US2461537A

US2461537A - Floating roof storage tank

Info

Publication number: US2461537A
Application number: US558099A
Authority: US
Inventors: Alexander S Felld
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1944-10-10
Filing date: 1944-10-10
Publication date: 1949-02-15
Anticipated expiration: 1966-02-15

Description

' Febw 15, 1949. A. s. FEILD 2,461,537

' FLOATING noor' STORAGE TANK Filed Oct. 10, 1944 2 Sheets-Sheet 1 \nvemor: Alzxandzr S. Fzild 5g his AflornegLlia im Feb. 15, 1949. A. s. FEILD 2,461,537;

FLOATING ROOF STORAGE TANK Filed Oct. 10, 1944 I 2 Sheets-Sheet 2 Patented Feb. 15', 1949 FLOATING ROOF STORAGE TANK Alexander S. Feild Houston, Tex., assignor to Shell Development Company,

San Francisco,

Calif., a corporation of Delaware Application October 10, 1944, Serial No. 558.099

1 15 Claims.

The present invention relates to devices for-- storing liquids and/or 8ases and more particularly to devices of the type in which the storage space is formed by a container having a side wall, a vertically-movable member in the con tainer that forms the top wall of the container and a sealing element of gastight'fabric or other suitable flexible or pliable, non-metallic material attached to the side wall of the container and to the peripheral edge of the vertically-movable top wall or, alternatively, formed as a part of the vertically-movable top wall of the container.

In the storage of sour crude oil containing corrosive vapors and other analogous materials in conventional metal storage tanks, severe cor,- rosion of the tank roof is generally encountered as a result of the combination of corrosive vapors and moisture condensation on the underside of the roof. A great many coating compositions have been utilized in the past in attempts to control this type of corrosion with little success; Consideration has also been given to the possibility of utilizing nickel-clad orpther corrosionresistant metals in the structure of such tanks. The cost in constructing large crude oil storage tanks of corrosion resistant metals is, however, prohibitive. Another system for overcoming this problem has been successfully employed at reflneries and other places where'groups o1 tanks are located in close proximity to each other-and involves a manifolding system whereby the corrosive vapors from a number of tanks are stored lnjav single gas storage tank. The arrangement, however, is economically practicable only in situations wherein a large number of tanks are closely spaced and is not feasible for most pipe line stations, tank farms and the like.

In addition to the corrosion problem, the conventional crude oil storage tanks are considered unsatisfactory because of the relatively large evaporation losses resulting from their use. Evaporation losses appear to result primarily from two phenomena encountered in conventional crude storage tanks. namely breathing losses and filling losses. As the vapors in a crude storage tank expand and contract with temperature changes. fresh air is drawn in during low temhydrocarbon vapors is displaced as the liquid level rises in the tank. Losses as a result of these two phenomena amount to as much as 0.5% of I the throughput, particularly in those cases where-' in the vapor pressure of the crude oil handled is high.

It is an object of the present invention to provide an improved gas and liquid storage device which both overcomes the corrosion problem discussed above and which greatly reduces the evaD-- oration losses encountered in handling and storing crude oils. A further object is to provide improved construction in gas and liquid storage devices of the type provided with a flexible fabric side wall sealing element "whereby abrasive wear of the sealing element is greatly reduced and in most instances entirely obviated. Other objects, together with someoi the advantages to be derived in utilizing the present invention, will become apparent from the following detailed description thereof, taken together with the accompanying drawings forming a part of the specification and wherein:

Figure I is a side sectional elevation of a gas and liquid storage device .according to the invention.

Eigure II is a fragmentary'horizontal sectional view of a type of weighting element suitable for use in weighting the flexible fabric side wall sealing element.

Figure III is a side sectional elevation of a second. embodiment of a gas and liquid storage device according to theinvention.

, Figure IV is a partial view in sectional elevation of a third embodiment of the invention.

Referring particularly to Figure I of the drawings. the storage device comprises a metal tank' consisting 01' a cylindrical side wall member i.

' center of the tank. Guide column 5 isclosed at perature periods and air mixed with hydrocar I bon vapors expelled as the temperature rises, the vapor passing out during the expansion cycle being'termed "breathing loss." When material is withdrawn from the tank, air is admitted to replace the volume of fluid withdrawn. During the refilling operation, the air mixes with. by-

drocarbon vapors and the mixture of air and the upper end thereof by means of a hatch 4 or other suitable closure means. Guide sleeve I 0 is slidably mounted on guide column 5 and supports gas accumulator I which is rigidlyattached thereto. Accumulator l is open at the lower end.

Bellows skirt I2 is attached at one end to guide column 5 towards the upper end thereof at I3.

The lower end of bellows skirt I2 is attached to" the top of'guide sleeveill, the interior of guide sleeve it being in flow communication with the" space defined by guide column 5 and bellows skirt l2. Bellows skirt I2 is formed of a flexibleor pliable. non-metallic material which is imperrubber material, and is further provided with a plurality of accordion pleats whereby the bellows skirt folds as the gas accumulator I rises and un-v foldsasaccumulator'l falls. I I

Annularfloat 8, which is rectangular in cross se tion. is ri idly attached to accumulator I', a plurality oi! angle pipes as at 8 providing ,flow communication between the interior or float 8 and the upper gas space of accumulator 1. A plurality of ports as at 20 provide flow cominunication between the interior or guide column at the lower end thereof and the contents of the tank, a plurality of similar ports, not shown, providing communication between the. interior of guide column 5 at the upper end thereof and the space between bellows skirt l2 and guide column IS. A plurality of ports as at 23 in guide sleeve in provide communication between the upper level of the storage space and the space between guide sleeve ill and guide column 5.

The floating diaphragm which forms the upper and part of the side wall of the storage space comprises a large, flexible or pliable element l6 of generally annular configuration and formed of a His and weak H2804 resistant material,

. such as is used in forming bellows skirt it, for

example. Diaphragm element I8 is attached at its outer periphery to approximately the midpoint of side wall I at iii. The inner periphery of diaphragm element It is attached to the bottom of accumulator 1 at IT. Diaphragm ele-' ment I6 is of sufilciently large diameter to depend in a loop from the. side wall I. a circular row of weights l9 being disposed in the loop and serving to maintain tension on the loop and to prevent folding or creasing of the material forming element l6. Rollers l9 are not attached to diaphragm element l6 and .are free to roll in the depending loop as the diaphragm rises and falls. A suitable form of weighting roller arrangement is shown in Figure II, the roller weights l9 being formed of short sections of metal pipe which are strung upon an annular shaped Conduit 8 serves to introduce or withdraw material from the storage space. Conduit I4 is in flow communication with the interior of guide column 5 at the upperend thereof and is provided with an adjustable pressure relief valve IS. A similar pressure relief valve II is mounted on the accumulator I.

In the embodiment oi the invention shown in Figure III, the storage device comprises a metal tank consisting of a cylindrical side wall 3!. bottom element 53 and truss supported rain shed 82. Cylindrical guide column 85 extends from bottom element 53 through rain shed 32 and is disposed in the center of the tank. Guide column 35 is closed at the upper end by means of a hatch 33 or other suitable closure means and is further provided with an adjustable pressure relie! valve 84 which vents to the atmosphere. An annular gas accumulator 50 of rectangular cross amass? vious to the action of ms and weak H2894, such as fabric impregnated with a suitable synthetic The floating diaphragm which forms the upper and part of the side wall of the storage space comprises ;a large, flexible or pliable element 38 of generally annular configuration and formed of r of float ll, as at 42.

a material which is resistant to H28 and weak H2804, as, for example. fabric coated or impregmated" with synthetic rubber. Diaphragm element 38 is attached at its outer periphery to approximately the mid-point of side wall M at 40. The inner periphery of diaphragm element 38 is attached to gas accumulator 50 at 39.. A closed, annular float ll of lesser diameter than the tank is rigidly attached to diaphragm element 38 at a plurality of points along the bottom face A plurality of conduits as at 46 are sealed to diaphragm element. 38 at approximately the mid-point between accumulator 50 and side wall 3!, each of conduits 86 providing flow communication between the storage space beneath diaphragm 38 and-gas accumulator Bil by means of flexible conduits as at 45 and accumulator connections as at 41. I8 depends in a loop which is weighted by circular weights l9 as described above with respect to Figure 1. Pressure equalizing conduit 43 connects the interior of the tank below the hinge point 40 v with the interior of the column 35 at its top.

'A flexible branch conduit 68 connects conduit and extends within skirt H. A plurality of ports as at 62 provide flow communication between the interior of guide column 35 and the space enclosed by skirt 51.

Referring to Figure IV, a third embodiment of the invention comprises a metal tank consisting of a cylindrical side wall 6i, bottom element 62 and a rain shed 63 which is supported by a truss system 64. Guide column 65 extends from bottom element 62 through rain shed 63 and a ring 68 formed in the truss system. A housing comprising an outer shell Ill and an inner shell 81 is supported on rain shed 63, the top portion of outer shell 10 forming'a gas tight seal with the extension of guide column 65. The annular section is rigidly mounted on guide sleeve 36 which is in turn slidably mounted on guide column space defined by outer shell Ill and inner shell 61 is packed with rockwooi 69 or the like. A plurality of air inlet vents as at Hill are provided in the lower part of outer shell Iii and a plurality of air outlet vents are provided in the upper sectionof inner shell 68. An annular ring II is provided on the top of outer shell 10, forming a water trough 12. The annular section 14 of outer shell 10 which is below air inlet vents I00 forms a second water trough below packing 69. A plurality of perforations in the top of outer shell 10 permit water contained in trough 12 to drain through packing 69 and a drain conduit 15 leads from the trough beneath packing 69 to sewer. Water is admitted through conduit 13 to trough 12. Exhaust ventilator 99 discharges air from the top interior of the tank to atmosphere, intake air passing through vents 1B0. wet packing 89 and vents 68 to the interior of the tank. I

Gas accumulator 16, which is open atthe bottom. is rigidly mounted on and supported by roller-mounted guide sleeve 18 which moves freely along the vertical length of guide column 65. A closed annular float I1 is rigidly mounted on accumulator l8. Perforated conduit '19 extends irom bottom element 82 to the top of outer Diaphragm shell Iii of the guide column housing, passes through outer shell 10 in a gas tight seal therewith and continues as an imperforate conduit provided with an adjustable pressure relief valve. 98 venting to atmosphere. Conduit I9 passes through a hole provided in the top of accumulator I9. A bellows skirt 80 is attached at one end to the interior top of outer shell ill at 92, forming a gas tight seal therewith around conduit 19, the other end thereof being attached to the periphery of the hole in the top of accumulator .10 at sl through which conduit 19 passesfa gas tight seal also being formed at 8|. The interior of bellows skirt 80 is thus in flow communication with the interior of accumulator 18. the skirt at all times enclosing that portion of conduit 19 which is perforated and extends above the top of accumulator I8. Bellows skirt 90 is preferably formed of a flexible or pliable, non-metallic material which is resistant to attack by ms or weak H280. such as fabric coated or impregnated with a suitable synthetic rubber material. and is further provided with a plurality of accordion pleats whereby the bellows skirt folds as accumulator 1B rises and unfolds as accumulator It falls. The upper end of the conduit 19 carries an adjustable pressure relief valve 83.

Floating diaphragm 90, which may be formed of light metal or flexible material such as used in forming bellows skirt 80 is of annular configuration, the inner periphery thereof being rigidly attached to annular float Tl. The outer periphery of diaphragm 90 is attached to a circular angle iron member 8i to which in turn a second annular float 92 is attached by means of uprights l! mounted on angle iron 9|. A cylindrical sealing member 99. formed of a flexible or pliable material as in the case of bellows skirt 80, is attached at one end to circular angle iron 9i and at the other end is secured by circular sealing ring 94 which is rigidly attached to side wall 8| at approximately the vertical mid-point thereof. The vertical dimension of sealing member 93 is sufficient to provide a depending loop regardless of the relative vertical disposition oi floating diaphragm 90 with respect to the point of attachment of sealing member 93 to side wall and floating diaphragm i6 and accumulator I resting on the bottom, the liquid components I comprising the major portion of the crude 9|. A circular roller I9 is provided in the loopto prevent folding or creasing of sealing member 99, as previously described with respect to the embodiments of Figures I and II.

Conduit 99 serves to introduce and withdraw material from the storage space and extends to a point within metal skirt 81, open at the bottom, which is provided around the base of guide column 95. A plurality of ports as at 98 provide flow communication between the interior of guide column 95 and the space enclosed by metal skirt- 91. Conduit 95 including an adjustable pressure relief valve 84 is in flow communication with the interior of guide column 65 and provides a vent to the atmosphere. Pressure equalizing conduit 95 connects the interior of the tank below the sealing ring 94 to the top of the conduit 19.

Accumulators 98 are sealed to the diaphragm 90 and connect the space beneath the diaphragm to the. interior of the accumulator 18 by means of conduits 91.

The storage devices according to the present gradually urge diaphragm I6 upwardly, floating the same to the position shown in the drawingor higher. Volatile'components of the crude oil, including HzS, which separate from the crude oil enter accumulator 1 through the open bottom thereof and are retained by the liquid seal formed at the bottom of accum'ulator I by the liquid material in the tank and beneath diaphragm I6. In the event that excessive quantities of volatile components are present, the pressure developed by these components displaces the liquid seal at the bottom of accumulator with consequent formation of a vapor phase beneath diaphragm l9. Vifhen the volume of the vapor phase increases to a point sufilcient'to displace the liquid level to a point below ports 23, the vapor escapes through the space between guide sleeve Ill and guidecolumn, passing into the space defined by bellows skirt l2 and guide column 5 from whence it is free to pass into the interior of guide column 5 through ports provided in the upper portion thereof A portion of the gas or vapor in accumulator I passes into float 8 through conduits 9, thus increasing the vapor storage space and at the same time stabilizing accumulator 1. Relief valves lland I5 are set to vent vapor to atmosphere from guide column Sand accumulator 1 in the event that the pressure therein approaches the maximum that may be safely contained by the vapor storage system.

As floating diaphragm it rises and falls, it is apparent that the hydrostatic pressure of the liquid contained beneath the diaphragm will exert an outward pressure urging the depending part of the diaphragm against side wall I and against the fold of the loop adjacent side wall I. In order to'avoid frictional wear and other mechanical damage to the diaphragm, the hydrostatic pressure of the liquid beneath diaphragm i6 is compensated by maintaining a liquid level 22 above the diaphragm. Any noncorrosive liquid of relatively low volatility may be utilized for this purpose, preferably a relatively high boiling liquid hydrocarbon such as weathered sweet crude oil. or the like. Water may be used for this purpose. but does not have the desired action in protecting the metal parts of the tank, as described below. This inert liquid layer above diaphragm l6 serves four primary purposes as follows:

1. With the top of diaphragm i6 below hinge po nt is, the liquid fills the space between the two folds of the depending loop of the diaphragm, thereby preventing the hydrostatic pressure of the liquid contained beneath the diaphragm from urging the inner fold of the loop against the outer fold thereof. -With the top of diaphragm l6 above hinge po nt IS, the liquid a so fills the space between the vertical face of d aphragm l6 and side wall I and exerts a hydrostatic pressure sufllcient to prevent contact between the diaphragm and side wall, thereby eliminat ng skin friction as the d aphra m rises and falls.

2. A layer of weathered sweet crude oil of approximately 1 foot on the top of diaphragm '6 will exert a pressure on the surface of the liquid material within the tank of approximately 6 ounces per sq. in. which is about 6 times as much pressure as can be safely held by a conventional,

with consequent reduction in evaporation losses.

3. If small pin holes should develop in diphragm IS, the liquid layer 22 prevents escape of sour crude or H28 from beneath the diaphragm through the pin holes, a liquid having a specific gravity at least approximately equal to or preferably slightly greater than that of the crude oil being preferably selected for this reason.

4. When a non-corrosive oil is utilized as the liquid layer 22, a large portion of the interior metal surfaces of the tank above hinge point I8 becomes coated with the oil as the diaphragm rises and falls, thus greatly reducing atmospheric corrosion of these parts when the tank is only partially filled or empty.

In the handling of most crude oils, the liquid level 22 above diaphragm It should be sufilcient to provide a depth of at least approximately one foot when the diaphragm is at its highest level. Since the volume of liquid contained in the space defined by the side wall of the diaphragm and the tank wall decreases to a minimum when the diaphragm is at its lowest level, the liquid level above the diaphragm will increase somewhat as the diaphragm falls.

In the embodiment of the invention shown in Figure III, floating diaphragm 38 functions in the same manner as floating diaphragm l6 of Figure I except that annular float 4| is provided to insure an approximately plane surface of diaphragm above the liquid stored therebeneath, whereas in the embodiment of Figure I the hydrostatic pressure of the stored liquid is depended upon to maintain the diaphragm IS in approximately the position shown. In Figure III, the

level of liquid layer 22 is maintained high enough to permit flow over the top of annular float 4| into the depending loop of diaphragm 38 as the diaphragm rises, or alternatively, a plurality of ports may be provided in the lower part of annular float 4| to provide flow communication between liquid layer 22 and the diaphragm loop. Gas accumulator 50, which is not open .at the bottom as in the embodiment of Figure 1, serves as a float and stabilizer for guide sleeve 36. Since it has been found that the major portion of the volatile components of the crude usually collect beneath that section of diaphragm 38 between annular float 4| andaccumulator 50, resulting in a slight upward bellowing of the diaphragm, a'

plurality of flexible conduits as at 45 are provided to pass the separated vapors from beneath diaphragm 38 to accumulator 50. Flexible conf duitfl is loosely wrapped around guide column 35 d is of sufficient length to extend from conduit 43 to accumulator 5|] when the accumulatoris in its lowest position. It will be seen that" in this arrangement the pressures in the various parts of the storage system are equalized, conduit 43 being in flow communication with the storage space of the tank, with the interior gasholding space of guide column 35 and with accumulator 50 through conduit 48. Relief valve 34 serves to vent gas to atmosphere in the event that the vapor pressure in the system exceeds a safe maximum. 7

which are extant as a discrete vapor phase at the time of introduction to the tank, are separated by passing the liquid material through conduit 6 to a point beneath cone skirt 5|, the vapors collecting in the upper portion thereof and passing to the interior of guide column 35 through ports as at 52.

, Referring to the embodiment of Figure I], gas accumulator I6 is open at the bottom and is provided with a closed, annular supporting float l'l. Vapors separating from the crude oil or other liquid beneath floating diaphragm 90 pass, into a plurality of small accumulators as at 96 which are spaced around diaphragm 90 approximately midway between annular float 92 and accumulator 18. The accumulators as at 96 are mounted on the top of diaphragm 80 and in flow communication with the storage space therebeneath and with accumulator 16 through flexible conduits as at 81. Bellows skirt 80 folds and unfolds as diaphragm 90 rises and falls, the interior of the bellows skirt being in direct flow communication with the interior of accumulator l6 and in indirect flow communication therewith through perforated conduit 19. The imperforate portion of conduit 19 extending above the top of the tank is in flow communication with pressure equalizing conduit 95 and with relief valve 83 for venting excess pressure to atmosphere. In this arrangement, the only vapor contained within guide column 65 is that which separates as the crude oil enters the tank through conduit 62 into cone skirt 81, the vapors entering guide column 85 through ports as at 88. Conduit 85 and relief valve 84 provide means for venting excess pressure to atmosphere from the interior of guide column 65.

Annular float 92 is'mounted on a plurality of uprights as at llll whichare in turn mounted on angle iron 9|. In this manner liquid layer 22 provided above diaphragm 90 is free to pass into and from the loop of sealing member 93 beneath float 92 as the space volume defined by the loop changes with the rise and fall of diaphragm 80.

Breathing losses are greatly reduced in the arrangement shown in Figure IV by means of the air-conditioning system provided. Air is withdrawn from above floating diaphragm 90 through a plurality of exhaust ventilators as at 99 which are spaced around rain shed 83 near the periphery thereof, resulting in air being drawn in through air inlet vents I00, through packing B9 and into the space above floating diaphragm 90 through vents 68. Packing 69 is wetted by water Volatile components of crude oil or other liquid material which is to be stored in the tank and from trough I2. as deta led hereinbefore, and the air. circulating above diaphragm is cooled by the resultant evaporation and heat exchange with the water contained in packing 89.

As a specific example of the advantages to be derived in utilizing storage devices constructed as described above, a test was carried out to compare a crude oil storage tank constructed according to Figure III of the drawings with a conventional cone roof tank. The tanks, of substantially identical size and shape, were simultaneously filled at the same rate with a crude oil having a vapor pressure of 10.7 lbs. per square inch at 100 F. and an -A. P. I. gravity of 41.8". Filling of the tanks was completed over a period of 6 hours. Determinations as to the change in gravity and vapor pressure of the oil in the tanks over a pe-' riod of 6 days were made and the following results obtained. In thetable, tank No. 1 designates the tank constructed according to Figure 111 and standard cone roof.

tank No. 2 designates the tank movided with a Table I I Corrected Vapor Period Ela sed After T k A. P. I. Pressure Tm Gravity at 100 F It will be noted that the A. P. I. gravity of the oil entering the tank constructed according to the present invention'decreased only 0.4" A. P. I. during the filling operation, whereas in the case of the tank with a standard cone roof the gravity decreased 1.4 A. P. I. during filling. At the end of the 6 day test period, the gravity difference between the oils in the two tanks was 1.5 A. P. 1., representing a volume loss in the standard tank of approximately 3% over the losses encountered in the tank constructed according to Figure III. Further, it will be noted that the vapor pressure of the oil in the standard tank 2.8 lbs. per square inch at the end of the fifth day, a decrease of 7.9 1

lbs. per square inch from the initial vapo'r pressure of the crude, whereas the vapor pressure of the crude in the bank according to the present' invention had only dezreased 0.7 lb. per square inch over the five day period.

The construction principles embodied in the various modifications of the invention described above are employed with particular advantage in the construction of vessels for the storage of crude oil containing H2S or other corrosive volatile components, since the primary corrosion problem in such cases arises from the moist Has-containing atmosphere coming in contact with the roof of the storage vessel. In vessels constructed according to the instant invention, the volatile components are separated from the liquid components and passed to storage zonesof relatively small size which may be practicably formed of corrosion resistant materials. Furthermore, since the volatile components do not come in contact with the atmosphere, the moisture content of these corrosive vapors is sufliciently low that the rate of corrosion of metals coming in contact therewith is much less than in those instances wherein the vapors are permitted to contact metal surfaces after mixing with atmospheric air and/or moisture condensate from the atmosphere which may already be present on the metal surfaces. The feature of providing a liquid on top of the flexible sealing element is claimed in my copending application Serial No. 558,100.

I claim as my invention:

1. In a storage device of the class described, the combination comprising a container. a guidecolumn extending upwardly in said container, gas

accumulator means slidably mounted on said guide column, a floating diaphragm attached to said gas accumulator means, a non-metallic, flexible sealing element attached to said floating diaphragm and to the side wall of said container, said floating diaphragm and said sealing element forming at least a portion of the top and side walls of a liquid storage chamber. an annular float mounted on said floating diaphragm adjacent the periphery thereof and a plurality of" conduits extending through said floating diaphragm between said gas'accumulator means and said annular float in flow communication with said storage chamber and leading to said gas accumulator means in flow communication therewith.

2. In a storage device of the class described, the combination comprising a container, 9. guide column extending upwardly in said container, gas accumulator means slidably mounted on said guide column, an annular float mounted on said gas accumulator means, a floating diaphragm attached to said annular float, a non-metallic, flexa ible sealing element attached to said floating diaphragm and to the side wall of said container, said floating diaphragm and said sealing element forming at least a portion of the top and side walls of a liquid storage chamber, an annular float mounted on said floating diaphragm adjacent non-metallic sealing element attached to said floating. diaphragm and the side wall of said container, said floating diaphragm and said sealing element forming at least a portion of the top and sidewalls of a liquid storage chamber, means for folding said sealing element into a loop which depends from said floating diaphragm during the operation of filling and emptying said storage chamber, an annular fl-oat mounted on said floating diaphragm adjacent the periphery thereof, a plurality of conduits extending through said floating diaphragm between said annular floats in flow communication with said storage chamber and leading to said gas accumulator means in flow communication therewith, and flow communication including a pressure relief valve leading from said gas accumulator means to a point exflow communication means leading from saidstoragechamber to said gas accumulator means in flow communication therewith. and flexible conduit means leading in flow communication. from said gas accumulator means to the interior of said tubular guide column adjacent the upper end thereof.

ascassr 5. In a storage device of the class described, the combination comprising a container, a tubular guide column closed at the upper end and extending upwardly in the center of said container, gas accumulator means slidably mounted on said guide column, a non-metallic, flexible sealing element sealed to said gas accumulator means and the side wall of said container, said sealing element forming at least a portion of the top and side walls of a liquid storage chamber, flow communication means leading from said storage chamber to said gas accumulator means in flow communication therewith, flexible conduit means in flow communication with said gas accumulator means, and a vent conduit including a pressure relief valve in flow communication with said last named flexible conduit means.

6. In a storagedevice of the class described, the combination comprising a container, a tubular guide column closed at the upper end and extending upwardly in the center of said container, gas accumulator means slidably mounted on said guide column, a floating diaphragm attached to said gas accumulator means, a non-metallic,

flexible sealing element attached to the periphery of said floating diaphragm and the side wall of said container, said floating diaphragm and said sealing element forming at least a portion of the top and side walls of a liquid storage chamber, flow communication means leading from said storage chamber adjacent said floating diaphragm to said gas accumulator means in flow communication therewith, a perforated conduit extending upwardly through said gas accumulator means adjacent and parallel to said guide column, said gas accumulator means being vertically movable with respect to said perforated conduit, and a flexible conduit in flow communication at one end thereof with said gas accumulator means and in flow communication at the other end thereof with a vent conduit including a pressure relief valve, said flexible conduit being of larger diameter than said perforated conduit and disposed concentrically with respect to said perforated conduit- 7. In a storage device of the class described, the combination comprising a container, a tubular guide column closed at the upper end thereof and extending upwardly in the center of said container, a gas accumulator slidably mounted on said guide column, an annular float mounted on said gas accumulator, a floating diaphragm attached to said annular float, a second annular float mounted on said floating diaphragm adjacent the periphery thereof, a non-metallic, flexible sealing element attached to the periphery of said floating diaphragm and the side wall of said container, said floating diaphragm and said sealing element forming at least a portion of the top and side walls of a liquid storage chamber, means for folding said sealing element into a loop which depends from said floating diaphragm during the operation of filling and emptying said storage chamber, a plurality of flexible conduits in flow communication with said storage chamber through said floating diaphragm at radially spaced points between said annular floats and in flow communication with said gas accumulator; flexible conduit means in flow communication with a vent conduit and with said gas accumulator, a pressure relief valve in said vent conduit and a pressure equalizing conduit extending in flow communication between said storage chamber and said vent conduit.

8. In a storage device of the class described, the

combination comprising a container,- a tubular guide column closed atthe upper end thereof and extending upwardly in the center of said container, a gas accumulator slidably mounted on said guide column, an annular float mounted on said gas accumulator, a floating diaphragm attached to said annuiar float, a second annular float mounted on said floating diaphragm adjacent the periphery thereof, a non-metallic, flexible sealing element attached to the periphery of said floating diaphragm and the side wall of said container, said floating diaphragm and said sealing element forming at least a portion of the top and side walls of a liquid storage chamber, means for folding said sealing element into a loop which depends from said floating diaphragm during the operation of filling and emptying said storage chamber, a plurality of flexible conduits in flow communication with said storage chamber through said floating diaphragm at radially spaced points between said annular floats and in flow communication with said gas accumulator, a perforated conduit extending upwardly through said gas accumulator adjacent and parallel to said guide column, said gas accumulator being vertically movable with, respect to said perforated conduit, a flexible conduit in flow communication at one end thereof Witlisaid gas accumulator and in flow communication at the other end thereof with a vent conduit including a pressure relief valve, said flexible conduit being of larger diameter than said perforated conduit and disposed concentrically with respect to said perforated conduit, a pressure equalizing conduit extending in flow communication between. said storage chamber and said vent conduit, a rain shed covering the top of said container and means for circulating air through said container above said floating diaphragm at a temperature below prevailing atmospheric temperature.

9. A storage device according to claim 8 includ- I ing an inverted cone skirt mounted on said guide column adjacent the lower end thereof, flow communication means between the lower part of said cone skirt and said storage chamber, flow communication means between the upper part of said cone skirt and the interior of said guide column, a conduit extending from a point external to said container and terminating within the upper part of said cone skirt, and a vent conduit including a pressure relief valve in flow communication with the interior of said guide column at the upper end thereof.

10. In a storage device of the class described, the combination of a container, a tubular guide column extending upwardly in said container, said column being closed at its upper end and having perforations near the bottom, forming flow communication between the interior of said column and the sealed-off space, described hereafter, a pressure relief valve connected to the top of the column for venting gas therefrom, a gas accumulator comprising-a closed top and side walls slidably mounted on said guide column and providing an annular gas space surrounding said guide column, a non-metallic, flexible sealing element connected to the side wall of said container and sealed to said accumulator to provide a sealed-off storage space between the sealing element and the bottom of the container, and flow communication means between said sealedoif space and the gas accumulator.

11. The storage. device according to claim 10, wherein the interior of the guide column is con- 13 nected near the top by a pressure equalizing conduit to a point within said sealed-off space at the side of the container.

12. The storage device according to claim 10, wherein the interior of the guide column is in flow communication with the annular gas space of the gas accumulator.

13. In a storage device of the class described, the combination of a container, a tubular guide column extending upwardly in said container, a sleeve slidably mounted around said guide column, a gas accumulator comprising a closed top and side walls mounted on said sleeve and providing an annular gas space surrounding said sleeve, a non-metallic, flexible sealing element connected .to the side of said container and sealed to said accumulator to provide a sealed-oil storage space between the sealing element and the bottom of the container, flow communication means between said sealed-off space and the gas accumulator, perforations near the bottom of the tubular guide column forming flow communication between the interior of said column and said sealedofi' space, and vent means for releasinggas from the top of the tubular guide column.

14. A storage device according to claim 13 including a flexible conduit means surrounding the tubular guide column sealed at its top to the tubular guide column and at its bottom to the 14 sleeve forming a'gas space between the flexible conduit, and fiow communication means between said gas space and the interior of the guide column.

15. A storage device according to claim 13 including an inverted cone skirt mounted on said tubular guide column adjacent to the lower end thereof, surrounding said perforations near the bottom, fiow communication means between the lower part of said cone skirt and said sealed-off storage space, and a conduit extending from a point external to said container and terminating within the upper part of said cone skirt.

' ALEXANDER S. FEILD.

REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS