Abstract:
A vessel for containing liquefied petroleum gas and a method for loading a semitrailer with a plurality of vessels is disclosed. The vessel may include a tank with an outside diameter that is greater than thirty inches and less than thirty-four inches. The tank may be configured to contain at least 119 water gallons, and may be further configured to contain liquefied petroleum gas.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 60/911,791, filed Apr. 13, 2007, entitled Vertical Storage Vessel, which is hereby incorporated by reference. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present disclosure is related to storage vessels and more particularly, to vertical storage vessel systems and methods for example, for storing liquefied petroleum gas (“LPG”). 
       BACKGROUND OF THE INVENTION 
       [0003]    Storage vessels or tanks are used to store volatile liquids and gases. For example, LPG tanks are often used to contain liquefied petroleum gas such as propane. LPG tanks come in a variety of sizes and are used in both commercial and residential applications. LPG tanks are often used in residential applications to provide fuel for fireplaces, stoves, and dryers. LPG tanks may be used in commercial application to provide fuel to heat a building. 
         [0004]    To get an LPG tank from the manufacturer to a retailer or other user that may fill the tank and offer it for sale, multiple LPG tanks may be transported on a semitrailer(s) having certain dimensions governed by federal regulations. 
       SUMMARY OF THE INVENTION 
       [0005]    The teachings of the present invention include a storage vessel that has dimensions selected to increase the number of vessels that can be transported on a semitrailer. In accordance with a particular embodiment of the present invention, a vessel for containing liquefied petroleum gas includes a tank. The tank may have an outside diameter that is greater than thirty inches and less than thirty-four inches. The tank may be configured to contain at least 119 water gallons, and may be further configured to contain liquefied petroleum gas. 
         [0006]    In accordance with another embodiment of the present invention, a method for loading a semitrailer with vessels includes providing a plurality of vessels. Each vessel may have an outside diameter that is greater than thirty inches and less than thirty-four inches. Each vessel may be configured to contain at least 119 water gallons, and may be further configured to contain liquefied petroleum gas. At least thirteen stacks of vessels may be loaded on a semitrailer, wherein each stack comprises nine vessels, and wherein an imaginary centerline of each vessel is substantially horizontal. 
         [0007]    Technical advantages of particular embodiments of the present invention include an LPG tank that has the capacity to hold 119 water gallons and is sized to increase the number of tanks that may be loaded on a semitrailer for transport. 
         [0008]    Further technical advantages of particular embodiments of the present invention include a tank that is relatively shorter and has a greater outer diameter than a conventional LPG tank, that is still capable of being used in conventional tank applications. 
         [0009]    Still further technical advantages of the present invention include an LPG tank that is less than four feet tall, which is the standard height for the sill of a window in a residence. Therefore, an LPG tank in accordance with the teachings of the present invention may be placed on the outside of a residence near a window and not block a view out of the window. 
         [0010]    Still further technical advantages of the present invention include valve and fitting placement that may make fluid communication among multiple LPG tanks easier. Allowing fluid communication among LPG tanks may substantially increase the quantity of available propane for certain applications. Still further technical advantages of the present invention include an improved design of an LPG tank collar and lid interface that may improve manufacturing and assembly. 
         [0011]    Other technical advantages will be readily apparent to one of ordinary skill in the art from the following figures, descriptions and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0012]    A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description, taken in conjunction with accompanying drawings, in which like reference numbers indicate like features, and wherein: 
           [0013]      FIG. 1  is a schematic drawing of an embodiment of the present invention having an illustration of a conventional LPG tank superimposed; 
           [0014]      FIG. 2A  is a schematic drawing of a side view of an LPG vessel in accordance with an embodiment of the present invention; 
           [0015]      FIG. 2B  is a schematic drawing of a top view of an LPG vessel in accordance with an embodiment of the present invention; 
           [0016]      FIG. 2C  is a schematic drawing showing the detail of a head to shell seam in accordance with an embodiment of the present invention; 
           [0017]      FIG. 2D  is a schematic drawing of an embodiment of the present invention showing a lid and collar interface in partially exploded view; 
           [0018]      FIG. 3  is an illustration of an embodiment of the present invention showing a load layout of a semitrailer loaded with LPG vessels in accordance with an embodiment of the present invention; 
           [0019]      FIG. 4  is a schematic drawing of another embodiment of the present invention showing a second load layout of a semitrailer loaded with LPG vessels in accordance with an embodiment of the present invention; 
           [0020]      FIG. 5  is a schematic drawing of an embodiment of the present invention showing an end view of a semitrailer loaded with LPG vessels in accordance with an embodiment of the present invention; 
           [0021]      FIG. 6  is a schematic drawing illustrating a detailed view of an embodiment of the present invention showing LPG vessels separated by protective material; and 
           [0022]      FIG. 7  is an illustration of a load layout of a semitrailer loaded with 320 gallon LPG vessels in accordance with a further embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    The present disclosure is directed to a liquefied petroleum gas (“LPG”) tank assembly which may also be referred to as a vessel. Dimensions of the tank assembly may be selected to allow the tank to hold a certain quantity of liquid or pressurized gas while still allowing a maximum number of tanks to be transported on a semitrailer having length and width dimensions in compliance with United States federal size regulations for commercial vehicles. 
         [0024]      FIG. 1  illustrates an improved LPG tank assembly  12  which may also be described as a vertical storage vessel, a bottle, or a cylinder. Improved LPG tank assembly  12  is shown in  FIG. 1  by solid lines. Superimposed over improved LPG tank  12  is conventional LPG tank  10 , illustrated by broken lines on the drawing. Both improved LPG tank  12  and conventional LPG tank  10  are capable of holding 119 water gallons. Improved LPG tank  12  is shorter and wider than conventional LPG tank  10 . The outer diameter of conventional LPG tank  10  (OD 1 ) may be 30 inches while the outer diameter of improved LPG tank  12  (OD 2 ) may be 33 inches. In accordance with particular embodiments of the present invention, OD 2  may be greater than 30 inches and less than or equal to 35 inches. OD 2  may also be greater than 31 inches and less than 34 inches. 
         [0025]    Conventional LPG tank  10  includes a domed lid  14  and a standard collar  17 . Improved LPG tank  12  also achieves reduced height for example, by replacing domed lid  14  with flat lid  16  and replacing standard collar  17  with shorter, improved collar  18 . 
         [0026]    By reducing the height of the collar, flattening the lid, and increasing the outer diameter, improved LPG tank  12  may have an overall height (H 2 ). H 2  may be greater than or equal to 44 inches and less than or equal to 55 inches. In accordance with other embodiments of the present invention, H 2  may be greater than or equal to 44 inches and less than or equal to 48 inches. In accordance with particular embodiments of the present invention, H 2  may be equal to 44.085 inches. A reduced height base  19  may also contribute to reduced height H 2 . Improved LPG tank  12  achieves a significant reduction in height from height H 1  of conventional LPG tank  10  which may be 55.375 inches to H 2 , which may be 44.085 inches, the difference being H 1 −H 2  or 11.290 inches. 
         [0027]    Consistent with the teachings of the present invention, LPG vessels of various capacities may have reduced length and increased outer diameter compared to conventional tanks of the same capacity or volume. For example, LPG vessels that are capable of containing 320 water gallons may be made to have a reduced length of 84 and 3/16ths inches and an outer diameter of 33 inches. 400 water gallon LPG vessels may also have a 33 inch outer diameter consistent with the teachings of the present invention. 
         [0028]    A 119 water gallon LPG vessel in accordance with the teaching of the present invention may have a volume or capacity in water gallons that is greater than or equal to 3.4 and less than or equal to 3.9 times its outer diameter in inches. It may also have a volume in gallons that is less than or equal to 3.8 and greater than or equal to 3.5 times its outer diameter in inches. In accordance with a particular embodiment of the present invention, a 119 water gallon LPG vessel may have a volume or capacity (119 gallons) that is 3.6 times the outer diameter of the vessel in inches. In addition, the volume or capacity in water gallons (119 water gallons) of an LPG vessel in accordance with the teachings of the present invention may be 2.7 times its height in inches. 
         [0029]    In accordance with a particular embodiment of the present invention, a 320 water gallon LPG vessel may have a volume or capacity in water gallons that is 3.8 times its length in inches. 
         [0030]    In accordance with particular embodiments of the present invention, an LPG vessel may have a height in inches that is greater than or equal to 1.33 and less than or equal to 1.67 times its outer diameter in inches. A particular embodiment of the present invention may have a height in inches that is equal to 1.45 times its outer diameter in inches. 
         [0031]      FIG. 2A  illustrates an LPG tank assembly or vessel  20  in accordance with a particular embodiment of the present invention. Tank assembly  20  includes base  22 , tank  32 , lifting lug  26 , and cover assembly  30 . A cylindrical collar  34  is fixed to the top of tank  32  and includes two visible access openings  35 . Cylindrical collar  34  may surround valves and fittings located at the top of tank  32 . The valves and fittings allow access to the contents of tank  32  and further allow tank  32  to be filled. 
         [0032]    Lid  36  includes top surface  19  that is flat and generally perpendicular to an imaginary centerline  43  of tank  32  when lid  36  is in its closed position. Being flat, top surface  19  of lid  36  decreases the overall height E of LPG tank assembly or vessel  20 . By decreasing the overall height of LPG tank assembly  20 , more tank assemblies  20  may fit on a semitrailer as shown in  FIGS. 3 and 4 . The height of cylindrical collar  32  may be selected to allow cylindrical collar  32  to adequately protect the valves and fittings and also to minimize the overall height of LPG tank assembly  20 . 
         [0033]    The outer diameter of tank  32  and LPG tank assembly  20  is designated in  FIG. 2A  as G. LPG tank assembly  20  may be a 119 gallon LPG tank. Outer diameter G may be selected such that LPG tank assembly  20  is capable of holding 119 water gallons and also selected to allow three tanks on their side and positioned generally tangent to each other on a semitrailer to maximize the surface of the semitrailer occupied by the vessels (see  FIG. 5 ). In certain embodiments of the present invention, outer diameter G may be equal to 33 inches and overall height E may be equal to 44.085 inches Tank  32  includes shell ring  42 , bottom head  38  and top head  40 . Shell ring  42  may be 0.192 inches thick and 22 inches long (dimension C). It may also have longitudinal seam  44  created by welding two lateral edges of shell ring  42  together with a full weld. Shell ring  42  may be fixed to top head  40  and bottom head  38  with a spot weld performed in accordance with UW-11(a) (5) (b). See  FIG. 2C . 
         [0034]    Bottom head  38  and top head  40  may each be a 2:1 elliptical head with a 0.172 inch minimum thickness in accordance with ASME standards. Bottom head  38  and top head  40  may also have thicknesses in accordance with U.S. Department of Transportation standards. Bottom head  38  and top head  40  may have an outer diameter of 33 inches. Top head  40  may be substantially similar to bottom head  38  with the exception that top head  40  may have prepunched holes to receive couplings that will fit valves and other fittings of tank assembly  20 . Top head  40  and bottom head  38  may have respective heights B and D of 8.340 inches. 
         [0035]    LPG tank assembly  20  may be composed of material in accordance with ASME standards or may be material specified by U.S. Department of Transportation regulations for portable cylinders. In accordance with ASME standards governing pressure vessels, top head  40  and bottom head  38  may be made of SA414G steel. Shell ring  42  may be made of SA455 steel. A36 steel or equivalent may be the material for collar  34 , base  22 , and lift lug  26 . The couplings welded to top head  40  may be SA105 steel. Collar  34  may have 3 tabs to facilitate welding to top head  40 . Lid  36  may have a 16 inch outer diameter and may be made of C.Q. G-30 galvanized carbon steel. 
         [0036]    Reference number  46  indicates a reference line at the level of tank assembly  20  to which liquid would rise when the tank is 80% full. Dimension H shows 80% liquid level  46  being 10.1 inches below the top of coupling  48 . Cover assembly  30  may have an overall height of A, where A equals 5.8125 inches. Base hole  50  may be aligned with lift lug  26 . 
         [0037]      FIG. 2B  illustrates a top view of tank assembly  20 . The location of the valve couplings are visible from  FIG. 2B . Valve couplings are located on arcs I and K. Arc I may have a radius of 3.250 inches, and arc K may have a radius of 4.298 inches. Valve coupling  64  and valve coupling  68  are located on arc I. Valve couplings  66  and  70  are located on arc K. This configuration allows valve couplings  70 ,  68 , and  66  to be substantially in a straight line. 
         [0038]    Valve couplings  64 ,  66 ,  68 , and  70  may be a 3000# half coupling and may be three quarters of an inch, one inch, or one and one quarter inches in diameter. Valve coupling  64  may be capable of receiving a fill valve. Valve coupling may be capable of receiving a relief valve, and valve coupling  68  may be capable of receiving a service valve. Coupling  70  may be capable of receiving a float gauge. 
         [0039]    The specific location of valve couplings  64 ,  66 ,  68 , and  70  may allow a T-block to be coupled to a service valve secured to valve coupling  68 . This T-block may allow multiple LPG tank assemblies to be coupled to each other through a conduit that is received by the T-block through collar  34  at a access opening  35 . This may allow multiple tank assemblies to be coupled together while lid  36  remains in a closed position. By coupling multiple tanks, available propane is increased to 240 gallon capacity or more without having to install a larger capacity tank. 
         [0040]    Lid stop  60  may be coupled to cover assembly  30  by cotter pin  62 . Cotter pin  62  may be 4 inches long. See  FIG. 2D  for more detail. Valve couplings  64 ,  66 ,  68 , and  70  may be located at angles designated by J, L, M, and N, where J equals 15 degrees, L equals 30 degrees, M equals 19 degrees, and N equals 11 degrees. 
         [0041]      FIG. 2C  illustrates a detail of the seam where top or bottom head  38  or  40  may be welded to shell  42 . Dimension N equals approximately 13/16 inches, and dimension O equals a minimum flat portion of 1 and ½ times the thickness of the steel. The seam shown may be created by in accordance with ASME standards by a spot x-ray per UW-11 (a) (5) (b) with a weld re-enforcement inside and outside of ⅛th of an inch. The seam may also be created in compliance with U.S. Department of Transportation regulations governing portable cylinders. 
         [0042]      FIG. 2D  illustrates an isometric view of the coupling between lid  36  and collar  34 . Two collar tabs  82  each may have an aperture to receive cotter pin  62 . Two corresponding lid tabs  86  each may also include an aperture  84  to receive cotter pin  62 . 
         [0043]    Collar tabs  82  may be formed by a multi-stage die as opposed to being welded to collar  34 . A first stage of a multi-stage die may form the basic features of collar  34 . A second stage may form collar tabs  82  by removing material to create tab apertures  92  and the shape of collar tabs  82 . A third stage of a multi-stage die may bend collar tabs  82  approximately 90 degrees such that they are in the position shown by  FIG. 2D . 
         [0044]    Similar to the formation of collar tabs  82 , lid tabs  86  may also be formed by a multi-stage die. A first stage of a multi-stage dye may form the basic shape of lid  36 . A second stage may remove material to form the shape of lid tabs  86  and apertures  84 . A third stage may bend lid tabs  86  approximately 90 degrees to the position shown in  FIG. 2D . 
         [0045]    Collar tabs  82  may be spaced 3 inches apart and lid tabs  86  may be spaced 3.17 inches apart. Coupling lid  36  to collar  34  may be accomplished by aligning collar apertures  92  with lid apertures  84  and inserting cotter pin  90  through the four apertures. In accordance with a particular embodiment of the present invention, lid stop  60  may be formed and function in accordance with the teachings of U.S. patent application Ser. No. 11/563,992, which is hereby incorporated by reference as if fully set forth herein, and be inserted between collar tabs  82 . Cotter pin  62  may couple lid  36 , lid stop  60 , and collar  34 . 
         [0046]    Tank assembly  20  may conform to the ASME code for pressure vessels, Section VIII, Division I or U.S. Department of Transportation regulations governing portable cylinders, NFPA 58. In compliance with ASME standards, the maximum allowable working pressure may be 250 PSIG at 125 degrees Fahrenheit. The minimum design metal temperature (“MDMT”) may be −20 degrees Fahrenheit at 250 PSIG. The hydrostatic test pressure of tank assembly  20  and the maximum allowable stress of top head  40 , bottom head  38 , and shell ring  42  may be in compliance with ASME or DOT standards. The weight of tank assembly  20  including the valve fittings may be approximately 320 pounds. The outside surface area may be 35 square feet, and the relief capacity required for LPG may be 990 standard cubic feet per minute. 
         [0047]      FIGS. 3 and 5  illustrate an embodiment of the present invention.  FIG. 3  is a side view of semitrailer  110  loaded with tank assemblies or vessels in accordance with an embodiment of the present invention. The tank assemblies or vessels may be 119 water gallon vessels.  FIG. 5  is an end view of loaded semitrailer  110 . 
         [0048]    As shown in  FIG. 3 , loaded semitrailer  110  includes trailer bed  112 . Trailer bed  112  may have a length R and a width W. Length R may be 48 feet and width W may be 102 inches. Length T and width W may be required to comply with federal size regulations for commercial motor vehicles, and thus may have particular length and width requirements. Multiple LPG tank assemblies  100  are shown on trailer bed  112 . In accordance with a particular embodiment of the present invention, LPG tank assembly  100  may have height Q and outer diameter Y (see  FIG. 5 ) that allow a maximum number of LPG tank assemblies  100  to be loaded and transported on trailer bed  112 . 
         [0049]    LPG tank assemblies  100  may be positioned on trailer bed  112  in groups of nine. As shown in  FIG. 5 , three LPG tanks  20  may be positioned substantially tangent to each other while laying on their sides. Three tank assemblies  100  may rest on shipping timbers  114 . When tanks  100  are positioned substantially tangent to each other, they may occupy an overall tank width X. X may equal 8 feet 3 inches (99 inches) . Shipping timbers  114  may be 1 and 11/16ths inches thick. The overall height of loaded semitrailer  110  from the level of the ground to the top of the tank stacks is shown as dimension U. Height U may be selected to be less than certain state regulations governing the maximum height of a load carried by commercial motor vehicles. This maximum height may be 13 feet 6 inches. Dimension U may equal 12 foot 8 and ⅝ths inches. 
         [0050]    In accordance with a particular embodiment of the present invention, between each tank  100  may be material to protect each tank from contacting another tank and thereby damaging it. Protective material  118 , shown in  FIG. 6 , may be padding, web strapping, or compressed foam. Protective material  118  may be selected and/or positioned so as to not significantly increase overall tank width X over 99 inches. Overall tank width X may be equal to or greater than 99 inches and less than or equal to 102 inches. 
         [0051]    Shipping timbers  114  may be placed on top of three tank assemblies  100  to allow three more tank assemblies  100  to be stacked on top thereof. A stack of tank assemblies  100  may comprise nine tank assemblies created by stacking three sets of three tank assemblies on top of each other. The outer diameter of tank assembly  100 , Y, may be selected such that it is less than trailer width W divided by three. 
         [0052]    Each stack of nine tank assemblies  100  may be loaded onto trailer bed  112  for transport. The overall height Q of tank assembly  100  may be selected such that it is less than trailer length R divided by thirteen. Q may be 44.085 inches. This may allow thirteen stacks of nine tank assemblies  100  ( 117  tank assemblies) to be loaded and safely transported on trailer bed  112 . The overall length of thirteen stacks of nine tank assemblies,  13 Q, may be 47.76 feet. (44.085 inches×13). Each stack of nine tank assemblies  100  may be positioned on trailer bed  112  such that each tank assembly&#39;s imaginary center axis  106  is generally parallel to trailer bed  112 . Each stack of nine tank assemblies  100  may be positioned such that base  102  of a tank assembly of a first stack is directly adjacent and nearly contacts a lid of a tank assembly  100  in an adjacent stack. 
         [0053]    Another embodiment of the present invention is illustrated in  FIG. 4 . Trailer bed  112  may be capable of transporting fourteen stacks of nine tank assemblies  100  with the aid of an extension to trailer bed  112 . The extension  116  to trailer bed  112  may be approximately 1 foot 3 and 13/16ths inches long. In addition to extension  116 , a stack of nine tanks may extend approximately 1 foot 2 inches beyond the length of the trailer bed  112 . This extension is shown by dimension S. 
         [0054]    In accordance with a particular embodiment of the present invention, 126 tanks may be transported with one trailer load. The overall length of the fourteen stacks of tank assemblies may be  14 Q.  14 Q may equal 51 feet and 3 and ¾ths inches. 
         [0055]      FIG. 7  illustrates a further embodiment of the present invention.  FIG. 7  shows stacks of 320 gallon tank assemblies or vessels  130  loaded on semitrailer  132 . Each 320 gallon tank  130  may have an overall length dimension Z of 84 and 3/16ths inches, and an overall radius BB of 33 inches. The overall length of six stacks of nine 320 gallon tanks may be shown by dimension  6 Z.  6 Z may be less than semitrailer length R, which is 48 feet.  6 Z may be equal to 42.094 feet.  FIG. 7  illustrates a side view of a 320 gallon tank load that is similar to  FIG. 3  illustration of a 119 gallon tank load. Thus, each stack showing three tanks  130  on top of each other from a side view represents nine tanks positioned similar to the configuration shown in  FIG. 5 . 
         [0056]    Accordingly,  FIG. 7  depicts fifty-four 320 gallon vessels as they might be loaded on semitrailer  122 . Conventionally sized 320 gallon tanks would require that less than fifty-four be transported on a 48 foot semitrailer that complies with federal size regulations for commercial motor vehicles. Conventional 320 gallon tanks may be transported in loads of 45 tanks. The teachings of the present invention may also be used for a 400 gallon tank assembly with a 33 inch outer diameter and a reduced length. 
         [0057]    Although the present invention has been described in several embodiments, a myriad of changes and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes and modifications as fall within the scope of the present appended claims.