US3095107A - Stabilization means for storage tanks - Google Patents

Description

June 25, 1963 H. w. BERGMANN 3,095,107

STABILIZATION MEANS FOR STORAGE TANKS Filed March 16, 1961 2 Sheets-Sheet 1 JNVENToR. .Heznrzch ZU. Bergmann 2 Sheets-Sheet 2 n INVENToR. Hez'nrzchlllevymdnn Ww H. W. BERGMANN STBILIZATION MEANS FOR STORAGE TANKS FIG.e 4

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June 25, 1963 Filed March 16, 1961 3,095,167 Patented June 25, 1963 dine 3,095,107 STABILIZATION MEANS FR STORAGE TANKS Heinrich W. Bergmann, Norman, Okla., assignor to Couch International Methane Limited, Nassau, Bahamas, a corporation of the Bahamas Filed Mar. 16, 1961, Ser. No. 96,120 8 Claims. (Si. 22d-15) This invention relates to the storage and transportation of liquid having a temperature differing Widely from ambient temperature and it relates more particularly to the over-water transportation of a low boiling liquefied gas, such as liquefied natural gas.

The invention will be described with reference to the storage of large volumes of gas in a liquefied state for ship or over-water transportation of the natural gas from a source of plentiful supply to an area where a deficiency exists. It will be understood that the concepts of this invention will have application also to the storage and transportation of other loW boiling liquefied gases or liquids maintained at an extremely cold temperature and that the concepts of this invention are applicable also to other means of transportation in which the storage container might be subject to rocking, rolling or pitching movements, in addition to the expansions and contractions due to temperature change.

vFor the storage and transportation of natural gas in large quantities, it is desirable, from the standpoint of space utilization, to reduce the gas to a liquefied state whereby it is reduced about 60G-fold in volume. It is also desirable to house the liqueiied gas in containers of large capacity with the result that it becomes impractical to consider storage under pressure conditions departing Widely from atmospheric pressure. Under such circumstances, the liquefied gas will 4be maintained in the storage container at about atmospheric pressure, which, for liquefied natural gas composed mostly of methane, will mean storage at a temperature of about --248 F. to about 258 F., depending upon the amount of higher molecular weight hydrocarbons present in the liqueed natural gas.

There are a number of extremely important problems presented in the storage and transportation of such extremely cold liquid in large volume. For one thing, it is desirable to surround the liquid storage tank or container with an effective amount of thermal insulating material not only to minimize loss of cargo by vaporization due to heat loss into the liquid from the surrounding atmosphere, but it is also desirable to protect the steel hull and structure of the ship or other transportation means from the cold of the liquid, otherwise the ship will be subject to destruction since the steels of which such ships are constructed begin to lose their strength and ductility at low temperatures and cracking can be experienced upon reduction of the steel to a temperature below 100 F.

-For another thing, the storage tank is exposed to extremely wide temperature `change in use which, in the storage and transportation of liquefied natural gas, may range from about -}-l F. during installation or -When the tank is empty to a temperature of about 258 F., when the tank is :filled with liquid cargo. When, as in the usual practice, the tanks are fabricated of a metal which is relatively insensitive to the temperature change, such as aluminum or alloys of aluminum, stainless or the like high nickel steels, copper, brass, etc., a rather wide change in dimension of the tank will take place by reasons of expansions and contractions due to temperature change. In a storage tank with a length of about 100 feet, a change of 3 or more inches in any direction can occur. As a result, the tanke cannot be rigidly tied into the ship structure which is not subjected to the same change in dimension. Instead, it becomes necessary to support the tank within the thermally insulated space in a manner which -Will enable the tank yfreely to expand and contract relative to the ship structure. On the other hand, it is undesirable to allow the tank to move =from a stabilized position, for example, in response to the pitching and rolling movements of the ship, otherwise uncontrolled forces will be developed which might lead to the development of undesirable and dangerous conditions.

Thus it is an object of this invention to provide a means for maintaining a tank of large capacity within a storage space in a manner to permit freedom of movement of the tank within the space by reason of thermal expansion and contraction While at the same time stabilizing the position of the tank within the storage space to maintain full control of the tank during such expansion and contraction movements or other movements of the space in which the tank is mounted.

More specifically, it is an object of this invention to provide a means for mounting a storage tank or tanks of large capacity Within an insulated storage space of a ship Without direct attachment to the ship structure to enable thermal movement of the tank relative to the supporting ship structure, yet with means for stabilizing the position of the centerline of the bottom of the tank ywithin the supporting ship structure to prevent uncontrolled movements of the tank from a stabilized position Within the ship.

These and other objects and advantages of this invention will hereinafter appear and for purposes of i1- lustration, but not of limitation, an embodiment of the invention is shown in the accompanying drawings, in which- FIG. l is a schematic sectional elevational view of a ship, in which a number of storage tanks of large capacity are mounted in accordance with the practice of this invention within the hold space of the ship;

FIG. 2 is a cross-sectional elevational view taken along the line 2-2 0f -FIG. 1;

FIG. 3 is a perspective view partially in section of the bottom side of a tank and supporting flooring with the elements shown in their separated relationship and embodying the features of this invention;

FIG. 4 is a sectional View of the tank in its mounted relationship on the supporting ooring in a bottom sta- -bilized position;

FIG. 5 is a plan view partially in a section of a modification in the key construction;

FIG. 6 is a fragmentary sectional elevational view showing a further modification in the key construction;

FIG. 7 is a fragmentary sectional elevational view similar to that of FIG. 6 showing a still further modification in the key construction; and

FIG. 8 is a plan view partially in section of a further modification in the key construction.

Referring now to the drawings, the numeral 10 represents a ship having a hull structure formed of an outer steel hull 12 and an inner steel hull 14 spaced a short distance from the outer hull and interconnected therewith periodically to provide a sealed space in between deiining wing tanks 16 for ballast of the ship and for circulation of water or the like therethrough to control the temperature of the walls forming the inner hull thereby to .protect the outer hull in the event of escape of cold liquid to the walls of the inner hull. The inner hull represents a preferred construction but it is not essential and thus reference which will hereinafter be made to the hull structure will include a single hull as well Vas a double hull of the type described.

Coiferdams 1S which extend crosswise of the ship beytween the hull structure subdivide the hold space of the ship into a plurality of longitudinally spaced apart separated hold compartments 20. A relatively thick layer 22 of thermal insulating material is applied as a lining to the side walls of the compartments and as a flooring 24 on the bottom wall to insulate the hold space. Mounted within the insulated hold space are one or more tanks 26 of large capacity for housing the liqueed natural gas or other extremely cold liquid. Such storage tank or tanks may be of rectangular shape for fuller utilization of the space available -in the insulated hold of the ship or they may be of other coniigurations in crosssection but usually they will be formed with a relatively flat bottom wall 28 so that the bottom wall can rest on the insulated flooring 24. As previously pointed out, the tanks of this invention are tanks having suflicient wall thickness and strength for self-sul'ciency under load and they will be formed of a temperature insensitive, structurally strong material which does not experience excessive loss in strength Vor ductility when reduced to low temperature.

The Itank will be tted with the usual connections such as inlet pipes 30 for filling, outlet pipes 32 for the removal of liquid cargo, pressure relief valves 34 and the like gauges for the control of fluid flow, fluid levels and pressures within the tank. Usually these iittings will extend into the tank through a trunk 36 which projects upwardly from about the central portion of the tank through an aligned opening 38 in the deck 40 of the ship to a point above the deck where access can be had to the iittings.

Having briefly set forth the environment, detailed description will now be made of the means for positioning the -tank within ,the insulated hold space without direct attachment to the ship structure whereby the tank is free to move relative to the ship structure in response to expansion and contraction forces due to temperature change, yet is stabilized along a center line in a predetermined position within the insulated hold space to militate against uncontrolled movements relative tothe ship in response to the pitching and rolling movements of the ship.

As illustrated in FIGS. 3 and 4, the insulating oor 24 on which the tank rests is formed of -a relatively thick layer of a structurally strong and dimensionally stable thermal insulating material. In the illustrated embodiment of the invention, such flooring is constructed of a relatively thick layer of balsa wood having a relatively flat top ply 42 of hardwood to more or less protect the softer and more porous balsa wood from the forces and impacts to which it might otherwise be subjected during installation of the tank or during use.

Fixed to the top surface of the hardwood layer is an elongated key 44 which extends lengthwise of the storage space, preferably in lengthwise alignment with about the center Vof the tank adapted to rest upon the supporting ooring. The key is formed of hardwood sections with the grain of Athe Wood in the lower and thinner section 46 extending lengthwise of the key and with the grain of the wood forming the upper and thicker of the sections 48 extending crosswise of the key and in the direction of the more substantially rolling movements of the ship.

Preferably the key 44 is a continuous key as long as or substantially as long as the tank. However, it may beV that because of method of construction, the floor 24 may be formed with 4thin scabs between modular panels whereby it becomes impractical to construct the hardwood key describedras a continuous key having a length corresponding tothe length of Ithe tank. Thus the key 44 may be fabricated of a plurality of shorter key segments 60 spaced lengthwise one from the other to provide an open space .62. therebetween across which Vthe scabs may extend. In such construction, it is desirable either .to cover the key segments by a metal sheath 70 (see FG. 8), such as an aluminum sheath, or it.may be desirable to interconnect the keys by beam 64 secured to the lateral edges of the key segments with `the grain of the wooden meni- 4 ber running in the lengthwise direction, as illustrated in FIG. 5.

The bottom 28 of the tank is provided with a keyway 5t) adapted to engage the key in fitting relationship therein, preferably without the key extending entirely into the keyway and without the keyway coming to rest upon the hardwood layer 42 on the oor. For this purpose, the bottom wall of the tank is provided with a pair of elongated angle irons 52 and 54 secured to the bottom side of the tank with the upright portions 56 spaced cross- Wise one from the other by a distance corresponding to the width of the oor key 44 so as Ito receive a portion of the key in sliding relationship therebetween. The upright portions 56 of the angle irons extend downwardly for a distance substantially corresponding to the thickness 0f the key to receive a major portion of the key therebetween when the tank is properly positioned on the supporting ooring. The load is taken od of the key and keyway construction by a pad 58 of dimensionally stable material interposed between the bottom wall 28 of the tank and the top surface 4Z of the supporting flooring beyond the key and keyway construction. Such pad which may be formed of balsa wood is dimensioned to have a thickness slightly greater than the thickness of the key and also slightly greater than the depth of the keyway so that the pad and flooring will carry the entire weight of the tank while the key and keyway will carry loads having a crosswise direction other than those which had been dissipated by the frictional resistance to relative movement available over the substantial area of contact -between the bottom of the tank and its supporting surfaces. It is possible to line the inner surfaces of the upright portions 56 of the metal angle irons with a butter material, such as wood, in order more uniformly to distribute the crosswise loads.

By way of illustration with respect to the relative proportions of the described elements, a key dimensioned to have a width within the range of l2 to 24 inches and a height of -about 2 inches will be formed with the lengthwise grained portions 46 about `1/2 inch in thickness and with lthe crosswise grained portion 48 of about l1/z inches in thickness. The depth of the key Sti will also correspond to about 2 inches and the pad 58 located between the flooring and the bottom wall of the tank will be dimensioned to be about 2.1/2 inches whereby to space the upper end of the key about 1/z inch from the bottom wall of the -tank and to space the far ends of the keyway about 1/2 inch from the hardwood flooring. It will be understood that the dimensional characteristics can be varied aswell as the relative position of the longitudinally grained and crosswise `grained portions making up the key.

The assembly to eect a tting relationship between the key and keyway, without exposing the keys to destructive unbalanced forces which might become possible when considerable play exists between the lateral edges of the key and the corresponding surfaces of the keyway, can be beneiited greatly by a modification in the construction of the continuousand preferably the keys formed of discontinuous but aligned segments. Such modication, illustrated in FIGS. 6 and 7, include side panels 66 fixed to the lateral edges of the key segments 60 to function as rupturable load bearing elements. In the preferred practice, the segments are deemed to have a thickness greater than the difference between the width of the key and the keyway so that the segments will extend laterally from the key members to a point beyond the upright members deiining the keyways.

Such additional side panels are selected of structural materials which are easily rupturable along the lines of force applied vertically but which are capable of retaining the forces applied laterally. Suitable material is available commerciaily as Panelyte marketed by the St. Regis Paper Company. Such material comprises a plurality of fibrous sheets of paper, etc. arranged in parallel relationship and laminated into a composite structure with a relatively high percentage of a somewhat brittle resin, such as phenol formaldehyde resin, urea formaldehyde resin, melamine formaldehyde resin, and the like.

In response to a force aligned with the edge of the panel, parallel with the laminations, the force elements would easily cut through the panel, yet the panel remains capable of taking lstrong forces in compression applied against its side faces.

The improvement from the standpoint of ease of assembly that is derived by the use of such rupturable load bearing extensions stems from the difficulty perfectly to align the key and keyway during installation. The result of improper alignment between the described elements while lowering the tank into position of use may expose on key segment to `substantially the entire load with the possible rupture thereof. On the other hand, when such extensions are employed, such misalignment as might occur merely results in the misaligned key portion engaging the extension in a manner which would cause said key portion to cut into the extension. This operates to stabilize the tank to the point where it is immediately held against inadvertent rocking movements as would otherwise result in progressive engagement of the key segment or segments with possible destruction thereof.

In the arrangement where the extensions 67 are of such dimension as to require the keyway members to cut into the extensions during installation, it will be apparent that no uncontrolled or otherwise destructive movements will be permitted. The key extensions will be cut by the keyway to provide a snug tting relationship between the key- Way and the key elements disposed therebetween.

It is desirable to locate the key to extend lengthwise of the ship because the greatest destructive forces to which the elements will be exposed will be the forces operating crosswise of the ship in response to rolling movements of the ship. The key and keyway construction is preferably located along the center line of the tank whereby the expansion and contraction movements of the tank will take place with reference to the stabilized center line. It will be understood, however, that the key and keyway means for stabilization can be located other than along the center line of the tank to define the reference point from which expansion and contraction movements occur.

Because of the relatively small forces acting to displace the tank lengthwise in the ship, the frictional resistance to movement under load between the bottom wall of the tank and its supporting flooring will usually be sufficient to stabilize the lengthwise position of the tank without additional stabilization means. However, it will be understood that a similar single key and keyway construction can be provided to extend crosswise of the tank to stabilize the tank at a 'single reference point from which expansion and contraction movements will take place.

Such reference point can also be embodied, if desired, in the longitudinally extending key and keyway by iixing an abutment to confront a crosswise extending portion of the key or by dropping the ends of the keyway slightly beyond the ends of the key to confine the ends of the key whereby the key can shift only a limited distance within the keyway.

It is also desirable to stabilize the position of the tank at the top to minimize rocking movement of the tank responsive to rolling movement of the ship. Various means for top stabilization have been developed, one of which is illustrated in FIG. 2 and is more fully described in my copending application tiled concurrently herewith and entitled Stabilization Means for Tank Mounting. Other techniques are described in the Farrell et al. Patent No. 2,954,003, the copending application of Murphy, Ser. No. 71,085, filed November 22, 1960, now abandoned, entitled Tank Construction for Storage of Cold Material, and the copending application of Beam, Ser. No. 744,225,

. 5 tiled June 24, 1958, now Patent No. 3,007,598, entitled Tank Construction.

It will be understood that the concepts of this invention will have application to the stabilization of tanks of large capacity independent of the cargo where the tank is subject to expansion and contraction characteristics differing from that of the support and where the tank is exposed to movements which tend to unstabilize the position of the tank.

It will be understood that changes may be made in the details of construction, arrangement and operation without departing from the spirit of the invention, especially as defined in the following claims.

I claim:

l. In the storage and transportation of a material having a temperature differing widely from ambient temperature, a container of large capacity having a relatively flat bottom, means for mounting said container within a supporting structure in a manner to stabilize the position of the container within the supporting structure while permitting free expansion and contraction due to temperature change, comprising a iiooring forming a part of the supporting structure having a relatively ilat top surface upon which the container rests, an elongated key member extending upwardly from the surface of the floor to extend lengthwise of the container, a pair of elongated members secured to the bottom of the container in alignment with the key member and spaced one from the other laterally by an amount corresponding to the width of said key member to form a keyway dimensioned slidably to receive the key member therebetween when the container is properly positioned within the supporting structure, and a spacer between the bottom wall of the container and the supporting floor dimensioned to have a thickness greater than the maximum thickness of any one of the members including the key and keyway but less than the sum of the thicknesses thereof whereby the key will be received within the keyway without engagement with the bottom wall of the container and without the keyway engaging the surface of the floor when in the assembled relationship.

2. In the ystorage and transportation of an extremely cold liquid in large volume in a tank of large capacity which is formed of a material characterized by substantial expansion and contraction due to temperature change and which has -a relatively flat lbottom, means for mounting said container within an insul-ated structure in a manner to stabilize the position of the tank within the insulated structure while permitting free expansion and contraction, comprising a flooring Iforming a part of the insulated structure upon which the t-ank rests, an elongated key extending upwardly from the surface of the floor in lengthwise alignment -with the container, a pair of elongated angle members fixed to the bottom side of the bottom wall of the tank and spaced one yfrom the other laterally 'by an amount corresponding to the width of the key member -to dene a keyway dimensioned slidably to receive the key member therein when the tank is properly positioned within the insulated structure, a pad positioned between the bottom wall of the tank and the floor and having a thickness greater than the maximum thickness `of any one of the elements including the key and keyway but less than the sum of the thicknesses thereof whereby the key will be disposed within the key- Way without the key engaging the bottom Wall of the tank and without the keyway engaging the surface of the floor when the tank is properly mounted within the insulated structure.

3. A system as claimed in claim 2 in which the key member comprises a wooden member.

4. A structure as claimed in cl-aim 3, in which the key comprises a wooden laminate having one layer with the wood grain extending in the crosswise direction `and another layer with the wood grain extending in the lengthwise direction, said one layel being of greater thickness than the other layer.

5. A system as `claimed in claim 2 in which the pad disposed Ibetween the bottom wall rand the floor comprises a balsa Wood layer which extends substantially continuously ibetween the at bottom wall of the tank `and the` relative top surface of the floor other than Within the key and keyway portion.

6. A system as claimed in `claim 2, in lwhich the key is ysu-bdivided into separated linearly aligned segments, and a sheath extending continuously over the segments to define la continuous key therebetween,

7. A system as claimed in claim 2, in which the key is subdivided int-o separated linearly aligned segments and which includes elongate members extending continuously alongside the key segments and secured thereto.

8. A system as claimed in Iclaim 2, which includes members extending laterally from the sides of the key formed lbetween the width of the key and width of the keyway thereby -to project in the path of the keyway upon insertion.

References Cited in the tile of this patent UNITED STATES PATENTS 2,906,352 Henry Sept. 22, ,l959` FOREIGN PATENTS 667,215 Great Britain Feb. 27, 1952 1,230,091

France Mar. 2S, 1960 j

Claims (1)

1. IN THE STORAGE AND TRANSPORATION OF A MATERIAL HAVING A TEMPERATURE DIFFERING WIDELY FROM AMBIENT TEMPERATURE, A CONTAINER OF LARGE CAPACITY HAVING A RELATIVELY FLAT BOTTOM, MEANS FOR MOUNTING SAID CONTAINER WITHIN A SUPPORTING STRUCTURE IN A MANNER TO STABILIZE THE POSITION OF THE CONTAINER WITHIN THE SUPPORTING STRUCTURE WHILE PERMITTING FREE EXPANSION AND CONTRACTION DUE TO TEMPERATURE CHANGE, COMPRISING A FLOORING FORMING A PART OF THE SUPPORTING STRUCTURE HAVING A RELATIVELY FLAT TOP SURFACE UPON WHICH THE CONTAINER RESTS, AN ELONGATED KEY MEMBER EXTENDING UPWARDLY FROM THE SURFACE OF THE FLOOR TO EXTEND LENGTHWISE OF THE CONTAINER, A PAIR OF ELONGATED MEMBERS SECURED TO THE BOTTOM OF THE CONTAINER IN ALIGNMENT WITH THE KEY MEMBER AND SPACED ONE FROM THE OTHER LATERALLY BY AN AMOUNT CORRESPONDING TO THE WIDTH OF SAID KEY MEMBER TO FORM A KEYWAY DIMENSIONED SLIDABLY TO RECEIVE THE KEY MEMBER THEREBETWEEN WHEN THE CONTAINER IS PROPERLY POSITIONED WITHIN THE SUPPORTING STRUCTURE, AND A SPACER BETWEEN THE BOTTOM WALL OF THE CONTAINER AND THE SUPPORTING FLOOR DIMENSIONED TO HAVE A THICKNESS GREATER THAN THE MAXIMUM THICKNESS OF ANY ONE OF THE MEMBERS INCLUDING THE KEY AND KEYWAY BUT LESS THAN THE SUM OF THE THICKNESSES THEREOF WHEREBY THE KEY WILL BE RECEIVED WITHIN THE KEYWAY WITHOUT ENGAGEMENT WITH THE BOTTOM WALL OF THE CONTAINER AND WITHOUT THE KEYWAY ENGAGING THE SURFACE OF THE FLOOR WHEN IN THE ASSEMBLED RELATIONSHIP.

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