US3498249A

US3498249A - Tanker vessel

Info

Publication number: US3498249A
Application number: US768590A
Authority: US
Inventors: Terrell Montgomery Jones
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1968-09-16
Filing date: 1968-09-16
Publication date: 1970-03-03
Anticipated expiration: 1987-03-03

Description

T. M. JONES TANKER VESSEL Mamba, 1970 3 Sheets-Sheet 1 Original Filed Dec. 14," 1967 INVENTOR 727:5 Mao/v59 W M ATTORNEY March 3, 1970 T. M. JONES 3,493,249

TANKER VESSEL Original Filed Dec. 14, 1967 5 Sheets-Sheet 2 INVENTOR iimezzfiwmar ELIE-Mk ATTORNEY March 3, 1970 T. M. JJ'OQYNES 3,498,249

TANKER VESSEL OriginaLI-iled Dec. 14, 1967 v- 3 Sheets-Sheet 3 5 M l ATTORNEY United States Patent 3,498,249 TANKER VESSEL Terrell M. Jones, Morris Plains, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware Continuation of application Ser. No. 690,552, Dec. 14, 1967. This application Sept. 16, 1968, Ser. No. 768,590 Int. Cl. B63b /14, /08 U.S. Cl. 114-74 13 Claims ABSTRACT OF THE DISCLOSURE A cargo vessel having a prestressed concrete hold compartment for liquid storage and transport. The concrete hold section may be fitted with steel bow and stern portions and may include an inner lining of insulation to which a liquid impervious membrane barrier is attached. The vessel is particularly adaptable to the transport of liquefied natural gas cargoes at atmospheric pressure and cryogenic temperatures.

This application is a streamline continuation of US. Ser. No. 690,552 which has been abandoned.

Description of the invention The present invention relates to cargo vessels in general and, in particular, to novel improvements in vessels for the transportation of liquids at cryogenic temperatures such as liquefied natural gas (LNG) at --259 F. and atmospheric pressure. The invention also relates to a novel method of constructing a tanker vessel for the transport of cryogenic cargoes.

In the past, in the transport of liquefied petroleum gases at cryogenic temperatures and atmospheric pressure, it has been the practice to contain the cryogenic liquid cargo within an insulated container in the hold of the conventional carbon steel ship. Because of the likelihood of a rupture in the tank containing the super-cool cargo, it has normally been a requirement that a second liquid impervious barrier be provided exterior of the primary barrier of the cargo tank in order to insure that the super-cool liquid cargo would not contact the ship hull upon a failure of the primary barrier. Without such a secondary barrier, low temperature embrittlement would be experiencedwith a possible resultant fracture of the ship hull. Accordingly, it has been conventionalpractice in the past to resort to elaborate double-walledvapor barriers for containing, isolating and insulating the cold of the cargo from the hull of the ship. Obviously, this design requirement has imposed serious economic disadvantages to the transport of cargoes of this temperature in conventional ships. In ships including a primary and secondary rear barrier, it has not been unusual, for the cost of the tankage or container part of the ship to comprise well over of the total cost of the ship. Accordingly, in ships for the transport of cryogenic cargoes, large cost savings are possible if economics can be made in this area of the overall ship cost; namely, the low temperature liquid container.

With the foregoing in mind, applicants invention relates to a new and novel ship construction which includes a hull structure of prestressed concrete surrounding the cryogenic cargo containing portion of the ship. Concrete, being a substance that is not subject to any substantial degree of embrittlement at lower temperatures, is an ideal material for this service because the need for a secondary liquid impervious barrier within the hold of the ship is avoided.

Accordingly, the present invention relates to a new and novel, low cost ship containing a prestressed concrete 3,498,249 Patented Mar. 3, 1970 cargo hold portion including but a single layer of membrane vapor barrier and a layer of load-bearing insulation isolating the cold of the cargo from the primary hull structure as well as transmitting the hydrostatic load of the cargo from the membrane through the insulation to the hull structure.

In the past, while the low cost nature of the concrete hull structure has been Well known and previously attempted for the transport of general cargoes in bulk cargo carriers or crude in oil tankers, it has not reached wide-spread acceptance in view of the large weight penalty paid for the use of the low cost concrete material. This weight penality increased the size of the ship necessary for the transport of the same amount of cargo. Unlike the disadvantage experienced with concrete ships in the past, the specific gravity of liquefied natural gas is substantially less than that of crude oil and for this reason the relatively heavy concrete hull structure, rather than being detrimental to the ship, will in fact add necessary ballast in the loaded as well as unloaded condition to enhance the sea-keeping ability of the tanker.

Accordingly, it is a primary object of the invention to provide a new and improved prestressed concrete tanker having but a single impervious membrane structure within the cargo hold.

Another object of the invention is to provide a new and improved cryogenic liquid tanker vessel having a concrete cargo section and steel bow and stem sections.

A further object of the invention is to provide a novel tanker design employing concrete portions in the critical cargo areas where the hull form is simplest to construct and where the danger of conventional hull embrittlement due to cold fracture is greatest.

A further object of the invention is to provide a composite steel and concrete tanker having a concrete center section of uniform cross-section throughout its length.

These and other advantages and novel features of the present invention will be more fully understood in reference to the following description and drawings in which:

FIG. 1 is a side elevation view showing portions in section of a tanker in accordance with the invention;

FIG. 2 is a fragmentary cross-section of a midship portion of the tanker taken along line 22 of FIG. 1;

FIG. 3 is a fragmentary prospective view of the membrane and insulation system applied to the inner wall of a cargo hold;

FIG. 4 is a view taken along line 4--4 of FIG. 3, looking in the direction of the arrows;

FIG. 5 is a cross sectional view taken along line 5-5 of FIG. 4;

FIG. 6 is across sectional view taken along line 6--6 of FIG. 4;

FIG. 7 is a fragmentary schematic view of a lower inner edge portion of an insulation module employed in the invention; and

FIG. 8 is an enlarged cross sectional view of a portion of FIG. 1.

Referring in more detail to the drawings, a cargo vessel 10 includes a prestressed concrete tank mid-section 12 having attached to the opposite ends thereof a steel bow portion 14 and a steel stern portion 16. The concrete mid-section 12 includes a plurality of individual cargo tanks or holds 18. In accordance with the invention, it should be understood that the cargo mid-section of the present tanker may be prestressed on an individual cargo tank 18 basis or the entire assemblage of tanks 18 may be prestressed as one continuous member. In either event the entire length of the cargo mid-section portion is of extermely high stiffness and fully capable of withstanding the loads imposed by the cargo and the prevalent sea conditions.

Each of the tanks 18 includes an outer concrete hull 20 and an inner concrete hull 22, separated by a plurality of longitudinally extending web portions 24. The web portions 24 are obliquely inclined to the inner surfaces of the inner and outer hull'in truss like fashion to form a lurality of triangular ducts extending longitudinally of the hull. The upper deck portion of the hull is formed in similar fashion as is the hull bottom. The intersection of adjacent web portions 24 are preferably provided with a plurality of conduits 26 (see FIGS. 2 and 3) through which a plurality of prestressing cables 28 may pass. The cables 28, in known prestress manner, are effective to place the entire concrete mass in-between the ends of the cables 28 in compressive relationship so that upon flexure of the concrete mid-portion, the imposed load is taken by the cables rather than the placement of the concrete into tension in the regime of its minimum strength. The bulkheads 30 provided at the ends of the foremost tank 18 and the rearmost tank 18 are in adjacent relationship with a steel bulkhead wall 32 of the bow and stem portions. The steel bulkhead wall 32 is shown as a single metallic plate in FIG. 8, but it will be understood that a double wall bulkhead may also be provided. As shown in FIG. 8, the ends of the cables 28 extend through the concrete bulkhead 30, through the steel bulkhead 32, to engage the retaining anchors 34. The anchors are effective to maintain the desired level of prestress or tension in the cables 28.

Referring in more detail to the insulation system applied to the inside surface of the inner wall 22, reference should be made to FIGS. 3 to 7. In FIG. 3 the insulation system 36 is comprised of a plurality of rigid load bearing wooden boxes 38, which may be made of plywood or other suitable material. The boxes 38 are filled with a suitable insulation material 40 such as polyurethane foam, perlite, polyvinylchloride foam, etc. The lateral or vertical ends of the boxes 38 include a pair of tenon strips or moldings 42 which are fastened securely to the box. Each of the tenon strips provides a suitable surface for fixedly securing the boxes to the inner wall of the inner hull 22. The tenon strips 42 straddle a plurality of inwardly disposed anchor studs 44 suitably embedded in the inner wall 22. The studs 44 extend between adjacent strips 42 and include suitable fastening means 50 at the innermost end, engaging the faces of the tenon strips to thereby hold each of the boxes rigidly to the inner hull 22. The ends of the boxes 38 also include a plurality of second tenon or filler strips 46 which provide the necessary support for an impervious membrane 54 laid thereover. The strips 46 are fastened rigidly to the ends of their respective boxes and include a semicircular access groove 48 so that the fastening means 50 may be tightened during the assembly of the insulation system. Fastened to the upper edge of the boxes 38 is a J-shaped channel 52 which is effective to engage an elongated intermediate J-shaped member 58. Each of the members 52 are individual and securely fastened to each box. The member 58 is a continuous member and extends horizontally between insulation boxes 38 to bridge the filler strips 46. The inner edge of the intermediate J- strips 58 provide a metallic securing surface to which the upturned and inwardly turned lip portions 56 of an Invar membrane channel 54 may be secured by a suitable weld 62 running the entire length of the edge of each of the individual channels 54.

Referring specifically to FIGS. and 6, a better appreciation of the foregoing description may be had. It should be noted that a recesss 60 is provided in the inner lowermost edge of each of the insulation boxes 38 to provide the necessary relief for the raised portion of the J-shaped channel 52 and its interlocking intermediate J-shaped channel 58. In this way lengthwise expansion and contraction of the channel 54 may readily occur due to the sliding fit between the interlocking portions of the J- shaped

channels

52 and 58. The void between the box ends between the front and rear face tenons or filler strips 42 and 46 may be filled with any suitable insulation 64, such as perlite, polyurethane foam, etc.

Those skilled in the art will readily appreciate from the foregoing description that a new and novel low cost LNG tanker transportation system is provided wherein a single Invar or other low tempertaure resistant membrane barrier such as that disclosed may be provided within a concrete hold portion of a ship. The concrete portion of the ship provides the necessary ballast for the lighter specific gravity cargo, generally typified by liquefied petroleum gases. Furthermore, the concrete portion of the ship may be of relatively simple shape and is preferably of uniform cross-section throughout its length, the necessary hull form being provided at the bow and stern portions of the cargo sections by conventional carbon steel ship sections.

While the present invention has been specifically described with a low thermal expansion Invar membrane system of single layer construction, similar in many respects to that disclosed in US. Patent No. 3,339,778, it should be appreciated that other and equally suitable membrane systems of single layer may be employed to equal advantage in the practice of applicants invention.

What is claimed is:

1. A cargo vessel for transporting liquids at cryogenic temperatures comprising, in combination, conventional metallic bow and stern portions; and a concrete cargo hold mid-portion fastened between said bow and stern portions, said mid-portion including a concrete inner wall, a concrete outer wall spaced from said inner wall, structural web means separating and securing said inner wall to said outer wall, and a plurality of elongated prestressed tension means holding the inner and outer walls of said concrete mid-portion in compression.

2. The combination of claim 1 wherein said mid-portion contains at least one cargo hold of uniform crosssection throughout its length.

3. The combination of claim 1 wherein the ends of said prestressed tension means engage portions of said bow and stern portions to secure said portions to said mid-portion.

4. The combination of claim 1 including liquid imprevious lining means Within said hold, said lining means including insulation means secured to the interior wall of said hold, and a flexible metallic membrane lining the interior surface of said insulation means and secured thereto.

5. The combination of claim 4 wherein said insulation means includes a plurality of load bearing box structures and thermal insulation means within said box structures.

6. The combination of claim 5 wherein said flexible metallic membrane includes a plurality of horizontally elongated adjacent Invar strips having inwardly-turned edges abutting with corresponding edges of the adjacent strip, and weld means securing said inwardly turned edges of adjacent strips.

7. The combination of claim 6 including metallic strip means disposed intermediate the adjacent inwardly turned edges, said strip means engaging said box structures for securing said strips thereto.

8. The combination of claim 6wherein said mid-portion includes at least three cargo holds of substantially uniform cross-section throughout their length, the forward and rearward of said hold being joined directly to said bow and stern portions.

9. A cargo vessel for transporting liquids comprising, in combination, conventional metallic bow and stern portions, and a concrete cargo hold mid-portion fastened between said bow and stern portions, said mid-portion including a concrete inner wall, a concrete outer wall spaced from said inner wall, structural web means separating and securing said inner wall to said outer wall, and a plurality of elongated prestressed tension means holding the inner and outer walls of said concrete midportion in compression, said tension means extending longitudinally through said inner and outer walls the substantial length of said mid-portion.

10. A cargo vessel for transporting liquified gases comprising, in combination, conventional metallic bow and stern portions; and a concrete cargo hold mid-portion fastened between said bow and stern portions, said midportion including a plurality of elongated prestressed tension means holding said concrete mid-portion in compression, and an impervious liquid-tight barrier lining the interior surface of said mid-portion.

11. The combination of claim 10 wherein said midportion contains at least one cargo hold of uniform crosssection throughout its length.

UNITED STATES PATENTS 1,380,693 6/1921 Whaley 114-65 3,283,734 11/1966 Gorrnan 114-74 3,339,782 9/1967 Segura et a1. 11474 TRYGVE M. BLIX, Primary Examiner US. Cl. X.R.