US3305122A

US3305122A - Keyed cargo container

Info

Publication number: US3305122A
Application number: US394533A
Authority: US
Inventors: Gordon R Pringle
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1964-09-04
Filing date: 1964-09-04
Publication date: 1967-02-21
Anticipated expiration: 1984-02-21
Also published as: ES317131A1; SE320397B; GB1097147A; NO116763B; FR1459050A; DE1265172B; NL6511473A

Description

G. R. PRINGLE KEYED CARGO CONTAINER Feb. 2l, 1967 Filed Sept. 4, 1964 FIG. 5

I N VENTOR.

ATTORN EYS United States Patent O 3,305,122 KEYED CARGO CONTAINER Gordon R. Pringle, Farnham, England, assignor to Esso Research and Engineering Company, a corporation of Delaware Filed Sept. 4, 1964, Ser. No. 394,533 6 Claims. (Cl. 220-15) The present invention relates to storage containers and more particularly to insulated tanks used in the storage and shipment of liquefied gas cargoes at atmospheric pressure and at cryogenic temperatures in tankers and the like.

Practical and economic considerations have dictated the feasible conditions of transport and storage of liquefied gases. That is to say, the liquefied gases should be maintained at atmospheric pressures and the storage containers employed should be of relatively large size and capable of insulating the supercooled cargo from the ambient temperatures to prevent volatilization thereof. To this end, containers designed for the purpose of storing liqueed gases have included a large inner tank, fabricated from a material such as aluminum or stainless steel, which retains its strength and ductility at the eX- tremely low temperatures involved, and an enveloping insulated chamber supporting the tank. One known eX- pedient for the support of such a cargo tank employs keys and keyways to secure the tank to its supporting structure while accommoda-ting contraction of the tank due to the severe temperature changes encountered in normal use.

In accordance with the principles of the present invention, a storage system for a liquid gas cargo incorporates new and improved key and keyway arrangements, characterized by the use of special intermediate heat insulating bearing blocks, between the key and the keyway, as an integral part of the supporting system. As an important aspect of the invention, the fit of the key and keyway is maintained substantially uniform under all conditions of expansion and contraction of the tank. Accordingly, the dimensions of the key, keyway and intermediate insulating bearing blocks are proportioned and displaced such that the bearing 'blocks are maintained in uniform contact with both the key and keyway throughout the entire range lof temperatures to which the cargo container 4is -to be subjected. Optimum performance of the supporting system is insured by the uniform fit of the key and keyway at all temperatures.

For a more complete understanding of the present invention and its attendant advantages, reference should be made to the following detailed description takenin conjunction with the accompanying drawing, in which:

FIG. 1 is a side elevational View of a liquefied gas tanker embodying the container system of the invention;

FIG. 2 is a plan View of the tanker of FIG. l; and

FIG. 3 is an enlarged, fragmentary, cross-sectional view of an insulated, keyed supporting system embodying the principles of the present invention, taken along line 3 3 of FIG. 1.

Referring to the drawing, the improved cargo container system of the present invention is generally indicated by the reference numeral and is typically included as part of the structure of a seagoing vessel such as a tanker 11. The container system includes an inner tank 12, which may be conventionally filled with a cargo of liquefied gas, such as liquefied methane, through a dome 13 on the deck of the tanker. The tank 12, which is constructed from a material such as aluminum or stainless steel and possesses adequate strength to withstand the internal stresses induced by the cold cargoes, is shaped to be housed generally within the cargo hold 14 of the Ship 11 or within an equivalent supporting struc- ICC ture. The cargo hold itself is completely clad with suitable thermal insulation 20, such as balsa wood, urethane foam or the like, and as shown in FIG. 3, vertical keyways 15 are formed on each of the vertical walls 16 of the tank 12 by elongate jaw member 17. For balanced support of the tank, the keyways are disposed along the major planes of the tank 12 which pass through the center of gravity of the tank, as shown in FIGS. l and 2. In accordance with the invention, the keyways 15 of the tank 12 are positively keyed to the supporting cargo hold structure 14, at all temperatures and under all conditions` of expansion and contraction, by means of elongate key members 19 formed thereon and intermediate insulating bearing blocks 21 which, along wtih a tapered insulating block 26, form an insulating key generally designated lby reference numeral 25. In the illustrated preferred embodiment of the invention, the insulating bearing blocks 21 are secured by adhesive or other suitable means to the side walls of the key member 19 and form an effectively integral part thereof. As shown, the tapered thermal insulating blocks 26 are constructed of similar material to that used in cladding the cargo hold and are secured to the keys 19 by adhesive or other suitable means to become an effectively integral part thereof.

As an important specific aspect of the invention, the insulating plastic bearing blocks 21, which are fabricated fram suitable insulating bearing material such as a composite mixture of urethane foam, Fiberglas, and resin, are disposed and arranged between the jaws 17 and the key members 19 for bearing contact therewith throughout Ithe range of temperatures to which the tank is to be subjected (normal ambient temperature to as low as -435 F. for a cargo of liquid hydrogen).

Specifically, since the key member 19 is an integral part of the hull structure of a ship, sufficient thermal insulation therefor must be provided to maintain it at ambient temperature to prevent undue cracking stresses to be induced therein. Consequently, the key 19;, when properly thermally insulated, will tbe unaffected by the temperatures of the cargo and its width will be constant or fixed. However, the tank 12 will be subject to great temperature changes and to relatively large amounts of shrinkage causing the separation and contraction of the jaw members 17 and the keyway 15 defined thereby. Therefore, it is necessary to provide bearing blocks of sufficient width to accommodate this movement, as well as to provide sufficient insulation of the key 19 to prevent the cooling and possible cracking of the hull structure.

Accordingly, since the change `in width of the keyway 1S must be compensated for by a like change in width of the insulating bearing blocks, alone, it being understood that the key member dimensions as part of the hull structure remain fixed, the Arespective widths of the keyway, key and insulating bearing blocks may be specifically proportioned, when the specific coefficients of expansion of the materials are known and the width of either the key or keyway is initially chosen. More specifically, and in accordance with important principles of the invention, the substantially uniform fit of the insulated key 25 within the keyway 15 will be ensured when Wi=iWt at or when Wk= t2 wt at where:

Wk=width of the key member 19 Wt--width of the keyway 15 formed between the jaws 17 on the tank 3 Wi=width of each bearing block 21 at=coeiiicient of expansion of the tank material a=coeicient of expansion of the insulating bearing material Furthermore, it has been determined that, as a practical limit, the coetlicient of expansion of the bearing block must be at least about 2.25 times greater than the coetiicient of the expansion of the tank material. Therefore, the width of the key member 19 must be at least one-fourth (0.25) the Width of the insulating bearing block and the width of the keyway 1S must be at least about two and one-fourth (2.25) times the width of each insulating block.

Thus, in accordance with the principles of the invention, the width of the keyway 15, defined by the distance between the inner faces 26 of the jaw members 17, is specically proportioned in relation to the Width of the insulating bearing blocks 21, the Width of the key member 19, and the respective coeicients of expansion of the insulating material and the tank material to ensure that the fit of the effectively insulated keys 25 is substantially uniform Within the keyways at all temperatures, i.e., that positive bearing contact of the insulating blocks 21 is maintained with the keyways 15 at all temperatures and under all conditions of expansion and contraction of the tank 12 as well as the supporting structure.

Accordingly, it should be appreciated that the support of a cargo tank, through keyways formed thereon, by the new and improved insulated keys which are in constant Contact with the keyways under all conditions of expansion and contraction provides for the safe storage and transportation of liqueied gases.

It should be understood that the specific construction herein -illustrated and described is intended to be representative only, as certain changes may be made therein Without departing from the clear teachings of the disclosure. Accordingly, reference should be made to the following appended claims in determining the full scope of the invention.

What is claimed is:

1. In a cargo container system for liquefied gases at cryogenic temperatures including an inner rigid tank supported Within an outer supporting structure by a key and keyway arrangement the improvement in which (a) said keyway -is of substantially greater widththan said key and defines predetermined gaps therebetween,

(b) heat insulating bearing blocks each having a width equal to the Width of said keyway multiplied by the coeicient of thermal expansion of the material from which said keyways fabricated divided by the thermal expansion of the material from which said bearing blocks are fabricated are located in said gaps and in Contact with said key and keyway.

2. A container system for cryogenic cargoes, comprising (a) an external supporting structure,

(b) an internal rigid tank of predetermined geometric configuration,

(c) elongate keyways formed along vertical axes of said tank,

(d) key members formed on said supporting structure,

(e) insulating means disposed between said supporting structure and said rigid tank completely enveloping said tank,

(i) said insulating means including plastic bearing blocks disposed in said keyways and in bearing contact with said key members at all temperatures, said plastic bearing blocks each having a width equal to the width of said keyway multiplied Iby the coeicient of thermal expansion of the material from which said keyway is fabricated divided by the thermal expansion of the material from which said bearing blocks are fabricated.

3. A container system in accordance with claim 2 in which (a) the coeicient of expansion of said bearing blocks is at least 2.25 times greater than the coefficient of expansion of the material of said keyways.

4. A container system in accordance with claim 2,

in which (a) the widths of said key members are substantially 0.25 times the width of said insulating means.

5. A container system in accordance with claim 2 in which (a) said plastic bearing material is a composite mixture of urethane foam, Fiberglas, and resin.

6. In la cargo container system for liqueiied gases at cryogenic temperatures including an inner rigid tank supported within an outer supporting structure by key and keyway arrangement, the improvement in which intermediate heat expandable bearing blocks having a predetermined coeicient of thermal expansion are interposed between said key and keyway; said bearing blocks each having a Width equal to the width of said keyway multiplied by the coeflicient of thermal expansion of the material from which the keyway is fabricated divided by -the coeiiicient of thermal expansion of the material from which said bearing blocks are fabricated, whereby said bearing blocks are maintained in bearing contact with said keyway and key at all temperatures from ambient to those of cryogenic temperatures.

References Cited by the Examiner UNITED STATES PATENTS 2,614,856 10/1952 Beyer et al. 220-15 2,823,822 2/1958 Altman 220-15 2,896,416 7/1959 Henry 220-9 2,905,352 9/1959 Henry 220-9 3,064,612 ll/l962 Gardner et al. 220-15 3,095,107 6/1963 Bergmann 220-15 THERON E. CONDON, Primary Examiner. JAMES R- GARRETT@ Examfne

Claims

6. IN A CARGO CONTAINER SYSTEM FOR LIQUEFIED GASES AT CRYOGENIC TEMPERATURES INCLUDING AN INNER RIGID TANK SUPPORTED WITHIN AN OUTER SUPPORTING STRUCTURE BY KEY AND KEYWAY ARRANGEMENT, THE IMPROVEMENT IN WHICH INTERMEDIATE HEAT EXPANDABLE BEARING BLOCKS HAVING A PREDETERMINED COEFFICIENT OF THERMAL EXPANSION ARE INTERPOSED BETWEEN SAID KEY AND KEYWAY; SAID BEARING BLOCKS EACH HAVING A WIDTH EQUAL TO THE WIDTH OF SAID KEYWAY MULTIPLIED BY THE COEFFICIENT OF THERMAL EXPANSION OF THE MATERIAL FROM WHICH THE KEYWAY IS FABRICATED DIVIDED BY THE COEFFICIENT OF THERMAL EXPANSION OF THE MATERIAL