Abstract:
The present invention is a containment tank or a generator set including an outer tank and an inner flexible tank that offers a storage area for diesel fuel for a diesel engine powered generator set. So that the generator set diesel engine have ready source of clean diesel fuel the inner flexible tank provides a corrosion-free storage area that will not corrode or contaminate the diesel fuel. The outer tank is designed to provide a structure that not only protects the inner tank from damage, but acts as a support structure for the diesel engine generator set and other components (enclosure, switchgear, etc.) that are needed for the generator sets protection from wind, rain or snow or to act as control devices for diesel engine generator set. Also, since the design of the inner tank is flexible, it can be replaced easily through a manway formed on the outer tank without having to disconnect or disassemble the generator set.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to storage tanks, and more particularly to storage tanks with redundant containment structures for containing hazardous materials. 
       BACKGROUND OF THE INVENTION 
       [0002]    Storage tanks are used throughout the world for a variety of purposes. One of the more significant uses for tanks of this type is for the containment of fuels for use at the location of the tanks, such as to store diesel fuel for emergency power diesel engine generator sets. With hazardous materials such as fuels, it is necessary to provide certain safeguards for the storage tanks to protect the environment from a tank leak. These safeguards are normally the requirements of the authority having jurisdiction that necessitate these tanks have the capability for secondary containment of any liquid that could leak from the primary or inner tank. 
         [0003]    As best shown in  FIGS. 1 and 2 , an example of a prior art containment tank  10  on which can be mounted a generator  1000 , a diesel engine  2000  and a fan  3000  is shown which includes a primary inner tank  12  formed with a lower member  14  and an upper member  16 . The lower member  14  is generally rectangular in shape with a bottom wall  18 , a number of upwardly extending side walls  20  secured to each side of the bottom wall  18 , and one or more support or bracing walls  22  secured to the bottom wall  18  and to opposed side walls  20  at each end. The upper member  16  is affixed to each of the side walls  20  opposite the bottom wall  18  to form an enclosed interior  24  within the inner tank  12 . Within the structure of the upper member  16  are included a number of fittings  25  to which various hoses (not shown) can be connected in order to introduce and withdraw fluids from within the inner tank  12 . The upper member  16  can also be strengthened by attaching a stiffener  26  to the upper member  16  that extends across the upper member  16  to each of the side walls  20  to be attached thereto and enhance the strength and rigidity of the inner tank  12 . 
         [0004]    Each of the components of the inner tank  12  are formed from a metal, such as steel, to provide the required integrity and rigidity to the tank  12  and to enable all of the component to be affixed to one another by welding, to attempt to minimize the formation of leaks between the components of the inner tank  12 . 
         [0005]    The inner tank  12  is dimensioned to be able to fit within a secondary outer tank  28  to form the containment tank  10 . The outer tank  28  includes a bottom wall  30  and a number of side walls  32  secured to the bottom wall  30  at one end. The side walls  32  define and enclosure  34  within which the inner tank  12  can be positioned and secured. The inner tank  12  is affixed to the outer tank  28  using an outwardly extending edge  36  of the upper member  16  of the inner tank  12 . When the inner tank  12  is positioned within the enclosure  34 , the outwardly extending edge  36  rests on each of the side walls  32  of the outer tank  28  and can be secured thereto, such as by welding. This additionally seals the enclosure  34  formed in the outer tank  28 , which can retain any fluid escaping from the inner tank  12 . 
         [0006]    In prior art containment tank constructions, as described above, the primary inner tank is constructed of steel and is welded into a secondary containment or outer tank to form one contiguous tank construction. Thus, in the event of a leak in the primary inner tank which is contained by the secondary outer tank, due to the unitary construction of the containment tank, the entire tank including both the damaged primary inner tank and the undamaged secondary outer needed to be replaced. This results in excessive replacement costs and extended downtime for the particular device connected to the storage tank, such as an emergency power diesel engine generator set. 
         [0007]    Additionally, in the applications for prior art storage tanks in containing fuels, such as for providing a local fuel source for stand-alone power generation systems, e.g., generator sets, these systems are used primarily to provide emergency electrical power in the event of a utility electrical power outage. The ability of the stand-alone power generation system to start and take-over as the primary source of electrical power coupled to life safety system within seconds following a utility power outage is paramount to sustaining human life. The performance of these power generation systems is dependent upon having a fuel source in the form of the storage tank that is clean and free of contaminants. However, with the construction of prior art tanks with a steel inner tank, the steel forming the inner tank can oxidize and/or corrode when in storage or over years of operation. This particulate matter formed as a result of the corrosion can contaminate the fuel held within the inner tank, can obstruct fuel filters located in output channels for the fuel dispense from the tank, and/or can clog engine the fuel injection mechanisms of the power generation systems. As a result, the emergency power generator set connected to the storage tank may not be able to start when it is needed during a utility power failure in order to support the critical or life-safety load, which is highly undesirable. 
         [0008]    Therefore, it is desirable to develop a storage tank for hazardous materials, such as fuels, having a primary inner tank that is formed of a material capable of reliably holding the hazardous material therein to prevent leaks that resists corrosion and is rugged enough to withstand testing in accordance with the applicable requirements of the code under which they are built (NFPA, etc.). Further, if it should become necessary to replace the primary inner tank due to a leak that has formed in the inner tank, the inner tank should be able to be removed from within the secondary outer tank in a manner that enables the outer tank to be reutilized, to minimize the downtime for the tank and to maximize the operating time for the emergency power source. 
       SUMMARY OF THE INVENTION 
       [0009]    According to one aspect of the present invention, a storage tank for a hazardous material is provided that includes an internal flexible bladder forming the inner tank that is contained within a more conventional rigid outer tank. The flexible material forming the inner tank has properties that enable the material to resist degradation of the flexible material over a longer period of time than necessary for the corrosion of a conventional steel inner tank, such that the flexible inner tank provides longer corrosion and contaminant resistance than prior art storage tank constructions. 
         [0010]    According to another aspect of the present invention, the flexible inner tank is releasably connected to the outer tank. Therefore, when a leak has formed in the inner tank, the inner tank can be removed from the outer tank and replaced without having to also replace the outer tank. This interchangeability of the inner tank structures within a single outer tank greatly decreases the downtime for a tank that has formed a leak. 
         [0011]    According to still another aspect of the present invention, the top of the tank contains one or more openings to which the collar of the flexible inner tank can be attached to the secondary containment outer tank. The collar of the inner tank is attached to the top of the outer tank around the periphery of the opening and the opening itself is covered with a removable manway. The manway permits a person to at least partially enter the inner tank, such as to inspect the interior of the inner tank, and contains fittings therein that permit solid or flexible pipe connections to be attached. 
         [0012]    Numerous other features, aspects, and advantages of the present invention will become apparent from the following detailed description taken together with the drawing figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The drawings illustrate the best mode currently contemplated of practicing the present invention. 
           [0014]    In the drawings: 
           [0015]      FIG. 1  is an isometric view of a prior art storage tank; 
           [0016]      FIG. 2  is an exploded, isometric view of the prior art storage tank of  FIG. 1 ; 
           [0017]      FIG. 3  is an isometric view of a storage tank including a flexible inner tank constructed according to the present invention; 
           [0018]      FIG. 4  is an exploded, isometric view of the storage tank of  FIG. 3 ; 
           [0019]      FIG. 5  is a cross-sectional view along line  5 - 5  of  FIG. 3 ; 
           [0020]      FIG. 6  is a partially broken away circular sectional view along line  6 - 6  of  FIG. 3 ; 
           [0021]      FIG. 7  is a partially broken away circular sectional view along line  7 - 7  of  FIG. 3 ; and 
           [0022]      FIG. 8  is a partially broken away circular sectional view along line  8 - 8  of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    With reference now to the drawing figures in which like reference numerals designate like parts throughout the disclosure, a containment tank constructed according to the present invention is illustrated generally at  100  in  FIG. 3 . The tank  100  is constructed similarly to the prior art tank  10  with an inner tank  112  and an outer tank  114 . The outer tank  114  that can be utilized in the construction of the container tank  100  can be virtually the same as that used in the prior art tank  10 , with a bottom wall  116  and a number of side walls  118  formed from a suitable metal material and secured to one another to form a fluid-tight seal between the respective walls, such as by welding. The side walls  118  each include a central panel  120 , a lower flange  122  and an upper flange  124 , with the lower flange  122  affixed to the side of the bottom wall  116 . The lower flange  122  and the upper flange  124  are joined at each end by an end plate  126 , and between the end plates  126  by a number of spaced pairs of support gussets  128 . Each pair of gussets  128  are joined by a mounting plate  130  including an aperture  132  therein that is used as an attachment point for the lifting of the tank  100  and any generator system components mounted thereto. Adjacent, and preferably between the pairs of gussets  128 , the upper flange  124  also includes openings  134  to be utilized in securing the generator system components to the tank  100 . Due to the reinforced construction for the side walls  118 , these mounting openings  134  for attaching the generator system components, such as a generator  1000 , a diesel engine  2000  and a fan  3000  or, in some cases, an enclosure (not shown) to the outer member  114  can support a minimum of five thousand (5,000) lbs per mounting location to directly support the generator system components. 
         [0024]    At one end of the bottom wall 116 , the side wall  118  are joined by an end wall  136  that is secured to the bottom wall  16  and to each of the side walls  118  in a manner to provide a fluid-tight seal between the end wall  136  and each of the bottom wall  116  and the side walls  118 . The end wall  136  also has an inwardly extending flange  138  disposed slightly below, but parallel with and between the upper flanges  124  of each side wall  118 . The end wall  136  may also have certain fittings  140  disposed therein or attached thereto, such as an emergency vent or vent fitting. 
         [0025]    Generally opposite the end wall  136 , but spaced inwardly from the opposite end of the bottom wall  116 , a second end wall  142  is positioned and secured to the bottom wall  116  and the side walls  118 . The end wall  142  is formed similarly to the end wall  138  with an inwardly extending flange  144 , and is secured to the bottom wall  116  and the side walls  118  in a similar manner to provide a fluid-tight seal therebetween, and to effectively create an enclosure  146  between the bottom wall  116 , the side walls  118  and the end walls  138  and  142 . The enclosure  146  may also have a number of different elements positioned therein, such as one or more internal boxed segments  148  and  150  that provide areas that are open to the enclosure  146  of the outer tank  114  to maintain spatial separation for a leak detection switch (not shown). These structures  148  and/or  150  allow any build-up of internal pressures within the enclosure  146  of the outer tank  114  to escape through the emergency vent (not shown) located within the fitting  140  within the end wall  138 . 
         [0026]    An enclosure wall  151  is secured to the bottom wall  116  and between the side walls  118  a distance from the end wall  142  to form a space  153  between the enclosure wall  151  and the end wall  142 . This space  153  formed therein can receive various components (not shown) that are used to operate the generator system components to be secured to the tank  110 . The wall  151  is preferably secured to the side walls  118  by suitable fasteners  155  so that the wall  151  can be removed if necessary to access the space  153  without having to remove any of the generator system components from the tank  110 . 
         [0027]    Looking now at  FIGS. 3-7 , the enclosure  146  formed by the walls  116 ,  118 ,  138  and  142  is covered by an upper wall  152  formed from a metal material, such as steel. The upper wall  152  is affixed in a fluid-tight manner to each of the flanges  138  and  144  on the end walls  138  and  142 , respectively, and to the side walls  118  at a point below the upper flanges  124 , to position the upper wall  152  generally coplanar with the flanges  124 . The upper wall  152  can include various fittings  154  and  156  ( FIGS. 3 and 8 ) for holding different devices, such as leak detection units and emergency vents (not shown) similarly to the fitting  140  in the end wall  138 . The upper wall  152  can also include a stiffening support  158  secured to the underside thereof to enhance the structural integrity of the outer tank  114 . 
         [0028]    As best shown in  FIGS. 4-6 , the upper wall  152  also includes an access aperture  160  therein. The aperture  160  provides a means for access into the enclosure  146  of the outer tank  114 , and can be covered by a plate  162  that is releasably secured thereto. The plate  162  is formed of a metal material similar to the upper wall  152 , and includes a number of openings  164  that can receive suitable fasteners  166  therethrough. The fasteners  166  extend through aligned apertures  168  in the upper wall  152  located around the access aperture  160 . The fasteners  166  are held within the openings  164  and apertures  168  by nuts  170  attached to the exposed ends of each of the fasteners  166 . 
         [0029]    Additionally, the cover plate  162  includes a number of fitting apertures  172  formed therein that provide a connection points for supply and return of fluid into and out of the tank  100 , such as diesel fuel, and for other devices, such as an emergency vent, a fuel fill, a fuel level gauge, an atmospheric vent, an engine fuel return/supply dip tubes, and a fuel level switch, among others. 
         [0030]    The inner tank  112 , as best shown in  FIGS. 4 and 5 , is a unitary structure formed of a flexible and corrosion-resistant material, such as a suitable polymeric resin. The inner tank  112  includes a single opening  174  formed therein around which is formed a peripheral rim  176  that can be integrally formed with the inner tank  112 , or separately formed and secured thereto. The rim  176  has an inner diameter slightly less than that of the access aperture  160 , and an outer diameter that is greater than the access aperture  160 , such the rim  176  can be engaged around the aperture  160 , as best shown in  FIG. 5 . To hold the rim  176  in this position, the rim  176  includes apertures  178  formed therein that are aligned with the openings  164  in the cover plate  162  and the apertures  168  in the upper wall  152  to receive the fasteners  166  therein. Thus, the fasteners  166  extend through the upper wall  152 , the rim  176  and the cover plate  162  to enclose the opening  174  into the inner tank  112 , as well as the access aperture  160  into the outer tank  114 . Further, due to the compressible and flexible nature of the material forming the rim  176 , the compression of the rim  176  between the upper wall  152  and the cover plate  162  effectively seals both the inner tank  112  and the outer tank  114  from the outside environment. 
         [0031]    The inner tank  112  is preferably integrally formed with the rim  176 , but can be formed of a separately of a different material that is securely attached to the tank  112  in any suitable manner, such as by bonding or any other suitable means. The tank  112  extends inwardly from the rim  176  through the aperture  160  and into the enclosure defined by the outer tank  114 . The inner tank  112  is dimensioned to generally conform to the interior of the outer tank  114 , such that when filled with a material, such as a fuel, the inner tank  112  unfolds to contact and conform to the shape of the outer tank  114 , filling the enclosure  146 . Further, the inner tank  112  can be formed of a material than can expand or stretch to conform to the shape of the outer tank  114 , while retaining sufficient strength to prevent any leaks in the inner tank  112 . 
         [0032]    To achieve a UL Listing the inner tank  112  must undergo a hydrostatic pressure test whereby the inner tank  112  is completely filled with water and all air is expelled from the inner tank  112 . Then air pressure is gradually applied to the inner tank  112  in five (5) psi increments at a rate not to exceed two (2) psi per minute. The pressure is held for two (2) minutes after each five (5) psi increment until the test gauge pressure of fifteen (15) psi is reached or twenty-five (25) psi for a ULC listing. 
         [0033]    With this construction, should a leak develop in the inner tank  112  that is detected by a suitable device secured within the tank  110 , after the inner tank  112  is emptied of the material contained therein, the cover plate  162  can be removed to detach the rim  176  from the upper wall  152 . With the rim  176  detached, the rim  176  can be drawn away from the outer tank  114  to remove the inner tank  112  from within the enclosure of the outer tank  114 . The flexible material forming the inner tank  112  can be compressed, bent or folded to be removed through the access opening  160 , allowing the damaged inner tank  112  to be completely removed from within the outer tank  114  without affecting the structure of the outer tank  114 . Once removed, a new inner tank  112  can be inserted into the outer tank  114  through the access opening  160  and expanded to return the tank  110  to normal operation. 
         [0034]    In some alternative embodiments, multiple inner tanks  112  can be affixed to the rim  176 , with each tank  112  being positioned within the enclosure  164  and having an opening (not shown) through which the material can be introduced into the inner tank  112 . 
         [0035]    Various alternatives are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.