Abstract:
Railroad tank cars are provided that include an inner tank, an outer tank, and tank to tank clearance between the inner tank and the outer tank. Insulation and spacers can be located within the tank to tank clearance. The inner tank can shift within the outer tank, and spacers can crush, under significant force loading, such as impact forces generated during a collision or derailment. The inner tank, insulation, spacers, and outer tank thus form an energy absorbing system that reduces the likelihood that the inner tank will be breached, and that a hazardous material contained therein will be released, under such conditions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Continuation of U.S. Non-Provisional application Ser. No. 12/966,335 filed Dec. 13, 2010, which claims the benefit of U.S. Provisional Application Ser. No. 61/285,644, filed on Dec. 11, 2009. The entirety of all the above-listed applications are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    Railroad tank cars are designed to transport liquid commodities, gaseous commodities, and commodities that are gas-liquid mixtures. The interior of a tank car is sometimes lined with a material to isolate the structural components of the tank car from the commodity being transported. Tank cars can be insulated or non-insulated, pressurized or non-pressurized, and can be designed for single or multiple loads. Non-pressurized cars have plumbing at the bottom for unloading, and may have an access port and a dome housing with various valving on the top. Pressurized cars can have a pressure plate, valving, and a protective cylindrical dome housing at the top through which loading and unloading can be accomplished. 
         [0003]    Various designs of tank cars have been developed for the transportation of specific types of commodities, including for example, foodstuffs and other materials, including hazardous materials that can pose a threat to safety and health if they are spilled. Traditionally, railroad tank cars have been engineered to contain their commodity based on the commodity&#39;s physical and chemical properties, and the inherent stresses placed upon the tank car due to those properties. However, in instances of collision and derailment, a tank car can be subjected to additional forces. In recent years, work has been done towards developing standards and criteria for strengthening railroad tank cars to reduce the risk of spills and increase public safety should a train accident occur. 
         [0004]    In response to safety concerns, trends in tank car design have resulted in tank cars that are constructed of thicker steels than what would be required based solely upon the structural loading of specific commodities. Current tank cars thus have steel thickness in excess of what is required to retain the commodity pressure and sustain structural loads, and the additional thickness improves the puncture resistance and crashworthiness of the tank car so that the tank car can be less prone to damage. However, the amount of benefit derived from adding thickness to the outer structure of a tank car is limited, and may not suffice to meet desired criteria for avoiding the release of hazardous materials during events such as collisions or derailment. 
       BRIEF SUMMARY 
       [0005]    The present technology relates to railroad tank cars that contain a commodity according to its physical and chemical properties, and also provides increased levels of puncture resistance and energy absorption to resist release of the commodity in the event of a collision or derailment. In particular, tank cars of the present technology have an outer tank, and an inner tank within the outer tank. 
         [0006]    The inner tank is supported by a bottom support structure, where there is a tank to tank clearance defined between the inner tank and the outer tank. Spacers and insulation are located within the tank to tank clearance defined between the inner tank and the outer tank. The inner tank can shift within the outer tank under impact loading conditions and the insulation and spacers absorb energy of the impact loading conditions. 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         [0007]    Specific examples have been chosen for purposes of illustration and description, and are shown in the accompanying drawings, forming a part of the specification. 
           [0008]      FIG. 1  illustrates a side cross sectional view of one example of a tank car of the present technology. 
           [0009]      FIG. 2  illustrates a detail view of the cross sectional view of the tank car of  FIG. 1 . 
           [0010]      FIG. 3  illustrates an end cross sectional view of the tank car of  FIG. 1 . 
           [0011]      FIG. 4  illustrates one embodiment of a spacer for use in the tank car of  FIG. 1 . 
           [0012]      FIG. 5  illustrates a perspective view of a second example of a tank car of the present technology. 
           [0013]      FIG. 6  illustrates an upper spacer of the tank car of  FIG. 5 . 
           [0014]      FIG. 7  illustrates a lower spacer of the tank car of  FIG. 5 . 
           [0015]      FIG. 8  is a cross-sectional view of one example of a lower support structure of the tank car of  FIGS. 1 and 5 . 
           [0016]      FIG. 9  illustrates one examples of a dome that can be used with the tank car of  FIGS. 1 and 5 . 
           [0017]      FIG. 10  illustrates a tank car of  FIG. 5  undergoing shell impact energy absorption testing through finite element analysis, prior to the ram impacting the shell of the tank car. 
           [0018]      FIG. 11  illustrates a tank car of  FIG. 5  undergoing shell impact energy absorption testing through finite element analysis, after the ram impacts the shell of the tank car. 
           [0019]      FIG. 12  illustrates a tank car of  FIG. 5  undergoing head impact energy absorption testing through finite element analysis, prior to the ram impacting the head of the tank car. 
           [0020]      FIG. 13  illustrates a tank car of  FIG. 5  undergoing head impact energy absorption testing through finite element analysis, after the ram impacts the head of the tank car. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Tank cars of the present technology are designed to have improved impact resistance as compared to conventional tank cars. The tank cars have an outer tank that surrounds an inner tank. The inner tank is enclosed by the outer tank, and is supported within the outer tank. 
         [0022]    Tank cars of the present technology can be used to transport commodities, including but not limited to liquid commodities, gaseous commodities, and commodities that are gas-liquid mixtures. The transported commodities can be hazardous or non-hazardous, and can be pressurized or not pressurized. 
         [0023]      FIGS. 1 through 4  illustrate one example of a tank car  100  of the present technology, which includes an outer tank  102 , an inner tank  104 , and a tank to tank clearance  106  between the outer tank  102  and the inner tank  104  that contains insulation  108  and spacers  110 . The outer tank  104  and the inner tank  102  can each be generally cylindrical, having substantially circular cross-sections that are preferably concentric, as shown in  FIG. 3 . As illustrated further in  FIG. 3 , the tank car  100  also includes a bottom support structure  112  that serves to support the inner tank as well as maintains the inner tank&#39;s independence from the outer tank. The tank car can also include a dome  114 , which can be located at the top of the tank car to provide access for loading and unloading a commodity stored within the inner tank  104  of the tank car  100 . In at least one example, the inner tank  104  is rigidly connected to the outer tank  104  only at the dome  114 . 
         [0024]    The inner tank  104  can be made of any suitable material or materials, and includes an inner tank heads  116  and an inner tank shell  118 . In one embodiment, the inner tank heads  116  and the inner tank shell  118  are both made from TC 128 Gr B steel. The thickness of the inner tank heads  116  can be from about ¾ of an inch to about 1 inch. The thickness of the inner tank shell  118  can be from about 7/16 of an inch to about 9/16 of an inch, and preferably has a thickness that is at least about 15/32 of an inch. 
         [0025]    The outer tank  102  can also be made of any suitable material, and includes outer tank heads  120  and an outer tank shell  122 . In one embodiment, the outer tank head  120  and the outer tank shell  122  can both be made from TC 128 Gr B steel. The thickness of the outer tank head  120  can be at least about ½ an inch, and can preferably be from about ¾ of an inch to about 1 inch. The thickness of the outer tank shell  122  can be at least about 15/32 of an inch, and can preferably be from about ¾ of an inch to about 1 inch. 
         [0026]    In one embodiment, the outer tank  102  may be constructed from a special high toughness steel. The high toughness steel is produced by continuous casting from a melt produced in either basic oxygen or electric furnaces. The steel may either be hot rolled with a maximum finishing temperature of 1125° C. or normalized after rolling in order to achieve optimal toughness properties. If normalized, the temperature for the normalization treatment is 950° C. for 1 hour and air cooled. The composition of the steel is: 0.05% C, 0.94% Mn, 0.52% Si, 1.29% Cu, 0.74% Ni, 0.07% Nb, 0.08% Ti, 0.005% S maximum, 0.005% P maximum, remainder Fe. This composition is nominal and may be adjusted for manufacturing and physical property optimization. 
         [0027]    In some embodiments, the inner tank shell  118  and the outer tank shell  122  have a combined thickness of at least about 1.5 inches, and the inner tank head  116  and the outer tank head  120  have a combined thickness of at least about 1.7 inches. 
         [0028]    The tank to tank clearance  106 , which is measured from the outside surface of inner tank shell  118  to the inside surface of the outer tank shell  122 , can be any suitable distance. In at least one example, the tank to tank clearance  106  is about 4 inches. As another example only, the clearance could be in the range of approximately 2 to 5 inches. 
         [0029]    Spacers  110  are placed between the inner tank  104  and outer tank  102 , and can allow for energy absorption. The spacers  110  can be designed to crush under impact loading conditions of significant force loading, such as when the tank car experiences an impact or derailment. The spacers can be made from any suitable material, including, but not limited to, A516-70 or TC128 Gr B steel. 
         [0030]    One example of a spacer is indicated in general at  110  in  FIG. 4 . In this example, the outer tank  102  includes one or more openings  124 , and the spacer  110  extends through each opening  124  to abut the inner tank  104 . The spacer  110  has a cover plate  128 , at least two legs  130   a  and  130   b  that extend away from the cover plate  128 , and a bottom  132  connected to the legs  130   a  and  130   b  that contacts the inner tank shell  104  when the spacer  110  is inserted into the opening  124 . In such an embodiment, under impact conditions, the spacers  110  can crumple or crush as the inner tank  104  shifts within the outer tank  102 , or the spacers can be dislodged and pushed outwardly by the inner tank  104  shifting within the outer tank  102 . 
         [0031]    An alternative arrangement of spacers is illustrated in  FIGS. 5 through 7 . As shown in  FIG. 5 , a tank car  200  having an inner tank  202  and an outer tank  204  has a plurality of upper spacers  206   a - 206   f  and a plurality of lower spacers  208   a - 208   e . One side of the tank car  200  is shown in  FIG. 5 , and it should be understood that the other side has a symmetrical arrangement of spacers. The upper spacers  206   a - 208   f  are spaced apart along the length of the upper half of the tank car  200 , and the lower spacers  208   a - 208   e  are spaced apart along the length of the lower half of the tank car  200 . As illustrated, each side of the tank car preferably has six upper spacers  206   a - 206   f  and five lower spacers  208   a - 208   e , but the number of upper and lower spacers will vary with the size of the tank. 
         [0032]    One example of an upper spacer  206  is shown in  FIG. 6 . Each upper spacer  206  can be secured to the outer tank shell  204 , such as, for example, being welded to the outer tank shell  204 . An upper spacer  206  can be generally U-shaped, having two legs  210   a  and  210   b  that extend away from the outer tank shell  204  towards the inner tank shell  202 , and a cross piece  212  that extends from one leg  210   a  to the other leg  210   b , connecting the two legs. In some examples, the connection points  214   a  and  214   b  between the legs  210   a  and  210   b  and the cross piece  212  are squared or rounded. The upper spacers can be made of any suitable material, including, for example, A516-70 or TC128 Gr B steel. A572-50 steel can be used in place of A516-70 in any situation that is not pressure retaining. In at least one example, each leg  210   a  and  210   b  and the cross piece  212  of an upper spacer  206  can have a thickness from about ¼ of an inch to about 1 inch, including for example having a thickness of about ⅜ of an inch. Additionally, an upper spacer  206  can have any suitable height, measured from the end of the leg  210  that is secured to the outer tank shell  204  to the outer surface of the cross piece  212 , and preferably has a height that spans the tank to tank clearance so that the cross piece  212  of the upper spacer  206  abuts the inner tank shell when the upper spacer  206  is installed in the tank car. Further, an upper spacer  206  can have any suitable width, measured from the outer edge of one leg  210  to the outer edge of the other leg  210 , such as a width of from about 3 inches to about 5 inches, including for example about 3.5 inches. 
         [0033]    One example of a lower spacer  208  is illustrated in  FIG. 7 . Each lower spacer  208  can be secured, such as by welding, to the inner tank shell  202 , or preferably to a tank reinforcing pad  216  that is secured to the inner tank shell  202 . As illustrated in  FIG. 7 , the lower spacer  208  is secured to the tank reinforcing pad  216  at a first end  218  and a second end  220 . Between the first end  218  and the second end  220  of the lower spacer  208 , the lower spacer curves outwardly, away from the inner tank shell  202  and the reinforcing pad  216 , forming an apex  222  and two legs  224   a  and  224   b . The lower spacers can be made of any suitable material, including, for example, A516-70 or TC128 Gr B steel or A572-50 steel (for non-pressure retaining components). In at least one example, the lower spacer  208  can have a thickness from about ¼ of an inch to about 1 inch, including for example having a thickness of about ⅜ of an inch. The lower spacer can have any suitable length, measured from the outer edge of the first end  218  to the outer edge of the second end  220 , including but not limited to a length of from about 8 inches to about 15 inches, including for example a length of about 12 inches. The lower spacer  208  can also have any suitable height, measured from the edge of the lower spacer secured to the inner tank shell  202  or the reinforcing pad  216  to the apex  222  of the lower spacer, and preferably has a height that spans the tank to tank clearance so that the apex  222  of the lower spacer  208  abuts the outer tank shell  204  when the lower spacer  208  is installed in the tank car. 
         [0034]    Referring back to  FIGS. 1-3 , insulation  108  can surround the shell of the inner tank  104 . Preferably, the insulation  108  substantially entirely surrounds the inner tank,  104 , filling any area within the tank to tank clearance  106  that is not taken up by the spacers  110 , the bottom support structure  112 , and the dome  114 . The insulation can be any suitable material, and can contain multiple layers. In one embodiment, the insulation includes a first insulation layer and a second insulation layer. The first insulation layer can be, for example, 4.5 pound cuft ceramic fiber, and can be about 2 inches thick. The second insulation layer can be, for example, ¾ pound cuft fiberglass, and can be about 2 inches thick. Insulation layers can vary with the clearance between tanks. As another example, more insulation may be compressed down to the four inches clearance so that a single layer of insulation is used. 
         [0035]    Referring to  FIGS. 1-3  and  8 , the bottom support structure  112  can be made of any suitable materials, including, but not limited to A516-70 or TC128 Gr B steel. The bottom support structure  112  is preferably located between the inner tank  102  and outer tank  104  in the region of the bolsters  126 . The bottom support structure  112  includes a curved inner tank support  300  that is secured, such as by welding, to the inner tank  104 , or to an inner tank repad  302  as illustrated in  FIG. 8 . The inner tank repad  302  is secured, such as by welding, to the inner tank  104 . The bottom support structure  112  also includes a tank cradle  306  that is secured, such as by welding, to the outer tank  102 . The tank cradle  306  is shaped to receive the inner tank support  300 . Support can thus be provided to the inner tank  104  by bottom support structure  112  when the inner tank support  300  rests on the tank cradle. While the inner tank support  300  and the tank cradle  306  are preferably in contact under normal operating and loading conditions, they are not mechanically connected. The inner tank support  300  can slide along the tank cradle  306  or lift off the cradle  306  under significant force loading conditions such as collision, derailment, and tank car rollover. In at least one embodiment, the bottom support structure  112  also includes foam  308 , such as, for example DOW beta foam, to provide additional support. The foam  308  is located between the inner tank support  300  and the inner tank  104  or the inner tank repad  302 , between the tank cradle  306  and the outer tank  102 , or both. An alternative material for the bottom support includes A572-50 steel. In addition, a urethane foam may be used in place of DOW beta foam, but it would serve only a thermal function, not a structural one (which is acceptable). 
         [0036]      FIG. 9  illustrates a cross-section of one example of a dome  114  that can be used with tank cars of the present technology. The dome  114  includes a nozzle  400 , through which the commodity can be placed into and removed from the inner tank  104 . When the tank car is in operation, a cover plate  402  can be used to cover and close the nozzle  400 . The cover plate  402  is removably secured to the nozzle  400 , such as being secured by a number of bolts  404 . The dome  114  can include a sidewall  406 , which can be circular, and which preferably extends above the nozzle  400  and cover plate  402 . A circular reinforcing plate  408  can also be included, to provide additional structural support to the dome  114 , including the sidewall  406 . 
         [0037]    The outer tank  102 , insulation  108 , spacers  110 , and the inner tank  104  act as an energy absorbing system in the event of a derailment or other event that would possibly lead to a puncture, or other breach, of the inner tank  104 . The energy absorbing system of the tank car  100  allows the inner tank  104  to move independently of the outer tank  102 , which can absorb at least a significant amount of the force applied to the tank car  100  in an impact or derailment scenario, thus reducing the likelihood that the shell of the inner tank  104  will be breached. 
       Puncture Resistance 
       [0038]    The tank car  100  preferably has a shell impact energy absorption of at least about 2.5 million foot-pounds at the tank centerline, and a head impact energy absorption of at least about 1.5 million foot-pounds at a point that is about 29 inches below the tank centerline. This can be about a 1.5 times increase in shell impact energy absorption, and a 1.4 times increase in head impact energy absorption, over current tank car designs, as shown in the Table 1 below. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Shell Impact energy 
                 Head Impact energy 
               
               
                 Type of Tank Car 
                 (ft-lbs) 
                 (ft-lbs) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Conventional 500 lb. Car 
                 1,261,000 
                 782,000 
               
               
                 Interim 600 lb. Car 
                 1,742,000 
                 1,100,000 
               
               
                 Subject Tank Car 
                 2,500,000 
                 1,500,000 
               
               
                   
               
             
          
         
       
     
       Example 1 
     Shell Puncture 
       [0039]    With reference to Table 2, tank cars having an inner tank and an outer tank were analyzed, using finite element analysis, for shell impact energy absorption using a ram, as shown in  FIGS. 10 and 11 . The ram had a total weight of 286,000 pounds and a wedge shaped ram head  502  with a 6 inch by 6 inch impact face  504 . As shown in  FIGS. 10 and 11 , the test was conducted by driving the ram into tank car at the centerline  506  of the tank outer shell  508 . The impact energy, delivered by the ram was varied by changing the speed of the ram when it impacts the tank car, known as the ram impact speed. The shell impact energy absorption of a particular tank car is the maximum amount of impact energy that the shell of the tank car can absorb without puncturing. 
         [0040]    The first and second tank car designs each had an inner tank shell  510  having a cylindrical length of about 472 inches and an inner diameter of about 100 inches, made of TC 128 GR B steel having a thickness of 0.4688 of an inch. The inner tank was pressurized at about 100 psi. The inner tank heads were 2:1 ellipsoidal heads made of TC 128 GR B steel, and the overall length of the inner tank car was about 522 inches as measured from the center point of the inner tank head at one end of the inner tank to the center point of the inner tank head at the opposite end of the inner tank. 
         [0041]    The first tank car design had an inner and outer tank shell  508  made of TC 128 GR B steel having a thickness of 0.4688 inches, and a tank to tank standoff of about 4 inches. The ram impact speed was about 16.2 miles per hour (mph), delivering an impact energy of about 2.5 million foot-pounds. The impact energy delivered by the ram upon impact with the first tank car caused deformation of the outer tank shell and the inner tank shell, and also resulted in both shells being punctured. Calculations showed that the outer tank shell punctured at a ram displacement of about 29 inches and a peak force of about 855,000 pounds. The inner tank shell punctured rapidly after failure of the outer tank shell. The impact energy absorption at failure was calculated to be about 1.32 million foot-pounds. The results of the testing for the first tank car design are shown in row 7 of Table 2 below. 
         [0042]    The second tank car design had an outer tank shell  508  made of TC 128 GR B steel having a thickness of 0.777 inches, and a tank to tank standoff of about 4 inches. The ram impact speed was about 16.2 miles per hour (mph), delivering an impact energy of about 2.5 million foot-pounds. As shown in  FIG. 11 , the impact energy delivered by the ram caused deformation of the outer tank shell  508  and the inner tank shell  510 , but the outer jacket resisted the impact forces of the ram and neither outer tank shell  508  nor the inner tank shell  510  was punctured. The maximum ram displacement was about 42 inches, and the shell impact energy absorption was at least 2.5 million foot-pounds since the delivered impact energy of that amount was absorbed and dissipated by the tank deformation. The results of the testing for the second tank car design at this ram speed are shown in row 8 in Table 2 below. 
         [0043]    The second tank car design was also tested at ram impact speeds of 17.7 mph, and 18.8 mph, and 20.0 mph, which delivered impact energies of 3.0 million ft-lbs, 2.6 million ft-lbs, and 2.6 million ft-lbs, respectively. The 3.0 million ft-lb impact energy was sufficient to initiate fractures in the 0.777 inches thick outer tank shell, but the outer tank shell was not fully penetrated and no fractures were initiated in the inner tank shell. Thus, the puncture threshold of the tank car is higher than the 3.0 million ft-lb impact energy. However, when the impact speed was further increased to 18.8 mph and 20.0 mph, puncture of the tank car resulted. Calculations determined that the puncture occurred at a an impact energy of approximately 2.6 million ft-lbs. Without being bound by any particular theory, it is believed that the puncture resulted due to additional dynamic effects that are introduced in the tank car response to impact at these higher speeds. Accordingly, the inertial effects at the higher speeds resulted in the impact forces exceeding the puncture threshold for the tank car at a lower displacement than was achieved when the impact speed was at the slightly reduced 17.7 mph. However, in each instance, the tank car still maintained a impact energy absorption above 2.5 million ft-lbs. The additional results of the testing for the second tank car design at these higher speeds are shown in rows 9-11 of Table 2 below. 
         [0044]    The third tank car design had an outer tank shell  508  made of TC 128 GR B steel having a thickness of 0.7145 inches, and a tank to tank standoff of about 4 inches. The third tank car design had an inner tank shell  510  having a cylindrical length of about 472 inches and an inner diameter of about 100 inches, made of TC 128 GR B steel having a thickness of 0.5625 of an inch. The inner tank was pressurized at about 100 psi. The inner tank heads were 2:1 ellipsoidal heads made of TC 128 GR B steel, and the overall length of the inner tank car was about 522 inches as measured from the center point of the inner tank head at one end of the inner tank to the center point of the inner tank head at the opposite end of the inner tank. The third tank car design also tested at ram impact speed of 17.7 mph, which delivered impact energies of 3.0 million ft-lbs. The 3.0 million ft-lb impact energy was determined to be at the puncture threshold for the third tank car design. The results of the testing for the third tank car design are shown in row 12 of Table 2 below. 
         [0045]    Testing was conducted on additional tank car designs as reported in Table 2 below. The dimensions and materials of the tank car designs, and the ram impact conditions, were the same as those above except for the dimensions noted in Table 2. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Inner 
                 Outer  
                   
                 Internal 
                 Puncture 
                 Puncture 
               
               
                   
                 Tank 
                 Tank 
                 Impact 
                 Pressure 
                 Force 
                 Energy 
               
               
                 No. 
                 Shell 
                 Shell 
                 Speed 
                 (psi) 
                 (lbs) 
                 (ft-lbs) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 0.5625 in 
                 0.119 in 
                 20.0  
                 100 psi 
                   676,000 
                   673,000 
               
               
                   
                 TC128B 
                 A1011 
                 mph 
                   
                   
                   
               
               
                 2 
                 0.777 in 
                 0.119 in 
                 20.0  
                 100 psi 
                   915,000 
                 1,261,000 
               
               
                   
                 TC128B 
                 A1011 
                 mph 
                   
                   
                   
               
               
                 3 
                 0.981 in 
                 0.119 in 
                 20.0  
                 100 psi 
                 1,152,000 
                 1,742,000 
               
               
                   
                 TC128B 
                 A1011 
                 mph 
                   
                   
                   
               
               
                 4 
                 0.777 in 
                 0.375 in 
                 20.0  
                 100 psi 
                 1,010,000 
                 1,732,000 
               
               
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
                   
               
               
                 5 
                 0.5625 in 
                 0.119 in 
                 20.0  
                 100 psi 
                   686,000 
                   675,000 
               
               
                   
                 TC128B 
                 A1011 
                 mph 
                   
                   
                   
               
               
                 6 
                 0.777 in 
                 0.5625 in 
                 20.0  
                 100 psi 
                 1,090,000 
                 2,175,000 
               
               
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
                   
               
               
                 7 
                 0.4688 in 
                 0.4688 in 
                 16.2  
                 100 psi 
                   855,000 
                 1,320,000 
               
               
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
                   
               
               
                 8 
                 0.4688 in 
                 0.777 in 
                 16.2  
                 100 psi  
                 (1,100,000) 1   
                 (2,500,000) 1   
               
               
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
                   
               
               
                 9 
                 0.4688 in 
                 0.777 in 
                 20.0  
                 100 psi 
                 1,230,000 
                 2,590,000 
               
               
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
                   
               
               
                 10 
                 0.4688 in 
                 0.777 in 
                 17.7  
                 100 psi  
                 (1,190,000) 1   
                 (3,000,000) 1   
               
               
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
                   
               
               
                 11 
                 0.4688 in 
                 0.777 in 
                 18.8  
                 100 psi 
                 1,220,000 
                 2,600,000 
               
               
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
                   
               
               
                 12 
                 0.5625 in 
                 0.7145 in 
                 17.7  
                 100 psi 
                 1,210,000 
                 3,000,000 
               
               
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
                   
               
               
                   
               
               
                 Note: 
               
               
                   1 Tank was not fully punctured at this impact velocity. 
               
             
          
         
       
     
       Example 2 
     Head Puncture 
       [0046]    Tank cars having an inner tank and an outer tank were analyzed for head impact energy absorption using a ram, as shown in  FIGS. 12 and 13 . The ram had a total weight of 286,000 pounds and a wedge shaped ram head  602  with a 6 inch by 6 inch impact face  604 . As shown in  FIGS. 12 and 13 , the test was conducted by driving the ram into head tank car at a point  606  that is about 29 inches below the tank centerline. The impact energy, delivered by the ram was varied by changing the speed of the ram when it impacted the tank car, known as the ram impact speed. The head impact energy absorption of a particular tank car is the maximum amount of impact energy that the head of the tank car can absorb without puncturing. 
         [0047]    Three test designs for the outer tank were evaluated, each having identical inner tank geometries, with a 0.879 inch thick TC128 Gr B steel inner tank head  610  and a 0.4688 inch thick TC128 Gr B steel inner tank shell  614 . The inner tank head  610  for each tank car tested had a diameter that was nominally about 100 inches, and the inner tank was pressurized to an internal pressure of 100 psi. The geometry of the inner tank head  610  for each tank car was a 2:1 ellipsoid. The outer tank head  612  for each tank car had a 108 inch inner diameter and a dished geometry with a tank to tank clearance of 4 inches from the inner tank head  610 . 
         [0048]    The ram impact speed used for the initial head impact energy absorption analyses of all three outer tank test designs was 12.52 mph, which delivered an impact energy of 1.5 million ft-lbs. As shown in  FIG. 13 , the impact energy delivered by the ram caused at least deformation of the outer tank head  612  and the inner tank head  610  for each tested design, and also resulted in puncturing some of the tested designs as described below. 
         [0049]    The first outer tank design had a 0.500 inch thick TC128 Gr B steel outer tank head  612 , and a 0.375 inch thick TC128 Gr B steel outer tank shell  616 . The outer tank head  612  was punctured at a ram displacement of approximately 18 inches and a peak ram force of approximately 1.06 million lbs. The inner tank head  610  was punctured at a ram displacement of approximately 22 inches and a ram force of 1.06 million lbs. The head puncture energy at puncture of the inner tank head  610  was calculated to be about 1.11 million ft-lbs. The results for the first design are listed in row 16 of Table 3 below. 
         [0050]    The second outer tank design had a 0.879 inch thick TC128 Gr B steel outer tank head  612 , and a 0.375 inch thick TC128 Gr B steel outer tank shell  616 . The outer tank head  612  was partially penetrated late in the impact response, at a ram displacement of approximately 20 inches and a peak force of approximately 1.57 million lbs. However, the ram was stopped at a maximum displacement of approximately 21 inches, and the inner tank head  610  was not punctured. The entire impact energy of 1.5 million ft-lbs was absorbed and dissipated by this second design. The results for the second design are listed in row 17 of Table 3 below. 
         [0051]    The third outer tank design had a 0.879 inch thick TC128 Gr B steel outer tank head  612 , and a 0.777 inch thick TC128 Gr B steel outer tank shell  616  to be consistent with some of the outer tank shell designs of Example 1. The outer tank head  612  was partially penetrated late in the impact response, at a ram displacement approximately 19 inches and a peak force of approximately 1.59 million lbs. The ram was stopped at a maximum displacement of approximately 21 inches, and the inner tank head  610  was not punctured. The entire impact energy of 1.5 million ft-lbs was absorbed and dissipated by this third design. The results for the third design are listed in row 18 of Table 3 below. 
         [0052]    To establish the maximum puncture energy that the third outer tank design can withstand, additional testing was performed at a higher ram impact speed of 14.5 mph, corresponding to an impact energy of 2.0 million ft-lbs. The higher speed impact was sufficient to puncture both the outer tank head and the inner tank head with a puncture energy of 1.86 million ft-lbs. The results for the third design at the higher speed are listed in row 19 of Table 3 below. 
         [0053]    Testing was conducted on additional tank car designs as reported in Table 3 below. The dimensions and materials of the tank car designs, and the ram impact conditions, were the same as those above except for the dimensions noted in Table 3. The inner tank heads were all made of TC128 Gr B steel having a thickness indicated in Table 3 below, and the inner tank shells were all 0.4688 inch thick TC128 Gr B steel. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                   
                 Inner 
                 Outer 
                 Outer  
                   
                 Puncture 
                 Puncture 
               
               
                   
                 Tank 
                 Tank 
                 Tank 
                 Impact 
                 Force 
                 Energy 
               
               
                 No. 
                 Head 
                 Head 
                 Shell 
                 Speed 
                 (lbs) 
                 (ft-lbs) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 1.1360″ 
                 0.500″   
                 11 gauge  
                 14    
                 1,206,000 
                 1,121,000 
               
               
                   
                   
                 A572-50 
                 A1011 
                 mph 
                   
                   
               
               
                 2 
                 0.8281″ 
                 0.500″  
                 11 gauge  
                 10    
                   966,000 
                   916,000 
               
               
                   
                   
                 A572-50 
                 A1011 
                 mph 
                   
                   
               
               
                 3 
                 0.8281″ 
                 0.8281″ 
                 11 gauge  
                 14    
                 1,289,000 
                 1,321,000 
               
               
                   
                   
                 TC128B 
                 A1011 
                 mph 
                   
                   
               
               
                 4 
                 1.1360″ 
                 0.500″  
                 11 gauge  
                 11    
                 1,229,000 
                 1,110,000 
               
               
                   
                   
                 A572-50  
                 A1011 
                 mph 
                   
                   
               
               
                 5 
                 0.6030″ 
                 0.8281″ 
                 0.375″  
                 11    
                 (1,240,000) 3   
                 (1,190,000) 3   
               
               
                   
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
               
               
                 6 
                 0.6030″ 
                 0.500″   
                 11 gauge  
                 10    
                   813,000 
                   782,000 
               
               
                   
                   
                 A572-50 
                 A1011 
                 mph 
                   
                   
               
               
                 7 
                 0.6030″ 
                 0.8281″ 
                 0.375″  
                 14    
                 1,316,000 
                 1,537,000 
               
               
                   
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
               
               
                 8 
                 0.8281″ 
                 0.8281″ 
                 11 gauge  
                 14    
                 1,311,000 
                 1,482,000 
               
               
                   
                   
                 TC128B 
                 A1011 
                 mph 
                   
                   
               
               
                 9 
                 0.8281″ 
                 0.680″   
                 0.375″  
                 14    
                 1,292,000 
                 1,390,000 
               
               
                   
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
               
               
                 10 
                 0.8281″ 
                 11 gauge  
                 11 gauge  
                 10    
                   813,000 
                   610,000 
               
               
                   
                   
                 A1011 
                 A1011 
                 mph 
                   
                   
               
               
                 11 
                 0.8281″ 
                 0.8281″ 
                 11 gauge  
                 10    
                 1,218,000 
                 1,494,000 
               
               
                   
                   
                 TC128B 
                 A1011  
                 mph 
                   
                   
               
               
                 12 
                 0.8281″ 
                 0.680″   
                 0.375″  
                 14    
                 1,195,000 
                 1,252,000 
               
               
                   
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
               
               
                 13 
                 0.8281″ 
                 0.500″   
                 11 gauge  
                 14    
                   952,000 
                 1,100,000 
               
               
                   
                   
                 A572-50 
                 A1011 
                 mph 
                   
                   
               
               
                 14 
                 0.8281″ 
                 0.680″   
                 11 gauge  
                 14    
                 1,189,000 
                 1,281,000 
               
               
                   
                   
                 TC128B 
                 A1011 
                 mph 
                   
                   
               
               
                 15 
                 0.8281″ 
                 0.8281″ 
                 0.375″  
                 14    
                 1,466,000 
                 1,661,000 
               
               
                   
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
               
               
                 16 
                 0.8790″ 
                 0.5000″ 
                 0.375″  
                 12.5 
                 1,056,000 
                 1,110,000 
               
               
                   
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
               
               
                 17 
                 0.8790″ 
                 0.8790″ 
                 0.375″  
                 12.5  
                 (1,565,000) 3   
                 (1,500,000) 3   
               
               
                   
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
               
               
                 18 
                 0.8790″ 
                 0.8790″ 
                 0.777″  
                 12.5  
                 (1,586,000) 3   
                 (1,500,000) 3   
               
               
                   
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
               
               
                 19 
                 0.8790″ 
                 0.8790″ 
                 0.777″  
                 14.5  
                 1,586,000 
                 1,860,000 
               
               
                   
                   
                 TC128B 
                 TC128B 
                 mph 
                   
                   
               
               
                   
               
             
          
         
       
     
       Example 3 
       [0054]    A tank car of the present technology having a tank to tank clearance of about 4 inches was made having the following dimensions:
       An inner tank shell having an inner diameter of 100.625 inches made of TC 128 GR B steel having a thickness of 15/32 of an inch.   An inner tank head made of TC 128 GR B steel having a thickness of 0.879 inches.   An outer tank shell having an inner diameter of 109.5625 inches made of TC 128 GR B steel having a thickness of 0.777 inches.   An outer tank head made of TC 128 GR B steel having a thickness of 0.879 inches.       
 
         [0059]    The shell impact energy absorption of the tank car was determined to be about 3.0 million foot-pounds at the tank car centerline, and the head impact energy absorption was determined to be about 1.9 million foot-pounds at a point about 29 inches below the tank car centerline. 
         [0060]    From the foregoing, it will be appreciated that although specific examples have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit or scope of this disclosure. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to particularly point out and distinctly claim the claimed subject matter.