US 2905352 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
Sept. 22, 1959 Filed June 24, 1958 J- J. HENRY STORAGE TANK AND MEANS FOR SUPPORT OF SAME 2 Sheets-Sheet 1 BY M,MM M/,
Jmes JHw 'y WyM flttornggs Sept. 22, 1959 J. J. HENRY 2,905,352
STORAGE TANK AND MEANS FOR SUPPORT OF SAME Filed June 24, 1958 2 Shets-Sheet 2 United States Patent STORAGE TANK AND MEANS FOR SUPPORT OF SAME James J. Henry, New York, N.Y., assignor to Constock International Methane Limited, Nassau, Bahamas, a corporation of the Bahamas Application June 24, 1958, Serial No. 744,278
6 Claims. (Cl. 220-15) This invention relates to the storage and transportation of a commodity which needs to be maintained at extremely low temperature, and it relates more particularly to the transportation of a liquefied gas in large volume in tanks which are mounted in or on a moving vehicle, such as a ship.
This invention will be described with reference to natural gas and its transportation in a liquefied state from a source of plentiful supply to an area where a deficiency exists wherein the liquefied gas can be revaporized to the gaseous state for use. While it is more economical to make use of a pipeline for the transmission of natural gas in a gaseous state, such pipeline operation is not economical where the source of supply is separated from the area where a deficiency exists by a large body of water. As a result, to make natural gas available in such isolated areas, it becomes necessary to confine the gas in suitable containers for transportation on a moving vehicle, such as a ship or the like. When such means of transportation is employed, it becomes wholly impractical to transport the gas while in a gaseous state.
It is known that when natural gas is reduced from a gaseous state to a liquefied state it will occupy about of the space of a corresponding amount of natural gas at equivalent pressure so that it becomes practical to liquefy the natural gas at the source of plentiful supply for transportation in a liquefied state to the area where a deficiency exists, where the liquefied gas can be reconverted to the gaseous state for use.
For transportation of the liquefied gas in large volume, it is desirable to house the liquefied gas in suitable containers maintained at about atmospheric pressure or, preferably slightly above. Natural gas is composed mostly of methane which has a boiling point at -258 F. at atmospheric pressure. However, the liquefied gas will be found to have a boiling point slightly above 258 F. because of the small amount of heavier hydrocarbons which are present, but the critical point will usually be below 240 F. Thus, the liquefied gas will have to be maintained at a temperature below 240 F. for transportation in the tanks.
It is contemplated that the liquefied natural gas will be housed in large metal tanks of thousands of barrels capacity and that these tanks will be confined within a hold space of the ship which is heavily insulated on its outer walls to minimize heat loss into the tanks and corresponding loss of liquid by vaporization. It will be apparent that a number of problems exist which are peculiar to the described situation. In the use of metal tanks of such large capacity in a moving vessel, it is desirable to maintain absolute control of the movements of the tanks so as to avoid bumping or shifting movements thereof in response to the erratic movements of the transportation means, such as the pitching and rolling move ments of a ship on water. If it were otherwise, the cargocarrying tanks would themselves soon become demolished and the insulation and ship would become damaged to the end that an impractical and dangerous situation would soon develop.
The complexity of the problems of harnessing the tanks to hold the tanks in the insulated space is increased by the need to provide for movement of the tanks in expansion or contraction. This need arrises from the fact that the tanks will be installed in the insulated ships hold while at ambient temperature, but will be reduced to a temperature within the range of about -240 to 258 F. when filled with the cargo of the liquefied natural gas. Such change in temperature will naturally result in considerable contraction in the dimensions of the tanks when filled with a liquefied gas, and in corresponding expansions when the tanks are emptied and allowed to rise in temperature.
Thus, it is an object of this invention to provide a construction in a moving vehicle, such as a ship, wherein tanks can be stationarily mounted in the ship while permitting the tanks naturally to expand and contract responsive to temperature change.
More specifically, it is an object of this invention to provide a mounting for ship transportation of tanks of large capacity for housing a cargo which has to be maintained at extremely low temperature and which permits movements of the tanks solely in response to the forces of nature in expansion and contraction, but which maintains the tanks in a predetermined position within the ship notwithstanding the variable movements of the ship on the water.
These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, an embodiment of the invention is shown in the accompanying drawings, in which Figure l is a schematic sectional elevational view of a fragmentary portion of a ships construction showing the tanks in their mounted relation within the ships hold;
Figure 2 is a plan view of the bottom side of a cargo tank shown in Figure 1; 1
Figure 3 is a sectional elevational View taken along the line 33 of Figure l; and
Figure 4 is a sectional view taken along the line 4-4 of Figure 3.
In the illustrated modification, the transportation means comprises a ship 10 formed with an outer hull 12 and an inner hull 14 spaced a short distance inwardly and periodically connected to the outer hull to provide wing tanks in between. The inner hull 14 defines the hold space 15 of the ship in which cargo tanks 18 filled with liquefied natural gas 20 are adapted to be housed for transportation of the liquefied gas at about atmospheric pressure and at a temperature of about -240 F. to 258 F. from a source of plentiful supply, where the gas is liquefied, to an area where a deficiency exists, where the liquefied gas is revaporized for use.
To minimize heat loss into the tanks, the hold space is fully insulated. For this purpose, use is made of thick panels 22 of balsa wood insulation which are secured to the inside surface of the inner hull 14 and to the floor to provide a thick insulation lining the hold space. The tanks are mounted within the insulated hold space and then the tops of the tanks are covered with a packing of insulation material 16 such as batts of glass wool fibers, after which the space is sealed off and made inert by the displacement of air and vapor therein with nitrogen, or other inert gas. It will be understood that other insulating materials may be employed in the panels and in the batts, but detailed description thereof will not be made 7 tion wherein the large metal tanks l 'are mounted within the hold space to secure the tan-ksin a predetermined position out of contact QneWith-theother andtheside walls of the insulation lining the hold space, notwithstanding the pitching and rolling movements of the ship but, -at' the'same timegper'rriit'ting niovement of tliatahk's in expansion and contraction responsive to temperature changes which take-place When-the cargo is introduced or removed from -the" tanks;
For this ptupose; the floor panels 24 f the insulatien layer are provided with elongate slots 26* extending; lengthwise of the ship in-lengthwi's'e alignment with thecenter's-of-thet'ankor tanks when measured in the direction crosswise of the ship'. Onesuch elongateslot 28 is provided at the center of the' tanle to extend an equivalent distance in each direction from the center While othersspacedtheref'rom may comprise a single slot but are preferably formed as a series of spaced slots in endwise alignment.
Each of the tanks 18 is formed-with corresponding keys-30 which-extend downwardly from the bottom wall of the tank and are dimensioned to-be received within the slots. The keys are dimensioned to have a width corresponding t'o-the' width of the slots topermit the keys to be received in fitting relationship within the slots; The center key 3011 is dimensioned to" have a length corresponding tothe length of the center slot 2'8; but the remainder of the keys aredimensioned to have a length lessthan the lengths of'tlie corresponding slots 25 so-that the keys will be received within the slots in a manner topermit relativeendwise movement but not relative crosswise movement. Sincemovement from the assembled relationship will be in the direction towards the center key in response to contraction of the tank upon cooling down by theintroduction of the cargo, it is" desirable to arrange the keys, other'than the center keys, to he received in the outer end portions of the" slots' to provide a spaced relationship 32 between" the inner ends of the keys" and the innerends of the slotsv which is at least as great as the amount of contraction calculated to take place in the relative portion of the tank.
By way of explanation, it will lie apparent that the interconnection between the tank and the supporting i'nsulated floor along the center of the tank' lengthwise" of the ship will enable the latter portions of the tank freely to expand or contract relative to its center, whereas the comparatively small amount of contraction-which takes place in the width of the key inthe corresponding} keyway will provide for a continued fitting relationship ther'ebetwee'n to maintain the tank in it's-centered'relation and resist displacement responsive to movements of the shiponthe Water. Thus, support is providedthroughout the length of each oi the tanks to resist sidewise'movement which constitutes the principal activating forces during ship transportation.
The movements ofthe ship which would tend to cause lengthwise displacement ofthe tanks are relatively small. Thus it is sufiicient to rely upon the fitting relationship between the center key in the center keyway or slot. The amount of expansion and contraction which occurs in the length of the key at the center is insignificant, thereby to maintain a good fitting relationship in the lengthwise as well as in the crosswise direction to minimize relative movements of the tank from its predeterminedl position. The amount of relative-movements in other portionsof the tank responsive to contractions and expansions increases in proportion: with the distance from the center, thus the slots or keyways spaced from the center are formed to a length greater than-the corresponding key received thereinto permit displacement of the key in the lengtl iwise direction withinthe slotin accordance withthe lengthwise movement of the tank relative to the center, while still retainingoperativeengagement between the keys and keyways in the crosswise direction to resist sidewise thrust generated by the tossing ship. 7
To stand up under the forces in operation, the floor 24; formedof panels-ofbalsw'wood; paper honeycomb or the like insulation panels, isconstructed with hardwood sections 34 in the portions lengthwise aligned with the centers of the tanks. The hardwood is formed to a depth greater than the distance of the slots or keyways 26 to provide a high strength", wear-resistant surface in contact with: the keys'of the tanks;'- The depth?v of: the keys 30 and the keyways-l6?- is not critical since the bottom of the tanks will generally rest upon the floor notwithstanding, expansions and contractions in the vertical direction; *(firdin'arily, keys form'editoa depth. of about 1 /2 to 3 inches will be suflicient, with a corresponding or greater depthiin therkeywaya.
A similar key and keyway construction can be employed to intercoimfthe top ofth'e tanks with the framework of the ship. Instead of forming the keyways in the insulation layer, the keyways will be provided i'ntheform ofwooden or metallic members secured to the framework of the ship'with' the slotted portionextending downwardly into sliding engagement with" keys formed to extend upwardly from" the top wall of the tanks rscompensate for the" expansion and" contraction of the tank in the vertical direction, the keys; and keyways should he dimensioned so that the key will extend into-the" key-way, at normal temperature; for'a distance greater than the amount of contraction calculated to take place" in the tank sothat the keys will remaininthe keyways'wh'en thetank is reduced to open atingtemperatureby the liquid carg'cr In the preferred modification, usei will" be' made of tanks of rectangular shape for more efiicient utilization. of the holdspace. It will be' apparent, however, that the concepts described will have the same application under thesameconditionswl'ietlier the tanks' are formed of rectangular, square, round, oblong" or of'oth'er shapes in cross-section.
It will be understood that changes may be made in the details of. construction, arrangement and operation and in the materials of which the various elements are formed without departing from the spirit of the invention, especially'as defined'in the following claims.
1. In the storage and't'ransport'ation-of a liquid which needs to" be maintained at extremely cold temperature in a tank of large capacity housed in an insulated space, means for supporting the tank in the insulated space in a manner which minimizes displacement ofthe tank from. a pr'edetermined'position while permitting free-expansion and contraction of the tank in response to temperature change comprising a-tank having a relatively flat bottom wall which is adapted to rest upon the floor of the insulated" space, keys extending downwardly from the bottom wall of the tank in lengthwise alignment withthe center of' the tank with one of said keys disposed in the center portion of the tank, keyways. formed in corresponding portions of the surface of the insulated floor, sai'd' keyways being dimensioned to have a width corresponding to the width of the keys to receive the keys therein in fitting relation, the center keyway being dimensioned to have a length corresponding to the length of the center key to receive the latter therein in fittingv relation, the other keyways being dimensioned to: have a length greater than the corresponding keys received there in to enable displacement of the keys in the keyways responsive to contraction and expansion. of the tank.
2 An assembly as claimed inv claim. 1 in. which the keys spaced outwardly from the center are adaptedtobe disposed in. the outer portions ot the corresponding keyways at normal temperature to provide a spaced relationship between the inner ends of the keys and the keyways into which the keysmay be displaced upon contraction of the tank 3. An assembly as claimed claim. 1. in. whichthe insulated floor includes lengths of hardwood aligned lengthwise with the center of the tank and in which the keyways are formed.
4. An assembly as claimed in claim 1 in which the keyways are dimensioned to have a depth greater than the depth of the keys so that the tank will rest on the floor.
5. An assembly as claimed in claim 1 which includes similar keys in the top wall of the tank and similar keyways in the adjacent supporting structure in which the keys are received to position the upper end portion 10 of the tank in the insulated space in a manner to permit free expansion and contraction movements.
6. An assembly as claimed in claim 5 in which the keys in the top wall of the tank are dimensioned to extend into the corresponding keyways by an amount greater than the change in dimension of the tank in height so as to maintain operative engagement between the keys and keyways.
No references cited.