US3818664A

US3818664A - Insulated tank base and insulated block

Info

Publication number: US3818664A
Application number: US00330549A
Authority: US
Inventors: E Hillberg; L Isenberg
Original assignee: Rockwell International Corp
Current assignee: Boeing North American Inc
Priority date: 1973-02-08
Filing date: 1973-02-08
Publication date: 1974-06-25
Anticipated expiration: 1991-06-25

Abstract

An insulated base for a cryogenic liquid storage tank is formed of a plurality of horizontally extending layers of base insulation blocks having a high compressive strength, low thermal conductivity and which are impervious to water vapor. Each block comprises a closed paperboard box of 20'''' X 40'''' X 4'''' thick having a plurality of vertical divider panels forming a loadbearing grid within the box. All space within the box is filled with a foam-in-place polyurethane that bonds itself to all surfaces of the box and to the divider panels to thereby laterally support and stiffen the load-bearing panels. Each box is individually encapsulated by being completely covered with a vapor-impervious coating. Additional strength is provided by a tension strip completely encircling the 4-inch sides of the box.

Description

United States Patent 1191 Hillberg et a1.

[ June 25, 1974 [54] INSULATED TANK BASE AND INSULATED 3,383,004 5/1968 Closwer 161/68 X BLOCK 3,553,054 1/1971 Maus 3,587,479 6/1971 Geschwender 161/68 X [75] Inventors: Ernest T. Hillberg, La Habra; Lionel Isenberg Downey both of Cahf' Primary Examiner.lohn E. Murtagh [73] Assignee: Rockwell International Corporation,

El Segundo, Calif. [57] ABSTRACT [22] Filed: 1973 An insulated base for a cryogenic liquid storage tank [21] Appl. No.: 330,549 is formed of a plurality of horizontally extending layers of base insulation blocks having a high compressive strength, low thermal conductivity and which are [52] US. Cl 52/309, 52/618,2126(1//g% impervious to water vapor Each block comprises a closed paperboard box of 20X40"X4 thick having a 2; plurality of vertical divider panels forming a load- 1 7 2? 60 22029 A B 5 bearing grid within the box. All space within the box is F g 3 filled with a foam-in-place polyurethane that bonds itself to all surfaces of the box and to the divider panels to thereby laterally support and stiffen the load- [56] References Cited bearing panels. Each box is individually encapsulated UNITED STATES PATENTS by being completely covered with a vapor-impervious 2,911,076 11/1959 Saunders 161/68 X coating. Additional strength is provided by a tension 2,912,940 1 1/1959 Barowi 52/309 strip completely encircling the 4-inch sides of the box. 3,264,165 8/1966 Stickel 52/406 3,295,279 l/1967 Wilkins 52/615 7 Claims, 3 Drawing Figures 1 [W77 1 1 h 74 f W5"? '3 I 7i (Li s 5:1 7 I I I I I I y \Y/ 7/ AV AV/N/AV A 7 7//, \Y/

INSULATED TANK BASE AND INSULATED BLOCK BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to insulation of cold liquid storage tanks and more particularly concerns an insulated base for supporting and insulating the tank upon and from its foundation.

2. Description of Prior Art In the storage of cold materials and, in particular, cryogenic liquids including the various liquified gases, it is not only necessary to provide a thermal insulation between the tank and the ambient atmosphere, but also between the tank and the supporting ground. Supporting large liquid-containing tanks above ground is neither practical nor economically feasible. The tanks may be as much as 150 feet in diameter and anywhere from 50 to 100 feet in height, whereby the weight of the liquid exerts large compressive forces on a tank base and support. It is necessary to provide a base structure that will not only accept these large compressive loads but which also will provide a significant amount of thermal insulation between the surrounding earth and the tank body.

Storage tanks for cryogens of the type not requiring vacuum insulation are currently supported and isolated from the ground by a complicated and expensive insulation system. From the lowermost element upward, major elements of the present systems comprise a dishshaped concrete foundation, a layer of sand, a number of courses of foam glass or foam ceramic bricks and a second layer of sand over the top course of bricks. The bottom of the tank rests upon the upper layer of sand and is supported by the bricks. Foam glass is a relatively poor thermal insulator, having a thermal constant of 0.78 BTU per square foot per hour per degree Fahrenheit. Insulation properties of foam glass or foam ceramic are rapidly degraded because in use, these materials soak up moisture which thereupon freezes. Accordingly, the tank is ultimately supported by a block of ice which has even poorer thermal insulation properties.

A base of foam glass having poor thermal insulation efficiency requires up to 40 inches or more of glass thickness to limit thermal leakages to BTU per hour per square foot. Glass brick, furthermore, is quite expensive to fabricate and requires high labor costs for installation. Another serious disadvantage of the glass block is its fragility (which is also true of ceramic glass) and much of the expense of a glass block base insulation system is involved in the breakage of the bricks during shipment and installation.

Because of the relatively poor thermal insulation properties of foam glass and foam ceramic brick, and because of the degradation of such thermal properties when moisture is drawn to the blocks, it is found that the supporting ground for a distance as much as 75 yards from the tank will often be frozen. To avoid such problems, it is common to provide heating ducts within the lowermost concrete supporting layer. Thus, in the present state of the art, one is faced with the anomalous requirement of supplying heat to a device whose purpose is to prevent heat from flowing.

Accordingly, it is an object of the present invention to provide a lightweight stable building material having a higher resistance to heat flow, which can withstand long term compressive loads, whose thermal and structural characteristics are unaffected by moisture, and which is readily fabricated, transported and installed.

SUMMARY OF THE INVENTION In carrying out principles of the present invention in accordance with a preferred embodiment thereof, a base insulation block is formed of a closed container having a top and bottom, and a continuous sidewall extending between the top and bottom. Divider panels within the container separate the interior into several compartments, all of which are substantially entirely filled with a plastic foam that is firmly in contact with inner surfaces of the container and with the divider panels to thereby support and stabilize the panels when the latter are subjected to compressive loads applied to the top and bottom of the container. A vaporimpervious barrier encapsulates the entire container.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates part of a cryogenic liquid tank base formed of base insulation blocks of the present invention, together with a portion of a tank supported thereon;

FIG. 2 is a pictorial view, with parts broken away, of a base insulation block of the type employed in the base shown in FIG. 1;

FIG. 3 illustrates a modified form of insulation block adapted for use as a cryogenic pipe support saddle.

DETAILED DESCRIPTION A tank 10 for cold storage of materials such as cryogenic liquids including the various types of liquified gases, includes a sidewall 12 having an external sidewall supporting and thermal insulating structure 14 and a bottom wall 16 resting upon a layer of fine particles 18 that supports the bottom wall 16 throughout its entire extent. Particles 18 may be of many different types such as sand, fiber, plastic and the like. The bed of sand 18 rests upon the uppermost layer'20 of a plurality of superposed layers of base insulation blocks including an intermediate layer 22 and a lowermost layer 24. Lowermost base insulation block layer 24 rests upon a second or lower bed of sand 26 which in turn, rests upon a solid concrete foundation 28 that may be suitably reinforced with structural steel (not shown) or the like, as deemed necessary or desirable.

Each of the

layers

20, 22 and 24 is formed of a plurality of base insulation blocks of the type illustrated in FIG. 2, as will be more particularly described hereinafter. As can be readily seen in FIG. 1, the blocks are laid so that the adjoining layers are in a staggered relation, with the blocks of one layer overlapping several blocks of an adjoining layer. The blocks have a thickness of from 2 to 6 inches and a width and length each from 10 to inches. A convenient block size that is presently deemed to be preferable for a base system such as shown in FIG. 1 is 22 44 4". The 4-inch dimension, of course, extends vertically, the blocks being laid with their larger dimensions extending horizontally.

As the lowermost layer of blocks is installed, the several blocks are positioned closely adjacent to one another, and when a significant area has been covered, or when the entire area of the space has been covered, a layer of fine particles, such as a fine sand, is swept over the upper surface of the blocks so as to penetrate the vertically extending joints between adjoining blocks. The upwardly extending horizontal surfaces of the blocks are kept clean so that when the second layer 22 of blocks is laid upon the first, the lower surface of blocks of layer 22 are all in close and intimate contact with the upper surface of the blocks of layer 24.

The blocks of layer 22 are also positioned in relatively close juxtaposition with regard to adjacent blocks in the same layer, and the vertically extending joints therebetween again are filled with fine particles such as sand. The third layer of blocks, layer 20, is likewise placed upon the second layer 22 so as to provide a close and intimate contact between the bottom of the blocks of the upper layer and the top of the blocks of the lower layer. This contact between layers is enhanced upon application of the weight of a load to be supported by the several layers, and therefore provides a liquidand vapor-impervious barrier (since each of the blocks is individually vapor impervious as will be described below). At the same time, the sand between vertically extending joints of the blocks in any given layer permits a degree of relative motion and settling of the entire arrangement.

If deemed necessary or desirable, additional moisture barriers in the form of continuous vapor-

impervious sheets

19, 21 and 23 are positioned atop the upper layer and upon either side of the bottom layer.

As illustrated in FIG. 1, the layers of base insulation blocks extend to the outer periphery of the insulation and supporting structure 14 of the tank wall. As stated above, neither the blocks in any given layer nor the adjacent layers of blocks are in any way secured or adhered one to another. If deemed necessary or desirable, a fixed wall of concrete, steel or the like, such as outer wall 28, may extend about the periphery of the several layers of blocks to confine these layers to the enclosed area and to prevent horizontal travel under load or vibrations that may be experienced. Nevertheless, other than such confining boundary, no block is secured to any other block, whereby settling and shifting of the

base layers

20, 22 and 24 may occur without adverse effect to the base.

As shown in FIG. 2, each block comprises a container 32 having a continuous sidewall formed of sides 34, 36 and ends 38, 40. The container also has a bottom 42 and a top 44. If deemed necessary or desirable, the top and bottom each may be formed of a pair of mating flaps, each integral with a respective one of the sides or ends, for example. In a preferred form of construction employing a block 4 inches in thickness having a width of 22 inches and a length of 44 inches, the

bottom is formed of a pair of flaps, each 44 inches in length and ll inches in width. Similarly, the top is formed as a pair of flaps, each integral with the respective sides of 34, 36 and each having a length of 44 inches and a width of 11 inches. Accordingly, when the top and bottom flaps are folded to lie in the plane of the top and the bottom of the container, respectively, a fully closed 6-sided container is provided.

Positioned within the container are a plurality of divider and

support panels

48, 50 and 52 which form a reticulated or grid pattern. Each of the panels extends between a pair of opposite sides of the container and extends vertically from the bottom 42 to the top 44. Preferably, the several

intersecting support panels

48, 50 and 52 are notched as indicated at 54 to facilitate interconnection and intersection of the support panels without degrading the vertical support afforded thereby. Although a grid of three support panels is illustrated, it will be readily appreciated that the grid may be formed of two or more than three panels, as deemed necessary or advisable.

The grid of support panels is placed within the container with the bottom of the latter in closed position. With the top open, a suitable plastic, preferably polyurethane foam, is either sprayed or poured in place to fill the entire interior of the container. The foam expands as it cures, and after placing the appropriate amount of foamable material within the container, the top is placed in closed position or, in the case of the top flaps, the flaps are folded over to the plane of the top to thereby completely enclose the container with the expanding and curing foam confined therein. The container is held or clamped in such a position until the foam has completed its expansion and cure. During this time the foam will adhere itself to all of the interior surfaces of the container and to all the surfaces of the divider panels, thereby firmly supporting all of the divider panels and all of the box sides, to therefore stabilize these elements and enhance their compressive load-bearing ability. Where the top and bottom are formed of mating flaps or otherwise, the top and bottom are suitably secured in position as by adhesive tape (not shown) or the like. However, such adhesive tape may not be required where the vapor-impervious coating employed to encapsulate the entire foam-filled container has sufficient strength to hold the portions of the container in place.

After filling the compartmented container with the foam, the entire exterior of the container is encapsulated as by covering with a vapor-impervious coating 56 extending entirely around and over the outside surfaces of the container.

For economy of construction and durability, it is preferable to form the container of a nonmetallic sheet material such as paper, fiberboard, plastic, cardboard or a glass fabric. Typically, a cardboard self-lid box (having integral mating top or lid flaps) is impregnated with a phenolic and found suitable for use in the described base insulation blocks. Preferably, the cardboard is of the type having a corrugated core between a pair of facing sheets.

Various types of foam may be employed, either sprayed or poured in place, including syntactic foam, phenolic foam, reinforced polyvinylchloride foam, urea formaldehyde foam, polystyrene foam or urethane foam, among others. The urethane foam is preferred because of its relatively low cost and low thermal conductivity. Preferably, such a foam, having a density of from 2 to 12 lbs. per cu. ft. is employed. It will be readily observed that the urethane foam extends over the major portion of the area of the base and, accordingly, provides the maximum portion of the thermal barrier. The cardboard box or container, which may be formed of a material approximately 0.25 inches thick, provides but a small and relatively poor thermally conductive path for heat flow. The divider panels carry nearly all of the compressive load.

Obviously, various types of sealing coatings or encapsulating coatings may be employed. Typically, a plastisol or urethane elastomer is used as the outer vaporproof coating.

To increase the compressive strength of the described base insulation block or to enable use of cardboard container and divider panels (the divider panels being formed of the same material as the container) of lesser thickness without loss of compressive strength, a tensile stiffening member such as the strap 58 extends entirely around the 4-inch

continuous wall

34, 36, 38, 40 and is bonded thereto. The tensile strap 58 may be formed of the same material (the same cardboard or paper material) as the container and adhesively secured thereto. The additional tensile strength further restrains outward bowing of the container when subjected to large compressive loads. When the tensile strap 58 is employed, it is also encapsulated by the outer coating 56.

If deemed necessary or desirable, an appropriate adhesive may be placed upon the top and bottom edges of the

divider panels

48, 50, etc. and upon the end edges of these panels to better adhere the panels to the sides and to the top and bottom of the container. However, it is found that as the poured or sprayed-in-place foam expands and cures, it penetrates to some extent between the edges of the divider panels and the container to thereby provide an adequate bond.

Illustrated in FIG. 3 is a modification of the base insulation block of FIG. 2, specifically adapted for support of a pipe 60. In the arrangement of FIG. 3, an integral pipe saddle having ability to support large compressive loads and good thermal insulation properties is formed of a container having a continuous sidewall 62, a bottom 64'and a top 66. The top 66 is curved across the length of the support to conform to the lower surface of the pipe 60 that is to be supported thereby. A plurality of divider support panels, of which those designated at 68, 70 and 72 are shown, form a reticulated pattern or grid extending from side to side and end to end of the container, each bearing firmly against the bottom and top of the container. The upper edges of the several divider panels are curved to conform with the concavity of the top 66.

As in the base insulation block illustrated in FIG. 2 and described above, the interior of the container, which is compartmented by the several support and divider panels 68, 70, 72, is filled with a spray-in-place or pour-in-place plastic such as the above-described urethane foam which self-bonds to all of the surfaces of the support panels and completely fills the container.

The container is formed with a pair of laterally extending oppositely disposed securing

flanges

74, 76 and the entire assembly is encapsulated in a vaporimpervious coating 78 in a manner previously described in connection with base insulation block of FIG. 2. The materials and thicknesses of materials of the pipe saddle of FIG. 3 are preferably the same as those described in connection with the base insulation block in FIG. 2. The dimensions and curvature of the saddle of FIG. 3 will, of course, be determined by the pipe to be supported thereby.

In use, the pipe saddle of FIG. 3 is supported from a foundation 80 that is provided with suitable means such as an integral flange 82 to facilitate attachment of the saddle thereto. Preferably, the attachment is such as to allow a sliding motion of the saddle relative to the support 80 and may comprise a channel 84 fixed to the support flange 82 by means of a bolt or bolts 86 and including a clamping flange 88 overlying the flange 74 of the pipe saddle. An identical clamping channel 90 is provided to hold the flange 76 of the pipe saddle in FIG. 3. Obviously, two or more of the clamping channels may be employed for each flange, if desired.

There has been described an insulated base for a cryogenic liquid storage tank, the base being formed of a number of lightweight boxes capable of supporting large sustained compressive loads, exhibiting superior thermal insulation properties and being substantially free of adverse effects of ambient water. The blocks are simple and inexpensive to fabricate, transport and install, whereby a greatly improved insulated base may be constructed.

The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims. i

What is claimed is:

1. For use in an insulated base for supporting a storage tank for cryogenic liquids, a plurality of base insulation blocks adapted to be laid in a plurality of horizontally extending, relatively staggered layers beneath the bottom of the tank, said blocks each having a high compressive strength, a low thermal conductivity and being impervious to water vapor, each said block comprising a closed cardboard container having sides, ends, top

and bottom,

a divider grid having intersecting divider panels extending from side to side, end to end and top to bottom of said container to divide the container into a number of separate compartments,

a foam-in-place urethane foam emplaced within said container and substantially entirely filling the interior thereof in close and bonded contact with the interior surfaces of the container and the surfaces of said divider grid, to thereby laterally support and stiffen the panels of said divider grid, and

a vapor-impervious coating entirely covering the exterior of the container.

2. The apparatus of claim 1 including a tensile reinforcing strip entirely encircling the exterior of said container.

3. The base insulation blocks of claim 1 wherein said container is of a rectangular configuration having substantially horizontal top and bottom of relatively large dimensions and having sides and ends of relatively small dimensions, and including a tensile reinforcing strip entirely encircling said sides and ends bonded thereto.

4. A base insulation block comprising a closed container having a top and bottom and a continuous sidewall extending between said top and bottom,

a plurality of divider panels within said container extending from said top to said bottom,

a urethane foam substantially entirely filling said container and in contact with the inner surfaces thereof and with said divider panels to thereby support and stabilize said divider panels when the latter are subjected to compressive loads applied to said top and bottom of the container, and I a vapor-impervious barrier encapsulating said container.

5. The block of claim 4 wherein said container is made of phenolic impregnated paper.

6. The block of claim 3 wherein said sidewall in cludes first and second opposite sides, said top being formed in two mating flaps, each integral with a respective one of said first and second opposite sides.

7. The block of claim 6 wherein said block has a thickness of from 2 to 6 inches, and a length and width from 10 to inches each.

Claims

1. For use in an insulated base for supporting a storage tank for cryogenic liquids, a plurality of base insulation blocks adapted to be laid in a plurality of horizontally extending, relatively staggered layers beneath the bottom of the tank, said blocks each having a high compressive strength, a low thermal conductivity and being impervious to water vapor, each said block comprising a closed cardboard container having sides, ends, top and bottom, a divider grid having intersecting dIvider panels extending from side to side, end to end and top to bottom of said container to divide the container into a number of separate compartments, a foam-in-place urethane foam emplaced within said container and substantially entirely filling the interior thereof in close and bonded contact with the interior surfaces of the container and the surfaces of said divider grid, to thereby laterally support and stiffen the panels of said divider grid, and a vapor-impervious coating entirely covering the exterior of the container.

4. A base insulation block comprising a closed container having a top and bottom and a continuous sidewall extending between said top and bottom, a plurality of divider panels within said container extending from said top to said bottom, a urethane foam substantially entirely filling said container and in contact with the inner surfaces thereof and with said divider panels to thereby support and stabilize said divider panels when the latter are subjected to compressive loads applied to said top and bottom of the container, and a vapor-impervious barrier encapsulating said container.

6. The block of claim 3 wherein said sidewall includes first and second opposite sides, said top being formed in two mating flaps, each integral with a respective one of said first and second opposite sides.

7. The block of claim 6 wherein said block has a thickness of from 2 to 6 inches, and a length and width from 10 to 80 inches each.