Patent Grant
9001488
1. Field of the Invention
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.
2. Description of the Background Art
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.
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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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
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
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
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.
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.
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.
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.
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.
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.
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.
Another object of this invention is to provide a static electricity dissipation drain for storage tanks having a fixed roof or a floating roof.
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.
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.
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.
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.
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.
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.
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.
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.
(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.
(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.
(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.
(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.
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).
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.
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.
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.
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 by-pass conductor extends through the tubular standoff and is then mechanically and electrically attached to the upper edge of the tank by means of a rim bracket.
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.
Preferably, the 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.
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.
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.
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:
Similar reference characters refer to similar parts throughout the several views of the drawings.
Referring to
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.
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.
The standing end of the static electricity dissipator drain 10 of the invention is preferably suspended from the top wall 24. As shown in
As shown in
As shown in
As shown in
As also shown in
As also shown in
When used in conjunction with a floating top wall 24, as shown in
As shown in
Referring to
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.
As shown in
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.
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.
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.
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).
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
More specifically, the grounding clamp 100 of
The grounding clamp 120 of
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.
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.
Referring to
Referring to
A tubular socket 232 is welded to the flat portion of the U-shaped connector 228 for receiving the lower end 212L of the tubular standoff 212. The socket 232 is preferably slotted 232S and includes a tension fastener 232F to allow tightening about the lower end 212L of the tubular standoff 212 to mechanically secure it in the socket 232.
It is noted that the pivotal connection between the flanges 226 and ears 228E 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
Still referring to
As shown in
Referring now to
The upper end 212U 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 234C is connected to the U-shape to securely affix the by-pass conductor 212 thereto and provide additional strain relief
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.
It is noted that the rim bracket 234 may be positioned along the edge of the tank 218 in alignment with the upper end 210U 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.
Referring to
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 210U of the tubular standoff 210. More particularly, referring to
Alternatively or in addition to the arcuate channel 250, a segment of semi-rigid flex conduit may extend from the upper end 210U of the tubular standoff 210, to provide strain relief and guidance to the by-pass conductor 212.
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.
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.
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.
As shown in
As shown in
More particularly, as shown in
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.
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.
Now that the invention has been described,
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.
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| Entry |
|---|
| Alan Roachell & Bruce Kaiser, “Static Lightning protection for tanks” Well Servicing May/Jun. 2010. |
| Number | Date | Country | |
|---|---|---|---|
| 20130176656 A1 | Jul 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61684857 | Aug 2012 | US | |
| 61550001 | Oct 2011 | US |
