Abstract:
A discharge outlet is provided for attachment to a double wall containment tank assembly having an inner tank and an outer containment vessel. The discharge outlet includes a conduit fluidically connected to the fluid receiving chamber of the inner tank and extending exteriorly of the outer containment vessel, a flexible annular sealing member positioned between the inner tank and the outer containment vessel, and couplers for attaching the sealing member to the inner tank and the outer vessel in surrounding relationship to the conduit. The containment area between the two tanks which is designed fro containing spills from the inner tank is thereby fluidically isolated form the access opening through which the conduit passes.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention concerns a discharge outlet for use with a double wall tank assembly used for storing and dispensing large quantities of liquid. More particularly, it is concerned with a sealing boot for the discharge outlet which enables the liquid to be dispensed through openings in the side walls of the inner tank and outer vessel of the double wall tank assembly. 
     2. Description of the Prior Art 
     Storage of liquid in bulk is well known, and has evolved in importance due to environmental concerns over the escape of chemicals. In the past, it was common to store chemicals underground in large tanks where gravity was used to fill the vessels and the contents were periodically pumped for use. However, the problems associated with leading underground storage tanks has increased the usage of above ground storage tanks. Typically, one or more above-ground vessels have been placed in a “tank farm” where a concrete pad and berm help to contain and capture any problem. Rainwater received in the containment area must be monitored and treated if leakage is detected. This has proven very expensive, as the rainwater represents a large volume of liquid even though the leakage is isolated. 
     As a result, storage containers have been developed which include a double walled construction. Examples of containment tanks utilizing such construction are shown in U.S. Pat. Nos. 5,287,986 to Frost and U.S. Pat. No. 5,333,752 to Harding, Jr. While the double walled construction therein is an improvement over single walled tanks, they require filling and discharge to be accomplished from atop the tanks. This requires extra energy to be expended in pumping the liquid. The need to prevent leakage from a double walled containment tank assembly has thus not heretofore permitted effective discharge openings through the sidewalls of the component inner and outer tanks. Thus, there has developed a need for a containment tank assembly which is capable of use in a variety of environments, minimizes, leakage, and has reduced energy demands. 
     SUMMARY OF THE INVENTION 
     These objects have largely been met through the discharge outlet and sealing boot of the present invention. That is to say, the present invention effectively seals openings provided in the sidewalls of a containment tank assembly having an inner tank and an outer vessel. Moreover, the discharge outlet includes a sealing boot which captures liquid which might leak into the containment area between the inner tank and outer vessel. Advantageously, the sealing boot is flexible and thus accommodates relative movement between the inner tank and outer vessel, such as may be encountered by expansion of the inner tank during filling and external forces applied to the outer vessel. 
     The discharge outlet of the present invention broadly includes an inner tank flange assembly, an outer vessel flange assembly, and a sealing boot interconnecting the two flange assemblies, piping or conduit is preferably provided which extends from the inner flange assembly exteriorly of the outer vessel for attachment of a valve, piping or the like to effect the transfer of liquid from the tank. The sealing boot is preferably of a flexible material and is provided in the shape of a tire, whereby liquid leaking may be readily visually detected and repair of the inner tank assembly may be effected without deterioration of the containment capabilities of the double wall tank assembly. The piping of the discharge outlet, which is positioned relatively near the bottom of the side of the double wall tank assembly, may be further provided with additional piping interiorly of the inner tank and include a pipe opening near the bottom wall of the inner tank, thereby facilitating removal of most of the liquid within the inner tank when it is desired to be emptied. 
     These and other advantages of the discharge outlet of the present invention will be readily appreciated by those skilled in the art with reference to the drawings and the following description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a exploded view of a double wall containment tank assembly, showing the opening in the outer vessel for receiving the discharge outlet positioned relatively low on the side thereof; 
     FIG. 2 is a perspective view of the double wall containment tank assembly shown in FIG. 1 with the inner tank nested in the outer vessel and showing anchor assemblies for holding the double wall containment tank assembly against movement relative to the supporting surface; 
     FIG. 3 is an enlarged, vertical sectional view taken through line  3 — 3  of FIG. 2 showing the discharge outlet mounted on the double wall containment tank assembly; and 
     FIG. 4 is an exploded view of the discharge outlet hereof. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawing, a discharge outlet  10  in accordance with the present invention is provided for mounting as part of a double wall containment tank assembly  12  used for bulk storage of liquids. The double wall containment tank assembly  12  includes an inner tank  14 , an outer vessel  16 , and a plurality of anchor assemblies  18  for securing the tank assembly  12  to a pad or other supporting surface  20 . The details of the structure of the tank assembly  12  are further described in my U.S. Patent Application entitled Containment Tank Assembly filed contemporaneously herewith as application Ser. No. 09/519,323 filed Mar. 6, 2000, the disclosure of which is incorporated herein by reference. 
     In greater detail, the inner tank  14  includes a lower section  22 , an upper section  24  which extends radially outwardly of lower section  22  and is connected thereto by a lip presenting a trough, and a roof  26  which acts as a cover to define a liquid-receiving chamber  28  therewithin. The lip includes a plurality of circumferentially spaced chutes to permit drainage from the trough back into the interior of the lower section  22 . A plurality of upstanding lugs  30  project upwardly from the roof  26  for the attachment of cables  32  of anchor assemblies  18  thereto. The anchor assemblies  18  also include anchors  34  which are bolted into the supporting surface  20  (such as a concrete pad) and connected to the cables  32  by eyebolts  36 . A manhole cover  38  is interfitted into a manhole in the roof  26  to permit access into the chamber  28 . The lugs  30  provide pairs of tie-down flanges  40  and lifting flanges  42 , each provided with holes for the passage of cables  32  therethrough. An opening through the side of the upper section  24  permits the attachment of fill pipe  44  thereto. In addition, the roof  26  receives vent  46 , filler inlet  48 , and level indicator  50  thereon, the latter including a probe for determining the amount of the liquid in the chamber  28 . The lower section  22  includes a substantially cylindrical sidewall  52  and a bottom wall  58  which are joined at the lower perimeter  60  of the sidewall  52 . A port  54  is provided in the cylindrical sidewall proximate to the lower perimeter  60 , with four surrounding circumferentially spaced bolt holes  62  provided through the side wall  52 . 
     The outer vessel  16  includes a multifaceted lower wall portion  64  and a substantially cylindrical upper wall portion  66 . The lower wall portion  64  includes a plurality of alternating arcuate sections  68  and chord sections  70 . The lower wall portion  64  tapers inwardly in transition area  72  to cylindrical wall portion  66 , which lies closely adjacent the cylindrical sidewall  52  when the inner tank  14  is nested in the outer tank  16 . The upper wall portion  66  has an upper margin provided with a plurality of notches  74  for receiving the chutes of the inner tank  14  therein. The arcuate sections  68  are spaced from the cylindrical sidewall  52  of the inner tank  14  to define therebetween a containment area  76 . An access opening  78  is provided in one of the arcuate sections  68  for receipt of the discharge outlet  10  therein, with a plurality of surrounding, circumferentially spaced holes  80  for the receipt of the bolts therethrough. A leak detection system  82  may be mounted in the lower wall portion  64  and include a probe extending downwardly into the containment area  76  to detect the presence of liquid therein. The base wall  84  connects to the lower wall portion  64  and receives the bottom wall  58  of the inner tank  14  thereon. Both the inner tank  14  and the outer vessel  16  are rotationally molded of synthetic resin, such as high density linear polyethylene or cross-linked, high density polyethylene. 
     The discharge outlet  10  includes an inner coupler assembly  86 , an coupler flange assembly  88 , sealing boot  90 , and piping  92 . The inner coupler assembly includes interior flange  94  and intermediate flange  96  which each include a ring  98  and a neck  100 , each flange  94  and  96  having a central opening  102  to permit the flow of liquid therethrough. Annular gaskets  104  and  106  abut the cylindrical sidewall  52  in sealing relationship thereto. The rings  98  and gaskets  104  and  106  each include apertures  108  aligned in registry with the bolt holes  62  in the cylindrical sidewall  52  for the receipt of bolts  110  therethrough. The bolts  110  are secured by suitable nuts and washers. 
     The sealing boot  90  is located in the containment area  76  and preferably rotationally molded of synthetic resin such as either high density linear or low density polyethylene for flexibility. The sealing boot  90  is provided in the shape of a tire, including a flat inner wall  112  provided with surrounding, circumferentially spaced apertures  114  for the receipt of bolts  110  therethrough, and a central hole  56  for alignment in registry with the port  54  and the central opening  102  of the neck  100 . An circumferentially extending cup-shaped protrusion  116  extends radially outwardly from the flat inner wall  112 , with flat outer wall  118  extending radially inwardly therefrom in spaced, opposed relationship to flat inner wall  112 . The flat outer wall  118  includes an inner margin  120  having a transverse dimension D which is substantially the same as that of the access opening  78  and smaller than the diameter of the central hole  56  of the flat inner wall  112 . The sealing boot  90  thus defines an annular, circumferentially extending channel  122  which permits flexing of the boot  90  and captures liquid leaking past the inner coupler assembly. 
     The outer coupler assembly  88  has an inner flange provided as semi-annular inner flange plate halves  124  and  126  positioned within the channel  122 , annular gaskets  128  and  130  sandwiching the flat outer wall  118  therebetween, and outer flange plate  132  for engagement against the exterior  134  of the outer vessel. The inner flange plate halves  124  and  126  and the outer flange plate  132  are preferably stainless steel or other corrosion resistant metal. The flat outer wall  118 , inner plate halves  124  and  126 , gaskets  128  and  130 , and outer flange plate include holes which are positioned in registry with the holes  80  in the outer vessel  16  for receipt of bolts  136  therethrough. The bolts  136  are secured in place by suitable nuts and washers as shown in FIGS. 3 and 4. The gaskets  104  and  106  and also  128  and  130  are preferably elastomeric, and provided of a chemically resistant natural or synthetic rubber material. 
     The piping  92  is preferably of a chemical resistant synthetic resin material such as polyvinyl chloride and provides a conduit for the passage of liquid in the chamber  28  out of the containment tank assembly  12 . The piping  12  includes a discharge tube  138  having an inner end which is preferably chemically welded to the neck  100  of the intermediate flange  96  and an outer end which receives a connection flange  140  for the attachment of further piping or a discharge valve to control the flow of liquid from the chamber  76 . An inner tube  142  extends into the chamber  76  and has one end which is preferably chemically welded to the neck  100  of interior flange  94  and another end which receives thereon elbow  144 . The elbow  144  is oriented downwardly and a pickup pipe  146  is connected at one end thereto, the pickup pipe  146  having an open, lower end  148  adjacent the bottom wall for providing an intake into the pipeline  92  for the discharge of liquid therethrough. 
     In use, the sealing boot  90  and the access opening  78  of the outer vessel are trimmed to fit with the flange plate halves  124 ,  126  and outer flange plate  132 . The flange plate halves  124 ,  126  are placed in the channel  122  with the gaskets positioned as shown in FIG.  3  and the bolts  136  are inserted and tightened. The inner tank  14  is lowered into the outer vessel  14  in nesting relationship with the chutes received in the inner notches and the port  54  aligned with the access opening  78 . The inner tank  14  is then preloaded, and the port  54  is trimmed to receive the inner flange assembly  86 . The inner tube  142 , elbow  144  and pickup pipe  146  are installed into the inner flange assembly  86  mounted on the cylindrical sidewall  52  to permit liquid to flow through the central opening  102 . The discharge tube  138  with connection flange  140  is then chemically welded to the neck  100  of intermediate flange  96 , and a control valve such as a ball valve or further piping is attached to the connection flange to permit filling of the chamber  28 . 
     The discharge outlet  10  thus effectively permits the inner tank  14  to be emptied of liquid through gravity rather than pumping, because the integrity of the containment area  76  is preserved by the sealing boot  90 . The boot  90  is sufficiently flexible to permit limited relative movement between the inner tank  14  and the outer vessel  16  due to seismic events, wind forces or thermal expansion. If liquid begins to leak from the inner tank  14  through the inner flange assembly  86 , the leakage is nonetheless contained within the channel  122  and can be readily visually observed. Other leaking from the inner tank  14  is confined to the containment area  76  between the inner tank  14  and outer vessel  16 , such that even if the leakage rises above the access opening  78  in the side of the outer vessel  16 , it does not escape. 
     Although preferred forms of the invention have been described above, it is to be recognized that such disclosure is by way of illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention. 
     The inventor hereby states his intent to rely on the doctrine of equivalents to determine and assess the reasonably fair scope of his invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set out in the following claims.