US2968161A - Bulk helium transportation - Google Patents

Description

Jan. 17, 1961 A. BLISS BULK HELIUM TRANSPORTATION Filed Aug. 16, 1956 E5 d E 2 INVENTOR LYMAN A. BLISS ATTORNEY United States Patent BULK HELIUM TRANSPORTATION Lyman A. Bliss, New York, N.Y., assignor to Union Carbide Corporation, a corporation of New York Filed Aug. 16, 1956, Ser. No. 604,556

6 Claims. .(Cl. 6245) This invention relates 'to improvements in containers for storing and transporting gas products, and more particularly concerns an apparatus and method for the bulk shipment of gas products under high pressure conditions.

v A principal-factor contributing to the high cost of valuable'gases, such as helium, is the cost of shipping it from the manufacturing plant to the consumer.

The standard high pressure container for conveying helium is customarily fabricated from heavy gauge carbon steel stock in accordance with existing safety regulations to form a steel cylinder capable of withstanding internal gas pressures of about 2200 p.s.i. at ambient temperature. In the standard helium railway tankcar, a major part of the weight is taken up by the container, and only a smallfractional part of the weight represents the useful helium product. Disregarding the weight of the relatively light helium gas, the tank car, including the heavy container weight, represents the transportation costs incurred both in the delivery of helium and in the return of the empty tank cars.

With the uses of helium growing ever wider in industry and science, it has become increasingly necessary to resort to more economical means for shipping helium to the consumer in an effort to reduce the overall cost.

Attempts to increase the useful payload of a railway tank car by increasing its volumetric capacityhave been unsuccessful for a number of reasons. The principal reason is that existing tank cars presently in use are close to the maximum weight limitations set by present safety standards.- Hence, any significant increase in weight,

such asby increasing the number of gas cylinders, or

increasing the storage pressure and wall thickness or the volume of the tank car, will exceed this standard.

It has been suggested that valuable gas products like helium could be shipped as a liquid, thus increasing the payload of the railroad car to approximately three times its present capacity. However, due to high liquefaction costs and high evaporation and filling losses, the above suggestion'does not appear to be feasible. Many other alternatives have been proposed, but these in general have proved to'be academic rather than commercially satisfactory.

According to the present invention, a substantial increase in' the maximum tank car capacity for a given weight of tank car can be obtained by utilizing the increased strength characteristic of certain metals at low temperatures. As an example of this phenomenon, 9% nickel steel, which at room temperature (70 F.) has an ultimate strength of about 119,000 p.s.i., has an ultimate strength of about 170,000 p.s.i. at 320 F. By applying the results of such data to a container for bulk helium, a tankcar may be constructed with a container Nickel 8.66 Silicon .t..'.' .24 Manganese .64. Carbon .09'.= Phosphorus i .014 Sulfur .016]: Iron and incidental impurities Balance I ice wall thickness substantially less than that of a conventional tank and having the same, if not greater strength at about 320 F. than the conventional tank car at ambient temperature. The increased strength of certain metals at low temperatures also permits use of standard wall thickness containers at pressures substantially greater than that permissible in conventional carbon steel containers.

It is, therefore, an important object of the present invention to provide an improved method of, and apparatus for the bulk transportation of gases such as helium, in which all other things being equal, the container has considerably less weight for its volumetric capacity at relatively low temperatures than a container of comparable capacity at ambient temperatures.

Another object of the present invention is to provide improved means for conveying gaseous products, which is simple and economical to use.

Other objects, features and advantages of the present invention will be apparent from the following detailed description.

In the drawings:

Fig. 1 is a view of a longitudinal section through an apparatus constructed in accordance with the principles of the invention; and

Fig. 2 is an enlarged fragmentary sectional view of a portion of the apparatus shown in Fig. 1, but showing a modification thereof.

The invention will be described in connection with a receiver for storing and transporting bulk helium, using as a refrigerant, liquid nitrogen. But it is to be understood that the invention is not limited to such use, and

that the same principles apply, regardless of the nature of the specific materials employed.

Referring to the drawing, Fig. 1 illustrates an exem-' plary gas material holding container or double-walled container 10 of the tank car type comprising an elongated receptacle or inner vessel 11 of impervious metal, which is not embrittled at low temperatures, such as 9% nickel The inner vessel 11 is suspended in a larger gas-tight shell or jacket 13 of suitable metal materiahfor exam-.- ple, carbon steel, and held in spaced relation in. respect.

thereto by suitable supports having low heat conduction and not shown. Such supports may be similar to those] described in US. Patent No, 2,587,204 to G. WJPatch,

In, May 21, 1946. The intervening space between the vessel 11 and the jacket 13 provides an evacuable insulating space 15, which may be filled with a comminuted thermal insulation 16 such as disclosed in US. Patent No 2,396,459 issued to L. I. Dana, March 12, 1946. The

interveningspace 15 is filled with insulating material 16 and evacuated through an opening 17 in the jacketwall, according to methods well known in the art. The repleri- Percent ishment of the liquefied gas material 12 in the vessel 11 is achieved through a valve-controlled liquid fill and drain line 18 in conjunction with a liquid level device 19.

For the purpose of relieving any excessive gas pressures that may develop in the inner vessel 11, a pressure relief pipe 20 in communication with the gas space in said vessel is connected gas tightly through the upper wall thereof. The outer end of the relief pipe 20 terminates in a pressure relief valve or blow-off vent 21 to allow gas to escape into the atmosphere when a specified pressure condition obtains in the vessel 11.

The double-walled container 10 is provided with a supporting and enclosing structure 22, which forms a part of a railroad car 23.

According to the present invention, advantage is taken of the improved strength of certain metals at low temperatures by providing a reduced thickness gas receiver, or preferably a plurality of tubular receivers, which at the low temperatures to be employed are capable of safely withstanding the same pressure conditions as conventional, relatively thick-walled gas receivers at ambient temperatures. Being substantially thinner, the improved gas receiver or receivers may be constructed in larger sizes or installed in greater numbers to substantially increase the payload of helium tank cars without exceeding the maximum allowable receiver pressure or the weight limitation of the railway tank car assembly.

Alternatively the conventional relatively thick receivers may be fabricated from metals having a very high ultimate strength at low temperatures, so that the receiver operating pressure at low temperatures may be substantially increased, thus raising the railway car payload.

As a means for obtaining these features, I have provided a plurality of tubular receivers 25, which are immersed in the liquid nitrogen bath 12, the liquid nitrogen acting in the capacity of a refrigerant to cool the receivers to approximately -320 F. and maintain them at this approximate temperature during transportation. Other low-boiling liquefied gases which could be used instead of the liquid nitrogen refrigerant include low-boiling liquefied gases such as air, oxygen, argon and certain hydrocarbons such as methane, ethane and propane.

Any number of tubular receivers may be employed, three being shown in the drawing and designated therein as 25a, 25b and 25c.

The receivers 25 are made of impervious metal, which does not become brittle at low temperatures, and possesses a higher yield strength and ultimate strength at the low temperatures used in the present invention than at ambient temperatures. Examples of materials suitable for use in the fabrication of the receivers of the present invention are 9% nickel steel, low carbon stainless steels, copper based alloys such as aluminum-bronze and Everdur, aluminum, and aluminum alloys.

Suitable means are provided for supplying the tubular receivers 25 with gas product, such as helium, and for discharging gas product therefrom. As illustrated, such means comprise a fill pipe 26 having at its upper end a charging connection 27 controlled by a fill valve 28. The pipe 26 preferably extends through suitable gas tight openings in the shell 13 and inner vessel 11, and terminates in a charging manifold 30, provided with a plurality of short connecting lines 31a, 31b and 31c, connected gas-tightly to the respective receivers 25a, 25b and 250. The fill pipe may be formed of metal having high strength and low heat conductivity, such as stainless steel.

Fig. 1 illustrates a receiver relief system that may be employed in the practice of the invention. A relief pipe 33 having branches 33a and 33b is connected gas tightly to the upper portion of the fill pipe 26 at the cross connection 34, slightly below the fill pipe valve 28. The relief pipe 33a is provided with a safety relief valve 35, preset to open at a predetermined pressure condi tion in the receivers 25 to allow gaseous helium to escape into the atmosphere. Should the safety valve 35 fail to operate, a bursting disk assembly 36 is provided in the branch pipe 33b to open at a higher set pressure.

For the purpose of maintaining the receiver gas pressure at a safe level for the existing receiver temperature, a dual pressure control-relief system is preferred. Referring to the drawing, and particularly to Fig. 2, the pressure relief pipes 33a and 33b are modified, so that the safety relief valve 35 and bursting disk assembly 36 are provided at one end of the pipe 33b, and may be preset to open when a specified pressure condition obtains in the receivers 25 to allow gaseous helium to escape into the atmosphere. A control valve 38 interposed in pipe 33b, operating in conjunction with a temperature responsive element 39 immersed in the liquefied nitrogen in the refrigerating vessel 11, changes to the open position when the element 39 warms above a predetermined temperature to allow helium gas to escape through the safety valve 35. At higher pressures, a safety valve-bursting disk system comprising safety valve 40, and bursting disk 41, located in pipes 33a and 33b respectively, may also be provided to release helium gas product if the receiver pressure should rise to the maximum allowable value at low temperature. Valve 38 may also be constructed to automatically open if and when any part of the device fails to function properly.

To illustrate, in a liquid nitrogen refrigerated system for storing helium gas product in a 9% nickel stainless steel receiver having an outer diameter of 11.8" and a wall thickness of /z" the safety relief valve 35 and bursting disk assembly 36 may both be set at pressures lower than that prevailing in the helium receivers 25, and the safety valve 40 and bursting disk assembly 41 may be set at higher pressures. For instance, the settings of the lower and higher pressure relief valves might be 2750 p.s.i. and 3925 p.s.i., respectively, with the corresponding bursting disk settings slightly higher. In the event that temperature sensitive element 39 warms above a predetermined temperature, for example 300 F., due to excessive refrigerant evaporation, the control valve 38 opens, and high pressure helium gas product in the receivers 25 escapes through the safety valve 35 (or the bursting disk assembly 36 if the safety valve should for some reason he inoperative) to lower the receiver pressure to below the safety valve setting.

A principal requirement of this invention is that the gas product in the receivers 25 be maintained at a low temperature, and preferably be kept in thermal equilibrium with the refrigerant 12. This low temperature storage requirement must be met regardless of whether the refrigeration system is of the sealed type, or the evaporative type shown.

While the refrigerant 12 is shown in surrounding relationship and in contact with the liquefied gas product in the receivers 25, there are numerous types of heat exchange equipment which may be employed to effect temperature equilibrium between the product and refrigerant. For example, the product and refrigerant vessels may be adjacent each other and heat conducting paths of metal of high conductivity such as copper may connect the vessels. The heat conducting paths may also include metal fins or projections extending into the liquid refrigerant to aid in maintaining temperature equilibrium between the product and the refrigerant. The tubular receivers 25 may be disposed in any desirable arrangement in the vessel 11; a longitudinally disposed tubular bundle arrangement being preferred and illustrated herein.

In order to indicate still more fully the nature of the present invention, the following table is set forth showing comparative results of using standard helium railway tank cars having high pressure tubular carbon steel receivers at ambient temperature, with results of using various apparatus of my invention, comprising tubular 9% nickel steel seamless receivers immersed in liquid nitrogen. It is to be understood that the data in this table is presented as illustrative only, and that it is not intended to limit the scope of the invention.

TABLE I Comparison of helium railroad cars Refrigerated Car, 9% Standard Nickel Steel Tubes in Car-Car Liquid Nitrogen Bath bon steel Tubes at Ambient Based on Based on- Temperature Ambient Low Tem Temperaperature ture Stress Stress Capacity:

On. it. Helium NTP 230,000 414, 000 566,000 Lb. Helium 2, 370 4, 290 5, 860 Lb. Liquid Nitrogen in 37 37 11.8 11.8 Length, ft 33 33 Wal thickness, inches 0. 0. 27 O. 27 Working pressure, p.s.i. 2, 200 2, 200 3, 140 Maximum receiver stress, p.s.i 27, 500 33,100 47, 200 Weight:

Empty, lb 223, 200 Empty but including nitrogen, lb 181, 720 181, 720 Full, lb 225, 600 186, 010 187, 580

Referring to Table I, it will be seen that column 1 shows the prior art railroad car operating at 2200 p.s.i. and room temperature. Column 2 shows the advantage gained by shipping high density gas at low temperatures but at the same pressure (2200 p.s.i.). Although 9% nickel steel is used, its increased strength at low temperature is not utilized; instead the maximum ambient temperature work ing stress (33,100 psi) is used. In column 3 advantage has been taken of both the increased gas density and the higher safe working stress of 9% nickel steel at low temperatures.

From the above it will be seen that the apparatus of the present invention is a novel structure which is lighter in weight but provides equivalent strength with attendant savings in the metal and cost of shipping, and which is particularly adapted to the economical shipment of valuable low boiling gas products. The use of the superior physical properties of 9% nickel steel receivers at low temperatures permits the storage and transportation of approximately 1.8 times as much gas at 2200 p.s.i. than would be permissible at room temperature in standard railroad cars. At 3140 p.s.i. and -320 F., approximately 2.5 times as much helium may be transported as at 2200 p.s.i. and room temperature in standard railroad cars.

The improved results of the present invention are also manifested in the substantial reduction in receiver Wall thickness which may be effected. For example, disregarding the legal requirements for minimum wall thickness, a working pressure of 2200 p.s.i. in a 9% nickel steel tubular receiver having an outside diameter of 11.8 inches requires a wall thickness of about 0.27 inch at 70 F. In contrast, a receiver wall thickness of about 0.195 inch may theoretically withstand the same pressure conditions at 320 F.

Modifications and variations may be eifected without departing from the spirit and scope of the novel concepts of the present invention.

What is claimed is:

1. In a system for the high pressure storage of helium in the gaseous state and at a low temperature which comprises, a high pressure metallic receiver for holding a supply of the helium gas, a thermally insulated vessel surrounding said receiver to define a refrigeration space therebetween, said space providing a gas scalable closure and containing a liquefied refrigerant having a boiling point at atmospheric pressure warmer than -320 F said refrigerant eonductively associated with the high pressure receiver to maintain the outer surface thereof at a temperature approximating said liquefied refrigerant, whereby said metallic receiver will be characterized by a strength at said reduced temperature substantially greater than said receiver would have at ambient temperature.

2. In a system for the high pressure storage of gaseous helium substantially as described in claim 1 wherein the refrigerant is a liquefiable gas chosen from the group consisting of nitrogen, oxygen, argon, methane, ethane and propane.

3. In a system for the high pressure low temperature storage of helium in the gaseous state which comprises in combination an inner receiver for holding a supply of the helium gas at an elevated pressure, a gas scalable insulated vessel surrounding said receiver defining a refrigerating space therebetween, said space provided with a liquefied refrigerant to submerge the receivers therein, said refrigerant characterized by a boiling point at atmospheric pressure of not warmer than -320 F. and eonductively associated with the outer surface of said receivers to maintain said receiver at a temperature approximating that of said refrigerant thereby establishing between said helium and said refrigerant a condition of thermal equilibrium.

4. In a system for the high pressure storage of gaseous helium substantially as described in claim 3 wherein the liquefied refrigerant is liquefied nitrogen.

5. In a vessel for holding a supply of liquefied gas, a heat insulating jacket surrounding said vessel to reduce heat leakage therethrough, a receiver means comprising at least one high pressure gas material receiver immersed in said liquefied gas, a gas line connection from said receiver means and passing gas-tightly through said vessel, a gas connection at the outer end of said gas line for admitting gas into said receiver means, a pressure opening valve means in said gas line for discharging high pressure gas material when the pressure in said receivers exceeds a predetermined high pressure, a bursting disk assembly communicating with said gas line and operative at a higher pressure, a safety valve having a gas release setting at a pressure below the pressure in said receiver means and normally not connected therewith, and a temperature responsive element positioned to be responsive to the temperature within said liquefied gas holding vessel, and operatively associated with said safety valve for connecting said safety valve with said receiver means.

6. In a vessel for holding a supply of liquefied gas, a heat insulating jacket surrounding said vessel to reduce heat leakage therethrough, a receiver means comprising at least one high pressure gas material receiver immersed in said liquefied gas, a gas line connection from said receiver means and passing gas-tightly through said vessel, a gas connection at the outer end of said gas line for admitting gas into said receiver means, and a dual pressure valve system in said gas line comprising a low pressure safety valve and bursting disk assembly having a gas release setting at a pressure below the pressure in said receiver, and normally not connected therewith, a temperature-responsive means in said liquefied gas holding vessel and said gas line connection for connecting said safety valve with said receiver means, and a high pressure opening valve and bursting disk assembly in said gas line for discharging high pressure gas material when the pressure in said receivers exceeds a predetermined high pressure.

References Cited in the file of this patent UNITED STATES PATENTS 1,680,873 Lucas-Girardville Aug. 14, 1928 2,148,109 Dana Feb. 21, 1939 2,290,038 Folmsbee July 14, 1942 2,526,221 Goddard Oct. 17, 1950 2,675,682 Dobson Apr. 20, 1954 2,756,765 Agule July 31, 1956 2,834,187 Loveday May 13, 1958 2,863,297 Johnson Dec. 9, 1958

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