR THE LIKE AND TIE DOWN MEANS THEREFOR Inventors: Norman W. Edwards, Sewickjey;

Michael Petro, Coraopolis, both of Pa.; Jacques Guilhem, La Haver; Pierre Jean, Montervilliers, both of France Assignee: i ittshur gh-l es 11711116? Steel Company, Pittsburgh, Pa.

Filed: Sept. 22, 1972 Appl. No.: 291,373

us. 01. 114/74 R, 114/74 A, 220/9 LG 1m. (:1 B63b 25/08 Field 61 Search 114/74 R, 74 T, 74 A, .5 T;

220/14, 15, 17, 9 A, 9 LG; 105/358 References Cited UNlTEDSTATES PATENTS Monroe ll4/74 A Oct. 22, 1974 3,087,454 4/1963 Lorentzen 114/74 R 3,583,352 6/1971 Alleaume 114/74 A 3,680,323 8/l972 Bognaes 114/74 A 3,712,257 1/1973 Alleaume 114/74 A 3,713,560 1/1973 Slysh et al. 220/9 LG 3,724,411 4/1973 Alleaume 114/74 T Primary ExaminerGeorge E. A. Halvosa Assistant ExaminerCharles E. Frankfort Attorney, Agent, or Firm-Shoemaker and Mattare [5 7] ABSTRACT A tank for storing fluids, including a closed bottom and a side wall, a tank support in an inner bottom portion of a ship or the like, and unique tie down means fixed to and depending from said tank and fixed to said tank support to hold said tank and resist forces on the tank tending to move the tank relative to the support.

21 Claims, 15 Drawing Figures PATENI'EU BET 325974 3. 821! 7 7 5 SHEET 1 W 7 PAIENIED 01:?221924 SHEET 2 W 7 TTT FLIP

Pkk

TT TT TT TTT jTTT TT T TT TANK FOR STORING FLUIDS ON A SHIP OR THE LIKE AND TIE DOWN MEANS THEREFOR BACKGROUND OF THE INVENTION This invention relates to a tank for storing fluids on a ship or the like and to a tie down means for the tank for securely holding the tank in said ship to resist forces on the tank. e I

In recent years the storage of supply of natural resources has become critical, and it has become economically desirable to import materials to supplement the supply of natural resources. An example is the importation of liquid natural gas by means of ships or the like. Various ship designs are known in the prior art for transporting materials such as liquid natural gas and the like but conventional designs suffer from several serious disadvantages.

In the prior art, liquid natural gas, for example, is transported in a plurality of specially designed tanks secured in specially designed ships. Such prior art tanks are of several types. One such type comprises a free standing tank in which the tank is supported from its sides to the sides of the ships hull. This design imposes serious loads on the sides of the tank and on the sides of the hull of the ship, thus rendering the design of the ship and tanks difficult and expensive. Further, with these designs a large amount of insulation is required around the tank and accordingly, a greater space is required to be purged of gas or the like. Another prior art design utilizes a skirt integral with the tank at approximately its equator and extending downwardly to the bottom of the hull of the ship. This integral skirt is large and expensive to manufacture and install and does not enable the tank to freely expand and contract as cryogenic materials are added thereto and removed therefrom. Consequently, stresses are induced in the wall of the tank by the supporting skirt and the tank must accordingly be made sufficiently large in order to withstand the stresses. Moreover, in each of these prior art designs, the bottom of the tank must be designed as a pressure vessel and accordingly, the amount of material required is large and the tank design is expensive. Still other prior art designs support the tank on a bottom insulation and then key the sides of the tank to the sides of the ship. However, in these designs, the forces imposed on the sides of the tank and the ship are extremely difficult to analyze and the tank must accordingly be designed with sufficient strength to withstand such sidewardly imposed forces.

The present invention provides a tank designed wherein the tank is supported at its bottom on a bottom insulation, and a tie down means is secured to the tank and to the bottom support for holding the tank downwardly at the insulated support. The tie down means is constructed to enable the tank to freely expand and contract with changes'in ambient temperature and accordingly, the tie down means does not induce stresses in the tank due to this contraction and expansion. Moreover, the unique support and tie down means of the invention creates a large frictional resistance between the tank and bottom support, thus tending to resist overturning of the tank when the ship pitches and rolls and the like during transportation of the tanks and the fluid stored therein.

While the tank of the present invention has particular suitability for the transportation of cryogenic materials,

it can equally as well be used for the transportation of gases or other fluids at ambient temperatures or even of such materials at elevated pressures or the like, an example of which would be propane.

The tie down means of the present invention is economical and simple to manufacture and install, and the loads are transmitted from the tank through the tie down means to the inner bottom of the ship wherein supporting structure is readily available and thus minimizes the loads to the vertical sides of the hull of the ship, effecting economies in the hull structure. Still further, the unique tie down means of the invention serves to reinforce the lower portion of the tank, and the thickness of the plates in the bottom portion of the tank can accordingly be reduced.

OBJECTS OF THE INVENTION It is an object of this invention to provide a tank for storing fluids on a ship or the like, and a unique tie down means for the tank for holding the tank securely in the ship to resist forces on the tank, said tie down means secured to the tank and depending therefrom and fixed to the tank support in an inner bottom portion of a ship or the like.

Another object of this invention is to provide a tank for storing fluids on a ship or the like and a unique tie down means fixed to the tank and to a support in an inner bottom portion of the ship or the like for the tank, said tie down means constructed to enable relatively free expansion and contraction of the tank upon ambient temperature changes without inducing stresses in the tank. I

A still further object of the invention is to provide a unique tie down means for a large tank for storing fluid in a ship or the like wherein the tie down means is secured to the tank and to a tank support in an inner bottom portion of the ship'or the like on which the tank is supported, said tie down means holding the tank downwardly against said support.

Yet another object of the invention is to provide an insulated support in an inner bottom portion of a ship or the like and on which a tank is supported over substantially its entire bottom, and a unique tie down means secured to the tank and to the insulated bottom support for holding'the tank downwardly against said insulated bottom support to resist external forces on the tank.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 3 is a sectional end view of the ship of FIG. 1, showing some parts in section and other in elevation and illustrating first, preferred form of the invention.

FIG. 4 is an enlarged fragmentary perspective exploded view of a portion of the tank, tank support and tie down means of FIG. 3.

FIG. 5 is an enlarged fragmentary sectional view taken along line 55 in FIG. 3.

FIG. 6 is an enlarged fragmentary view in elevation, taken along line 6-6 in FIG. 5.

FIG. 7 is an enlarged fragmentary perspective exploded view of a second form of the tie down means.

FIG. 8 is an enlarged fragmentary sectional view of the modified tie down means of FIG. 7.

FIG. 9 is an enlarged fragmentary view in elevation, with a portion thereof broken away, of the tie down means of FIG. 8 and is taken along line 99 in FIG. 8.

FIG. 10 is an enlarged fragmentary sectional view of a third form of tie down means.

FIG. 11 is an enlarged fragmentary sectional view of the tie down means of FIG. 10, showing the tie down means in another operative position.

FIG. 12 is an enlarged fragmentary perspective .exploded view of a fourth form of tie down means according to the invention.

FIG. 13 is an enlarged fragmentary perspective view of a fifth form of tie down means of the invention.

FIG. 14 is an enlarged fragmentary sectional view of the tie down means of FIG. 13.

FIG. 15 is an enlarged fragmentary view in elevation of the tie down means of FIG. 14 and is taken along line 1515 in FIG. 14.

DETAILED DESCRIPTION OF THE INVENTION In the drawings, wherein like reference numerals indicate like parts throughout the several views, a ship is indicated generally at S in FIG. 1 and has a plurality of holds H therein which a plurality of tanks T are supported. Each tank T is supported at its bottom on an insulated tank support in the bottom of the holds H and a polygonally shaped cover C covers the upper portion of each tank T, and the space between the tank T, cover C, opposite inner longitudinal sides L of the hull of the ship, and transverse bulkheads B, separating adjacent tanks, is filled with a suitable insulating material I, such as granular perlite or the like.

The first and preferred form of the invention is seen best in FIGS. 3, 4, 5 and 6. In the preferred form the insulated tank support 20 is conically shaped, although it could have any other desired configuration, and extends upwardly at an angle [3 to the horizontal. The insulated support 20 comprises an inner bottom 21 of 9 percent nickel steel or the like in the ship, and a plurality of boxes 22 or the like filled with a suitable insulating material I, such as perlite, are supported on said inner bottom 21. In the specific example illustrated, there are two layers of staggered or offset boxes 22 arranged over the conical support 21. If desired, a barrier 23 of plywood or the like may be positioned on top of the boxes 22 and a layer 24 of Klegecell or the like may be positioned on top of the plywood barrier 23 for distributing the load from the tank bottom onto the insulated support 20. The inner bottom 21 is, of course, supported on the bottom structure of the ship. The tank support 20 includes an annular tubular support ring 25 having a rectangular cross-sectional configuration and suitably secured as by welding or the like to the inner surface of the sides L of the hold H and with the inner bottom 21 suitably secured as by welding or the like to the upper inner marginal edge of the support ring 25.

As seen best in FIG. 5, the support ring 25 includes a pair of vertically spaced

annular walls

26 and 27 and an annular vertical inner wall 28 welded or otherwise suitably secured together at adjacent marginal edges thereof. A plurality of membranes M are welded in transverse relationship between the top, bottom and side walls of the ring 25 and a man hole opening 29 is formed therein for enabling a workman to move through the ring completely around the tank T. Similarly, a manway 30 haVing a removable plate 31 thereover extends through the side L of the hold for gaining access to the interior of the ring 25.

As seen best in FIG. 3, the tank has a top, bottom and opposite sides and comprises a hemispherical top having a radius R1, a cylindrical middle portion having a radius R2, a torospherical knuckle portion having a radius of curvature of R4 and a part spherical bottom portion having a radius R5. The part spherical bottom portion extends over a height hl and has a radius in a horizontal plane of a. A conically shaped portion joins the part shperical bottom to the torospherical knuckle portion and has a dimension in a horizontal direction of b. The torospherical kunckle portion joins the conical portion with the cylindrical portion and has a horizontal dimension c. The sum of these dimensions a, b and c, equaling the overall horizontal radius R of the tank. The part spherical bottom extends over a vertical distance hl and the conical and torospherical knuckle portion extend over a combined vertical distance h2. The cylindrical portion extends over a vertical distance k3, and the hemispherical portion at the top of the tank extends over a vertical distance h4. The sum of the distances h1, h2, h3 and k4 equaling the total height h of the tank.

As seen, the conical bottom of the tank conforms to the shape of the conical insulated tank support 20 and rests on top of the insulated filled boxes 22. The sides of the tank are spaced radially inward from the sides L of the hold H of the ship, and the top of the tank is spaced inwardly from the cover C. This space is filled with the granular perlite insulating material I.

The preferred form of the tie down means is indicated generally at 32 and comprises a plurality of generally rectangularly shaped hold down or tie down plates 33 having upper and

lower edges

34 and 35 and opposite side edges 36 and 37. The upper edge has an angularly inwardly inclined portion 38, and this inclined portion 38 is received in slots 39 formed in a plurality of gusset plates 40 which are secured as by welding or the like to the outer surface of an elongate generally rectangularly shaped plate 41 which is in turn welded or otherwise suitably secured to the outer surface of the tank T. An adjustable fastening means is secured to the bottom edge of each plate 33 and comprises a plurality of elongate anchor bolts or the like 42 having bifurcated upper ends 43 in which the bottom edge 35 of the plate 33 is received and suitably secured as by welding or the like.

A plurality of circumferentially spaced openings 44 extend through the top 26 of the support ring 25 in alignment with the anchor bolts 42 and through which the anchor bolts extend. A washer 45 and nut 46 is received over the lower end of each anchor bolt 42 projected through the openings 44 in the plate 46 and the nuts 46 are adjusted on the anchor bolts to place the tie down plates 33 under tension and securely hold the bottom of the tank downwardly against the insulated support. By suitably adjusting nuts 46 on the anchor bolts 42, the tie down means 32 may be pretensioned as indicated in FIG. 6, with the lower edge of the tie down plates 33 pulled downwardly as indicated in phantom lines at 35 in FIG. 6. This distance is shown exaggerated since the amount of actual yielding or stretching of the tie down means is quite small in practice. However, the pretensioning of the tie down means is sufficient to continuously maintain tension on the tie cold fluid is placed thereinto. The opposite edges 36 and 37 of adjacent tie down plates 33 are spaced apart a predetermined distance such as, for example, in a specific embodiment, approximately 1 foot, 6 inches, so that the adjacent plates in the tie down means are enabled to move toward and away from one another in a circumferential direction as the tank expands and contracts to thus enable the tank to freely move and the tie down means will not induce any stresses in the tank uponcontraction and expansion thereof. In fact, the tie down means and particularly the plates 41, serve to reinforce the lower portion of the tank and thus enable the use of thinner plates in the tank bottom construction. The tie down plates, gusset plates, elongate plates 41 and the support ring 25, an inner bottom 21 are all preferably made of a material such as 9 percent nickel steel which is not adversely affected by the extremely cold temperatures of the material stored in the tank so that in the event of a leak of stored material from the tank, the tie down means and supporting structure will not be damaged.

The second form of the invention illustrated in FIGS. 7, 8 and 9 is similar to the first form of the invention except that rather than the anchor bolts 42 secured to the lower edge of the tie down plates 33, a plurality of elongate, rectangularly shaped bars 47 are welded or otherwise suitably secured to the outer face of the plates 33 at the bottom edge thereof with the opposite ends of the bars in spaced apart relationship. A pair of identical bars 48 are welded or otherwise suitably secured to the rear surface of the plates 33 opposite the bars 47. Also, rather than the annular rectangularly shaped support ring 25 as in the FIG. 3 embodiment,

- down means even though the vessel contracts when a I a pair of vertical, spaced apart annular walls 49 and are welded or otherwise suitably secured to the inner bottom 21 of the ship. A pluralityof elongate, generally rectangular shaped spaced apart bars 51 are welded to the inner upper edge of wall 49,and a plurality of identical, elongate, rectangular bars 52 are welded to the inner upper edge of wall 50 directly opposite bars 51. The

bars

51 and 52 are spaced apart in a radial direction a distance approximately equal to or slightly greater than the thickness of plate 33, and the spacing between the ends of

bars

47 and 48 on the plates 33 is at least as great as the length 'of bars Sland 52 on the

walls

49 and 50. An annular horizontal wall or ring 53 is welded between the

walls

49 and 50 spaced below the bars 51 and 52 a distance greater than the vertical dimension of the

bars

47 and 48 to enable limited vertical movement of the plates 33 and bars 47 and 48 relative to the

walls

49 and 50 and bars 51 and 52. The

annular walls

49 and 50 are suitably reinforced by means of a plurality of circumferentially spaced

gussets

54 and 55 suitably secured thereto as by welding or the like and to the inner bottom 21 of the ship.

In installing the form of the invention illustrated in FIGS. 7, 8 and 9, the

bars

47 and 48 are suitably secured as by welding or the like to the bottom edge of the plates 33 and the bottom edge of the plates is inserted downwardly between the

annular walls

49 and 50 and between the

bars

51 and 52 with the

bars

47 and 48 passing downwardly in the space between adjacent ends of

bars

51 and 52. The plates and bars thereon are then slid edgewise between the

annular walls

49 and 50 until the

bars

47 and 48 are positioned directly beneath

bars

51 and 52. Suitable means may then be connected to the upper edge of the plates 33 to urge the plates 33 upwardly and, if desired, to pretension the plates, and the plates 41 are then welded to the outer surface of the tank T with the upper surfaces of

bars

47 and 48 in engagement with the lower surfaces of

bars

51 and 52 as seen in FIG. 8. Also as seen in FIG. 8, rather than the perlite filled boxes 22 as in FIG. 3, the insulation I comprises a plurality of blocks 56 of PVC foam or the like having load carrying capabilities. Of course, the perlite filled boxes may be used in this form of the invention or the blocks 56 may be used in the other forms of the invention, if desired, or any other suitable load bearing insulation may be used.

The third form of the invention is seen best in FIGS. 10 and 11 and is substantially identical with the form of the invention illustrated in FIGS. 7, 8 and 9 except that rather than the rectangularly shaped

bars

47 and 48, 51 and 52, bars 47 and 48' are welded or otherwise suitably secured on the inner and outer surfaces of the plates 33 at the bottom edge thereof, and the bars 47' and 48 have upper

inclined surfaces

57 and 58 in vertically spaced parallel planes and bars 51', 52' on the confronting upper edges of walls 49' and 50 have lower

inclined surfaces

59 and 60 in vertically spaced parallel planes corresponding to the

upper surfaces

57 and 58 of bars 47' and 48. Also, the walls 49' and 50' are spaced apart a greater distance than the

walls

49 and 50 and the angle of inclination and spacing of the surfaces on the bars secured to the annular walls and to the lower edge of the tie down plates is such that the inclined surfaces of adjacent bars remain in engagement when the tank contracts and/or expands to maintain tension on the tie down means and to securely, hold the bottom of the tank against the insulated support means 20. Thus, as seen in FIG. 10, the tank is in an expanded condition, and the

upper surfaces

57 and 58 of bars 47' and 48' on the lower edge of tie down plate 33 are disposed in a radially outward and upward direction and are in engagement with the

lower surfaces

59 and 60 of the bars 511' and 52' on the upper edges of the annular walls 49' and 50.

In FIG. 11 the tank is in a contracted condition, and the plate 33 and bars 47', 48' are in a radially inward and downward position with the adjacent surfaces of the bars in engagement with one another. Otherwise, the method of installation and construction of this form of the invention is identical to that in FIGS. 7, 8 and 9.

Of course in the two forms of the invention illustrated in FIGS. 7-11, the bars need not be spaced apart as illustrated, but could be of one piece construction if desired, although the assembly of the tie down means would be rendered extremely difficult with such construction.

The fourth form of the invention is illustrated in FIG. 12, and this form of tie down means 32 is similar to the form of the invention illustrated in FIG. 3, except that rather than the anchor bolts 42 extended through openings 44 in the top wall 26 of support ring 25, a plurality of turnbuckles 61 are secured tothe lower edge of the tie plates 33 and to the top surface of the wall 26. Each ably secured through a bracket 64 welded or otherwise secured to the top surface of the wall 26. By this arrangement, as in the FIG. 3 arrangement, the turnbuckles may be adjusted to adjust the tension on the tie down means and thus adjust the amount of force with which the bottom of the tank is held downwardly against the insulated support. Also, with this form of the invention, as with the forms of the invention illustrated in FIGS. 7-11, there are no holes through the inner bottom of the ship so that if a leak occurs in the tank, the fluid is not able to seep downwardly into the bottom of the ship and thus create a dangerous situation.

The fifth form of the invention is illustrated in FIGS. 13, 14 and 15, and in this form of the invention, the tie down means 32 comprises an annular vertical wall 70 having a serpentine or scalloped upper edge 71 and a substantially straight bottom edge 72. The wall 70 is circumferentially divided into a plurality of

adjacent sections

70a, 70b, 706, etc. by means of a plurality of vertically extending slots 73 extending through the serpentine upper edge 71 toward the bottom edge 72 and terminating short of the bottom edge. These slots 73 enable the adjacent portions of the wall 70 to move circumferentially toward and away from one another to enable the tank to relatively, freely expand and contract upon changes in ambient temperature. This is illustrated in phantom lines in FIG. 15. The serpentine upper edge 71 presents a relatively large weld area so that a secure and reinforced attachment of the upper 30 edge of the tie down wall 70 is effected with tank T, and the bottom edge is suitably secured as by welding or the like to the top surface of wall 26 in the annular support ring 25. In addition to withstanding tensile forces thereon and resisting the tendency of the tank to slide 35 or overturn, the tie down wall 70 is capable of accommodating a relatively small amount of compressive force due to settling or compaction of the insulated support or the like, although the amount of compressive force asorbed by the tie down wall 70 is relatively small and it is intended primarily as a tensile structural member rather than a compressive structural member.

In a specific construction of a tank constructed in accordance with the invention, the radii R1 and R2 of the tank are approximately 59 feet, 6% inches; the radius R4 is approximately 13 feet, 1% inches; the radius R5 is approximately 30 feet, the subtended angle a is approximately 40, and the angle [3 is approximately 20. The dimension a is approximately 12 feet, 1 1 16 inches; the dimension b is approximately 38 feet, inches; the dimension c is approximately 10 feet, 9 5/32 inches, and the overall horizontal radius R of the tank is approximately 59 feet, 6% inches. The vertical extent hl is approximately 2 feet, 1 19/32 inches, the dimension h2 is approximately 26 feet, 6 /8 inches, the dimension h3 is approximately 26 feet, 3 inches, and the dimension k4 is approximately 59 feet, 6% inches. The overall height of the tank is approximately 114 feet, 5 inches, and the tank has a volume of approximately 25,797 cubic meters. The plates in the bottom portion of the tank also have a thickness of approximately onehalf inch in the invention.

The particular configuration and construction of the tank illustrated and described herein is'by way of specific example only, and the tank can have any desired configuration within the scope of the invention. Further, any number of tanks may be provided in a ship such as, for example, five tanks as illustrated and described herein, and any suitable insulation may be used surrounding the tank and in the load supporting insulation beneath the tank.

The unique tie down means of the present invention and the unique load supporting insulating means on which the tank is supported result in the tank being held securely downwardly against the insulated support so that the tendency of the tank to slide or overturn is effectively resisted without imparting excessive loads on the side of the tank and without subjecting the tank to stresses due to contraction and expansion at the point where the tie down means is secured to the tank.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within the metes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents, are therefore intendedto be embraced by those claims.

What is claimed is:

1. In combination, a tank and tie down means therefor, for containing and transporting low temperature fluid in a ship or the like, comprising a support for the tank in a bottom portion of a ship or the like, load bear- .ias asul qn 9& i s ppqnt e a up Orted il bottom on said load bearing insulatiGf, a epe fiding, annular skirt fixed to a lower outer surface portion of the tank and comprising a plurality ofcircumferentiafiy spaced apart tie down plates each extending circumferentially in a direction generally parallel to the curvature of the tank and fixed at an upper edge thereof to said tank at circumferentially spacedloc afions on a lower, outer surface portion of said tank and depending from said tank and connected at a lower edge portion thereof to an inner bottom portion of 0 the ship or the like to hold the tank downwardly against the insulation and prevent both overturning movement of the tank and vertical upward movement of the tank, the circumferential spacing of the plates and their points of attachment to the tank re- 5 ducing stresses on the tank from the tie down means due to circumferential expansion and contraction of the tank and the attachment of the plates to a lower portion of the tank reducing stresses on the tank from the tie down means due to vertical expansion and contraction of the tank.

ff/Yfank as in claiiii lfwherein thTedown p lates reinforce the lower portion of the tank, thus enabling the use of thinner plates in the lower portion of the tank.

3. A tank as in claim 1, wherein said tie down plates are oriented substantially parallel to the axis of revolution of the tank.

4. A tank as in claim 3, wherein said tank has a nonplanar bottom and said insulated support means has a configuration complementary to the tank bottom to increase the resistance of the tank to movement relative to said support.

5. A tank as in claim 1, wherein said insulated support comprises an inner bottom steel plate in said ship or the like and at least one layer of load supporting insulation means on said steel plate, said tank supported on top of said load supporting insulation means over substantially the entire bottom of the tank.

6. A'tankas in claim wherein said load supporting insulation means comprises a plurality of plywood boxes filled with perlite stacked on top of said steel inner bottom plate, and a layer of plywood on top of said perlite filled boxes.

7. A tank as in claim 5, wherein said'insulation means comprises a plurality of layers of PVC foam stacked on top of said steel inner bottom plate and a layer of plywood on top of said foam.

8. A tank as in claim 5, wherein said tie down means is pretensioned to hold the tank tightly against the insulated support and to compensate for any change in tank size or compression of the support or the like after in stallation of the tank.

9. A tank as in claim 8, wherein said tie down plates have upper and lower edges and side edges, the upper edges thereof secured to said tank and the lower edges thereof secured to said insulated support, the side edges of adjacent plates spaced from one another to enable said contraction and expansion of said tank.

10. A tank as in claim 9, wherein a plurality of elongate circumferentially extending plates having inner and outer surfaces and upper and lower edges are welded to the tank with the inner surface in flat abutting contact with the tank, and a plurality of gusset plates are welded to the outer surface of the plates, said gusset plates having a slot therein extending substantially perpendicular to the surface of the tank, and said upper edge of said tie down plates turned angularly inwardly and welded in said slots.

11. A tank as in claim 10, wherein the tie down means includes at least one elongate relatively narrow bar secured to each said tie down plate at the lower edge thereof and extending parallel to the lower edge of said tie down plate and having an upper surface, a pair of annular, vertical, radially spaced walls on said support means, at least one elongate, relatively narrow bar secured to at least one of said annular walls at the upper edge thereof and having a lower surface, the lower edge of said tie down plates received between said annular walls with said bars on said tie down plates positioned beneath the bar on said at least one annular wall with the upper surface of the bar on the tie down plate in engagement with the lower surface of the bar on said at least one annular wall to hold said tie down plates downwardly between the annular walls.

12. A tank as in claim 11, wherein there are two bars on the lower edge of each tie down plate adjacent the opposite edges thereof and extending parallel to the lower edge of the tie down plate toward one another, and a plurality of bars on said at least one annular wall at the upper edge thereof and spaced apart in end-toend relationship a distance at least as great as the length of the bars on the tie down plates, the adjacent ends of the bars on the tie down plates spaced apart a distance at least equal to the length of the bars on the annular wall, so that said lower edge of said tie down plates and the bars thereon may be inserted downwardly between the upper edges of the annular walls and the bars thereon and then slid edgewise to position the bars on the tie down plates beneath the bars on the annular walls.

13. A tank as in claim 12, wherein an annular plate is secured between the annular walls below the bars secured to the upper edge thereof a distance greater than the width of the bars on the lower edge of the tie down plates so that the lower edge of the tie down plates is enabled to move vertically a limited distance between the annular walls.

14. A tank as in claim 13, wherein there are a plurality of similar bars at the upper edge of each annular wall, the bars on each annular wall being coextensive in length and in alignment with one another, and there are a plurality of similar bars on opposite sides of the lower edge of each tie down plate.

15. A tank as in claim 14, wherein the upper surface of the bars on one side of the lower edge of the tie down plates are inclined in a first plane, the upper surface of the bars on the other side of the lower edge of the tie down plates are similarly inclined in a plane parallel to and spaced from the first plane, and the lower surfaces of the bars on the annular walls are similarly inclined in respective spaced parallel planes, parallel to the planes of the surfaces of the bars on the tie down plats, so that as the tank contracts and expands and the tie down plates thus move relative to the annular walls, the surfaces of the respective adjacent bars remain in engagement with one another.

16. A tank as in claim 10, wherein there are a plurality of adjustable fastening means secured to the lower edge of said plates and to said tank support, said adjustable fastening means enabling adjustment of the tie down means during and after insulation of the tank.

17. A tank as in claim 16, wherein said adjustable fastening means includes threaded bolt means secured to the lower edge of said plates and extending through corresponding holes in said support means, and nut means adjustably threaded onto said bolt means on the side of said support means opposite the tie down plates.

18. A tank as in claim 16, wherein said adjustable fastening means includes turnbuckle means secured at one end to the lower edge of said tie down plates and secured at the other end to the support means.

19. A unique tie down means a in claim 1, wherein insulating means substantially surrounds the tank.

20. A unique tie down means as in claim 19, wherein said tie down means is secured to said tank adjacent a lower portion thereof substantially tangential to the side of the tank.

21. A unique tie down means as in claim 20, wherein said tank has a nonplanar bottom and said insulated support means has a configuration complementary to to movement relative to said support.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nm 2,77 Dated October 22, 1974 NORMAN W. EDWARDS, PETRO, JACQUES GUILHEM and PIERRE JEAN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby ccrrected as shown below:

Pittsburgh-Des Moines Steel Company 50% and Gaz Transport 50% Interest Signed and sealed this 3rd day' of June 1975.

(SEAL) Attest: T r

C. MARSHALL DANN v RUTH C. MASON Commissioner of Patents Attesting Officer s and Trademarks

Claims

1. In combination, a tank and tie down means therefor, for containing and transporting low temperature fluid in a ship or the like, comprising a support for the tank in a bottom portion of a ship or the like, load bearing insulation on said support, said tank supported at its bottom on said load bearing insulation, a depending, annular skirt fixed to a lower outer surface portion of the tank and comprising a plurality of circumferentially spaced apart tie down plates each extending circumferentially in a direction generally parallel to the curvative of the tank and fixed at an upper edge thereof to said tank at circumferentially spaced locations on a lower, outer surface portion of said tank and depending from said tank and connected at a lower edge portion thereof to an inner bottom portion of the ship or the like to hold the tank downwardly against the insulation and prevent both overturning movement of the tank and vertical upward movement of the tank, the circumferential spacing of the plates and their points of attachment to the tank reducing stresses on the tank from the tie down means due to circumferential expansion and contraction of the tank and the attachment of the plates to a lower portion of the tank reducing stresses on the tank from the tie down means due to vertical expansion and contraction of the tank.

2. A tank as in claim 1, wherein the tie down plates reinforce the lower portion of the tank, thus enabling the use of thinner plates in the lower portion of the tank.

6. A tank as in claim 5, wherein said load supporting insulation means comprises a plurality of plywood boxes filled with perlite stacked on top of said steel inner bottom plate, and a layer of plywood on top of said perlite filled boxes.

7. A tank as in claim 5, wherein said insulation means comprises a plurality of layers of PVC foam stacked on top of said steel inner bottom plate and a layer of plywood on top of said foam.

8. A tank as in claim 5, wherein said tie down means is pretensioned to hold the tank tightly against the insulated support and to compensate for any change in tank size or compression of the support or the like after installation of the tank.

12. A tank as in claim 11, wherein there are two bars on the lower edge of each tie down plate adjacent the opposite edges thereof and extending parallel to the lower edge of the tie down plate toward one another, and a plurality of bars on said at least one annular wall at the upper edge thereof and spaced apart in end-to-end relationship a distance at least as great as the length of the bars on the tie down plates, the adjacent Ends of the bars on the tie down plates spaced apart a distance at least equal to the length of the bars on the annular wall, so that said lower edge of said tie down plates and the bars thereon may be inserted downwardly between the upper edges of the annular walls and the bars thereon and then slid edgewise to position the bars on the tie down plates beneath the bars on the annular walls.

21. A unique tie down means as in claim 20, wherein said tank has a nonplanar bottom and said insulated support means has a configuration complementary to the tank bottom to increase the resistance of the tank to movement relative to said support.