US2951348A - Method and apparatus for storage and distribution of low-temperature liquids - Google Patents

Description

p 1960 P. E. LOVEDAY ETAL 2,951,348

METHOD AND APPARATUS FOR STORAGE AND DISTRIBUTION OF LOW-TEMPERATURE LIQUIDS Filed July 24, 1956 3 Sheets-Sheet 1 INVENTORS PAUL E. LOVEDAY BY LYMAN A. BLISS ATTORNEY P 6, 1950 P. E. LO DAY ET AL 2,951,348

TRIBUTION METHOD AND APPA US STORAGE AND DIS v OF -TEMPERATURE LIQUIDS Filed July 24, 1956 3 Sheets-Sheet 2 IN V EN TORS PAUL E. LOVEDAY LYMAN A. BLISS 6 0 ATTORNEY 2,951,348 ION Sept. 6, 1960 P. E. LOVEDAY ET AL METHOD AND APPARATUS FOR STORAGE AND DISTRIBUT OF LOW-TEMPERATURE LIQUIDS Filed July 24, 1956 3 Sheets-Sheet 3 lastfl qjl 5/19 520/ INVENTORS PAUL E. LOVEDAY By LYMAN A.BLISS ATTORNEY United States Patent METHOD AND APPARATUS FOR STORAGE AND DISTRIBUTION OF LOW-TEMPERA- TURE LIQUIDS Paul E. Loveday, Kenmore, and Lyman A. Bliss, New York, N.Y., assignors to Union Carbide Corporation, a corporation of New York Filed July 24, 1956, Ser. No. 599,733

12 Claims. (Cl. 62-50) This invention relates to a method of and apparatus for storing and dispensing low-boiling liquefied gases; low-boiling gases may be defined as those having boiling points at atmospheric pressure below 230 K. More particularly, it concerns an improved method and container for delivering such gases to small users in liquid state, ready for immediate withdrawal in a gas state at superatmospheric pressure.

Consumers of industrial gases such as oxygen and nitrogen, who require a portable supply, as in the welding industry, are commonly served by high pressure gas cylinders furnished in sufiicient number to assure a dependable supply. In order to handle such gases economically at ambient temperatures, it is necessary to compress them to pressures on the order of 2,000 to 3,000 pounds per square inch. In the case of oxygen, this reduces the gas volume by a ratio of about 4 (stored volume/NIP. volume). However, storage at such high pressures requires sturdy, thick-walled and consequently heavy vessels. As a result, the weight ratio of tare (weight of empty container) to payload is very high. In the average compressed oxygen cylinder, it is approximately 6.55. Consequently, in order to distribute 20 pounds of oxygen, it is necessary to transport and return over 130 pounds of container. This obviously is expensive.

The need for safe and more economical distribution units has certainly been recognized for many years, for the cost of distribution of such gases constitutes a large part of the total cost of such gases. It has long been thought that the distribution costs of low-boiling industrial gases could be reduced substantially by a satisfactory portable liquid distribution vessel. Expensive gas phase compression could be eliminated, relatively lower pressures would be possible, and higher mass charge per unit of volume could be achieved. However, none of the liquid containers heretofore used in the distribution of low-boiling liquefied gases has fulfilled the need in this field, even though they have achieved much success in large quantity supply.

The distribution of low boiling liquefied gases in small containers presents problems of evaporation loss, selfcontainment and container construction which are either not found or at least are found to a much lesser degree in large liquid containers. For example, the ratio of container volume to its surface area is directly related to evaporation loss. The lower this ratio, the higher the loss. For long cylindrical vessels, this ratio approaches proportionately to the vessel diameter. Thus, it has been found much more economical to distribute liquid in a large diameter cylindrical container, such as a tank car, than in a small diameter portable container. Another factor which promotes higher evaporation losses in smaller vessels than in larger vessels is the proportionately higher ratio of easing diameter to container diameter. As this ratio increases, the mean cross sectional area of the path for heat flow through the insulation into unit area of the container surface also increases.

In order to minimize the evaporation losses in known 2,951,348 Patented Sept. 6, 1960 'ice 7 2 7 liquid distribution systems, the vessel is commonly charged with sub-cooled liquid at low pressure. In this Way the liquid can absorb appreciable quantities of heat before developing excessive pressure with consequent vapor losses. Such a practice necessarily requires pressure building means to bring container pressure to the delivery level when liquid is to be withdrawn for con sumption. This obviously increases the cost and complexity of the container and, moreover, adds additional heat losses which offset much of the advantages of sub cooling, for liquid from the liquid phase of the container must be vaporized and the vapor with its added heat is returned to the vapor phase of the container. Furthermore, containers using pressure build-up coils are not ready for instant service immediately after hook-up to a consumer line, for an appreciable period of time is required to boost pressure in a container to delivery pressure.

Conversion of a liquefied gas to a superheated vapor is also a requirement of liquid distribution which has heretofore been met in large supply systems by the provision of heating utilities'using steam, electricity or water to supply the necessary heat and to circulate the heating medium. While the provision of such utilities is practicable for permanent installations, since such units are normally located at or near industrial areas wherethe utilities are available and accessible, they arenot practicable for portable units which should be self-contained and to provide mechanical simplicity in replacement and in service and to obviate the need for on-the-job customerconverter equipment. a

The general purpose of this invention, therefore, is the provision of a practicable portable package for distributing low-boiling liquefied gases.

A more particular object of this invention is to provide a package for storing and distributing a'relatively small amount of a low-boiling liquefied gas, such as liquid oxygen, for example, which provides delivery of superheated gas to the consumer supply connection without outside utilities, and permits storage of such liquefied gas over reasonably long idle periods without loss of stored material.

Another object of this invention is the provision of a portable package for low-boiling liquefied gases that is provided with automatic controls which make it easy for the consumer to connect the container to his supply line and to discharge gas from the container with a minimum amount of attentiveness and skill on his part.

Another object of this invention is to provide a portable means for supplying low-boiling gases to customers, which is safer in transport, storage and use than known means.

Still another object of this invention is the provision of a container for supplying small quantities of a lowboiling liquefied gas, that has a low tare weight relative to the pay load carried, is durable so as to withstand rough handling, and contains its functional elements in a compact organization resulting in realtively small bulk.

Among objects of the present invention are: To provide instant gas delivery at supply pressure without any time delay. To provide a portable container for liquefied low-boiling gases which is adaptable for use with the same gas consuming apparatus as is used with conventional high pressure gas storage tanks. To provide such a container that has fewer operating elements for dispensing such liquefied gas in gaseous form and for controlling such delivery. To provide a more economical method and apparatus for supplying relatively small amounts of low-boiling gases to consumers. And to provide a method of storing liquid under pressure and withdrawing same without appreciable loss in pressure at any desiredrate without outside pressure building assistance.

The present invention involves a new concept for distributing relatively small quantities of low-boiling gas material directly to consumers, that departs radically from known methods of storing and dispensing such material in eithergaseous or liquid form. In accordance with this invention such material is stored, bottled up in liquid form at moderately high pressure that is at least as high as the operating pressure required to deliver at the lower end of a predetermined range of service pressures and saturated with respect to such pressure. Whereas it has been desirable in known practices to store such liquid at non-equilibrium conditions with respect to the vapor phase, it is desirable in the instant practice to maintain liquid-vapor equilibrium for as long as possible. Liquid is discharged from the storage body under its own vapor pressure without the need for bulky and expensive pressure building equipment, and is vaporized 'and superheated by ambient atmosphere heat exchange, thereby eliminating the need for auxiliary heating sources or utilities. Since bulk storage of low-boiling liquefied gases is normally held at saturation or sub-cooled at a low pressure, considerable warming of the liquid to be charged into the storage body of the present invention must be done in order to bring the liquid to saturation at the minimum operating pressure limit. Under certain conditions, the liquid could be charged into the storage body saturated at a pressure below the minimum operating pressure providing a considerable holding time is contemplated prior to initial withdrawal and providing the liquid is held in substantial equilibrium with respect 'to its vapor phase over this period. The holding period prior to use would have to be suflicient to allow a pressure build-up to minimum operating pressure by heat leak alone.

' Storage in small quantities in the manner described is made possible by limiting the rate of increase in heat content of the stored liquid due to heat leak. This is preferably accomplished by using a highly efficient insulation which will restrict heat leak into the stored liquid to a rate low enough to prevent evaporative loss in transit and during reasonably long idle periods. This is necessary because bottled storage at relative high pressure reduces the margin between filling pressure and the setting of relief device, and the decrease in pressure margin must be overcome by a corresponding reduction in heat inflow to the stored liquid. The setting of the relief device indicates maximum operating pressure and thus constitutes the upper limit to the service pressure range.

Other objects, features and advantages of the invention and the several new combinations and constructions which it provides will be apparent from the following detailed description and the accompanying drawings illustrating preferred embodiments thereof.

In the drawings:

Fig. 1 is a schematic diagram of a system for storing and dispensing liquefied gas material according to the present invention;

Fig. 2 is a transverse vertical section of a portable liquid package embodying the invention;

Fig. 3 is a view of a transverse horizontal section taken along line 33 of the package shown in Fig. 2;

Fig. 4 is an elevational view of a vaporizer used in the liquid package of Fig. 2;

Fig. 5 is a longitudinal cross section through a preferred manifold used for feeding the vaporizing coil of the vaporizer shown in Fig. 4;

Fig. 6 is a plan view of the package shown in Fig. 2;

Fig. 7 is an enlarged fragmentary vertical cross section through the top portion of the package of Fig. 2, taken along line 77 of Fig. 6, on an enlarged scale;

Fig. 8 is a horizontal transverse section through the head portion of the liquid package, taken along line 88 of Fig. 7

Fig. 9 is a transverse vertical section, partly in elevation, showing a modified form of a liquid package embodying the present invention;

Fig. 10 is a horizontal transverse section of said package taken along line 10-40 of Fig. 9;

Fig. 11 is a fragmentary vertical cross section through the head portion of the package shown in Fig. 9;

Fig. 12 is a fragmentary transverse section taken across the package insulation along line 12-12 of Fig. 9; and

Fig. 13 is a schematic diagram of the system for dispensing liquid from the package embodied in Fig. 9.

With reference now particularly to Fig. 1, there is shown a system illustrating storing and dispensing lowboiling gas material by the principles of this invention. Low-boiling gas material is received in liquid form into an insulated storage container 10 from a bulk storage source (not shown) by way of conduit 11 and a filling connection 12 on the container. The container encloses a liquid holding chamber 15 having a normal liquid space 1511 and a gas space 15b thereabove. Highly efiicient heat insulation 24 is disposed in surrounding relation to the chamber 15 to hold heat inflow to the chamber to a predetermined minimum value. Since the container is to be charged with liquid saturated at a pressure at least as high as the operating pressure required to deliver stored material at a minimum service pressure and since the liquid in bulk storage is saturated or subcooled at a low pressure, a warming coil 13 is provided in conduit 11 'to prewann the liquidto saturation at the minimum operating pressure. The term a liquid saturated at a (particular) pressure is intended throughout this application to mean that the liquid body contains at least an amount of heat equivalent to that of such a liquid at saturation temperature with respect to such particular pressure. The filling connection 12 is controlled by a stop valve 14 and is connected to. the liquid-holding chamber 15 within the container by way of a gas phase connection 16 opening into the top of gas space 15b. Since the liquid enters the storage chamber .15 through the gas phase, the vapor pressure in the container during filling is maintained at approximately the equilibrium pressure of the liquid.

After charging of the container has been completed, the filling connection valve 14, which is a check valve, closes and the bottled-up container, charged with liquid saturated at minimum operating pressure, is shipped as a package ready for immediate service. In order to make a withdrawal, a consumer merely makes a single connection to his ownline in the same way that compressed gas cylinders are presently connected. To this end a service connection 17 is provided having a coupling 18 at one end for connection with the consumer line (not shown) and a stop valve 19. The other end of the service connection has fluid communication with both the liquid and gas spaces of chamber 15, to the liquid space by an open liquid phase connection 20 leading to the bottom of the liquid space 15a and to the gas space 1512 by the gas phase connection 16 which has a valve 21 therein controlling-flow from the gas space to the service connection. When the service connection 17 is opened for withdrawal purposes, a pressure difierential is set up immediately between the chamber 15 and the service connection. Liquid is then forced through the liquid phase connection 20 into the service connection for discharge from the container. A vaporizer 22 is provided in the service connection for passing liquid withdrawn from the liquid space in heat exchange with a warmer material, preferably the atmosphere, in order to provide a discharge in gaseous form. The service connection may also be provided with a valve controlled liquid discharge line 23 for discharging liquid without prior vaporization in case a liquid discharge is desired.

In spite of the provision of the most eflicient types of insulation 24 around the container, unavoidable heat leak into the liquid holding chamber 15 warms the liquid and causes evaporation. Such evaporation if left unattended would slowly raise the container pressure.

If withdrawal of the chamber contents were made entirely from the liquid phase over a sufiiciently extended period, this pressure rise would continue-until vapor pressure reaches the setting of a relief device. In order to avoid a loss of vapor under these conditions, provision is therefore made for the automatic withdrawal of a quantity of vapor from the chamber that is approximately equivalent to the heat leak into the container. flow regulator, or back pressure control, is disposed in the gas phase connection for passing controlled amounts of vapor from the vapor space to the service connection. In the embodiment of Fig. 1, this regulator takes the form of the above-mentioned valve 21. The latter is made responsive to chamber pressure and is set to open when the pressure in such chamber exceeds a predetermined value slightly above the desired operating pressure in the chamber. The pressure at which the valve 21 opens is preselected to meet the desired service pressure conditions of individual consumers. Thus, when container pressure rises above the setting of the back pressure control valve 21 as a result of heat leak, the valve opens automatically and vapor is released to the service connection for delivery to the consumer supply line. As vapor is released, the heat leak absorbed by the liquid is removed by the evaporation attendant to pressure drop in the chamber, and the liquid is thus returned to a pressure not exceeding the setting of the back pressure control valve and at substantially saturation temperature.

If there is no withdrawal for a very long period, the heat leak to the chamber will cause a slow steady rise in pressure. The back pressure control valve 21 will, of course, open when chamber pressure exceeds its setting but is inefiectual to relieve pressure until vapor is withdrawn from the system at 18. Consequently, chamber pressure will continue to rise until it reaches the setting of a second pressure relief device, shown in Fig. l as a safety vent valve 25 in the service connection 17 at which time the vent valve will open and loss of vapor occurs. The vent valve may be set to open at a pressure substantially above the desired operating .pressure. Although storage of the liquid at moderately high pressure considerably reduces the margin between operating pressure and the setting of the relief device, limitation on rate of increase in the heat content of the liquid provides a reasonably extended idle period during which the material is held without loss.

As the contents of the vessel are consumed, the volume of liquid present for absorbing the heat is continually reduced, whereas the rate of heat inleak remains substantially constant. This means that the Worst condition from the standpoint of idle storage without loss is-at the near empty (e.g., of full volume) condition. It may be shown that by restricting the net gain in heat content of the stored liquid due to heat leak so that it does not exceed .0002 B.t.u./hr.F./lb. water capacity, a package containing liquid oxygen at an initial pressure of 50 p.s.i.g. and with a relief setting of 225 psig. can be held without loss for 72 hours (a long 3-day weekend) with the package only 10% full. This is a very stringent insulating requirement which dictates that an extremely low conductive insulation be used in order to prevent the bulk of the vessel from becoming so large as to prohibit economic handling.

The holding time without loss is maximized by maintaining or approaching equilibrium between the vapor and the total liquid in the chamber. This is to prevent the vapor pressure from reaching the relief valve setting before the liquid body has absorbed its full capacity of sensible heat; i.e. under non-equilibrium conditions, the main portion of the liquid body becomes subcooled with respect to the vapor pressure and only a fraction of its heat absorbing capacity can be utilized by the time the vapor pressure reaches the relief valve setting. Since I pressure building for Withdrawal purposes, which is necessary in known practices, is unnecessary here, the vapor To this end a pressure can be held at the equilibrium pressure of the entire liquid body during filling and during operation.

The provision of heat conducting members extending from the relatively warm upper parts of the gas space to at least the upper regions of the liquid space will promote distribution of heat uniformly and cause the body of liquid to approach homogeneous or equilibrium thermal conditions.

If the chamber vapor pressure is appreciably above the setting of the back pressure control (valve 21) when withdrawal is begun, the back pressure control valve 2 1 will of course be open. This will substantially equalize chamber pressure and service connection pressure and insufiicient pressure drop will then exist to force liquid up the liquid phase connection 20 and into the service connection 17. Vapor from the gas space will flow into the service connection, passing through the vaporizer 22 wherein it is superheated before discharge into the consumer supply line. Such tllOW will continue only until the container pressure is sufliciently reduced for the back pressure control valve 21 to close. At this time with the liquid again saturated at the desired operating pressure, withdrawal again takes place from the liquid space as described above.

A :bursting \disk 26 set to blow at a pressure appreciably higher than the setting of the relief device 25 but below the safe limit of the container is disposed in the gas phase connection 16 in open communication at all times with the gas space of chamber 15. In the event of operational failure of the relief device, chamber pressure is relieved by the blowing of the bursting disk, thereby insuring safe handling of the storage body.

Although heat leak into the container is reduced to a very low value, this condition does not adversely interfere with the rate of liquid withdrawal. By providing a storage body of low-boiling liquid at saturation at a pressure .at least as high as delivery pressure, the present invention stores the liquid with an appreciable heat content. By the principles of this invention, this heat content is controlled and utilized to maintain pressure in the container solely by adiabatic evaporation trom the liquid and without reliance upon heat leak. Excessive warming of the liquid body by evaporation due to heat leak cannot occur since vapor release from the container is controlled to regularly remove heat. Over a period of normal useage, this removal is equivalent to the amount of vapor produced by heat leak. The heat content of the liquid therefore acts as a heat ballast during liquid withdrawal so that as the liquid level falls, the heat present is apparently sufficient to generate enoughvapor to replace withdrawn liquid and maintain pressure. Although some cooling by evaporation will occur as the level of the container drops, it has been found that the entire content of saturated liquid can be withdrawn continuously in liquid form at maximum withdrawal capacity or in gas form at maximum vaporizer capacity with negligible loss of system pressure. Consequently, it is seen that even at high and continuous withdrawal rates, no pressure building system is required,

A liquid package embodying the present invention is shown in Figures 2 to 8, to which reference is now made. The liquid package includes a double-walled container, indicated generally at 30, which is made up of a pressure tight inner vessel 31, preferably made of metal, and a pressure-tight casing 32 surrounding said vessel in outwardly spaced relation so as to define therewith an intervening space. The form of the container is not limited to any particular shape. Elongated cylindrical con- .tainers are preferred. The inner vessel 31 defines a chamber having a normal liquid space L .and gas space therefor G.

The intervening space between the inner vessel 31 and the casing 32 houses a highly eflicient heat insulation 33 which will meet the specified restriction on in-' 7 crease in heat content without substantial bulk. For a vessel having a water volume on the order of 260 1b., a suitable insulation is opacified powder-inrvacuum insulation which is disclosed in copending application, Serial No. 580,897 filed by L. C. Matsch and A. W. Francis on April 26, 1956. The insulation may be briefly described as a finely divided powder made up of particles of low conductivity, such as Santocel, having dispersed and intermixed therewith small heat-reflecting and absorbing bodies. Adequate insulation can be obtained to meet the requirements specified above with a layer of such insulation 2.4 inches thick held under a vacuum below 50 microns, and with adequate care being taken'to minimize heat transmission through fluid connections and container supports. This will limit heat inflow to the container to .0002 B.t.u./hr.F/lb. water capacity and thus obtain the desired 72. hours holding time at only 10% of full capacity. The 2.4 inches of insulation will have a volume equal to only about 90% of the container volume and the bulk of the insulated vessel can be held to a low value. If the best practical insulation of the prior art is used, consisting of low conductive silica-in-vacuum, the required volume of insulation will be about 23 times the volume of the liquid container and would result in a container having an excessively large bulk for the amount of pay load carried.

The top of the casing 32 is formed with a central opening 34 for receiving a vacuum-sealing head member 35, which is fixed to the casing as by welding 36. In order to minimize heat leak to the inner vessel 31 and at the same time provide adequate support for such vessel, which must bear a heavy load of liquid, the vessel 31 is suspended by a single connection, a neck tube 36, from the head member 35. The neck tube is made of Hastelloy B, a material which was found to combine high strength, high impact at low temperature and low thermal conductivity. The neck tube 36 is thin-walled along the major portion of its length to minimize heat leak and has enlarged end sections, at 38, which are respectively welded to the head and inner vessel where highest bending stresses occur, so that stress in the welded joints connecting the neck to the head 35 and vessel 31 are low. A centering element having low thermal conductivityand here shown as a glass-fiber-reinforced plastic tube 39, is fixedly mounted on the inside wall of the casing along the longitudinal axis of the container, and is positioned to slidably and telescopically engage an annular element 40 centered on the bottom of the inner vessel 31. These cooperating elements center the vessel 31 in the casing 32 and provide lateral stability by taking side thrust loads on the container. At the same time they permit relative vertical movement and thereby allow for thermal contractions.

The container is supported on a base assembly 41 which comprises an inwardly and upwardly dished annulus 42, the inner rim 45 of which serves as a seat on which the container casing bears downwardly and to which the casing is Welded, as at 44, and the outer rim of which is fixed to a short downwardly extending flange 43 which rests on the ground. The lower end of the flange is bent inwardly and reversely at 46 for providing additional strength and for distributing load. The base assembly provides a predetermined amount of resiliency so that it will deform elastically under moderate impact and thereby reduce the rate of deceleration on the entire container. If too much resiliency were provided, the container would bounce if dropped, and this would be undesirable from the standpoint of safety. Moreover, a relatively soft, elastic base might prevent visual deformation of the container casing when it is subjected to a severe impact while internal parts may receive damage and go unnoticed. The elastic characteristics of the base are therefore limited to a shock load below which the internal parts of the container will not be damaged. Loads in excess of this limit will deform the base, and

the attendant permanent absorption of considerable energy during the deformation will avoid or minimize internal damage. In this way damage will generally be confined to the base Where repairs are relatively easy, inexpensive and rapid as compared to repairs which require entering the vacuum casing. Furthermore, a deformed base will serve as evidence that the container has received severe impact and will signal the need for close inspection to assure serviceability and safety.

Since the liquid package of this invention requires no pressure-building system, all fluid communication to the gas and liquid spaces G and L, respectively, in the vessel chamber can be made through the neck tube 36 at the top of the container, which thus serves the double function of providing not only the only vertical support for the inner vessel 31 but also the only avenue of fluid communication to the chamber therein. In this way minimum heat leak is achieved and all valve connections can be compactly centered in the container head 3-5.

The upper end of the neck portion 36 opens into a small chamber 47 in the head 35, which has several lateral connections for serving as entrances and exits to and from the vessel chamber 31. Liquid is delivered into the inner vessel chamber by way of a conduit 48 that is connected to a lateral passageway 49 in the head 35. A filling extension conduit 50 leads from the inner end of passageway 49 through chamber 47 and the neck tube 36 and terminates at the top of the gas space G. The extension thus serves as a nozzle for showering the liquid over the considerable portion of the vapor in the empty vessel, thereby maintaining the vapor pressure in the vessel at approximately the equilibrium pressure of the entering liquid.

Another lateral passageway 51 in the head 35 serves as a common connection between both the liquid and gas spaces of the inner vessel and a vaporizer 52 which is opened at one end to such passageway and at its other end to service connection 53 as described hereinafter. Passageway S1 is in open fluid communication with the lower part of the liquid space L, at least below the minimum operating liquid level, by way of a conduit '54, thereby providing free flow passage between the liquid space and the service connection 53. Passageway 51 is connected with the gas space G of the inner vessel by way of the neck tube 36, chamber 47 in the head 35, and an opening 55 in the side wall of the passageway 51 that communicates with the central chamber 47 through an eccentrically disposed valve chamber 56; flow through said opening is controlled automatically by a valve 57 responsive to pressure in chamber 31. The valve plunger 60 is mounted on a diaphragm 60a transversely disposed across the valve chamber '56, and is normally urged towards its seated position closing the opening 55 by a compression spring 61 acting on one side of the diaphragm. The other side of the diaphragm is subject to inner vessel pressure which will act to lift the plunger 60 when vessel pressure exceeds the setting of the valve 57, thereby opening the gas space G to the service connection through opening 55, passageway 51 and the vaporizer 52 until vapor pressure in the inner vessel 31 falls below the valve setting. The pressure at which the valve 57 is set to operate can be selected at any value over the operating range of the liquid package and below the operating point of safety valve 25. To this end an adjustable set screw 62 is provided to vary the force of the compression spring 61.

It will be seen that a single automatically operated valve, the back pressure valve 57, serves to control withdrawal of material from the inner vessel in a manner to provide a normal liquid Withdrawal, together with a selective gas withdrawal which provides automatic vessel pressure control and thereby limits excessive pressure build-up during operation. By leading the liquid withdrawn from the liquid space to a level above the normal liquid level, liquid will pass out of the vessel under the force of its existing vapor pressure whenever a pressure difference exists across the liquid withdraw connection which is at least equal to the flow resistance therein, but there will be a withdrawal of gas whenever the pressure drop across the gas path is less than the flow resistance in the liquid withdrawal path. Liquid would not flow under the latter condition.

The vaporizer 52 is disposed in the space between the inner vessel 31 and the casing 32 and includes a helical vaporizing coil 63 which is positioned against the inside surface of the casing. This position not only provides a means for absorbing heat passing through the casing but also provides protection against mechanical damage and eliminates the need for a heavy tube wall for ruggedness. Liquid is led from the passageway 51 to a coil inlet manifold 64 by a conduit 65. The latter enters one end 66 of the manifold and extends along the wall of the manifold for a considerable part of its length. The conduit 65 is provided within the manifold with a plurality of lateral apertures 67 which serve as orifices for spraying the liquid into the manifold before delivery into the coil 63 which is connected to the other end 68 of the manifold. The spray effect of the orifices plus the partial vaporization taking place within the manifold serves to disperse the liquid into droplets, and the mixture ofvapor and liquid then enters the coil 63 and flows therethroug'h in a manner similar to a homogeneous gas. This prevents unvaporized slugs of liquid from being carried into the vaporizer coil 63 and thus avoids pressure fluctuations which would otherwise be imposed on the system. If there is a gas withdrawal, the gas also passes through the vaporizer and is superheated before delivery to the consumer supply line.

, After traversing the coil 63, the material is passed back into the head 35, entering an off-set chamber 69 that opens to a passageway 70, into which is received the service connection 53. Flow through the service connection and, hence, withdrawal from the package is controlled by a single valve which is the only manual operating member which the consumer must manipulate. In practice, valve 71 is normally open when the container has been connected to a consumer supply line, and the valve opening and closing the service connection to a demand is part of the consumer system.

The container 30 is filled with liquid saturated at a minimum desired delivery pressure and is shipped as a package ready for use. The customer merely couples the package to his supply line, a coupling member 75a being provided for this purpose on the outward end of the service connection 53. It will be apparent from the foregoing that withdrawal is made by opening the service connection 53 to a demand. The demand for gas establishes a pressure differential between the inner vessel chamber and the service connection, and liquid is forced immediately under its own vapor pressure from the liquid space L out of the package by way of the vaporizer 52in the manner described. If the vessel pressure is above-the setting of the back pressure valve 57 at starting, or should possibly rise above such setting during operation, said valve automatically opens and withdrawal is made from the gas space G until pressure in the vessel. falls below such setting, whereupon the back pressure valve closes and withdrawal is made from the liquid space. The entire contents of saturated liquid can be withdrawn continuously and at maximum vaporized capacity with negligible loss of system pressure for the reason set forth above.

If the liquid package should stand for an extended period with no withdrawal, the back pressure valve cannot act to relieve pressure build-up in the inner vessel due to heat leak evaporation because the service connection 53 is closed. However, a vapor relief valve is provided to vent the inner vessel when pressure therein exceeds a predetermined value. For this purpose a small lateral bor -10 r ing- 72 is provided in the head to vent the chamber 69 to the atmosphere. This boring communicates with the chamber through an opening 73, the flow through which is controlled by a valve 74, substantially identical in construction as valve 57. As is apparent from Fig. 7, the valve diaphragm 75 is subject to pressure in chamber 69, and when pressure therein exceeds the pressure setting of the valve, it raises the valve and opens the inner vessel to the atmosphere until pressure therein falls below the setting of the valve.

In the event of failure of the vapor relief valve 74, a cylinder bursting disk 76 is provided and is designed to rupture when vessel pressure rises to a pressure appreciably higher than the setting of the relief valve but still at a safe container pressure. The bursting disk is contained in a fitting 77 that is received into an open passageway 78 in the head. Passageway 78 opens into chamber 47 and is thus in open communication With the inner vessel. Although the liquid package has a normal upright position, a trap is provided in the fitting 77 so as to prevent the bursting disk from becoming cold, which would affect its bursting pressure, should the container fall or be placed on its side. The trap comprises an adapter 79 that is threadedly received into the passageway 78 and that supports an open-ended tubular portion 80 of the fitting 77. The adapter carries a sleeve 81 that is closed at its free end and surrounds the inner end of tubular member 80 in outwardly spaced relation. The sleeve is provided with a series of circumferential apertures 82 which are positioned at a farther radial distance from the container axis than the inner end of the tubular member so that when the container is on its side a goose-neck trap is disposed in the How path to the bursting disk as indicated by arrow F in Fig. 8.

In order to minimize the holding period without loss, thermal conditions in the inner vessel are kept as uniform as possible so as to utilize the maximum heat holding capacity of the liquid. For this purpose radially extending vertical heat conducting plates 83 are supported on the inner wall of the vessel 31 and extend downwards from the gas space through at least the upper portion of the liquid space. Although they are shown as plates, for purposes of exemplification, it will be apparent that other forms are also suitable. These members accelerate the distribution ofheat and cause heat to be distributed more uniformly throughout the vessel, thereby minimizing subcooling with its attendant undesirable effects.

A removable plug 84 closes the outer end of the passageway 51 in the head 35. By replacing the plug with a suitable connection, the liquid withdrawal line will then discharge directly into such connection and a liquid delivery can be obtained.

A modified liquid package in accordance with the present invention is shown in Figs. 9 to 12, the flow diagram for such embodiment being shown in Fig. 13. This embodiment is similar in many respects to that shown in Figs. 2 to 8, and similar parts are identified by similar reference characters. Similar parts in the flow diagram of Fig. 13 will be identified with the same reference character as in Figs. 9 to 12.

The liquid package of Figs. 9 to 13 includes a doublewalled container 30a which has a different type of insulation 33a between the vessel 31a and the casing 32a. The insulation space is filled by a multiple layer insulation encircling the side wall of the inner vessel and consisting essentially of layers of heat reflecting foils extending vertically and in spaced parallel relation in the space between the casing 32a and the inner vessel 31a and of a plurality of sheets 101 of fibrous material disposed in estate vided in the intervening space along the side walls of the container in an absolute pressure of less than 1 micron. Special care is taken to minimize solid conduction through support members and fluid connections. For example, the neck tube 36a is made exceptionally long and slenderthis being permitted by the elastic characteristic of the multiple layer insulation which provides lateral support for the container thereby reducing the ruggedness requirements of the neck tube. The supporting function provided by the insulation also allows the elimination of the bottom support shown in Figure 2. Such an insulation system provided for a vessel having a water capacity of 69 lb. will limit heat inflow to the container to .0002. B. t.u./ hr.F./ lb. water capacity and will obtain the desired 72 hours holding time at only of full volume. The insulation space is equal to only about 47.5% of the liquid container volume and provides an insulated vessel of exceptionally low bulk. If the best practical insulation of the prior art is used, consisting of low conductive silica-invacuum, the volume of insulation required for this container will be 128 times the container volume. The excessive bulk of such insulation would be prohibitive in relation to the economy in handling small pay loads. The multiple layer insulation is of the type disclosed and described in copending application, Serial No. 597,947, filed by Ladislas C. Matsch on July 16, 1956. It is preferred on smaller packages because of the greater insulating efiect afforded even when using a container having a less favorable volume-surface ratio. A vacuum bursting disk 103 is provided on the top wall of easing 32a.

Aside from the insulation in its dual function as a heat barrier and as a lateral support, there are two other principal difierences between the embodiment of Fig. 9 and that of Fig. 2. The first of these involves the use of a fixed, built-in back pressure regulator for controlling vapor withdrawal from the inner vessel. The back pressure regulator is in the form of a restricted passageway or capillary tube 104 in the connection between the service connection 53a and the gas space G. When material is withdrawn from the container, passageway 104 provides a continuous but limited withdrawal of material from the gas space G of the container. The other principal difierence is in the head and vaporizer assembly. The head 105 is made up of two mating sections 105a and 105b that are detachably secured together in any convenient manner, as by bolts. The bottom section 10511 is fixed to the casing 32a, as by welding 106, and carries the inner vessel 31a by a neck tube 36a. The latter opens into a chamber 47:: in the head. Liquid is charged into the vessel 32a by way of a connection 48a that leads to a lateral port 49a in the wall of chamber 47a. The liquid entering the latter chamber flows through the chamber and down the neck tube 36a into the chamber within the inner vessel 3111. A passageway 51a in the lower section of the head registers with a boring 51b in the upper section of the head when the sections are in mated position. A vaporizing coil 52a is connected with boring 51b and leads material withdrawn from the inner vessel 31a.to a passageway 52b in the upper head section for delivery into the service connection 53 that is open to such passageway 52b. As can be seen in the drawing, the vaporizing coil 52a does not enter the vacuum-sealed insulation space but is disposed on the inside Wall of a removable dome or cover section 107 that fits over the head and the top of the casing 32a and snugly slides onto the side wall of the casing in telescopic relation. By this construction all vacuum joints are included in the fixed lower section of the head, and the vaporizer and upper section of the head can be replaced and/ or repaired without entering the casing 32a or breaking the vacuum. Other controls are also completely accessible when the dome 107 is removed.

Liquid withdrawal is efiected through a conduit 54a leading from near the bottom of the liquid space L through neck tube 36a and chamber 47a and terminating in passageway 51a, above the uppermost liquid level in the vessel. Gas Withdrawal is efiected through a connec-.

tion'104 that leads from chamber 47a (this being open tothe gas space G) to passageway 51a. The provision of the flow restriction, shown here as the capillary con nection 104, in the path of gas withdrawal serves a similar purpose as the back pressure valve of Fig. 2. The capillary tube 104 allows a small fraction of gas to be withdrawn continuously to remove heat-leak, i.e. a quantity of gas equivalent to that evaporated due to heat leak. Although the capillary is a passageway of fixed dimension, it is uniquely adapted for the liquid package of this invention. It the package has a high liquid level and is left standing without withdrawal for a long period, pressure builds up rather slowly because of the latent heat capacity of the liquid. However, by the time withdrawal is commenced, a pressure considerably higher than the desired operating pressure exists in the small gas space. Under this condition, the mass rate of gas withdrawal is increased because of the increased density of the gas at high pressure. Thus, the chamber in the inner vessel is more rapidly brought down to proper operating pressure. At a low liquid level, the pressure build-up is at a faster rate since the heat leak is constant but the heat absorbing capacity of the smaller liquid body is less. When Withdrawal is begun under these conditions, the capillary acts to release an even greater amount of gas to pull down the pressure. Here, the rate of mass withdrawal is not only increased by the density of the compressed gas but additionally by the larger pressure drop across the flow restriction or capillary because of the lower liquid level in the vessel 31a, for the pressure difference across the restriction will be equivalent to the head against which the liquid must be raised for delivery into the service connection.

The liquid package of Figs. 8 to 12 is also provided with a vessel bursting disk fitting 77a and a bursting disk 76a and a vent relief device a, each of which communicates with the inner vessel by way of chamber 470:. Although the flow restriction in the gas withdrawal passageway has been illustrated as a capillary, it is to be understood that other forms of flow restrictors, such as for example, orifices and porous plugs, are also suitable.

It should be apparent that various details of construction can be changed without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

1. A process for storing in a heat-insulated storage body low-boiling liquefied gas material having a boiling point at atmospheric pressure below 230 K. and received saturated at a low pressure and for dispensing such material from the storage body at a selected elevated service pressure, comprising charging said storage body with said liquefied gas under a pressure at least as high as the operating pressure required in the storage body to deliver such material at a selected elevated service pressure; prior to entry of said liquefied gas material into the storage body, prewarming said liquefied gas material to a condition wherein it is saturated at such operating pressure; during charging, maintaining the vapor pressure in the storage body approximately in equilibrium with the entering liquid; restricting the net gain in heat content of the stored liquefied material due to heat leak so that it does not exceed 0.0002 B.t.u. per hour per degree Fahrenheit per pound of water capacity; withdrawing any selected portion up to the entire amount of said liquefied gas material in said body at the selected service pressure under the force of the vapor pressure normally occurring within said body.

2. A process as defined in claim 1, wherein said material is oxygen.

3. A process as defined in claim 1, wherein said material is nitrogen.

4. A process for storing in a heat-insulated storage body low-boiling liquefied gas material having a boiling point at atmospheric pressure below 230 K. and received 13 H a saturated at a low pressure and for dispensing such material from the storage body in gaseous form at a selected elevated service pressure, comprising charging said storage body with said liquefied gas under a pressure at least as high as the operating pressure required in the storage body to deliver such material at a selected elevated service pressure; prior to entry of said liquefied gas material into the storage body, prewarming said liquefied gas material to a condition wherein it is saturated at such operating pressure; during charging, maintaining the vapor pressure therein approximately in equilibrium with the entering liquid; restricting the net gain in heat content of the stored liquefied material due to heat leak so that it does not exceed 0.0002. B.t.u. per hour per degree Fahrenheit per pound of water capacity; withdrawing any selected portion up to the entire amount of said material from the liquid phase in said body at the selected service pressure under the force of the vapor pressure normally occurring with said body, withdrawing said material from the gas phase in said body in sufiicient amount to obtain a pressure therein within a predetermined range above the operating pressure; passing such withdrawn material to a service connection; and vaporizing withdrawn liquid prior to delivery from the service connection.

5. A storage and dispensing package for low-boiling liquefied gas material having a boiling point at atmospheric pressure below 230 K., which package is ready for use immediately after filling, comprising a pressure-tight container having a service connection and a flow control valve therein for discharging material therefrom, a chamber within said container charged with low-boiling liquefied gas material under a pressure at least as high as the operating pressure required to deliver such material at a selected elevated service pressure and saturated at the time of charging at such operating pressure, insulation means limiting the net gain in heat content of the liquefied gas material due to heat leak so that it does not exceed 0.0002 B.t.u. per hour per degree Fahrenheit per pound of water capacity, said insulation means comprising an insulation jacket surrounding said chamber and containing a filling of finely-divided, metal opacified, low heat conductive solid material and being evacuated to a combined gas and vapor pressure below 50 microns of mercury absolute, means responsive to vapor pressure in the chamber for venting a top region of said chamber above the normal full liquid level therein to the atmosphere when pressure therein exceeds a preselected pressure above said operating pressure, and a liquid phase connection leading from a lower region of the chamber to said service connection and being open to the service connection so that selective opening of said control valve will cause any selected portion up to the entire amount of said liquefied gas material within the container to be forced through the liquid phase connection to the service connection for discharge from the container at the elevated service pressure under the force of the vapor pressure occurring normally within said chamber.

6. A storage and dispensing package for low-boiling liquefied gas material having a boiling point at atmospheric pressure below 230 K., which package is ready for use immediately after filling, comprising a pressure-tight container having a service connection and a fiow control valve therein for discharging material therefrom, a chamber within said container charged with low-boiling liquefied gas material under a pressure at least as high as the operating pressure required to deliver such material at a selected elevated service pressure and saturated at the time of charging at such operating pressure, insulation means limiting the net gain in heat content of the liquefied gas material due to heat leak so that it does not exceed 0.0002 B.t.u. per hour per degree Fahrenheit per pound of water capacity, said insulation means comprising an insulation jacket surrounding at least the side wall of said chamber and containing a filling of a multiple layer inassists sulationconsisting essentially of alternating layers of heat v below 50 microns of mercury absolute, means responsive to vapor pressure in the chamber for venting a top region of said chamber above the normal full liquid level therein to the atmosphere when pressure therein exceeds a preselected pressure above said operating pressure, and a liquid phase connection leading from a lower region of the chamber to said service connection and being open to the service connection so that selective opening of said control valve will cause any selected portion up to the entire amount of said liquefied gas material within the container to be forced through the liquid phase connection to the service connection for discharge from the container at the elevated service pressure under the force of the vapor pressure occurring normally within said chamber.

7. A storage and dispensing package as defined in claim 5, including a gas phase connection leading from a top region of the chamber to said service connection, means responsive to the pressure in said top region' and operative when said control valve is open for causing preferential withdrawal from said gas phase to said service connection when the pressure therein exceeds a predetermined value above said minimum operating pressure until the pressure therein falls to within a predetermined range above said operating pressure, and a vaporizer in at least the path of withdrawal of material from the liquid phase for vaporizing withdrawn liquefied material before delivery from the service connection.

8. A storage and dispensing package as defined in claim 6, including a gas phase connection leading from a top region of the chamber to said service connection, means responsive to the pressure in said top region and operative when said control valve is open for causingpreferential withdrawal from said gas phase to said service connection when the pressure therein exceeds a predetermined value above said minimum operating pressure until the pressure therein falls to within a predetermined range above said operating pressure, and a vaporizer in at least the path of withdrawal of material from the liquid phase for vaporizing withdrawn liquefied material before delivery from the service connection.

9. A storage and dispensing package as defined in claim 5, wherein said low-boiling liquefied gas material is oxygen.

10. A storage and dispensing package as defined in claim 5, wherein said low-boiling liquefied gas material is nitrogen.

11. A storage and dispensing package as defined in claim 5, including means operative within the confines of the container to cause heat transfer between at least the warmer and colder portions of the liquefied gas material over and above that afforded by normal heat transfer phenomena within the container to promote equalization of temperature throughout the container.

12. A system for handling low boiling liquefied gas material having a boiling point at atmospheric pressure below 230 K. and received from a source at which it is saturated at a low pressure and for dispensing such material at a selected elevated service pressure in a package ready for use immediately after filling, comprising a pressure-tight container having a service connection and a flow control valve therein for discharging material therefrom, a heat-insulated chamber within said container, charging means for filling said chamber with such lowboiling liquefied gas material from said source under a pressure at least as high as the operating pressure required in the chamber to deliver such material at a selected elevated service pressure, said charging means including heat exchange means for prewarming said liquefied material to a condition at which it is saturated at such operating pressure, means responsive to vapor pressure in the chamher for venting a top region of said chamber above the pressure therein exceeds a pre-selected pressure above,

said operating pressure, and a liquid phase connection leading from a lower region of the chamber to said service connection and being open to the service connection so that selective opening of said valve will cause any selected portion up to the entire amount of said liquefied gas material within the container to be forced through the liquid phase connection to the service connection for discharge from the container at the elevated service pres sure under the force of the vapor pressure occurring normally within said chamber.

References Cited in the file of this patent Dana Feb. 21, 1939 16 Fujiura Apr. 18, 1939. White Oct. 8, 1940 Hansen .Aug. 16, 1949 St. Clair Mar. 21, 1950 Preston Apr. 4, 1950 Larzelere Oct. 17, 1950 Wildhack Dec. 4, 1951 Cornell June 23, 1953 Wildhack Nov. 3, 1953 Morrison May 3, 1955 Schilling Jan. 10, 1956 FOREIGN PATENTS Germany Sept. 28, 1907 Great Britain Nov. 14, 1929 OTHER REFERENCES Refrigerating Engineering Application Data 48, pp. 1-4 20 (article by Staebler).

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