US3110157A

US3110157A - Transportation of cold liquids and safety means

Info

Publication number: US3110157A
Authority: US
Inventors: Radd Frederick
Original assignee: Conch International Methane Ltd
Current assignee: Conch International Methane Ltd
Priority date: 1960-09-12
Filing date: 1960-09-12
Publication date: 1963-11-12
Anticipated expiration: 1980-11-12
Also published as: DE1292459B; GB919755A; NL268746A; BE607357A

Abstract

919,755. Storing liquefied gases. CONCH INTERNATIONAL METHANE Ltd. July 18, 1961 [Sept.12, 1960], No. 25951/61. Class 8(2). [Also in Groups XXIX and XXXIII]. A system for protection against leakage of cold liquid, e.g. liquefied gas, from a storage tank 10 which is mounted within a thermally insulated space with the side walls of the tank being spaced from the insulation 16, comprises a liquid receiving means adjacent the bottom of the tank extending beyond the side walls of the latter and upwardly into the space 28 about the tank, and means for removing liquid from the liquid receiving means. As described, the tank is housed within the hull 14 of a ship which is lined with the insulation 16, e.g. balsa wood, the tank having an inlet pipe 18, a discharge pipe 24 and a vent pipe 25. The liquid receiving means is in the form of a receptacle 30 having a bottom wall 32 and side walls 34. The receptacle may be of metal, wood or plastic and may be reinforced. The bottom of the tank rests upon beams 38 supported on the bottom wall 32 of the receptacle. Alternatively, the beams 38 may be omitted, the tank resting on the bottom wall 32, or the bottom wall of the tank may be extended beyond the side walls thereof replacing the bottom wall of the receptacle, Fig. 2 (not shown), or the receptacle may be formed by a membrane, e.g. a film of metal or plastics, supported by and fixed to the insulation 16. Keys and keyways may be provided between the tank and the supporting floor 37. One or more drains 40 are provided in the receptacle, leading to a pump 44 which returns liquid collected in the receptacle through a pipe 46 to the tank 10 or to other receivers or to a pipe 47 having its outlet extending rearwardly of the ship. The pump 44 may be automatically started when the cold liquid contacts electrodes 50, 52; alternatively, a thermocouple may be used to start the pump. The side walls of the receptacle may be inclined outwardly towards the insulation 16 and the inner surface of the latter may be covered with a liquid and vapour impervious layer, e.g. a membrane of aluminium. More than one tank may be mounted in the insulated space and the liquid receiving receptacle may be provided for each tank or for each one of groups of the tanks or for all the tanks. The ship may be of double hull construction. Specifications 853,367 and 854,705 are referred to.

Description

NOV. 12, 1963 RADD 3,110,157

TRANSPORTATION OF COLD LIQUIDS AND SAFETY MEANS Filed Sept. 12, 1960 2 Sheets-Sheet 2 {KC f; FIG. 2

II V) w HAZHU United States Patent 3,110,157 TRANSPORTATION OE COLD LIQUIDS AND SAFETY MEANS Frederick Radd, Ponca City, Okla., assignor to Conch International Methane Limited, Nassau, Bahamas, a

corporation of the Bahamas Filed Sept. 12, 1960, Ser. No. 55,481 4 Claims. (Cl. 6249) This invention relates to the ship transportation of extremely cold liquids in self-suflicient containers of large capacity, and it relates more particularly to a safety feature employed in a system of the type described for the purpose of maintaining control of the extremely cold liquid cargo which might inadvertently or otherwise escape from the containers, thereby to avoid the extremely dangerous conditions which would otherwise develop.

It is an object of this invention to produce a means for the transportation in large volume of extremely cold liquid, and it is a related object to provide safety means employed in combination therewith to protect the ship or other structure from the extreme cold of the liquid in the event of escape of the liquid from the container.

These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, embodiments of the invention are shown in the accompanying drawings, in which FIGURE 1 is a schematic sectional elevational view of a system which may be employed for the safe transportation of an extremely cold liquid,

FIGURE 2 is a sectional elevational view similar to that of FIGURE 1, showing a modification in the safety means, and

FIGURE 3 is a similar sectional elevational view of a corner of a structure embodying a further modification.

This invention can best be illustrated by reference to the over-water transportationof natural gas in a liquefied state from a source of plentiful supply to an area where a deficiency exists. It will be understood that the concepts described will have similar application to ship transportation of other extremely cold liquids in large quantities, such as liquefied air, oxygen, hydrogen, nitrogen, and the like.

Ship transportation of such gas or gases in a liquefied state is desirable because of the greater volume of gas than can be housed within a storage space since a gas is reduced by circa 600 in volume when converted from a gaseous state to a liquid. To make the transportation commercially feasible, it is desirable to embody means for transportation of such liquefied gas in large volume. It becomes impractical to construct tanks or containers of large capacity for housing such liquids at pressures which greatly exceed atmospheric pressure because otherwise tanks of extremely high strength would be required, thereby markedly to increase the initial cost in equipment. As a. result, the practical concepts reduce the practice to the transportation of liquefied gas in large volumes in containers wherein the liquefied gas is housed at about atmospheric pressure.

With natural gas, composed mostly of methane, this means the transportation of the liquid in tanks of large capacity at about the boiling point temperature of the liquefied gas which, for natural gas composed mostly of methane, may range from -240 to 258 F., depending upon the amount of higher boiling hydrocarbons that are present.

It is known that the steel plate of which the ships hulls are usually constructed will lose their ductility and will therefore become embrittled and lose strength when reduced to a temperature below 100 F. As a result, such steel plate cannot be employed in the construction of the liquid storage tanks, and it becomes extremely important 3,110,157 Patented Nov. 12, 1963 to embody means within the ships structure to protect the structural elements of the ship from the cold of the liquid, otherwise the ship will be faced with possible destruction upoii transmission of cold from the liquid to the ships stee One means which has been developed for commercial practice in ship transportation of liquefied gas is fully described in the co-pending application of Henry, Serial No. 582,965, filed May 7, 1956, and entitled Ship. In accordance with the teachings thereof, the liquified gas atabout atmospheric pressure is housed within a large tank of polygonal shape and formed of such materials as aluminum or alloys of aluminum, stainless or other high nickel or austenitic steels, copper or alloys of copper and the like which do not become embrittled at cryogenic temperatures. The tanks are mounted within the hold space of the ship lined with a relatively thick layer of insulating material, as represented by blocks of balsa wood or other material having low heat conductivity. The ship is preferably formed with an outer steel hull and an inner hull in closely spaced parallel relationship with the outer hull to define a confined space therebetween through which water or other fluid may be introduced or circulated for temperature control as well as for ballast.

In a double hull construction of the type described, the insulation is applied as a lining to the inner surface of the inner hull. When adequate protection is available to prevent cold of liquid escaping from the tanks from transmission to the ships structure, it becomes possible to construct the ship without the inner hull. As a result, it will be understood that this invention is applicable to ships with or without the double hull construction.

The problem of the control of escaping liquid is complicated by the necessity to maintain freedom for expansion and contraction movements of the tank relative to the structural elements of the ship and the tank supports, since the tank will be subject to wide dimensional change between the time that it is charged with liquefied gas at about -258 F. and the time when the tank is free of liquid cargo such that the temperature of the walls can rise to as much as plus F. Stabilization to position the tank while permitting freedom for expansion and contraction can be achieved by means described in the previously issued patent of Henry, No. 2,905,352, or by cable means described in the copending application of Joseph F. Stroschein, Serial No. 31,403, filed May 24, 1960, and entitled Cold Cargo Transportation Means."

Another problem confronting the protection of the ships structure from the cold of the liquid which might escape from the tanks is the shifting forces and angles normally resulting from the pitching and rolling movements of the ship during navigation. A ship may roll by as much as 40 degrees in either direction in a bad sea, thereby to impose considerable shifting of the loads upon the walls of the tank and thereby also to impose problems with respect to maintenance of the liquids which find their way outside of the tank by reason of leakage, splash, or partial failure of the tank.

Referring now more specifically to the drawings for illustrations of the concepts of this invention, the metal storage tank is represented by the numeral 10 and the liquified gas stored therein is represented by the numeral 12. The tank is illustrated as being housed within an insulated hull 14 of the ship lined to provide a relatively thick layer 16 of a structurally strong and dimensionally stable insulation, such as balsa wood.

The tank is provided with an inlet pipe 18 which extends into the tank through the top wall 20 for the introduction of liquid cargo into the tank and which is provided with a fiow control valve 22 for regulating the flow of vapors and fiuid therethrough. A discharge pipe 24 extends downwardly through the tank to a point adjacent the bottom side for use in, the removal of liquid cargo, and it, too, is provided with a flow control valve 26 for regulating the flow of vapors of fluids therethrough and a vent pipe 25 extends into the tank into communication with the vapor space for release of vapors collecting above the liquid level.

In accordance with the concepts of this invention, a space 28 is provided between the side walls of the tank and the insulation 16 disposed outwardly thereof. Each tank is provided with a receptacle 30 extending outwardly from the bottom side of the tank, such for example, as the pan'illustrated' in FIGURE 1 shaped to correspond with the cross-section of the tank and dimensioned to have a" length and width greater than the corresponding dimensions of the tank to span the bottom wall 32 and extend into the space 28 between the side walls of the tank and the insulation. The side walls 34 of the pan extend upwardly into the space about the sidewalls of the tank to provide a trough 36 into which the liquid cargo escaping from the tank and flowing gravitationally downwardly along the side walls of the tank can collect. While it is sufiicient if the side walls 34 of the receptacle extend upwardly for a short distance beyond the bottom wall of the tank, it is preferred to dimension the side walls to extend beyond the lower quarter of the tank so as to retain liquid escaping from the tank and flowing gravitationally down the side, notwithstanding the angular movement of the ship at angles as great as 40 degrees responsive to the pitching and rolling movements of the shi its receptacle should be formed of materials which are impervious to the liquid cargo and insensitive to the cold of the liquid. For this purpose, the receptacle can be fabricated of metal suitable for tank construction, or of wood or of plastic, with or without reinforcement.

The bottom wall 32 of the receptacle can rest on the floor 37 of insulating material, and the bottom wall of the tank can rest upon the .top surface of the bottom wall of the receptacle, or the tank'bot-tom wall can be supported in spaced relationship with the bottom wall of the receptacle as by means of beams 38 to provide a spaced I relation therebetween and thereby increase the capacity of the receptacle to retain liquid as illustrated in FIGURE 1. Instead, the receptacle may constitute a side wall 34' and a bottom wall 32' dimensioned to correspond with the spaced relationship between said side wall 34' and the tank, and which is secured in sealing relationship to the lower edge of the tank to provide a receptacle in the form of a trough 36' which extends all about the lower edge of the tank, with the side wall of the container defining the inner wall of the trough, as illustrated in FIG- URE 2. By way ofstill further modification, use can be made of a receptacle which is not free standing but instead relies upon the insulation for support. For example, as shown in FIG. 3, use can be made of a membrane 34 such as a film of metal or plastics fixed to the lower part of the insulation surrounding the tank to form a receptacle.

When a key and keyway construction (not shown) is employed .to stabilize the position of the tank, the bottom wall of the pan can be constructed to provide recessed keyways dimensioned to be received in corresponding keyways in the supporting floor and into which the keys on the bottom side of the tank are received; or vice versa, the keys may be formed in the pan and floor for engagement into corresponding keyways provided in the bottom wall of the tank.

Since leakage occurring in the walls of the tank will usually continue until the ship is docked for removal of liquid cargo to enable repair of the tanks, it is desirable to provide means for the disposal of the liquid as it collects in the receptacle. In the preferred practice, the liquid collected in the receptacle will be displaced for disposal as by dumping the liquid overboard while the ship is at sea, but it will be understood that the liquid collected can be returned to the tanksor to other receivers on the transportation means. For this purpose, one or more drains 40 are provided in the bottom wall of the receptacle for connection by pipes 42 to the intake side of a displacement pump 44 by which the liquid is forced through a pipe 46 to the filling pipe 18, whereby liquid from the pan is returned to the tank, or to. a pipe 47 having itsloutlet preferably extending rearwardly of the ship for dumping the liquid into the sea. When the tank rests upon the top surface of the pan, or when the receptacle merely constitutes the trough, it will usually be suflicient to locate the drain or drains in the base of the trough for communicating the liquid with the displacement pump. When the tank is supported in spaced relationship with the bottom wall of the pan, as illustrated in FIGURE 1, one or more drains can be located in intermediate portions of the pan bottom wall, and such drains can be located advantageously in downwardly deformed basins or sumps for more complete drainage of liquid from the pans for return to the tank. V

With such cryogenic liquids, it is preferred to make use of means for direct displacement of the liquid without drainage or other below deck installations thereby to avoid bottom connections. For such purpose, as illustrated in FIGURE 2 use can be made of a deep well pump 60 or a gas lift means or other suitable ejector means for direct displacement of collected liquid upwardly through a pipe 62 extending upwardly through the space 28 and over the deck for release to the sea or else into communication with a pipe extending into the tank if it is desired to conserve the liquid.

It will be apparent that in the event of development of any cracks, breaks, or leaks in any of the walls of the tank, liquid escaping through said openings will, for the most part, remain in a liquefied state by reason of the extremely cold temperature of the portions of the wall below the liquid level. Such escaping liquid will flow by gravity down the side walls of the tank into the trough of the receptacle, notwithstandingthe normal angular movements of the ship in navigation. Such liquid will be collected and retained in the receptacle. In the event that the leakage is of such proportion as to cause substantial amounts of liquid to be collected in the receptacle, such liquid can be returned immediately to the tank thereby constantly to maintain control thereof. Since such leakage cannot alwaysbe immediately detected, it is desirable to provide means for automatically initiating activation of the liquid displacement means responsive to the presence of liquid in the receptacle. For this purpose, sensing means, such as electrodes 50 and 52, are provided in the base of the trough for initiating operation. of the displacement pump when the electrodes are contacted with liquid, thereby automatically to recircu-late liquid from the receptacle through the return pipe 46 to the always open portion of the supply line 18 for return to the tank.

Instead of the liquid level sensing means shown in FIGURE 1, use can be made of a thermocouple 54 connected by the conductor 56 to the displacement pump means to initiate operation thereof in response to the cold of the liquid present in the trough.

It will be obvious to those skilled in the art that the invention is capable of numerous modifications which will become apparent from the foregoing description. For example, the pump 44 could be mounted -in asuitable area within the insulated space or it could be mounted a substantial distance from the cargo tank and the insulation surrounding the tank. The

side walls

34 and 34 of the receptacle, illustrated in the drawings as extending perpendicularly from the bottom wall, can be inclined outwardly towards the insulation to enhance the the inner surface of the insulation can be provided with a suitable liquidand vapor-impervious layer, such as a membrane of aluminum and the like, which would operate to deflect liquid escaping from the tank into the trough or receptacle, thereby to enhance the control of the fluid flow.

It will be understood that the foregoing represent emergency means important to the safety of the ship transport or to storage handling such extremely cold liquids. The described means will be found to be extremely valuable when partial failure occurs in one or more of the tanks while, the ship is at sea. The means described will operate to maintain control of the liquid cargo for protection of the ship's structure from the cold of the liquid, while also minimizing loss of liquid until the ship can be docked for removal of the liquid cargo to land storage to enable more permanent repair of the tanks.

It will be understood that more than one tank can be mounted for use in the insulated space and that the described safety means may be adapted for each of the separate tanks or for combinations thereof or for the entire cluster of tanks within the hold space. It will be further understood that other changes in the details of construction and arrangement may be made without departing from the spirit of the invention, especially as defined in the following claims.

I claim:

1. A liquid protecting system in the storage and transportation of extremely cold liquids in self suflicient storage tanks mounted within a thermally insulated space with space between the sides of the storage tank and the thermal insulation comprising a liquid receiving means adjacent the bottom side of the storage tank and dimensioned to extend beyond the side walls of the tank and upwardly into the space about the tank between the outer wall of the tank and the thermal insulation spaced therefrom and to a height substantially less than the height of the tank, and means for removing liquid from said liquid receiving means, wherein the cold liquid receiving means comprises a pan-shaped member having a contour corresponding to the cross-section of the bottom of the storage tank and having side walls extending substantially perpendicularly upwardly from the edges of the bottom wall of the pan-shaped member into the space between the side wall of the tank and the insulation, and in which the pan-shaped member rests on the thermally insulating floor of the insulated space, and means for supporting the bottom wall of the tank in vertically spaced apart relation from the bottom wall of the pan.

2. 'A liquid protecting system in the storage and transportation of extremely cold liquids in storage tanks mounted within a thermally insulated space with space between the sides of the storage tank and the thermal insulation comprising a liquid receiving means adjacent the bottom side of the storage tank and dimensioned to extend beyond the side walls of the tank and upwardly into the space about the tank to a height substantially less than the height of the tank, liquid level sensing means for determining the presence of cold liquid within said cold liquid receiving means, and means responsive to theliquid level sensing means for withdrawing liquid from the cold liquid receiving means.

3. A leak protecting system for the storage and transportation of extremely cold liquids in containers of the type having at least one storage tank located within a thermally insulated space with there being an expansion space between the sides of the storage tank and the sides of the thermally insulated space comprising a cup-shaped cold liquid receiving container positioned at the bottom of the storage tank, the side walls of said container being positioned intermediate the sides of the storage tank and the sides of the thermally insulated space and extending upwardly to a height substantially less than the height of the tank, liquid level sensing means for determining the presence of liquid within said cold liquid receiving means, and recirculating pump means for withdrawing liquid from the cold liquid receiving means in response to the liquid level sensing means and returning it to the storage tank.

4. A liquid protection system in the storage and transportation of extremely cold liquids having a boiling point so low as to dangerously embrittle and weaken ordinary steel plate, comprising a self-supporting tank for such liquid having top and bottom walls and side walls, a thermally insulated container completely surrounding said tank and insulating its contents to provide a safe temperature at he outside surface of said insulated container, there being a space between the side walls of the tank and the adjacent walls of the insulated container, a liquid-impervious barrier in said space, the upper part of said barrier extending upward only a fractional part of the way from the bottom of said space and defining together with the outer wall of said tank a trap for collecting any liquid dripping down the outer side of said tank without permitting said liquid to reach the insulated container, and means for removing liquid from said trap to prevent the building up of substantial hydrostatic pressure against the inner walls of said trap, there being also a space between the bottom wall of the tank and the adjacent bottom wall of the insulated container,

the bottom part of said barrier being substantially horizontal and underlying the bottom wall of said tank and being spaced therefrom to define, together with said upwardly-extending' part of the barrier, a liquid-impermeable drip pan.

References Cited in the file of this patent

Claims

4. A LIQUID PROTECTION SYSTEM IN THE STORAGE AND TRANSPORTATION OF EXTREMELY COLD LIQUIDS HAVING A BOILING POINT SO LOW AS TO DANGEROUSLY EMBRITTLE AND WEAKEN ORDINARY STEEL PLATE, COMPRISING A SELF-SUPPORTING TANK FOR SUCH LIQUID HAVING TOP AND BOTTOM WALLS AND SIDE WALLS, A THERMALLY INSULATED CONTAINER COMPLETELY SURROUNDING SAID TANK AND INSULATING ITS CONTENTS TO PROVIDE A SAFE TEMPERATURE AT THE OUTSIDE SURFACE OF SAID INSULATED CONTAINER, THERE BEING A SPACE BETWEEN THE SIDE WALLS OF THE TANK AND THE ADJACENT WALLS OF THE INSULATED CONTAINER, A LIQUID-IMPERVIOUS BARRIER IN SAID SPACE, THE UPPER PART OF SAID BARRIER EXTENDING UPWARD ONLY A FRACTIONAL PART OF THE WAY FROM THE BOTTOM OF SAID SPACE AND DEFINING TOGETHER WITH THE OUTER WALL OF SAID TANK A TRAP FOR COLLECTING ANY LIQUID DRIPPING DOWN THE OUTER SIDE OF SAID TANK WITHOUT PERMITTING SAID LIQUID TO REACH THE INSULATED CONTAINER, AND MEANS FOR REMOVING LIQUID FROM SAID TRAP TO PREVENT THE BUILDING UP OF SUBSTANTIAL HYDROSTATIC PRESSURE AGAINST THE INNER WALLS OF SAID TRAP, THERE BE-