US 3473689 A
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Get. 21, 1969 L. -J. Hl JTTER 3,473,689
INSULATING FOUNDATION Filed May 29, 1967 INVENTOR A [mm/Q0 (IA 017i? 51 k J 110!! 30 ///I 42 BY Ml 7 m ATTORNEYS United States Patent US. Cl. 220-18 3 Claims ABSTRACT OF THE DISCLOSURE An insulating foundation is provided between a low temperature storage tank bottom and a supporting means or surface. This insulating foundation includes a first plurality of members of generally uniform size and rounded configuration having good load bearing characteristics and being of a substance so as not to transfer excessive heat therethrough. These first plurality of members are in contact with one another and with the tank bottom and the supporting means to transfer the load of the tank bottom to the supporting means. These first plurality of members may be formed for example of gravel or pre-formed insulating concrete. A second plurality of members of good insulating characteristics substantially fill the remaining space between the tank bottom and the supporting means. These second plurality of members comprise a loose granular fill of a size substantially less than that of the first plurality of members, and may comprise for example expanded perlite.
BACKGROUND OF THE INVENTION The present invention relates to an insulating foundation for use with fiat bottom low temperature storage tanks adapted to store substances at a temperature of +32 F. or lower.
Liquids stored at such low temperatures are normally stored in heavily insulated tanks which often have flat tank bottoms. When a flat bottom type of tank is used, it is necessary to provide an insulating material under the bottom of the tank, such material of necessity being such that it has good insulating qualities and also sufilcient strength to support the Weight of the storage tank and its contents. Additionally, the insulating material should preferably be of an inorganic nature, a requirement when storing liquid oxygen, for example.
Conventional foundation materials for low storage tanks have consisted of air entrained solids such as foamed glass, and similar materials. These materials are satisfactory since they have the necessary strength characteristics, and further comprise good insulating material.
However, conventional foundation materials have proved to be disadvantageous for a number of reasons. In the case of foamed glass, the principal disadvantage is the fact that this material has a high unit cost thereby making this type of construction very expensive.
Light aggregate insulating concrete has been employed in the prior art, and is less expensive than foamed glass, but such insulating concrete presents other problems. Firstly, excessive heat of hydration may be created by monolithically placing a large mass of concrete. Additionally, such concrete may not dry sufliciently within a reasonable time after placement because of its large mass. Furthermore, care must be taken to avoid excessive water in mixing the insulating concrete since the lightweight particles therein may float to the top thus creating voids which cause the concrete to break down under load.
SUMMARY OF THE INVENTION The insulating foundation according to the present invention includes a first plurality of members of good load Patented Oct. 21, 1969 bearing characteristics and of a substance so as not to transfer excessive heat therethrough, these members serving to transfer the load from the tank bottom to an underlying supporting means.
A second plurality of members substantially fill the remaining space between the tank bottom and the supporting means, these second plurality of members being in surrounding relationship to the first plurality of members and being of good insulating characteristics so as to provide the desired insulating characteristics for the over-all foundation.
The materials employed in the foundation are relatively inexpensive thereby providing a substantial economic advantage over the materials heretofore employed for this purpose and at the same time the foundation provides the desired structural characteristics sufiicient to adequately transfer the loads involved. The second plurality of members in particular is relatively inexpensive and readily available.
An object of the present invention is to provide a new and novel insulating foundation for use with low temperature storage tanks which provides an economical foundation incorporating good load bearing characteristics and which further exhibits good insulating characteristics.
BRIEF DESCRIPTION OF THE DMWING FIG. 1 is a view of a low temperature storage tank partly broken away illustrating the insulating foundation of the present invention; and
FIG. 2 is an enlarged view of a portion of an insulating foundation according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings wherein like reference characters designate corresponding parts throughout the several views, FIG. 1 illustrates a conventional double wall low temperature liquid storage tank indicated generally by reference numeral 10. The tank includes a dome-shaped roof 12 and an outer substantially cylindrical wall 14. This cylindrical wall 14 is supported on a flat tank bottom 16. An inner generally cylindrical wall 18 is also supported on the tank bottom, and is disposed concentrically within the outer wall 14. A body of insulating material 20 extends circumferentially about the tank between the outer and inner walls so as to provide the desired degree of insulation to the side walls of the tank. It will of course be understood that the roof of the tank is also adequately insulated.
A suitable supporting means 30 in the form of a concrete slab or the like is provided for supporting the weight of the tank. As seen most clearly in FIG. 2, the undersurface 32 of the bottom of the tank as well as the upper surface 34 of support means 30 present generally fiat parallel surfaces between Which the insulating foundation construction of the present invention is disposed.
The insulating foundation includes a first plurality of members 40 which are of a substantially uniform predetermined size and are of a generally rounded configuration. The material of the first plurality of members is selected so as to provide good load bearing characteristics and also so as to be a substance which does not transfer an excessive amount of heat therethrough. The first plurality of members are solid and in a typical example may comprise gravel or pre-formed insulating concrete and the like.
A second plurality of members indicated by reference numerals 42 substantially fill the remaining space between the tank bottom and the support means, these second plurality of members being disposed in surrounding relationship to the first plurality of members.
The second plurality of members comprise a loose granular fill of a size which is substantially less than the size of the first plurality of members. The material of the second plurality'of members is selected so as to be relatively inexpensive and to provide good insulating characteristics. In a typical example, the second plurality of members may comprise expanded perlite, mineral wool and the like.
As seen in FIG. 1, the members 40 are illustrated as being aligned in generally vertical rows, while in FIG. 2 the members 40 are shown as being ofiset from one another in adjacent rows. It is apparent that the members may assume any relationship with one another, and these members are in any event generally uniformly spaced throughout the space between the bottom of the tank and the supporting means and are in contact with one another as well as the bottom of the tank and the supporting means so as to transfer the load of the tank bottom to the underlying supporting means.
The insulating foundation of the present invention of course substantially fills the space between the tank bottom and the supporting means so as to effectively transfer the load of the tank to the supporting means and to provide good insulation therebetween.
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.
1. In combination, a tank bottom, a supporting means spaced from and beneath said tank bottom and defining a confined space of uniform depth therebetween, an insulating foundation disposed within and substantially filling said space, said insulating foundation compristivity, said first plurality of members being in contact with one another and also being in contact with said tank bottom and said supporting means and transferring the weight of the tank bottom to said supporting means, said first members being confined in said space in layers with substantially all of the members of the top layer being in substantial point contact with the tank bottom, a second plurality of members of loose granular material of good thermal insulating characteristics, said second plurality of members substantially filling the remaining space between said tank bottom and said supporting means.
2. Apparatus as defined in claim 1 wherein said first plurality of members comprise pro-formed insulating concrete.
3. Apparatus as defined in claim 2 wherein said second plurality of members are formed of expanded perlite.
References Cited UNITED STATES PATENTS 2,110,470 3/1938 Norton.
2,501,762 3/1950 Davis 220- [8 2,916,179 12/1959 Monroe 220[5 3,076,317 2/1963 La Fave.
3,274,785 9/ 1966 Lange 2209 X 845,046 2/1907 Bechtold 52-l67 948,541 2/1910 Coleman 52-382 FOREIGN PATENTS 538,089 3/ 1922 France. 683,855 12/ 1952 Great Britain.
JOSEPH R. LECLAIR, Primary Examiner ing a first plurality of substantially solid members of GARRETT Assistant Examiner generally spherical configuration, and of uniform predetermined size having good load bearing characteristics and being of a substance having low thermal conduc- U.S. Cl. X.R.