Patent Publication Number: US-6910427-B2

Title: Security device and method to prevent unauthorized discharge of contents from a tank

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application Ser. No. 60/418,650, entitled Security Device and Method to Prevent Unauthorized Discharge of Contents from a Tank, filed Oct. 15, 2002, which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention is related to railway tank cars and more particularly to security devices to prevent unauthorized access to valves, fittings and other components associated with such tank cars. 
     BACKGROUND OF THE INVENTION 
     Tank cars have been used for many years to transport a wide variety of commodities including liquids, gasses and other fluids. The contents of a tank car may sometimes be potentially hazardous if appropriate safety precautions are not taken. Also, the contents of a tank car may be valuable and subject to theft or misappropriation. 
     Most tank cars are designed with an access opening or manway located in the upper portion of the associated tank, proximate a midpoint between opposite ends of the tank car. A manway cover is typically bolted or otherwise secured to the opening to allow only limited access by personnel to the interior of the tank. Various pipes, valves, fittings and other components are also often located in the vicinity of the manway to control adding and discharging lading from the tank car. The valves, fittings and other components are typically selected based on characteristics and properties of the commodity or lading being transported. 
     Valves, fittings and other components are often mounted on the manway cover of modern pressurized tank cars. Pressure car fittings typically include two “liquid or fluid” valves for loading and unloading of an associated commodity. Respective check valves and induction piping are also provided with respective loading and unloading valves. One or more vapor valves, gauging devices and safety relief valves may also be mounted on the manway cover. Some tank cars may have smaller valves for drawing samples of lading and thermal wells for measuring the temperature of the lading. Non-pressurized tank cars may also have similar valves and fittings mounted on a manway cover similar to a pressurized tank car. 
     Various types of protective housing assemblies or dome structures are often disposed on the upper portion of a tank car adjacent to the manway to protect associated piping, valves, fittings and other components. All pressurized tank cars are required to have such protective housing assemblies or dome structures covering any pipes, valves, fittings and other components located on an upper portion of the pressurized tank car. A relatively thick, steel ring or cylindrical portion is often provided to protect the valves, fittings, and other components in the event the tank car is derailed and overturns. 
     Protective housing assemblies and/or dome covers on a typical railway tank car will often include one or more openings which provide access through a sidewall or cylindrical portion of the protective housing to facilitate loading and/or unloading of products carried by the tank car. Multiple ports or openings (sometimes referred to as “portholes”) formed in a protective housing assembly allow access to operate respective valves and fittings disposed within the protective housing assembly. Most portholes have a hinged, flap type cover that may be easily opened and closed as required to provide access through the porthole to an adjacent valve or fitting. Other portholes or openings may remain open without any cover. Unauthorized access may often be obtained to valves and/or fittings used to load or unload tank cars by simply moving these unsecured covers and reaching into the protective housing assembly to manipulate the associated valves and fittings. 
     SUMMARY OF THE INVENTION 
     In accordance with teachings of the present invention, security devices and methods are provided to prevent unauthorized access to, and unauthorized operation of valves, fittings or other components associated with discharging fluids from a railway tank car. The security devices may include respective porthole covers that restrict or block access to such components when an associated protective housing assembly has been properly closed and secured. The security devices and associated porthole covers are designed to prevent and/or minimize any damage to the porthole covers, protective housing assembly, fittings and/or valves during an attempt to gain unauthorized access to the valves and fittings. 
     In accordance with a particular embodiment of the present invention a protective housing assembly includes a cylindrical sidewall configured to be coupled with a tank to generally surround at least one valve of the tank. An access cover is configured to be removably disposed over the cylindrical sidewall. A diameter of the access cover is slightly larger than a diameter of the cylindrical sidewall, such that an outer portion of the access cover overhangs the cylindrical sidewall, when the access cover is in a first, closed position. A hinge assembly is coupled to the cylindrical sidewall and the access cover, and is configured to allow the access cover to be moved to a second, open position wherein an interior portion of the cylindrical sidewall is exposed to a user. The cylindrical sidewall may have at least one porthole disposed therein. The protective housing assembly also includes a porthole cover having a first position in which the porthole cover covers the porthole, and a second position in which the porthole is exposed. In accordance with a particular embodiment, the access cover prevents the porthole cover from being moved from the first position to the second position, when the access cover is in the closed position. 
     The protective housing assembly may also include a pivot pin that is disposed through the porthole cover and coupled to the cylindrical wall. The pivot pin allows rotation of the porthole cover from the first position to the second position. In accordance with one embodiment, the porthole cover is disposed upon an exterior surface of the cylindrical wall. In this embodiment, the upper portion of the access cover may cooperate with an upper edge of the porthole cover to prevent the porthole cover from being rotated from the first position to the second position, when the access cover is in the closed position. 
     In accordance with another embodiment, the access cover may form at least one slot in the outer portion of the access cover. In this embodiment, an upper portion of the porthole cover may be disposed in the slot, to prevent rotation of the porthole cover from the first position to the second position, when the access cover is in the closed position. 
     Technical benefits of the present invention include preventing unauthorized access to valves, fittings or components such as loading and unloading valves associated with a tank car. Security devices formed in accordance with teachings of the present invention prevent or block access through portholes or openings which are often formed in protective housing assemblies associated with tank cars. The security devices prevent operation of unloading valves or other components which would allow unauthorized removal of fluids from a tank car or unauthorized release of potentially hazardous fluids to the surrounding environment. Anhydrous ammonia is one example of a commodity that may be stolen from tank cars. Security devices incorporating teachings of the present invention prevent unauthorized access to valves and fittings used to control loading and unloading of lading from a tank car and at the same time allow normal loading and unloading procedures when proper access is obtained by opening the protective housing assembly. 
     Further technical benefits of the present invention include providing security devices which are relatively light weight and may be manufactured with relatively low cost. Such security devices may be activated or deactivated by normal opening or closing of an associated protective housing assembly or dome structure. The security devices may be formed as integral components of a protective housing assembly or dome structure. Alternatively, security devices formed in accordance with teachings of the present invention may be added on to an existing housing assembly or dome structure. Security devices incorporating teachings of the present invention do not interfere with normal emergency response procedures in the event of damage to an associated tank car or other emergency conditions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description, taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein: 
         FIG. 1  is a schematic drawing in elevation, with portions broken away, showing a conventional protective housing assembly or dome assembly mounted on a tank car surrounding a manway of the tank car, with the protective housing assembly in its first, closed position; 
         FIG. 2  is a schematic drawing showing an isometric view of a protective housing assembly formed in accordance with teachings of the present invention in its first, closed position which may block unauthorized access to valves, fittings or other components which control loading and unloading of commodities carried by an associated railway tank car (not shown); 
         FIG. 3A  is a schematic drawing showing the protective housing assembly of  FIG. 2  in its second, open position, which provides normal access to associated valves, fittings and other components; 
         FIG. 3B  is a schematic drawing in elevation, with portions broken away, illustrating an optional anti-bending lug that may be used with the protective housing assembly of  FIGS. 2 and 3A ; 
         FIG. 3C  is a partial, cross-sectional view, with portions broken away, illustrating a normal access cover suitable for use within the teachings of the present invention, which includes an optional vent opening cover and anti-access device; 
         FIG. 3D  is a schematic view in elevation, viewed from below, and illustrates the anti-access device of  FIG. 3C ; 
         FIG. 4  is a schematic drawing illustrating an isometric view of an alternative embodiment protective housing assembly formed in accordance with the teachings of the present invention, in its first, closed position; 
         FIG. 5  is a schematic drawing illustrating an isometric view of another alternative embodiment protective housing assembly formed in accordance with the teachings of the present invention, in its first, closed position (dotted lines illustrated partially open position); 
         FIG. 6A  is a cross-sectional view of an alternative embodiment protective housing assembly, including components suitable for use within the teachings of the present invention; 
         FIG. 6B  is a schematic drawing in elevation illustrating components of  FIG. 6A  in more detail; 
         FIG. 7A  is a cross-sectional view of an alternative embodiment protective housing assembly, including components suitable for use within the teachings of the present invention; and 
         FIG. 7B  is a schematic drawing in elevation, with portions broken away, illustrating components of the protective housing assembly of  FIG. 7A  in more detail. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the invention and its advantages are best understood by reference to  FIGS. 1-7B , wherein like numbers refer to same and like parts. 
     Various aspects of the present invention will be described with respect to a railway tank car satisfactory for carrying pressurized fluids. Such railway cars may sometimes be referred to as “pressure tank cars”. A protective housing assembly or dome assembly formed in accordance with teachings of the present invention may also be satisfactorily used on non-pressure tank cars to prevent unauthorized access to valves, fittings or other components which control loading or unloading of commodities carried by such tank cars. A protective housing assembly with one or more security devices formed in accordance with teachings of the present invention may also be used on other types of railway cars and other types of tanks such as tanks on highway trucks, tanks carried on barges and storage tanks located at either temporary or permanent facilities. The present invention is not limited to use with railway tank cars. 
     The terms “engage”, “engaged” and “engagement” are used in this application to describe various types of attachments, couplings, connections or mountings between one or more security devices and a protective housing assembly formed in accordance with teachings of the present invention. For example the term “engagement” may be used to describe a slideable connection between a security device and portions of a protective housing assembly. Engagement may be used to describe a rotatable or pivotable attachment between a security device and portions of a protective housing assembly. For some embodiments, the terms “engage”, “engaged” and “engagement” may be used to describe forming a security device as an integral component of a protective housing assembly. For other embodiments, the terms “engage”, “engaged” and “engagement” may be used to describe adding one or more security devices to an existing protective housing assembly. 
       FIG. 1  illustrates portions of a railway tank car  20  with a conventional protective housing assembly  30  mounted thereon. Tank car  20  preferably includes manway or access opening  22  located in an upper portion thereof, proximate a midpoint between opposite ends  21   a  and  21   b  of tank car  20 . Protective housing assembly  30  includes a generally hollow, cylindrical portion  32  and lid or normal access cover  34 . Hinge assembly  36  allows lid  34  to rotate between a first, closed position, as shown in  FIG. 1 , and a second, open position (not expressly shown). Cylindrical portion  32  may sometimes be referred to as a sidewall. 
     A protective housing assembly formed in accordance with teachings of the present invention may have various configurations and dimensions. The present invention is not limited to use with protective housing assemblies which have a generally hollow cylindrical portion or cylindrical sidewalls. A protective housing assembly having sidewalls with a wide variety of geometric configurations such as square, rectangular, triangular, etc. may be formed with security devices in accordance with teachings of the present invention. 
     The dimensions of cylindrical portion  32  may be selected to accommodate the outside diameter of manway  22  and manway cover  24 , to allow cylindrical portion  32  to generally surround the valves in manway cover  24 . Various valves and fittings designated  25 ,  26 ,  27 ,  28  and  29  may be mounted on manway cover  24  to control loading and unloading of commodities from tank car  20 . Protective housing assembly  30  prevents damage to valves and fittings  25  through  29  in the event tank car  20  is derailed and turns over. One of these valves will typically be a safety valve that discharges fluid from tank car  20  when the pressure of fluid contained therein exceeds a predetermined, maximum value. 
     A vent opening or discharge opening may also be formed in normal access cover  34  to allow any fluids discharged from the safety valve to exit from protective housing assembly  30 . The vent opening may also have a respective cover which opens and closes in response to any fluids discharged from the associated safety valve. 
     A plurality of portholes or openings  38  may be formed in cylindrical portion  32  of protective housing assembly  30 . Respective porthole covers  40  may be mounted on the exterior of cylindrical portion  32  adjacent to each porthole  30 . For the example shown in  FIG. 1 , portholes  38  and porthole covers  40  have generally circular configurations. Pivot pin  42  may be used to rotatably or pivotally mount each porthole cover  40  adjacent to respective porthole opening  38 . Porthole covers  40  may be rotated from a first closed position as shown in  FIG. 1  to a second, open position (not expressly shown) which allows access to and/or operation of adjacent valves  25  through  29 . 
       FIGS. 2 and 3A  illustrate protective housing assembly  70  formed in accordance with teachings of the present invention. Protective housing assembly  70  may include cylindrical portion  72 , normal access cover  74  and hinge assembly  76 . For the embodiment of the present invention as represented by protective housing assembly  70 , portholes  78  have a generally circular configuration. The dimensions associated with cylindrical portion  72 , normal access cover  74  and portholes  78  may correspond approximately with similar dimensions and configuration of cylindrical portion  32 , normal access cover  34  and portholes  38 , of FIG.  1 . 
     Protective housing assembly  70  is shown in  FIG. 2  in its first, closed position with normal access cover  74  blocking access to an associated manway, manway cover and any valves or fittings disposed on the manway cover.  FIG. 3A  shows protective housing assembly  70  in its second, open position which allows access to the associated manway cover and any valves or fittings disposed thereon. 
     For the embodiment of the present invention as shown in  FIGS. 2 and 3A , protective housing assembly  70  preferably includes at least four portholes  78  and at least four porthole covers  80 , respectively disposed on portholes  78 .  FIG. 2  illustrates porthole covers  80  in their first, closed position blocking access through the respective porthole  80 . In  FIG. 3A , one of the porthole covers  80  is shown in its second, open position (dotted lines), which allows access through the respective porthole  78 . 
     Respective pivot pins  82  may be used to rotatably or pivotally mount each porthole cover  80  adjacent to respective porthole opening  78 . The length of porthole covers  80  is selected such that when each porthole cover  80  is in its first position, the respective porthole cover  80  will extend from immediately adjacent to normal access cover  74  and cover the associated porthole  78 . The width of porthole covers  80  is preferably selected to be larger than the diameter of the associated porthole  78 . 
     For the embodiment of the present invention as shown in  FIGS. 2 and 3A , first end  81  of porthole cover  80  has an increased width that cooperates with normal access cover  74  to prevent rotation of each respective porthole cover  80  from its first position to its second position, when normal access cover  74  is in its first, closed position. The second end  84  of each porthole cover  80  may have a generally curved or accurate surface. The length of porthole covers  80  may be selected to be slightly less than the height of cylindrical portion or sidewall  72 . 
     The dimensions and configuration of porthole covers  80  are selected to prevent the opening of porthole covers  80  when normal access cover  74  is in the closed position. As illustrated in  FIG. 2 , normal access cover  74  overhangs cylindrical portion  72  and an upper edge  79  of porthole cover  80 , at first end  81 . Since porthole cover  80  is rotatably mounted to cylindrical portion  72  using pivot pins  82 , the cooperation of the upper edge of porthole cover  80  at first end  81  with the overhanging portion of normal access cover  74  prevents porthole cover  80  from rotating in either direction (clockwise or counterclockwise) with respect to pivot pin  82 . Thus, when normal access cover is locked or latched in the closed position, unauthorized access to the interior of protective housing assembly  70  is prevented. 
     In the illustrated embodiment, porthole cover  80  is formed from a metal plate that may generally conform to the circumference of cylindrical portion  72 . As long as the edge of normal access cover  74  overhangs at least a portion of the edge of the plate at first end  81 , porthole cover  80  will be prevented from rotating when normal access cover  74  is in its closed position. 
     Various configurations are available for porthole cover  80 , within the teachings of the present invention. In the illustrated embodiment, porthole cover  80  is generally a rectangular configuration proximate first end  81 . This configuration enhances the cooperation between porthole cover  80  and normal access cover  74  to prevent rotation of porthole covers  80  to expose portholes  78 , when normal access cover  74  is in the closed position. The second end  84  is arcuate and generally conforms to the curvature of porthole  78 , in order to fully cover porthole  78  when porthole  80  is in the closed position. Other sizes, configurations and features of porthole covers, portholes, and normal access covers that help prevent unauthorized access to the interior of the protective housing assembly are described herein. 
     Lid or normal access cover  74  may also include vent opening  86  and vent opening cover or flap  88 . A plurality of restrictions  90  and  91  are formed within vent opening  86  to prevent unauthorized access through normal access cover  74  when protective housing assembly  70  is in its first, closed position. For the embodiment of the present invention as shown in  FIG. 3A , restrictions  90  and  91  may be bars formed as integral components of normal access cover  74 . For other applications which will be discussed later in more detail, other types of restrictions, such as heavy metal screens may be engaged with an interior surface of a normal access cover  74  adjacent to an associated vent opening, to allow any fluids discharged from a safety valve to escape therethrough and at the same time to prevent access through the vent opening to one or more valves disposed within the associated protective housing assembly. 
       FIG. 3B  illustrates an additional feature that may be incorporated into protective housing assembly  70 , of  FIGS. 2 and 3 . An anti-bending lug  96  is incorporated into protective housing assembly  70 , to further prevent unauthorized access to the interior of protective housing assembly  70 . Anti-bending lugs  96  prevent an unauthorized user from prying porthole cover  80  away from cylindrical portion  72  to potentially fracture pin  82  and/or allow rotation of porthole cover  80  about pin  82  when normal access cover  74  is in the closed position. 
     Anti-bending lugs  96 , in the illustrated embodiment, comprise metal angles that are affixed to protective housing assembly  70 , independent of porthole cover  80 . Therefore, porthole cover  80  may slide through a gap between an upper leg  97  of anti-bending lug  96 , and cylindrical portion  72  of protective housing assembly  70 . Anti-bending lugs  96  may be welded or otherwise affixed to a lower edge of cylindrical portion  72 , or welded or otherwise affixed to another portion of protective housing assembly  70  (other than porthole cover  80 ). In an alternative embodiment, anti-bending lug  96  may be formed integrally with cylindrical portion  72  or another component of protective housing assembly  70 . 
       FIG. 4  illustrates an alternative embodiment of the present invention, as represented by protective housing assembly  70   a . Protective housing assembly  70   a  may include cylindrical portion  72   a , lid or normal access cover  74   a  and hinge assembly  76   a  having approximately the same overall dimensions and configurations as the corresponding components previously described with respect to protective housing assembly  70 . In  FIG. 4 , normal access cover  74   a  is shown in its first, closed position (solid lines). Cylindrical portion  72   a  of protective housing assembly  70   a  may also include portholes  78   a  (shown in dotted lines) having approximately the same dimensions and configurations as previously described with respect to protective housing assembly  70 . 
     Respective porthole covers  180  are pivotally or rotatably mounted on the exterior of cylindrical portion  72 , adjacent to each porthole  78   a  by pivot pins  42   a . Each porthole cover  80  preferably includes first portion  191  and second portion  192 . First portion  191  may be generally described as having an elongated, rectangular configuration. Second portion  192  has a generally circular configuration. Pivot pins  42  are disposed through porthole covers  180  proximate the juncture between first portion  191  and second portion  102 . The dimensions and configuration of second portion  192  are preferably selected to be greater than the associated porthole  78   a  such that when porthole covers  180  are in their first position, second portion  192  will block or restrict access through the respective porthole  78 . 
     First portion  191  is generally rectangular in configuration. The shorter leg of the rectangle is relatively narrow, and approximately equal to one third of the diameter of second portion  192 . The width (e.g., diameter) of second portion  192  is selected such that it is slightly larger than porthole  78   a , and completely covers porthole  78   a  when porthole cover  180  is in the closed position. The configuration of porthole cover  180  reduces the overall size of porthole cover  180 , for example by including the relatively thin, rectangular first portion  191 . Accordingly, porthole cover is smaller, lighter, easier to handle and install, and easier to operate. However, it still effectively prevents unauthorized access to the interior portion of the protective housing assembly  70   a.    
     Normal access cover  74   a  may have approximately the same configuration and dimensions as previously described with respect to protective housing assembly  70 . However, normal access cover  74   a  may also be provided with a plurality of slots  171  which are formed in lid  74   a . The location of each slot  171  may be selected to correspond with the location of porthole  78   a  in cylindrical portion  72   b . The width of each slot  171  is selected to be slightly greater than the width of first portion  191  of the associated porthole cover  180 . When lid or normal access cover  74   a  is in its first, closed position, a portion of porthole cover  180  will extend through respective slot  171 . Engagement between first portion  191  and slot  171  prevents movement of porthole cover  180  from its first, closed position to its second, open position, when normal access cover or lid  74   a  is in its first, closed position. 
     This configuration allows for a rectangular first portion  191  having a relatively thin profile, and still protect unauthorized access to the interior of protective housing assembly  70   a . In accordance with a particular embodiment of the present invention this configuration prevents an unauthorized user from bending the top edge of the porthole cover away from cylindrical portion  72  beyond the overhang of normal access cover  74  of  FIGS. 10 and 11 , which may provide unauthorized access to protective housing assembly  70 , if the associated components were not sturdy enough. 
       FIG. 5  illustrates another alternative embodiment of the present invention as represented by protective housing assembly  70   b . Protective housing assembly  70   b  may include cylindrical portion  72   b , normal access cover  74   b  and hinge assembly  76   b , having approximately the same overall dimensions and general configurations as similar components previously described with respect to protective housing assembly  70 . In  FIG. 5 , normal access cover  74   b  is shown in its first, closed position (solid lines) and its second, partially open position (dotted lines). Cylindrical portion  72   b  of protective housing assembly  70   b  may also include portholes  78   b  (shown in dotted lines) having approximately the same dimensions and configuration as previously described with respect to protective housing assembly  70 . 
     For the embodiment of the present invention as shown in  FIG. 5 , respective porthole covers  80   b  may be formed as integral components of normal access cover  74   b . For some applications, first ends  81   b  of each porthole cover  80   b  may be welded or otherwise bonded with the edge of normal access cover  74   b . For other applications, porthole covers  80   b  may be formed from the same sheet of material which is used to form normal access cover  74   b . The length of each porthole cover  80   b  from first end  81   b  to second end  82   b  may be approximately equal to, but less than the height of cylindrical portion  72   b . The width of porthole covers  80   b  may vary from first end  81   b  to second end  82   b . For example, in the illustrated embodiment, porthole cover  80   b  is wider proximate normal access cover  74   b  and tapers to a thinner portion at a lower end  82   b.    
     When lid or normal access cover  74   b  is in its first, closed position, a portion of each porthole cover  80   b  will extend over and block access through respective portholes  78 . When lid or normal access cover  74   a  is in its second, open position (dotted line position in  FIG. 9 ) porthole covers  80   b  will be in their second position, which allows access through respective portholes  78   b.    
     For some applications, protective housing assemblies  70   a  and  70   b  may have four portholes  78  formed therein and four porthole covers  180  and  80   b . However, a protective housing assembly may be formed in accordance with teachings of the present invention having any number of portholes and porthole covers. 
     For some applications, a generally cylindrical skirt (not expressly shown) may be attached to and extend from a normal access cover similar to the relationship between porthole covers  80   b  and normal access cover  74   b . Appropriate slots or openings (not expressly shown) may be provided in the cylindrical portion or skirt as required to accommodate hinge assembly  76  and locking mechanism  94 . Examples of locking mechanisms satisfactory for use with the present invention are shown in  FIGS. 2-6 . 
     Vent opening cover  88  is illustrated in more detail in FIG.  3 C. Vent opening cover  88  provides partial access to vent opening  86 , without allowing unauthorized access. Vent opening  86  may be disposed above a safety valve vent similar to vent  28  of FIG.  1 . The safety valve vent is used as a safety precaution to allow the release of any tank contents that are vented through a safety valve associated with the tank car. 
     Traditional safety vent covers allowed for unauthorized access to the interior of protective housing assembly  70 . Vent opening cover  88  is configured such that it may only be opened partially, but still allows for safe venting of gas and liquids from the interior of protective housing assembly  70 . 
     Vent opening cover  88  may have a similar configuration to previous vent covers and those described in this specification. However, vent opening cover includes an extension leg  100  that is disposed at an acute angle α to an adjacent portion of normal access cover  74 . Thus, when vent opening cover  88  is lifted, extension leg  100  cooperates with normal access cover  74  to prevent vent opening cover  88  from being opened beyond an amount where the angle between main plate  102  of vent opening cover  88  and the surface of normal access cover  74  exceeds the angle α. 
     Thus, vent opening cover  88  prevents access to the interior of the fittings protective housing through the protective housing vent, while the protective housing cover is closed and pinned. Permanent application of this semi-open closure prevents access to the interior of protective housing assembly  70  (when normal access cover  74  is locked, latched, or otherwise pinned), while still allowing mandatory venting of the protective housing assembly. 
     An anti-access device  103  suitable use in a particular embodiment of the present invention is illustrated in  FIGS. 3C and 3D . Anti-access device  103  can be of solid construction (e.g., cast or sheet metal), or multi-piece such as a ring with wire cross members, or wire cross members attached directly to the bottom side of the vent opening cover  88 . 
     As is most evident in  FIG. 3D , anti-access device  103  comprises a ring  104  having wire cross members  106  extending thereacross. Another set of wire cross member  108  extend across ring  104  and are oriented generally perpendicular with wire cross members  106 . 
     It should be recognized by those of ordinary skill in the art that anti-access device  103  is an optional component. Anti-access device  103  may be particularly suited for applications in which restrictions  90  and  91  are not formed in normal access cover  74 . In this embodiment, vent opening  86  will form a circular opening, as illustrated by opening  86   a  of FIG.  3 D. As further evident from  FIGS. 3C and 3D , anti-access device  103  is an optional component that may be attached to an interior surface of normal access cover  74 , to prevent unauthorized access to valves. 
     An alternative configuration for a porthole cover  110 , pivot pin  112 , and associated components of porthole cover  110 , is illustrated in  FIGS. 6A and 6B .  FIG. 6A  illustrates a mounting flange  114  that is used to secure protective housing assembly  108  to a tank car or other type of tank fitting. A cylindrical portion  116  of protective housing assembly  108  may be configured similarly to other cylindrical portions, or sidewalls described herein. Such a cylindrical portion includes a porthole at the location designated by the reference number  118 . A normal access cover  120  is also provided, that is similar in configuration to other normal access covers described within this specification. 
     Porthole cover  110  protects protective housing assembly  108  from unauthorized access by a user, since the porthole cover  110  is mounted inside the protective housing assembly, out of reach of the user when normal access cover  120  is in a closed position. The purpose of porthole cover  110  is to prevent access to the interior of the fittings&#39; protective housing through the porthole, while the protective housing lid is closed and/or pinned. The design is similar to others described within this specification, except that the porthole cover  110  is installed on the inside of the housing. Also, protective housing assembly  108  of  FIG. 6A , includes two retainer lugs  122 . Retainer lugs  122  are situated on either side of an anti-pivot tail  124  that is integral to porthole cover  110 . As illustrated in  FIGS. 6A and 6B , as normal access cover  120  is closed, retainer lugs  122  trap anti-pivot tail  124  in a space between retainer lugs  122 , preventing the porthole cover from opening. Thus, normal access cover  120  must be in an open position (at least partially) in order for porthole cover  110  to be free to rotate away from porthole  118 , and provide access to any valves within protective housing assembly  108 . 
     Protective housing assembly  108  also includes an anti-bending lug  126  that prevents porthole cover  110  from being bent inwardly, with respect to cylindrical portion  116 . Anti-bending lug  126  may be sized, configured, and formed from materials similar to anti-bending lug  96  of  FIG. 3B. A  washer  128  is provided upon pivot pin  112 , in order to maintain porthole cover  110  pivotally mounted upon pivot pin  112 . 
     Another alternative configuration for a porthole cover  140 , and associated components of porthole cover  140 , are illustrated in  FIGS. 7A and 7B .  FIG. 7A  illustrates a mounting flange  142  that is used to secure protective housing assembly  144  to a tank car or other type of tank fitting. A cylindrical portion  146  of protective housing assembly  144  may be configured similarly to other cylindrical portions, or sidewalls described herein. Such a cylindrical portion includes a porthole  148  (dotted lines in FIG.  7 B). A normal access cover  150  is also provided, that is similar in configuration to other normal access covers described within this specification. 
     Porthole cover  140  protects protective housing assembly  144  from unauthorized access by a user, since the porthole cover  140  is mounted inside the protective housing assembly, out of reach of the user when normal access cover  150  is in a closed position. The purpose of porthole cover  140  is to prevent access to the interior of the fittings protective housing through the porthole, while the protective housing lid is closed and/or pinned. 
     A pair of retainer guides  154  are coupled with cylindrical portion  146 , and configured to allow porthole cover  140  to slide vertically, with respect to cylindrical wall  146 . The configuration of porthole cover  140  is such that a lifting stop  156  protrudes upward toward normal access cover  150 , to within a distance d of a lower edge of normal access cover  150 . A lifting tab  158  protrudes inward from porthole cover  140 . Lifting tab  158  provides a surface for a user to engage porthole cover  140 , and slide porthole cover  140  upward with respect to cylindrical wall  146 . 
     In operation, when normal access cover  150  is in its closed position, porthole cover  140  will only be free to slide vertically a distance d, before lifting stop  156  engages a lower edge of normal access cover  150 . Thus, as long as normal access cover  150  is in its closed position, porthole cover  140  cannot be lifted by an amount sufficient to expose porthole  148 . Accordingly, an unauthorized user cannot gain access to the interior of protective housing assembly  144 , through porthole  148 , while normal access cover  150  is pinned and/or locked in a closed position. 
     Various materials may be used to form the various components of the protective housing assemblies described herein. For example, various metals, plastics, composites and/or metal alloys may be used. The particular material selected may be based upon the type of material carried in the associated tank. Furthermore, the specific type of material may be recommended or required by various governing bodies that control the transportation of materials carried in the tank, for example the American Association of Railroads (AAR). 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the following claims.