US2981071A - Safety apparatus for underground pressure fluid storage - Google Patents

Description

April 25, 1961 c. T. BRANDT SAFETY APPARATUS FOR UNDERGROUND PRESSURE FLUID STORAGE 2 Sheets-Sheet 1 Filed May 12, 1958 INVENTOR. c T. BRANDT ww QW A TTORNE VS April 25, 1961 C. T. BRANDT 2,981,071

SAFETY APPARATUS FDR UNDERGROUND PRESSURE FLUID STORAGE INV ENTOR. F/G' 4 C.T, BRANDT M3; i. W

ATTORNEYS United States Patente O "ice SAFETY APPARATUS FOR UNDERGROUND PRESSURE FLUID STORAGE Carl T. Brandt, Bartleswlle, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Filed May 12, 1958, Ser. No. 734,630

6 Claims. (Cl. 61.5)

This invention relates to an improved underground storage system for storing high vapor pressure fluids under superatmospheric pressure. In one aspect it relates to underground storage of L.P.G. (liquefied petroleum gas), such as propane and its safe transfer to and from storage. In another aspect it relates to apparatus and a method for preventing uncontrolled flow of an L.P.G., such as propane, from an underground storage cavern in the event of damage to or the rupture of aboveground vapor inlet and outlet lines.

In the storage of volatile products such as liquefied petroleum gases, propane, butane, ethylene, ethane, or ammonia, etc., in subterranean storage Caverns, it is customary to provide a liquid inlet, a main liquid outlet, an auxiliary liquid outlet and a liquid level gauge. Obviously, a shaft is originally sunk into the ground at least to a level initially intended to be the level of the cavern roof or top Wall in case the cavern is excavated by mining methods. Other openings, are frequently drilled into the ground to their intended depths with c'asings being cemented in place by usualwell practice prior to actual excavation of the cavern.

l nd that a vapor inlet and outlet or a pressure equali- Zation conduit to the cavern, in addition to the usual inlet and outlets, is advisable. This vapor inlet and outlet iinds utility in providing for pressure equalization for loading and unloading tank cars or trucks with liquid propane, and as a means through which cavern pressure is4 controlled within limits. This cavern pressure is controlled usually by withdrawal of vapor from the cavern, compressing the Withdrawn vapor, condensing the compressed vapor by heat exchange and adding the condensate to the cavern. This withdrawal of vapor obviously cools the liquid remaining by the latent heat of vaporization of that liquid vaporized. Thus, by lowering the temperature of the stored liquid, the pressure is simultaneously reduced. Furthermore, Vaporous propane required for any purpose is withdrawn through my vapor inlet and outlet means without need for interference with day-by-day liquid lling and unloading of the cavern. For example, Vaporous propane can be withdrawn through my vapor passage means for upgrading natural gas to a predetermined B.t.u. value. Vaporous propane ywithdrawn for use also assists in maintenance of reduced pressure in the cavern. Some natural gases contain noncombustible materials such as carbon dioxide or nitrogen, or both. Nitrogen, in particular, is ditlicult to remove from natural gas, and at the point near the ultimate consumer, the B.t.u. content can be brought up to that required by addition of Vaporous propane withdrawn from a storage cavern in case a storage cavern is available. Obviously, this upgrading in Btu. content can be made at any point along a natural gas pipe line wherever propane is available.

In transferring liquid propane from tank cars to a storage cavern, a connection is made from my cavern vapor inlet and outlet means to the tank car through the dome for pressure-maintenance during pumping of the 2,981,071 Patented Apr. 25, 1961 liquid and to prevent vapor lock in the transfer pump. Pressure maintenance in tank cars being unloaded is particularly important in cold weather when the pressure of the vapor in the tank car is relatively low. Also, when loading a tank car with liquid propane, the same vapor line connection is made so that vapors produced by pumping the liquid propane into a warm tank car are directed into the storage cavern rather than being blown into the atmosphere with the attendant fire hazard. Passage of vapors displaced from tank cars or trucks being loaded into the cavern is important at all times. The withdrawal of propane vapors from tank cars being loaded with liquid propane, rather than condensing the vapors in the cars, assists in cooling the liquid contents for maintenance of as low pressure as possible in the cars.

Because of the need for a vapor inlet and outlet to a liquid propane storage cavern, I provide herein safety apparatus, which is actually to control propane vapor flow,

in the event that tire, an aircraft or other collision ruptures or shears oif or otherwise substantially damages the well head portion of the vapor inlet and outletapparatus.

An object of my invention is to provide apparatus to prevent uncontrolled escape of inflammable vapors from an underground storage cavern in which L.P.G. is stored in the event of damage to or rupture of the surface end of a vapor conduit.

Another object of my invention is to providea foolproof apparatusr for closing olf the flow of propane from a propane vapor line extending from aboveground into a subterranean storage cavern in case of damage to or rupture of the aboveground end of the line.

Yet another object of my invention is to provide such an apparatus which is relatively inexpensive to manufacture, easy to install and to remove for servicing.

Yet other objects and advantages of my invention will be realized upon reading the following description which, taken with the attached drawing, forms a part of this disclosure.

In the drawing:

Figure lA illustrates, in elevation and partly in section, the upper portion of a preferred embodiment of my invention.

Figure 1B is a continuation of 1A, and illustrates in elevation and partly in section, the lower portion of the aforementioned preferred embodiment of my invention.

Figure 2 is a sectional elevational view of a'portion of the apparatus of Figure lA.

Figure l2 is a sectional elevational view of a portion of the apparatus of Figure 1B.

Figure 4 is a diagrammatic illustration of a storage cavern embodying my invention.

According to my invention I provide in a system for the storage of a liquefied petroleum gas in a subterranean cavern, an apparatus for providing for uid communication from aboveground to said cavern comprising in combination a rst conduit extending from aboveground into a space in said cavern normally occupied by vapor, a normally closed foot valve operatively within the lower end of said first conduit, a second conduit disposed within said first conduit in such a manner as to provide a first annulus therebetween, means supported by the lower end of said second conduit biasing said foot valve open, a normally closed hydraulically operable valve within the lower end of said second conduit, -an aboveground hydraulic oil supply, a third conduitoperably communicating said hydraulically operable valve with said oil supply, said second and third conduits being so disposed as to form a second annulus therebetween, means communicating with said second annulus aboveground for inlet and outlet of vapor to and from said cavern, a fourth conduit communicating said second annulus with said oil 3 supply for communication of cavern pressure to said hydraulic oil supply aboveground, and separate means sealing vapor tight the aboveground ends of said first annulus and said second annulus.

Furthermore, I have devised an apparatus wherein the means for sealing the aboveground ends of said first annulus vapor tight comprises a slip-joint assembly.

The vapor inlet and outlet assembly of my invention is intended to be installed at the highest point of the roof of the cavern so as to be able to withdraw any uncondensible gas which might be present in the cavern and tend to accumulate at the high point. By removal of an uncondensible gas or vapor trap, as it might be termed, provision is made for maximum use of cavern capacity.

Referring now to the drawing, and specifically to Figures 1A and 1B, reference numeral 10 identifies the earth through which a bore hole is drilled for connection with the uppermost portion of a cavern 11. Within the bore hole is positioned an outer pipe or casing 12 which is cemented or otherwise rigidly and tightly attached to the side walls of the bore hole. Within outer pipe or casing 12 is positioned a pipe 13 so disposed as to provide an annulus 13a between pipes 12 and 13. Pipes 12 and 13 extend from about ground level to a short distance below the roof or top wall of the cavern. The top end and the bottom end of casing 12 are attached fluid-tight to pipe 13, as illustrated. Within pipe 13 is disposed a pipe 14, as shown, and also within pipe 14 is disposed another pipe 15, as shown. Within pipe 15 is disposed a small diameter pipe 16. Reference numeral 17 identifies concrete used in providing a seal between the outer surface of casing 12 and the walls of the bore hole. A collar 18 is provided for connecting a nipple 41 to the lower end of pipe 15.

A collar 22 attaches a pipe section 24 to the lower end of pipe 14. Also a collar 37 is provided for attaching a nipple 36 to the lower end of pipe 13. A shoe 3S, carrying the hydrocarbon resistant O-ring 38, is attached to the lower end of pipe section 24. O-ring 3S provides a seal between the outer surface of pipe 24 and the inner surface of nipple 36. A stop ring 39 is welded to the inner end surface of nipple 36 so that, during installation of the apparatus, pipe 24 cannot `be lowered 'below the bottom end of nipple 36.

Within pipe 24 is disposed a foot valve 43. This foot valve includes a shaft or valve rod 31, a valve head or disc 34, a seat 33, and a compression spring 28. This valve assembly is supported operatively by a bushing 32 held rigidly in place by anchor lugs 29 welded to the inner surface of pipe 24. A top spring guide 27 is provided over the upper end of shaft 31 while a lower spring guide 30 surrounds the shaft and is supported by the bushing 32. The valve opening pipe 26 is not attached to the spring guide 27. The upper spring guide 27 and the valve disc 34 are, if desired, constructed similar to the corresponding members described in a copending application, Serial No. 556,853, filed January 3, 1956. Valve head 34 is, if desired, constructed with a bevel faced sealing disc 4S and a lower plate 47, both of which are metal, and are separated by a spacer plate 46, which also is metal. These plates and sealing disc are held in place on valve stem 31 by a nut 31a as illustrated. The beveled valve seat 33 is illustrated as being welded to the inner surface of pipe 24 at about the position illustrated. These several valve members are made of steel but obviously are well machined so as to provide positive seal against passage of tluid when the valve is in a seated position. Furthermore, since the sealing disc 4S and the plates 46 and 47 are intended to be horizontally adjustable to a small degree, positive sealing alignment is obtained in the seating of the valve.

At the lower end of nipple 41 are attached by welding anchor lugs or flanges, as they may be termed, which, in turn are attached by welding to the bottom valve open- 4 ing pipe 26. This valve opening pipe 26 is constructed of such length with respect to the bottom end of nipple 41 and stop lugs 20, as to bear against the top spring guide 27 to compress spring 28 and hold the foot valve 43 in an open position at such time as the bottom end of nipple 41 is resting against stop lugs 20. An O-ring sealing assembly 21 is provided as shown for sealing the annulus between pipe 15 and nipple `41, and pipes 14 and 24. A hydraulically operable valve 19 is disposed on the lower end of pipe 16, as shown. The valve 19 is held rigidly in place by the ends of pipe 15 and nipple 41 in combination with collar 18. A ring 23a if required, has such a thickness as to lill the space along with lange 71 of the valve between the lower end of pipe 16 and the upper end of nipple 41.

The hydraulically operable valve 19 is illustrated in Figure 3, in which reference numeral 71 identies the base of the valve. A flexible seat gasket 72 is provided, as illustrated, for forming a tight seal when the valve is in a closed position. A seat gasket retainer 73 is provided for retaining this seat gasket in its proper position. A cylinder 74 is provided with a closure cap 75 on its end and moves reciprocally with respect to a piston 77. Piston 77 is held rigidly with respect to base 71 by a piston support 76. The piston is held on support 76 by a nut 78. Packing 79 is held in position by a retaining washer 80 and a resilient wiper 83 and spring retainer 84. An O-ring 81, of resilient material, provides a fluid-tight seal between the piston and the piston support. A washer 82 is disposed between one end of the piston and a shoulder on the piston support and the retaining washer 80 is disposed at the other end of the piston, as shown. A gasket 85 is provided for assisting in obtaining a fluid-tight seal between cap 75 and the cylinder 74; A compression spring 86 is provided on the side of the piston illustrated and bears against a flange at the end of the cylinder adjacent the valve seat. This spring is a compression spring and biases the valve in a closed condition. A conduit 87 provides communication from the exterior of the valve to a space between the yhead of the piston and the cylinder cap 75. In this manner it is intended that when sufficient hydraulic pressure is provided through conduit 37 into the space between the piston and the cylinder cap, the valve will open against the bias of the cornpression spring. Threads 88 are provided as shown for attaching the valve to the lower end of pipe 16 when the valve is in an assembled position.

Referring to Figure lA, which illustrates the upper end of the assembly of my invention, concentrically disposed casings or pipes 12, 13, 14, 15, and 16 are shown. The upper end of casing 12 is attached fluid-tight in the manner of an orange peel connection to pipe 13. A casing head 50, which is conventional in the oil well art, is provided at the upper end of pipe 13 for supporting pipe 14. Above casing head 50 is disposed a slip-joint assembly which provides for movement or raising of pipe 15 with respect to pipe 14 in a uid-tight manner. Such a slip-joint as is suitable for use in my apparatus is illustrated diagrammatically in Figure 2. Above the slip-joint assembly is a gate valve 69 and above this valve is a pipe cross 54. The upper end of the pipe cross is flanged fluid-tight to serve as the support for additional equipment. Pipe 16 extends all the way through the several-mentioned pieces of apparatus. Packing gland 49 allows pipe 16 to pass from the pipe cross 54 without fluid leakage. An oil chamber or vessel 61 supported by supports 66 is provided, as shown. assembly and disassembly purposes a union 44, with valves 67 and 68, is provided. The upper end of pipe 16 communicates with a body of oil 62 in chamber 61. It is intended that the entire vertical length of Conduit 16 is maintained full of oil, with the oil in reservoir (52 providing a supply. A pipe 70 is attached to the top of oil chamber 61 in the manner illustrated for addition For ofoil, and is provided with a valve 64. Side arm 57 of the pipe cross 54 communicates with chamber 61 by way of a valve 58 and a pipe 59.

An annulus 40 is provided between the small diameter pipe 16 and pipe 15 for passage of vapors of the uid being stored into or out of cavern 11. This annulus 40 is intended to extend from the cavern all the way up the pipe apparatus and through the service ttings at the well head into the pipe cross 54. -A pipe 55 communicates with the pipe cross 54 and is intended to be the service outlet through which vapor is drawn for ultimate use or through which pressure equalizing connection is made to a tank car or truck being loaded or unloaded. Pipe 55 is provided with valves 65a and 66 and with a side arm 52 carrying a relief valve 56. Oil chamber 61 is provided with a suitable gauge 63 for indication of the level of oil within the chamber.

Perforations 42 in outer casing 12 are provided for passage of vapors of the lluid being stored in case there is vapor leakage from they reservoir through the containing formation. Vapors passing from the formation through perforations 42 into -annulus 13a are vented from the annulus through `a pipe 51 containing a valve 53. By observing pressure of leak-age gas in this annulus, it is possible to determine whether or not there is appreciable leakage from the cavern. The construction of this vapor leakage determining apparatus is fully described in the copending application, Serial No. 683,568, tiled September 12, 1957.

Slip-joint assembly 100 `is illustrated in detail in Figure 2. A slip-joint assembly is also fully described and illustrated in the above-mentioned copending application, Serial No. 556,853. In this particular case, a lower flange 103 is attached fluid-tight to one end of a pipe 104, the other end of which is attached fluid-tight to an upper flange 102. Lower llange 103 is illustrated in Figure lA as being attached to the upper end of the casing head 50. A ange 101 is disposed above flange 102, as shown. To ange 101 is attached in a fluid-tight manner, such as by welding, to the upper end of pipe 15. The outer diameter of pipe 15 and the inner diameter of pipe 104 lare such that an annulus is provided therebetween in which is disposed a cylindrical member 105. The upper end of this cylindrical member 105 is attached fluid-tight to the under surface of flange 101. The lower end of cylindrical member 105 terminates as an enlarged section provided with an O-ring 106, as illustrated. A suitable gasket 107 is provided between flanges 101 and 102 for providing a fluid-tight connection.

In Figure 4 is illustrated in a very diagrammatic form the general outlay of such a volatile fluid storage cavern as herein contemplated. Cavern 11 is defined by top, bottom and side walls as illustrated. Reference numeral 111 is intended to identify a liquid level gauge suitable for determining the level of the liquid stored in the cavern, Reference numeral 112 is intended to identify the assembly of my invention as installed in a storage cavern 11, and includes theapparatus illustrated in Figures lA and lB. The assembly 112 is positioned in the highest portion 106 of the roof 10a so l'as to be able to tap a vapor trap L11a for removal of uncondensible gases which are displaced upward by propane liquid and vapor. Reference numeral 113 illustrates an auxiliary liquid outlet which is suitable after insertion of a pumping mechanism for removal of liquid from the cavern in case the main removal` means is out of order. Reference numeral 114 identifies a liquid inlet apparatus which is used for transfer of liquid from a pipe line, tank car or truck into the cavern. Shaft 115 identifies a shaft which is sunk for the purpose of mining out the cavern. Reference numeral 116 identifies the main product liquid outlet which is used for pumping of stored liquid for loading into a tank truck, a tank car, or for passage into a pipe line. Reference numeral 117 identities the motor ofthe motor-driven centrifugal pump which is, in many instances, used for pumping stored liquid;

The compressive strength of spring 86 used in the hydraulically operable valve 19 is important to my invention. The compressive strength of this spring vis so selected that the weight of a column of oil extending from conduit 87 in the valve to the level of the oil 62 in the oil chamber 61 will not open the valve. However, with valve 58 open, Huid pressure from the cavern is transmitted upward through annulus 40, through `outlet 57, valve 58, and pipe 59 into the oil chamber 61; and, upon addition of this cavern fluid pressure to the column of oil, the cylinder 74 is forced downward to compress the spring 86 'and' open the valve. Thus, when uid pressure from the cavern is impressed on the surface of the oil,62, that pressure, plus the hydrostatic pressure of the column of oil, maintains the hydraulically operable valve 19 open. If relief valve 56 fails with valve 65a in a relatively large diameter pipe 55 open, or if pipe 55 is a large diameter pipe and it ruptures close to tting 54, or if any rupture occurs in outlet 57, valve 5S, pipe 59 or pipe 70, in valve 64, pipe 90, valve 91, valves 67 and 68, coupling 44, tting 49, or oil chamber 61 and gauge 63 to release the cavern uid pressure from the reservoir 61, compression spring 86 operates to close the valve against the bias of the hydrostatic pressure of the column of oil in pipe 16. For example, while loading or unloading a tank car or truck using the pipes as dagrammatically illustrated in Figure 4, or at any other occasion, if something, as an airplane crash or collision by a truck, should rupture or shear oi a vulnerable portion or portions of the well head and permit .voluminous outflow of vapor, pressure is relieved on the oil in the pipey 16 and the compression spring 86 causes the hydraulically operable valve to close, thereby preventing further outflow ofl gases through pipe 15 (annulus 40). In the case that the hydraulically operable valve 19 fails, or in case it is desired to remove the valve for servicing, it is merely necessary to disconnect the slip-joint flange 101 from flange 102 and raise flange 101 and pipe 15 upward Ya suflicient distance to remove bottom valve opening pipe 26 from contact with the top spring guide 27. Upon elevating pipe 26, compression spring 28 raises the shaft 31 and valve head 34, with the latter seating against valve seat 33, thereby preventing upilow of vapors from the cavern. When the valve head 34 is seated y against seat 33, valve 64 is opened to allow fluid from the annulus 40 to exhaust through outlet 57, valve 58,

valve 64 and pipe 70. Upon relief of pressure from the joint flange 101 and closing the hydraulically operable valve 19, the apparatus is then in condition to remove pipes 15 and 16 along with the valve 19 from within pipe 14.

The gate valve 69 is employed in the apparatus of my invention for safety purposes. It is closed to assist foot valve 43 in maintaining pipe 14 closed whenever pipe 16, pipe 15 and valve 19 are removed.

In case the foot valve 4.3 fails and needs to be withdrawn from within pipe 13, oil well methods are utilized for removing one string of pipe from within another string of pipe in a high-pressure well. Such methods are well known to those skilled in the art.

' As an example of a suitable assembly of apparatus for carrying out my invention outer pipe or casing 12 is of 12%-inch outer diameter. Pipe 13 is 10%-inch outer diameter, pipe 14 is 85/s-inch outside diameter while pipe 1S is 6% -inch outer diameter. Pipe 16 is a conventional 1/i-inch pipe.

A suitable hydraulically operable valve for use according to this invention is described in U.S. Patent 2,759,669. This valve, however, requires slight modification as to the base or base flange of the valve and with the sealing or removal of the side outlet portion of the hydraulic inlet conduit. Also, threads are provided corresponding to threads 88 of the present invention for attaching pipe 16 for conveyance of hydraulic fluid from above ground to the valve.

The several -O-rings required for sealing the several pipes Huid-tight to one another at the lower end of the apparatus are resilient material resistant to vapors to which they are exposed. In case propane is stored in the reservoir, it is necessary that these -rings be resistant to hydrocarbon vapors. The .gasket ring 107 is in many slip-joint assemblies made of steel and such are available from oil well supply houses. However, in this application, gasket 107 can usually be made of elastomeric materials resistant to the materials being stored. Similarly, O-ring 106 is made of suitable elastomeric material.

Under conditions when the valve 19 is closed, and the conduit 16 is full of oil, cavern pressure is not cornmunicated to the oil reservoir because the valve 19 is closed and an extraneous fluid pressure is required to be impressed on the oil, for example, through pipe 70, or through pipe 90, to open the valve. Thus, once the valve is opened, and with valve 58 in pipe 59 being open, the cavern pressure is impressed on the oil via annulus 40 and conduit S9 and the valve 19 remains open. This extraneous fluid pressure can be air pressure from a plant compressor, as from pipes 70 or 90, or it can be obtained by the manual actuation of an automobile tire pump through, for example, a pipe 90 and a check valve 91, with valve 64 and valve 58 being closed.

Valve 58 is maintained closed during this pressuring, particularly if an automobile pump is used, so that the entire volume of the annulus 40 will not be pressured manually. As soon as valve 19 opens, cavern pressure is admitted to annulus 40; then valve 5S is opened for pressure maintenanceon the oil 62 in tank 61.

In addition to storing a volatile liquid under pressure in the herein disclosed cavern, my apparatus is suitable and operable in the storage of a gas under pressure. In my apparatus, it is immaterial whether or not there is a liquid under the gas cap in the cavern.

Propane has a Reid vapor pressure of about 190 pounds per square inch at 100 F. If stored at this temperature, the propane would exert that pressure. However, liquid propane is usually maintained at a temperature appreciably below 100 F., for example, 60 or 70 F., at which temperatures the vapor pressure of pronane is approximately 100 pounds per square inch. Thus it is advantageous to store the propane at as low a temperature as practical in order to maintain a low working pressure.

The apparatus of my invention is also adapted for manual operation. For example, if a pipe or valve failure of minor importance occurs, as leaking of a valve packing, or if pipe 55 becomes bent between valve 65a and the 4-way fitting 54, even without vapor leakage, valves S and 65a are closed, then valve 64 is opened to relieve pressure on the hydraulic liquid 62 under which condition the hydraulic valve 19 closes. High pressure vapor is then bled from annulus 40 by opening valve 58 with valve 64 already open. Upon reduction of pressure within annulus 40 to atmospheric, the fitting 54 or other damaged member is removed for repair or replacement.

While certain embodiments of the invention have been described for illustrative purposes, the invention obviously is not limited thereto.

I claim:

1. A system for storing a fluid under a superatmospheric pressure comprising in combination a subterranean container having enclosing side, bottom and top walls for holding a fluid under superatmospheric pressure, a first tubular member extending from aboveground through said top wall and terminating at a level adjacent said top wall, a second tubular member disposed within said first tubular member and extending from aboveground to a level above the bottom end of said first tubular member, said first and second tubular members being so disposed as to provide a first annulus therebetween, a slipjoint means supported at the upper end of said first tubular member, said slip-joint means being affixed fluid-tight with respect to said first and second tubular members,

means sealing the lower end portion of said second tubular member fluid-tight to said first tubular member, stop means supported by said first tubular member limiting downward movement of said second tubular member when said second tubular member is installed in said first tubular member, a normally closed foot valve intermediate the lower ends of said first and second tubular members, a foot valve opening means supported by the lower end portion of said second tubular member, said foot valve opening means bearing against said foot valve thereby biasing said foot valve open when said second tubular member is disposed against said stop means, a normally closed hydraulically operable motor valve supported in said second tubular near its lower end but above said foot valve opening member, a third tubular member operatively communicating with said motor valve and extending from said motor valve through said slipjoint means to a level thereabove, said second and third tubular members being so disposed as to provide a second annulus therebetween, means sealing the upper end of said second annulus fiuid-tight, a conduit communicating said second annulus with said third tubular member and means sealing said first tubular member fluid-tight to the earth intermediate the ground level and said subterranean container.

2. The system of claim l wherein said motor valve is a spring loaded valve with said spring being adapted to close said motor valve when said motor valve is under only hydraulic fluid pressure from the weight of a column of hydraulic fluid in said third tubular member, and said spring being adapted to be compressed thereby to permit opening of said motor vaive under the influence of a combined pressure of said column of hydraulic fluid and pressure of fluid in said subterranean container.

3. A system for storing fluid under a superatmospheric pressure, the combination, comprising, a subterranean container having enclosing side, bottom and top walls for holding a fiuid under superatmospheric pressure, a first tubular member extending from aboveground through the top wall of said container and terminating at a level adjacent said top wall, a second tubular member disposed within and extending throughout the entire length of said first tubular member, a third tubular member disposed within and throughout substantially the entire length of said second tubular member, a casing head aixed to the upper ends of said second and third tubuf lar members and supporting said third tubular member, a fourth tubular member extending from aboveground downward within said third tubular member, the lower end of said fourth tubular member terminating above the lower end of said third tubular member, a foot valve within and adjacent the lower end of said tubular member, a hydraulically operable flow control valve within and adjacent the lower end of said fourth tubular member, means affixed to the lower end portion of said fourth tubular member to hold open said foot valve, a slip-joint assembly attached to the top end of said fourth tubular member, said slip-joint assembly being adapted to seal said fourth tubular member in a fluid-tight manner with respect to said third tubular member, a chamber disposed aboveground, said chamber being adapted to contain a hydraulic pressure uid, a Iifth tubular member within said fourth tubular member providing uid communication between said chamber and said flow control valve, a rst conduit communicating the upper portion of said chamber with said fourth tubular member for pressure maintenance in said chamber and a second conduit communicating with said fourth tubular member for inlet and outlet of fiuid to and from said container, respectively, said flow control valve being adapted to open under the combined inuence of hydrostatic pressure of a liquid column extending from said chamber through said fifth tubular member to said flow control valve and the uid pressure maintained in said chamber by communication through said first conduit to said fourth tubular member,l means for venting fluid pressure from said chamber, and means sealing said first tubular member to the earth formation intermediate the ground level and said subterranean container.

4. In the storage of a liquefied petroleum gas in a subterranean cavern, an apparatus for providing for uid communication from aboveground to said cavern comprising in combination a first conduit extending from aboveground downward and terminating in a space in said cavern normally occupied by vapor, a normally closed foot valve operatively supported within and by the lower end of said first conduit, a second conduit disposed within said first conduit in such a manner as to provide a irst annulus therebetween, means supported by the lower end of said second conduit biasing said foot valve open, a normally closed hydraulically operable valve within the lower end of said second conduit, an aboveground hydraulic oil supply, a third conduit operably communieating said hydraulically operable valve with said oil supply, said second and third conduits being so disposed as to form a second annulus therebetween, means communieating with said second annulus aboveground for inlet and outlet of vapor to and from said cavern, a fourth conduit communicating said second annulus with said oil supply for communication of cavern pressure to said hydraulic oil supply aboveground, and separate means 10 sealing vapor tight the aboveground ends of said irst annulus and said second annulus.

5. In the apparatus of claim 4, wherein the means for sealing the aboveground end of said iirst annulus vapor tight comprises a slip-joint assembly.

6. in the apparatus of claim 5, said slip-joint assembly comprising a pipe having first and second anges on its lower and upper ends respectively, said tirst flange being attached uid-tight to the aboveground end of said first conduit, a third ange disposed above said second flange, said third flange being fixed fluid-tight to the aboveground end of said second conduit, the inner diameter of said pipe having said first and second flanges being greater than the outer diameter of said second conduit thereby forming a third annulus therebetween, said third annulus being substantially an upward extension of said first annulus, slip means sealing said third annulus against leakage to the atmosphere, and said third ange, said second conduit and said means supported by the lower end of said second conduit being adapted to be elevated a sufficient distance to elevate said means supported by the lower end of said second conduit thereby permitting closing of said normally closed foot valve whereby the second conduit with the attached third ange of said slip joint and said third conduit with said hydraulically operable valve can be removed for servicing and whereby in operation upon exertion of an extraneous fluid pressure on said column of oil, said extraneous pressure plus oil pressure from said column of oil in said third conduit on said hydraulic valve, opens said valve thereby admitting cavern pressure through said second annulus and said fourth conduit to said oil supply thereby maintaining said hydraulic valve open.

References Cited in the file of this patent UNITED STATES PATENTS 2,192,945 Toney Mar. 12, 1940 2,211,845 Brown Aug. 20, 1940 2,703,696 Deters Mal'. 8, 1955 2,787,455 Knappen Apr. 2, 1957 UNITED STATES. PATENT, OFFICE CERTIFICATE 0F CORRECTION Patent No., 2V98l vOIl y April 25g l1961 v It s vhereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 8v line 67 after "said" insert third am.

signed and seaIed'thiS Ioph dayof April 196D,

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer 'Commissioner of Patents

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