Abstract:
A bonding system for a tank battery containing a flammable or combustible product being stored or conveyed, including a bonding conductor, an electrically conductive base member mounted on the tank, the electrically-conductive base member electrically connected to the bonding conductor and to ground installed within each tank and also including a flexible conductive medium with an upper end and a lower end and a plurality of fine electrically-conductive metal wires each having a proximal end and a terminal end, the proximal ends of which are intertwined with the flexible conductive medium to be in electrical connection with the electrical conductive medium, the upper end of the flexible conductive medium electrically connected with the electrically conductive base member and a plurality of static drains located proximate to the highest points of the tank battery and electrically bonded to said bonding conductor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of provisional patent application Ser. No. 61/550001 filed Oct. 21, 2011 and 61/684857 filed Aug. 20, 2012, the disclosures of each of which are hereby incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to static electricity dissipation drains for dissipating static charges within structures such as storage tanks to minimize a build-up of static electrical potential within the structure that might create an electrical spark within the storage tank. 
         [0004]    2. Description of the Background Art 
         [0005]    As set forth in my prior patent, U.S. Pat. No. 4,910,636, the disclosure of which is hereby incorporated by reference herein, static electricity dissipators have been used to dissipate electrical charges during a thunderstorm to thereby minimize the likelihood of a lightning strike that might otherwise occur due to the electrical potential between the earth and the atmosphere. My prior static electricity dissipator comprised an electrically-conductive base member having a plurality of fine conductive wires emanating therefrom in a uniform, mushroom-shaped configuration. The tubular base member was typically affixed to roof locations above the structure to be protected such as at locations in which conventional lightning rods would be installed. My static electricity dissipator has achieved substantial commercial success, and has been widely accepted throughout the industry. 
         [0006]    U.S. Pat. No. 4,605,814, the disclosure of which is hereby incorporated by reference herein, discloses a lightning deterrent which comprises a cable having a multiplicity of fine conductive wires captured within the strands of the cable to emanate therefrom in a brush-like manner. During use, the cable is formed in a circular or other configuration and mounted about the periphery of the structure to be protected. The terminal ends of the multiplicity of fine conductive wires function to dissipate electrons to the atmosphere, thereby minimizing the electrical potential differential between the structure and the atmosphere. The likelihood of a lightning strike is thereby minimized. 
         [0007]    Similar dissipators in which fine conductive wires are captured within the strands of a main cable are disclosed in the following U.S. Patents, the disclosures of each of which are hereby incorporated by reference here. 
         [0000]    
       
         
               
               
             
           
               
                   
               
               
                 Pat. No. 
                 TITLE 
               
               
                   
               
             
             
               
                 U.S. 1,757,172 
                 Aerial 
               
               
                 U.S. 2,631,189 
                 Static Wick Discharger 
               
               
                 U.S. 3,617,805 
                 Low-Noise Static Discharger Device 
               
               
                 U.S. 4,180,698 
                 System and Equipment for Atmospherics Conditioning 
               
               
                 U.S. 4,605,814 
                 Lightning Deterrent 
               
               
                 U.S. 5,638,248 
                 Static Dissipator 
               
               
                 U.S. 6,307,149 
                 Non-Contaminating Lightning Protection System 
               
               
                 U.S. 6,369,317 
                 Safer Lightning Rod and Warning System 
               
               
                 U.S. 6,943,285 
                 Bipolar Discharge-Dissipation Lightning Air Terminals 
               
               
                 U.S. D478,294 
                 Lightning Dissipation Assembly 
               
               
                 U.S. D478,295 
                 High Dissipation Discharge Terminal 
               
               
                 U.S. D478,525 
                 Point Discharge Dissipation Terminal 
               
               
                   
               
             
          
         
       
     
         [0008]    In addition to dissipating static electricity for lightning protection for buildings, it is likewise known that storage tanks, which store a combustible fluid, are in need of lightning protection. Representative patents disclosing lightning dissipators for protection of storage tanks and other structures are disclosed in the following U.S. Patents, the disclosures of each of which are hereby incorporated by reference herein. 
         [0000]    
       
         
               
               
             
           
               
                   
               
               
                 Pat. No. 
                 TITLE 
               
               
                   
               
             
             
               
                 1,617,788 
                 Device for Preventing Electrical Ignition of Stored Inflammable 
               
               
                   
                 Fluids 
               
               
                 1,743,788 
                 Apparatus for Treating Flotant Material 
               
               
                 1,974,315 
                 Lightning Protection for Storage Tanks 
               
               
                 5,694,286 
                 Lightning Protection Device 
               
               
                 6,815,606 
                 Bipolar Multi Electrostatic Inducing Discharge-Dissipation 
               
               
                   
                 Lightning Air Terminals 
               
               
                   
               
             
          
         
       
     
         [0009]    More specifically, during filling of a storage tank, particularly one composed of fiberglass or metal lined with insulative dielectric material, it is known that a static charge is created between the fluid inflow droplets and the inner wall of the storage tank. It is also known that as the static electrical potential accumulates, an electrical spark could eventually be created within the storage tank, and could thereby cause the flammable liquid therein to ignite or explode. 
         [0010]    Unfortunately, apart from lightning protection, there has been an unsatisfied need for a static electricity dissipator for reducing static electrical potential within the storage tank or other structure itself, particularly when the tank or structure is manufactured of a non-conductive material such as fiberglass (e.g., a fiberglass saltwater disposal (SWD) tanks) or metal lined with an electrically insulative material. Known prior art systems that employ a Carbon Veil, Chains or a Conductive Paint or that consist of a Catenary System or an Early Streamer Emitting System are discussed as follows. 
         [0011]    Carbon Veil is a conductive strip woven into a fiberglass tank with a grounding lug provided near the base of the tank. The intent is to dissipate static charge from the stored product onto the strip. The drawback of this system is that it presents a flat surface to, and is not in direct contact with, the stored product. Charge more readily dissipates into a liquid off small radius electrodes than off flat surfaces, limiting the effectiveness of the veil. If adjacent wraps of the veil do not overlap, it presents the possibility of arcing between wraps during a lightning strike or ground fault. The carbon veil does not provide bonding to miscellaneous masses of inductance on the tank. Neither does it provide air terminals (lightning rods) or a full-size conductor to ground. 
         [0012]    Chains (or other appliance suspended in tank) are intended to dissipate static charge from the stored product onto the chain or other appliance. The drawback of this system is that it presents a flat (curved) surface to the stored product. Charge more readily dissipates into a liquid off small radius electrodes than off flat surfaces, limiting the effectiveness of the appliance. The chain or other appliance does not provide bonding to miscellaneous masses of inductance on the tank. Neither does it provide air terminals (lightning rods) or a full-size conductor to ground. 
         [0013]    Conductive Paints are employed but only to coat the outside of the tank. Therefore, it cannot dissipate static charge from the stored product. Conductive paint may help by providing a path for energy from a direct lightning strike down the tank exterior. However, this division of current over the face of the painted surface is compromised, as there is only one or two ground lugs providing a path to ground at the base of the tank. Additionally, the painted surface will be only marginally effective in serving as a lightning attachment point. If lightning attaches to the tank, the paint will probably not be thick enough to prevent melt-through of the fiberglass, as it does not meet lightning protection code requirements (NFPA 780-3.6.1.3). 
         [0014]    A Catenary System consists of grounded masts or poles supporting a wire or wires over the site. This type of system is primarily intended to protect electric power utility company transmission and distribution lines by intercepting what would otherwise be direct strikes to the phase conductors. The overhead wires have no effect on streamer formation from the tanks, and therefore do not affect the likelihood of a direct strike to the tanks They are merely intended to “get in the way” of a direct strike, intercepting and conveying it to ground. When used to protect tanks or other structures, this system cannot mitigate secondary effect arcing, the primary cause of ignition. In fact, if a catenary system performs exactly as designed and intercepts a direct strike, it maximizes the likelihood of secondary effect arcing across the tank and appurtenances by bringing the lightning energy to ground near the base of the tank. The catenary system also has no effect on the static charge on the stored product, does not provide bonding to miscellaneous masses of inductance on the tank, and does not provide purpose-designed air terminals on the tank or tank battery. 
         [0015]    An Early Streamer Emitting System uses a small number of air terminals, usually a single air terminal, to protect an extended area. This type of air terminal works by emitting a streamer early in the streamer formation phase of a lightning strike. The streamer will therefore reach the downward reaching stepped leaders before any other, thereby becoming the preferred lightning attachment point. They often are labeled with names inferring that they protect the area by keeping away direct lightning strikes. Actually, the opposite is true. They attract lightning to themselves and to the site. Therefore, lightning will tend to attach to the ESE air terminal rather than to the tanks and other structures. However, lightning attachment is not the primary cause of ignition at the sites. Secondary effect arcing is the primary cause of ignition. As these devices attract lightning to themselves, they actually cause maximum secondary effect current flow right at the site, introducing, not preventing, the primary cause of ignition. 
         [0016]    Lightning protection for external floating roof tanks has been the subject of much discussion in recent years. The American Petroleum Institute has recently devoted much time and study to this subject and has promulgated API 545—Lightning Protection for Hydrocarbon Storage Tanks 
         [0017]    By way of background, a lightning strike consists of two components: a short duration, high-energy spike which is then followed by a longer duration, lower energy tail. While the high-energy spike is impressive, it is the lower energy, long duration component that is actually responsible for ignitions in external floating roof tanks 
         [0018]    More specifically, the roof of the tank floats on pontoons on the stored product. It is centered in the tank shell by centering shoes. Vapor is contained by a primary and a secondary seal. These tanks have traditionally been equipped with flexible, stainless steel grounding shunts spaced at frequent intervals around the perimeter of the floating roof. Additionally, the floating roof is usually bonded to the tank shell with one grounding conductor run along the stairway from the top of the tank shell to the floating roof 
         [0019]    Lightning becomes an issue when it strikes either the floating roof, the tank shell, or nearby. Ignition is not normally caused by the heat of the lightning channel igniting venting vapors. It is caused by arcing from the secondary effect of lightning. A thunderstorm is an electrically charged cloud mass, with a charge, usually negative, at its base. That charge induces an opposite charge, usually positive, on the surface of the earth beneath it. When lightning attaches to a tank or other object on the surface of the earth, the charge at the point of attachment changes dramatically and almost instantly. The surrounding ground charge rushes toward the point of the strike. If that in-rush of charge crosses a gap, it may arc. If that gap is between the floating roof and the side of the tank shell, and there are flammable vapors present, those vapors may ignite. 
         [0020]    Another way of looking at this phenomena is to consider a lightning attachment to the shell of the tank. The tank shell changes potential almost instantly. The floating roof, being somewhat electrically isolated from the shell, does not. That difference in potential between the floating roof and the tank shell must equalize. Unless a preferred path is provided, a potential equalizing arc may occur, once again igniting any flammable vapors present. 
         [0021]    Presently, most external floating roof tanks are equipped with flexible stainless steel grounding shunts around the perimeter of the floating roof. These shunts are attached to the roof, and bent upward and outward to press against the tank shell wall. They ride against the tank shell wall, up and down as the roof rises and falls. The electrical contact to the wall is adequate only when the tank is new and the wall is clean. After a few trips up and down, the tank wall becomes coated with a variety of substances that compromise the electrical bond. Because of the short length and frequent spacing of these shunts, they are the preferred path of equalization between the floating roof and tank shell for the high-energy short duration component of the lightning strike. API 545 recommends employing these shunts for this purpose. However, because of the contaminants on the tank wall, these shunts tend to emit a shower of sparks when they perform their intended function. One solution suggested by 545 is to relocate these shunts so they are submerged under the stored product and there is no oxygen available at the source of the sparks to support ignition. However, submerging the shunts creates other problems when the roof is landed. 
         [0022]    Further, to address the lower energy, long duration component of the lightning strike, API 545 recommends the installation of by-pass conductors between the floating roof and tank shell at intervals not to exceed 100′ around the roof perimeter. These conductors provide a low-resistance bonding path between the roof and tank shell, and are intended to prevent ignition-causing arcs generated by this current flow. 
         [0023]    In summary, by-pass conductors address the lower-energy longer duration component of the lightning discharge and simply attaching a length of conductor from the edge of the floating roof to the top of the tank shell is adequate. Unfortunately, however, the by-pass bonding conductors must be kept out of the way as the floating roof rises and falls. One embodiment comprised a grounding reel similar to that used to bond a fuel truck to an airplane. This grounding reel employed a flat, braided, tinned copper strap. The strap offered lower surge impedance than a round conductor, and, as the strap retracted into the reel, it was pressed against the inner windings of strap, effectively shortening the overall length of the conductor. Unfortunately, grounding reels were of questionable durability and were costly. 
         [0024]    Accordingly, there presently exists a need for a static electricity dissipator drain for use inside a structure such as a storage tank to dissipate the static electrical potential that may accumulate therein and otherwise create an electrical spark in the structure. 
         [0025]    Therefore, it is an object of this invention to provide an improvement which overcomes the aforementioned inadequacies of the prior art devices and provides an improvement which is a significant contribution to the advancement of the static electricity dissipator art. 
         [0026]    Another object of this invention is to provide a static electricity dissipation drain for storage tanks having a fixed roof or a floating roof. 
         [0027]    Yet another object of this invention is to provide a static electricity dissipation drain for storage tanks composed of metal, fiberglass, plastic or lined metal. 
         [0028]    Another object of this invention is to provide a static electricity dissipation drain for storage tanks to bond the stored product and suspended droplets in the vapor space to the bonded mass of the tank. 
         [0029]    Another object of this invention is to provide a static electricity dissipation drain for storage tanks to dissipate the static charge in the stored product and suspended droplets in the vapor space, preventing it from building to an incendive level. 
         [0030]    Another object of this invention is to provide by-pass conductors from the edge of the floating roof to the top of the tank shell to address the lower-energy longer duration component of the lightning discharge that is kept out of the way as the floating roof rises and falls. 
         [0031]    The foregoing has outlined some of the pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings. 
       SUMMARY OF THE INVENTION 
       [0032]    For the purpose of summarizing this invention, this invention comprises a static electricity dissipator drain for use within a storage structure, such as a storage tank, to minimize the build-up of static electrical potential between the product being stored and the structure itself, thereby minimizing the likelihood of an electrical arc within the structure. 
         [0033]    More particularly, the static electricity dissipation drain of the invention is particularly suitable for use in process vessels such as within a series of salt water separation tanks manufactured of metal, a non-conductive materials such as fiberglass or of a conductive material lined with a non-conductive material for separating petroleum from water after being pumped from the ground, whereupon the petroleum may be separated and the water, commonly salt water, injected back into the ground or otherwise disposed of Other applications include other production, flow back and process tanks, storage grain elevators and storage tanks (conductive or non-conductive) for storing petroleum and other fluids and for storing particulate matter such as plastic pellets used for injection molding. It should be appreciated, however, that the static electricity dissipation drain of the invention may be used in connection with many other applications in which products are stored and where a build-up of static electricity causing arcing may occur within the storage tank, vessel or other structure. Indeed, it is again emphasized that, without departing from the spirit and scope of the invention, the static electricity dissipation drain of the invention is intended to be used in conductive as well as non-conductive structures that are filled with conductive and/or non-conductive materials. Finally, while the static electricity dissipation drain of the invention has particular application to reduce static electricity build-up within the tank during filling of the tank, it likewise has the beneficial effect of protecting the structure from internal arcing that might otherwise occur upon build-up of the ambient ground charge that would naturally occur in the event of a nearby lightning strike that would increase the electrical potential inside of the tank. 
         [0034]    The best mode for implementing the invention solves the problem of ignition in hydrocarbon storage tanks caused by static and lightning and takes into account the four conditions that are necessary to allow ignition: (1) the creation of static charge, (2) that builds to an incendive level containing enough energy to cause ignition, (3) a source of ignition (arcing) and (4) a flammable mixture in the tank. These conditions are discussed as follows. 
         [0035]    (1) A static charge is created by normal tank operations (filling and emptying). Moving a stream of liquid through standing liquid strips ions, thereby creating a charge. Also, secondary effect from a direct or nearby lightning strike has the same effect. There is little that can be done to mitigate this condition. 
         [0036]    (2) Charge dissipates from the liquid in the tank onto points and edges. Even if the liquid is in a steel tank, the charge cannot dissipate into the steel, but must inductively couple. That takes time, allowing the charge to build more quickly than it dissipates. This condition is most likely as filling of the empty tank is commenced. Most tanks are splash-filled. In the case of salt water separation/disposal (SWD) tanks, splash filling is desired to break the liquid into smaller particles, enhancing separation. It also enhances the creation of static charge. Also, secondary effect from a direct or nearby lightning strike creates a charge much more quickly than it can couple. Either mechanism can allow the charge to build to an incendive level. This is one condition that is addressed by the subject invention. 
         [0037]    (3) Sources of ignition include masses of inductance (large metal masses) on or near the tank, including valves, piping, hatches, walkways, metering or gauging equipment, etc. Due to loosened connection between the masses, rattling between the masses and hence arcing may occur. This is another condition addressed by the subject invention because when the subject invention is installed on non-conductive tanks, all the masses are bonded together electrically with conductors, including bonding the thief hatch cover to its collar. 
         [0038]    (4) Drainage or emptying a tank (and certain servicing operations such as cleaning residue in the bottom of the tank) draws in ambient air to keep the tank from collapsing, allowing sufficient oxygen into the tank to create a flammable mixture. There is little that can be done to mitigate this condition. 
         [0039]    As described below in the Detailed Description of the Preferred Embodiment, the present invention addressed the potential conditions that are necessary to allow ignition by controlling conditions (2) and (3). 
         [0040]    More particularly, the present invention serves to bond the stored product and suspended droplets in the vapor space to the bonded mass of the tank, and to dissipate the static charge in the stored product and suspended droplets in the vapor space, preventing it from building to an incendive level. 
         [0041]    On non-conductive (fiberglass, plastic, etc.) tanks, the static electricity dissipator drain is bonded to metal masses (masses of inductance) on the tank, particularly at the top of the tank where such metal masses (e.g., hatches, covers, caps and other metal components) are not bonded through the stored liquid product. The stored liquid product, being at least semi-conductive, bonds any pipes, valves and other metal components at the base of the tank because they are submerged or semi-submerged in the liquid. Static charges can be equalized over high resistance, so the liquid is sufficiently conductive to equalize charges between metal masses it covers or touches. At the top of the tank, however, without implementing the subject invention the masses are not sufficiently bonded to equalize static charge, allowing an arc between the static charge on the suspended droplets in the vapor space above the stored product and a valve, hatch, or other conductive device. 
         [0042]    On a metal tank, no bonding conductors other than across hinged hatches are necessary, as the metal masses are bonded through the tank structure. Pipe dope and joint tape do not necessarily compromise this bond, as there is at least some metal-to-metal contact. 
         [0043]    This invention also comprises a non-conductive tubular standoff for by-pass conductors of floating roof tanks The standoff attaches mechanically and electrically to the perimeter of almost any type of floating roof by means of a unidirectional pivotal bracket. A bypass conductor extends through the tubular standoff and is then mechanically and electrically to the upper edge of the tank by means of a rim bracket. 
         [0044]    The unidirectional bracket allows the tubular standoff to be “aimed” to miss tank appurtenances that may otherwise foul the by-pass conductor. Guide wires may be provided as needed to more accurately aim the tubular standoff to miss tank appurtenances as the tubular standoff lays down onto the top of the floating roof. The rim bracket includes an arcuate channel that supports the by-pass conductor, defines its bending radius from the top of the tank and further assists the by-pass conductor from fouling on tank appurtenances. Likewise, the uppermost end of the standoff includes an arcuate channel that defines the bending radius of the by-pass conductor as it exists the tubular portion of the standoff 
         [0045]    Preferably, tube of the tubular standoff encloses and supports the by-pass conductor for slightly under half its length. Also preferably, the tube of the tubular standoff comprises a lightweight non-conductive construction such as fiberglass or Kevlar. 
         [0046]    In another embodiment in lieu of the tubular standoff, the invention comprises a helical by-pass conductor having a natural twist that is connected at one end to the upper rim of the tank by the rim bracket and at another end to the floating roof. The natural twist of the by-pass conductor urges the by-pass conductor into a coiled mass on top of the floating roof as the roof raises. However, according to the present invention, a plurality of spherical separators are fastened along the length of the by-pass conductor to assure that the coils do not become entangled as they lay down onto or played out from the floating roof and to assure that no part of the by-pass conductor becomes trapped or pinched in the joint between the outer periphery of the floating roof and the tank wall as the by-pass conductor as the by-pass conductor lays down onto or is played out from the floating roof. 
         [0047]    The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description of the invention that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0048]    For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which: 
           [0049]      FIG. 1  is a diagrammatic view of the static electricity dissipation drain of the invention showing the manner in which it is installed within a structure such as a storage tank; 
           [0050]      FIG. 2A  is a partial cross-sectional view of one manner in which the static electricity dissipation drain of the invention is mounted from the underside of the top of the storage tank via its thief-access hatch; 
           [0051]      FIG. 2B  is a partial cross-sectional view of another manner in which the static dissipation drain of the invention is mounted to a threaded rod to then be mounted from the underside of the top of the storage tank; 
           [0052]      FIGS. 2C ,  2 D and  2 E are partial cross-sectional views of another manner in which the static dissipation drain of the invention is mounted to a threaded bolt of a thief hatch of the storage tank and then to the cover of the thief hatch; 
           [0053]      FIG. 3  is a partial cross-sectional view of a floating top of a storage tank and the manner in which the top is sealed along the inner lumen of the storage tank as it slides upwardly during filling or downwardly during emptying; 
           [0054]      FIG. 4  is a cross-sectional view of the cable in which the fine wires are entrained during manufacturing of the static electricity dissipation drain of the invention; 
           [0055]      FIG. 5  is a schematic wiring diagram showing the grounding of a typical tank battery having a plurality of tanks used for separation of saltwater from oil pumped from the ground; 
           [0056]      FIGS. 6A ,  6 B and  6 C are perspective, side and top views of a grounding clamp used for electrically connecting the electrical ground to the catwalk and steps; 
           [0057]      FIGS. 7A ,  7 B and  7 C are front, section and bottom views of a grounding clamp used for electrically connecting the electrical ground to vent pipes and other circular cylindrical structures; 
           [0058]      FIGS. 8A-D  are perspective views at various tank levels showing the tubular standoff of the invention attached to the floating roof of the tank by means of the unidirectional bracket and showing the by-pass conductor extending therefrom connected to the upper edge of the tank by means of the rim bracket; 
           [0059]      FIGS. 9A-C  are perspective views of the unidirectional bracket connecting the lower end of the tubular standoff and the lower end of the by-pass conductor to the floating roof of the tank; 
           [0060]      FIGS. 10A-H  are perspective views of the rim bracket connecting the upper end of the by-pass conductor to the upper edge of the tank; 
           [0061]      FIG. 11  is a perspective view of the upper end of the tubular standoff showing the by-pass conductor extending therefrom; 
           [0062]      FIGS. 11A  and B are longitudinal cross-sectional views of an arcuate channel; 
           [0063]      FIG. 12  is a perspective view, partially exploded, of another embodiment of the tubular standoff having guide wires for more controllably guiding the path of the tubular standoff as it raises and lowers; 
           [0064]      FIGS. 13A-D  are perspective views of still another embodiment of the tubular standoff having guides (and the components thereof); 
           [0065]      FIGS. 14A-D  are perspective views of still another embodiment of the tubular standoff having guides (and the components thereof); and 
           [0066]      FIG. 15  is a diagrammatic view of another embodiment of the invention including a self-coiling by-pass conductor that interconnects the upper rim and the floating roof of the tank. 
       
    
    
       [0067]    Similar reference characters refer to similar parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0068]    Referring to  FIG. 1 , the static electricity dissipator drain  10  of the invention is intended to be installed within a structure  12  such as a storage tank  14  to dissipate the build-up of static electricity within the tank  14  as the product is filled with product  16  via inlet  18  or emptied via outlet  20 . 
         [0069]    More particularly, conventional storage tanks  14  comprise a generally cylindrical configuration composed of a side wall  22  covered by a top wall  24  and supported by a bottom wall  26 . In some storage tanks  14 , the top wall  24  is fixed whereas in other storage tanks  14 , the top wall  24  floats upon the fluid product  16  to move upwardly upon filling the tank via inlet  18  or to slide downwardly upon emptying the tank via outlet  20 . 
         [0070]    Without departing from the spirit and scope of the invention, the tank  14  may alternatively comprise barges and ships that have internal tanks for the storage of flammable or explosive material. 
         [0071]    The standing end of the static electricity dissipator drain  10  of the invention is preferably suspended from the top wall  24 . As shown in  FIG. 1 , in floating-roof tanks, the trailing end of the static electricity drain  10  may then be connected to either the side wall  22  or bottom wall  26  of the storage tank  14  so as to move upwardly during filling or downwardly during emptying of the tank, with the trailing end remaining submerged. 
         [0072]    As shown in  FIG. 2A , the static electricity dissipator drain  10  of the invention may be installed in the underside of the top wall  24  of the storage tank  14  by simply drilling a hole  28  through the top wall  24  within a reachable distance from the thief-access hatch  30 . Upon opening of the thief-access hatch  30 , the static electricity dissipator drain  10  may be fed therethrough with its upper portion grasped by the installer and then inserted upwardly through the hole  28  drilled in the top wall  24 . As shown, the upper end of the drain  10  comprises a threaded boss  32  (into which the drain  10  is crimped) for receiving a washer and threaded nut  34  once it is inserted back through the hole  28  in the top wall  24 . The lower end of the drain  10  may be clamped to the bottom or side wall of the tank as shown in  FIG. 1  by an end connector  35 L crimped onto the lower end of the drain  10 , or simply be left dangling. Notably, the natural helical lay of the drain  10  allows the drain  10  to fold as the top wall  24  moves upwardly or downwardly with respect to the bottom wall  22 . 
         [0073]    As shown in  FIG. 2B , an alternative embodiment for installing the static electricity drain  10  to the underside of the top wall  24 . Specifically, an end connector  35 U crimped onto the upper end of the drain  10  and bent at a 90° angle. The connector  35 U is fastened to a threaded length of rod  37  by opposing nuts and washers  37 A. The rod  37  is inserted into the holes  28  and secured by opposing nuts and washers  28 A. The end connector  35 L of the static electricity drain  10  may be sufficiently long to dangle in the storage tank  14  on or just above its bottom wall  26  or may be long enough to extend all the way to its bottom wall  26  and connected thereto as described in connection with the embodiment of  FIG. 2A . 
         [0074]    As shown in  FIGS. 2C , D and E, the static electricity dissipator drain  10  of the invention is preferably installed by via one of the mounting bolts  15  of the collar  30 C of the thief hatch  30 . More specifically, upon opening of the cover  30 CC of the thief hatch  30 , one of its mounting bolts  15  may be removed, and discarded. The static electricity dissipator drain  10  is then installed in a similar manner to that described above in connection with  FIG. 2B  with the rod  37  taking the place of the mounting bolt  15 . Note that the rod  37  is secured into position by a pair of opposing nuts and washers  31 . As noted above, the lower end of the drain  10  may be clamped to the bottom or side wall of the tank as shown in  FIG. 1  by an end connector  35 L crimped onto the lower end of the drain  10 , or simply be left dangling in contact with or slightly above the tank bottom. 
         [0075]    As also shown in  FIGS. 2C , D and E, the thief hatch collar  30 C and the thief hatch cover  30 CC are electrically grounded together by a flexible electrically conductive jumper  36 A having one end connected to a metal bracket  39  mounting onto the end of the metal rod  37  by another nut and washer  33  and the other end connected to the thief cover  30 CC by a crimped-on end connector  35 LL electrically connected to the thief cover  30 CC by a metal bolt and nut  30 B mounted through a drilled hole in the thief cover  30 CC. 
         [0076]    As also shown in  FIGS. 1 and 2A  and  2 B, the upper end  32  of the drain  10  may be connected via an electrical ground  36  to a catwalk and steps  38  surrounding the tank  14  which is itself electrically connected to earth ground via a ground electrode  40 . The electrical ground  36  may also be connected to the inlet  18  and outlet  20 . 
         [0077]    When used in conjunction with a floating top wall  24 , as shown in  FIG. 3 , it is noted that the top wall  24  is sealed against the lumen of the side wall  22  by means of an annular seal  42  formed about the annular periphery of the top wall  24 . It is also noted that conventionally the top wall  24  is composed of a material that would not otherwise float on the surface of the product contained within the tank  14  and, therefore, conventionally a pontoon  44  is affixed to the underside of the top wall  24  to provide the needed buoyancy. Conventionally, an annular deflector  46  is affixed to the top periphery of the top wall  24  to slide up and down the lumen of the side wall  22  to deflect dirt, precipitation, snow and other possible contaminants away from the annular seal  42 . However, it is noted that the deflector  46  traps vapors flowing from the product  16  contained within the tank  14  and thereby potentially creates an explosive environment. 
         [0078]    As shown in  FIGS. 2A and 2E , the static electricity dissipation drain  10  of the invention is preferably manufactured from a length of cable  48  whose upper end is crimped in the boss  32  or connector  35 U. The strands of cable wires  50  may be unfurled from the balance of the cable  48 , whereupon a multitude of very fine dissipator wires  52  may be laid into the remaining strands  52 . The removed strands  50  can then be refurled onto the cable  48  to securely retain the dissipator wires  52  to fully entrain the dissipator wires  52  within the cable. It should be appreciated, however, that other embodiments of a dissipator may suffice without departing from the spirit and scope of the invention. 
         [0079]    Referring to  FIG. 5 , the present invention substantially reduces or eliminates altogether the conditions (2) and (3) noted above that might otherwise result in combustion in or around the tank battery. 
         [0080]    More particularly, in the case of non-conductive (fiberglass) tanks  12 , all of the metallic masses are bonded electrically with a bonding conductor  36 . The bonding conductor  36  is bonded to the vent pipe  60  (the actual connection to the tank is usually metal) or the vent pipe manifold (if metal pipe is used) on top of the tank  12  (see Detail A), which is in turn bonded to any other metal masses associated with piping atop the tank  12 . It is noted that if plastic piping is used, conductors must be run along the piping to complete the necessary electrical bonding. 
         [0081]    As shown in  FIGS. 1 and 2A , the bonding conductor  36  is then run to the metal walkway  38  such that the metal walkway, supports and stairs (collectively  38 ) are employed as an integral component of the bonding conductor system. At the base of the tank, the bonding conductor is connected to the drain pipes and, if installed, the carbon veil. The bonding conductor is then run to the truck loadout provisions or injection well, using conductive product piping if available, or with conductor, if the piping is non-conductive. This eliminates any source of arcing. It also bonds the vacuum trucks, piping, injection well loading water or oil to the system, thereby eliminating another potential problem area. 
         [0082]    As noted above, the in-tank static drain  10  is installed in each tank  12 . Preferably the drain is sized to be approximately equal to the height of the tank  12  is tall. A connector is preferably installed at the bottom end of the static drain  10  (mostly to keep it from unraveling) and it just hangs in the tank  12 . The length is preferably short enough that it will not become fouled in valves or other tank appliances. It must be mechanically secured to the top of the tank, either through a purpose-drilled hole, or through an existing hole (preferably the bolt in the thief hatch collar is replaced with the stud atop the static drain). It is then bonded electrically to the conductor system described above. This brings the stored product in the tank to the same potential as the remainder of the site. 
         [0083]    It is noted that when installed in flow-back tanks  12  wherein the fluid is injected at a high volume or velocity, both ends of the drain  10  are preferably secured to prevent too much whipping around of the end of the drain  10  as the tank  12  is filled, with one end bonded to the filler pipe or support gussett. In the case of conductive, fixed roof tanks, the tank steel provides all on-tank bonding, except for the thief hatch flexible jumper, which is installed as noted above. At the base of the tank, conductors on non-conductive piping are installed, bonding the truck loadouts or injection well. Again, an in-tank static drain  10  is installed in each tank  12  as described above to bring the stored product to the same potential as the remainder of the site. Notably, drain  10  is also electrically connected to the metal catwalk surrounding the tank farm, which is in turn electrically connected to earth ground, to function as a grounding buss for the entire system. 
         [0084]    In the case of floating roof tanks, bonding is provided by the manufacturer in the form of shunts between the floating roof and tank shell wall. The most recent edition of API 545, Lightning Protection for Hydrocarbon Storage Tanks, will requires additional bonding in the form of conductors between the floating roof and tank shell wall installed at intervals not to exceed 100′. In-tank static drains are installed as these conductors. In this case, the drain must be approximately 20% longer than the height of the tank, and must be secured to both the floating roof and either the bottom of the tank or the side near the bottom in such a manner that it will not interfere with tank operations or maintenance. 
         [0085]    To incorporate structural lightning protection into the system, air terminals (lightning rods) of the streamer-delaying type (see dissapators  62 ,  64  and  66  of Details A, B and C) atop the tank or tank battery and associated walkway handrails. Air terminal layout should meet the requirements of NFPA 780 (the US lightning protection standard). 
         [0086]    In order to provide a convenient means for electrical bonding of the air dissapators  62 ,  64  and  66  and the bonding conductors  26 , specially configured grounding clamps  100  and  120  of  FIGS. 6 and 7  may be employed. 
         [0087]    More specifically, the grounding clamp  100  of  FIGS. 6A ,  6 B and  6 C comprises a metal base plate  101  to which is welded one end of a generally U-shaped metal arbor  102 . A metal nut  103  is welded to the other end of the arbor member  102  in alignment with the base plate  101 . A bolt  104  may then be threaded through the nut  103  to clamp the structure being clamped between the base plate  101  and the end of the bolt  104 . A cable bracket  105  is mounted to the underside of the base plate  101  by means of a nut  106  mounted onto another bolt  107  welded to the underside of the base plate  101 , thereby allowing the bonding conductor  26  to be electrically and mechanically fastened to the clamp  100 . It is noted that this clamp  100  is particularly suited for electrically and mechanically connecting the bonding conductor  26  to various “flat” components of the catwalk and steps  38 . 
         [0088]    The grounding clamp  120  of  FIGS. 7A ,  7 B and  7 C comprises a generally U-shaped channel  121  having opposing holes  122  positioned therethrough for receiving the opposing threaded ends of a C-clamp  123 . Nuts  124  threaded onto the opposing ends of the C-clamp  123  allowing it to be electrically and mechanically clamped onto generally circular cylindrical objects such as fill and vent pipes  60 . The sides of the generally U-shaped channel  121  may include arcuate cut-outs  125  for a tighter fit around the vent pipe  60 . To facilitate easy grounding by the bonding conductor  26 , the opposing ends of the C-clamp  123  each includes a cable bracket  126  held into position by the nuts  124 . 
         [0089]    Additionally, to facilitate connection of air terminals, the clamp  120  includes a threaded nut  127  welded to the inside surface of one side of the U-shaped channel  121  about a hole  128  and another threaded nut  129  welded to the inside bottom surface of the U-shaped channel  121  about a another hole  130 . It is noted that the resulting angles are at 90 degrees so that the air terminal may be positioned vertically irrespective of the orientation of the clamp  120  itself by simply installing the air terminal in to the appropriate nut  127  or  129  that is vertically oriented. 
         [0090]    Earth grounding may be provided for by the inherent self-grounding of steel tanks connected to the battery, driven ground rods (particularly at the base of the stairway for personnel safety), ground beds, counterpoises, etc. 
         [0091]    Referring to  FIGS. 8A-D , the invention also comprises a tubular standoff  210  through which is threaded a by-pass conductor  212  connected at a lower end  212 L to the floating roof  214  and an upper end  212 U to the upper edge  216  of a tank  218 . Preferably, the tubular standoff  210  is composed of a lightweight, electrically nonconductive material such as fiberglass or Kevlar. Preferably, the by-pass conductor  212  is composed of a multitude of fine conductive wires such as would be found in conventional welding cables. 
         [0092]    Referring to  FIGS. 9A &amp; 9B , the lower end  210 L of the tubular standoff  210  attaches mechanically to the perimeter of the floating roof  214  by means of a unidirectional pivotal bracket  220 . More specifically, the unidirectional bracket  220  comprises a base plate  222  with four corner holes  224  allowing it to be mechanically connected to the floating roof  214  by threaded fasteners or the like. A pair of opposing upstanding flanges  226  are welded to the base plate  222  to extend upwardly for receiving an inverted U-shaped connector  228  having a pair of opposing ears  228 E that fit between the corresponding flanges  226 . A bolt  230  extends through aligned holes in the flanges  226  and ears  228 E to create a pivotal connection therebetween. 
         [0093]    A tubular socket  232  is welded to the flat portion of the U-shaped connector  228  for receiving the lower end  212 L of the tubular standoff  212 . The socket  232  is preferably slotted  232 S and includes a tension fastener  232 F to allow tightening about the lower end  212 L of the tubular standoff  212  to mechanically secure it in the socket  232 . 
         [0094]    It is noted that the pivotal connection between the flanges  226  and ears  228 E assure that the tubular standoff  210  may pivot only in one arc (i.e., unidirectional) thereby defining the unidirectional pivoting of the tubular standoff  210  along such arc. In this manner, the base plate  222  may be fastened to the floating roof  214  at an orientation to miss any upstanding protuberances that might exist on the roof  214  as the tubular standoff  210  pivots from its generally horizontal position when the floating roof  214  is at its highest position (e.g., tank  218  is full) (see  FIG. 8A ) to its tilted upward position when the floating roof  214  is at its lowest position (e.g., tank  218  is empty) (see  FIG. 8D ). 
         [0095]    Still referring to  FIGS. 9A &amp; 9B , the by-pass conductor  212  is threaded through the tubular standoff  210  and then through a hole (not shown) formed in the flat portion of the U-shaped connector  228  to then be mechanically and electrically connected the floating roof  214  by means of an eye crimp connector and bolt (not shown). 
         [0096]    As shown in  FIG. 9C , a preferred embodiment of the ears  228 E of the U-shaped connector  228  comprises an offset hole  228 H formed through the flat portion and one of the elongated ears  228 S having an elongated slot  228 S formed therethrough. The purpose of the offset hole  228 H and elongated slot  228 S is to increase the bending radius of the by-pass conductor  212  to minimize chaffing as it passes through the U-shaped connector  228 . A cable clamp  228 C is attached to the other elongated ear  228 S to securely retain the by-pass conductor  212  in the U-shaped member  228 , thereby providing some strain relief to the by-pass conductor  212 . 
         [0097]    Referring now to  FIGS. 10A-D , a rim bracket  234  comprising a generally inverted U-shape is provided to be fitted over the upper edge of the tank  218  and electrically and mechanically connected to the upper edge of the tank  218  by means of a threaded bolt  236  threaded through a hole in one of the legs of the U-shaped rim bracket  234 . 
         [0098]    The upper end  212 U of the by-pass conductor  212  is stripped of any insulation and provided with a crimp eye connector  238  whose eye is mechanically and electrically connected to the flat portion of the U-shaped rim bracket  234  by a threaded bolt  240 . A cable clamp  234 C is connected to the U-shape to securely affix the by-pass conductor  212  thereto and provide additional strain relief 
         [0099]    The rim bracket  234  includes a downwardly extending arcuate channel  242  that supports the by-pass conductor  212  extending from the rim bracket  234 . The radius of the arcuate-shaped channel  242  defines and therefore limits the bending radius of the by-pass conductor  212  extending from the top of the tank  218 . The end of the channel  242  may be welded to rim bracket  234  or simply connected to the by-pass conductor  212  adjacent to the eye connector  238  by a cable fastener  244 . 
         [0100]      FIG. 10E-H  show alternative embodiments of the rim bracket  234  designed to accommodate different upper edges of tanks  218  (the upper edges being illustrated in bold). 
         [0101]    It is noted that the rim bracket  234  may be positioned along the edge of the tank  218  in alignment with the upper end  210 U of the tubular standoff  210  when it is in its uppermost position such that the by-pass conductor  212  is prevented from fouling on any tank appurtenances. 
         [0102]    Referring to  FIG. 11 , a strain relief  246  is provided at the uppermost end  210 U of the tubular standoff  210  to reduce any chaffing of the by-pass conductor  212  as is exists from the tubular standoff  210 . 
         [0103]    For added strain-relief protection and to provide more guidance to the by-pass conductor  212  while defining its upward bending radius, another arcuate channel  250  may be provided at the uppermost end  210 U of the tubular standoff  210 . More particularly, referring to  FIGS. 11A  and B, the arcuate channel  250  comprises a series of non-conductive rectangular tube segments  252  interconnected by a respective series of non-conductive U-shaped segments  254  pivotally connected by a respective series of hinge pins  256  extending through the respective overlapping ends of the rectangular tube segments  252 /U-shaped segments  254 . Importantly, the hinge pins  256  are offset from the centerline of the arcuate channel  250  to define a pathway through which the by-pass conductor  212  is threaded. Also importantly, the offset positioning of the hinge pins  256  limit the relative pivoting of the adjacent segments  254 / 256  thereby defining the minimum diameter that the arcuate channel  250  may be curved into due to the abutting of the edges  254 E against the rectangular tube segments  254 . Finally, as shown in  FIG. 11A , the arcuate channel  250  may be inserted into the tubular standoff  210  and secured therein by means of threaded fasteners  210 F or the like. 
         [0104]    Alternatively or in addition to the arcuate channel  250 , a segment of semi-rigid flex conduit may extend from the upper end  210 U of the tubular standoff  210 , to provide strain relief and guidance to the by-pass conductor  212 . 
         [0105]    Another embodiment of the tubular standoff  210  comprises a guywire-supported mast configuration  260 . In this embodiment, the tubular standoff  210  comprises a mast  262  and mast extension  264  interconnected by a mast extension adaptor  266 , each of which are composed of a non-conductive material. 
         [0106]    To allowing pivoting of the mast  262 , its bottommost end is connected to a mast receiver assembly  268 . The mast receiver assembly  268  comprises a hinge tube receiving tube  272  for rotatably receiving a hinge tube  270 . The hinge tube  270  is rotatably connected to the floating roof  214  by means of a series of co-linearly aligned hinge tube receiving tubes  274  mounted to pivot brackets  276  connected to mounting pads  280  affixed to the floating roof  214 . 
         [0107]    A guy wire tube  282  is connected to the opposing ends of the hinge tube  270 . Opposing non-conductive guy wires  284  extend therefrom to the mast extension adaptor  266 , thereby providing lateral support to the mast  262 / 264 . 
         [0108]    As shown in  FIGS. 13A-D , for added support each tube bracket  276  may be more rigidly connected to the floating roof  214  by providing four pads  280 . Further, to provide longitudinal support for the mast  262 , longitudinal non-conductive guy wires  286  may be provided along its longitudinal length and tensioned by a tensioner  288 . Finally, as shown in  FIG. 13B , the upper end  210 U of the mast  262 /tubular standoff  210  may be fitted with a non-conductive arcuate channel  250  to limit the bending radius of the by-pass conductor  212 . 
         [0109]    As shown in  FIG. 14A , the perimeter of some floating roofs  212  are provided with a knee-height wall  290  supported by a triangular framework  292  to define a space between the wall  290  and the inside of the tank to capture the fire-retardant foam that is released in the event of a fire. These “foam” walls  290  may be used by the present invention to support the guywire embodiments of the invention. 
         [0110]    More particularly, as shown in  FIGS. 14A  and B, the tubes  274  may be welded to the brackets  276  which are then in turn bolted to the angular members of the triangular framework  292 . As shown in  FIGS. 14C  and D, the center bracket  276  may b provided with an adjustable stop  294  to limit the backward travel of the mast  262 /tubular standoff  210 , thereby preventing it from contacting the inner side of the tank  218 . 
         [0111]    In lieu of the tubular standoff  210 , in another embodiment the invention comprises a helical by-pass conductor  212  having a natural twist that is connected at one end to the upper edge  216  of the tank  218  by the rim bracket  234  and at another end to the floating roof  214 . The natural twist of the by-pass conductor  212  urges the by-pass conductor  212  into a coiled mass on top of the floating roof  214  as the roof  214  raises. A plurality of spherical separators  300  are fastened along the length of the by-pass conductor  212  to assure that the coils do not become entangled as they lay down onto or played out from the floating roof  214  and to assure that no part of the by-pass conductor  212  becomes trapped or pinched in the juncture between the outer periphery of the floating roof  214  and the inner tank wall as the by-pass conductor  212  lays down onto or is played out from the floating roof  214 . 
         [0112]    The present disclosure includes that contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention. 
         [0113]    Now that the invention has been described,