Patent Publication Number: US-2012037377-A1

Title: Aluminum auxiliary lines for drilling riser

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application No. 61/175,393, entitled “Aluminum Auxiliary Lines for Drilling Riser”, filed on May 4, 2009, which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     As will be appreciated, oil and natural gas have a profound effect on modern economies and societies. Indeed, devices and systems that depend on oil and natural gas are ubiquitous. For instance, oil and natural gas are used for fuel in a wide variety of vehicles, such as cars, airplanes, boats, and the like. Further, oil and natural gas are frequently used to heat homes during winter, to generate electricity, and to manufacture an astonishing array of everyday products. 
     In order to meet the demand for such natural resources, companies often invest significant amounts of time and money in searching for and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired resource is discovered below the surface of the earth, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource. Further, such systems generally include a wellhead assembly through which the resource is extracted. These wellhead assemblies may include a wide variety of components, such as various casings, valves, fluid conduits, and the like, that control drilling and/or extraction operations. 
     To extract the resources from a well, a drilling riser may extend from the well to a rig. For example, in a subsea well, the drilling riser may extend from the seafloor up to a rig on the surface of the sea. A typical drilling riser may include a flanged assembly formed from steel, and the drilling riser may perform multiple functions. In addition to transporting drilling fluid into the well, the riser may provide pipes to allow drilling fluids, mud, and cuttings to flow up from the well. 
     As subsea wells are placed in deeper subsea locations (e.g., 10,000 to 12,000 ft.), conventional steel drilling risers may become difficult to install and operate. Because of the tension and pressure load at such depths, typical drilling riser joints are heavier to withstand this increased tension and pressure. However, such heavier drilling risers may exceed the derrick capacity of the rig supporting the riser. Additionally, longer drilling risers may require increased tension to ensure stability and rigidity of the riser. Further, assembly, replacement, and repair of such drilling risers may present challenges in these deeper subsea installations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying figures in which like characters represent like parts throughout the figures, wherein: 
         FIG. 1  is a block diagram of a mineral extraction system in accordance with an embodiment of the present invention; 
         FIG. 2  is a side view of a drilling riser joint having aluminum auxiliary lines in accordance with an embodiment of the present invention; 
         FIG. 3  is an end view of the drilling riser joint taken along line  2 - 2  in accordance with an embodiment of the present invention; 
         FIG. 4  is a cross-section of the drilling riser joint taken along line  3 - 3  of  FIG. 2  in accordance with an embodiment of the present invention; 
         FIG. 5  is a cross-section of a region of the drilling riser joint of  FIG. 4  in accordance with an embodiment of the present invention; 
         FIG. 6  is a cross-section of a region of the drilling riser joint of  FIG. 4  in accordance with an embodiment of the present invention; 
         FIG. 7  illustrates assembly of the drilling riser joint of  FIG. 2  in accordance with an embodiment of the present invention; 
         FIG. 8  is an alternate embodiment of a drilling riser in accordance with an embodiment of the present invention; and 
         FIG. 9  is an embodiment of a process for assembling a drilling riser joint and auxiliary line in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments of the present invention will be described below. These described embodiments are only exemplary of the present invention. Additionally, in an effort to provide a concise description of these exemplary embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “top,” “bottom,” “above,” “below,” and variations of these terms is made for convenience, but does not require any particular orientation of the components. 
     Embodiments of the present invention include aluminum and steel auxiliary lines for a drilling riser. In one embodiment, each joint of the drilling riser may include an auxiliary line having an aluminum tube axially disposed between a first steel portion and a second steel portion at opposite axial end portions. The drilling riser joints may be coupled together by steel flanges at opposite axial ends of the joint, such that only the first steel portion and the second steel portion of the auxiliary line extends though the steel flanges. The first and second steel portions at axial ends of the auxiliary line reduce or eliminate any contact between the aluminum tube and the steel flanges. Further, in some embodiments, the drilling riser joint may be assembled by inserting the aluminum tube radially or laterally between the first and second steel portions. Additionally, in some embodiments the drilling riser may be weighted at one end by including steel auxiliary lines along one section of the drilling riser and aluminum and steel auxiliary lines along another section of the drilling riser. 
       FIG. 1  is a block diagram that illustrates an embodiment of a subsea mineral extraction system  10 . The illustrated mineral extraction system  10  can be configured to extract various minerals and natural resources, including hydrocarbons (e.g., oil and/or natural gas), or configured to inject substances into the earth. In some embodiments, the mineral extraction system  10  is land-based (e.g., a surface system) or subsea (e.g., a subsea system). As illustrated, the system  10  includes a wellhead  12  coupled to a mineral deposit  14  via a well  16 , wherein the well  16  includes a well-bore  18 . 
     The wellhead assembly  12  typically includes multiple components that control and regulate activities and conditions associated with the well  16 . For example, the wellhead assembly  12  generally includes bodies, valves and seals that route produced minerals from the mineral deposit  14 , provide for regulating pressure in the well  16 , and provide for the injection of chemicals into the well-bore  18  (down-hole). In the illustrated embodiment, the wellhead  12  may include, a tubing spool, a casing spool, and a hanger (e.g., a tubing hanger or a casing hanger). The system  10  may include other devices that are coupled to the wellhead  12 , such as a blowout preventer (BOP) stack  30  and devices that are used to assemble and control various components of the wellhead  12 . 
     A drilling riser  22  may extend from the BOP stack  30  to a rig  24 , such as a platform or floating vessel. The rig  24  may be positioned above the well  16 . The rig  24  may include the components suitable for operation of the mineral extraction system  10 , such as pumps, tanks, power equipment, and any other components. The rig  24  may include a derrick  28  to support the drilling riser  22  during running and retrieval, a tension control mechanism, and any other components. 
     The wellhead assembly may include a blowout preventer (BOP)  30 . The BOP  30  may consist of a variety of valves, fittings and controls to block oil, gas, or other fluid from exiting the well in the event of an unintentional release of pressure or an overpressure condition. These valves, fittings, and controls may also be referred to as a “BOP stack.” 
     The drilling riser may carry drilling fluid (e.g., “mud) from the rig  24  to the well  16 , and may carry the drilling fluid (“returns”), cuttings, or any other substance, from the well  16  to the rig  24 . The drilling riser  22  may include a main line  32  having a large diameter and one or more auxiliary lines  34 , as described further below. The main line  32  may be connected centrally over the bore (such as coaxially) of the well  16 , and may provide a passage from the rig to the well. The auxiliary lines  34  may include choke lines, kill lines, hydraulic lines, glycol injection, mud return, and/or mud boost lines. For example, some of the auxiliary lines  34  may be coupled to the BOP  30  to provide choke and kill functions to the BOP  30 . 
     As described further below, the drilling riser  22  may be formed from numerous “joints” of pipe, coupled together via flanges, or any other suitable devices. Additionally, the drilling riser may include flotation devices, clamps, or other devices distributed along the length of the drilling riser  22 . 
       FIG. 2  depicts a side view of a drilling riser joint  36  of the drilling riser  22  in accordance with an embodiment of the present invention. The drilling riser joint  36  may include flanges  38  to couple the joint  36  to other joints and make-up the drilling riser  22 . In this manner, a drilling riser  22  may be constructed to any desired length using a specific number of joints  36 . The flanges  38  may include a plurality of bolts  40  to enable coupling to a flange of another joint of the riser  22 . 
     As shown in the  FIG. 2 , the drilling riser joint  36  includes the main line  32  and auxiliary lines  34 . The drilling riser joint  36  may include any number of auxiliary lines  34  surrounding the main line  32 . In some embodiments, the main line  32  of the drilling riser joint  36  may be a relatively larger diameter than the auxiliary lines  34 . The drilling riser joint  36  may also include one or more clamps  46  located axially at intervals along the length of the drilling riser joint  36 . The clamps  46  may secure and stabilize the auxiliary lines  34  and/or the main line  32 . As described above, during operation of the mineral extraction system  10 , tools, drilling fluids (e.g., mud), or any other substance or device may be provided down the main line  32 . Drilling fluid, cuttings, or any other material from the well  16  may return up the auxiliary lines  34 . 
     One or more of the auxiliary lines  34  may each include an aluminum tube  48  axially between a first steel portion  50  and a second steel portion  52  at opposite axial end positions. As described further below, the aluminum tube  48 , a first steel portion  50 , and a second steel portion  52  may be coupled together by pin and box fittings, as described below in  FIG. 4 . To couple segments of the auxiliary lines  34  together, the first steel portion  50  may be coupled to a steel portion of an adjacent auxiliary line of an adjacent riser joint. Similarly, the second steel portion  52  may be coupled to a steel portion of an adjacent auxiliary line of an adjacent riser joint. Thus, when assembling a plurality of drilling riser joints  36  together to form the drilling riser  22 , the auxiliary lines  34  may be joined to form a continuous line along the length of the riser  22 . 
       FIG. 3  is a front view of the drilling riser joint  36  taken along line  2 - 2  of  FIG. 2  in accordance with an embodiment of the present invention. As shown in  FIG. 3 , the flange  38  includes a central bore  56  and may couple to the main line  32  (e.g., via welding the flange  38  and main line  32 ). The flange  38  may include an annular seal  58  to seal the flange  38  against an adjacent flange. Additionally, the flange  38  includes a plurality of receptacles  60  (e.g., threaded receptacles) configured to receive the plurality of bolts  40 . To provide for assembly of the auxiliary lines  48 , the flange  38  may include one or more holes  62  to allow for passage of the auxiliary lines  34  through the flange  38 . For example, the flange  38  may include holes  62  for a choke line, a kill line, a mud boost line, a hydraulic line, etc. In some embodiments, the holes  62  may be of the same diameter or different diameters. 
     The aluminum tubes  48  of the auxiliary lines  34  aid in reducing the weight of the drilling riser joint  36 . For example, in some embodiments, the weight of the drilling riser joint  36  may be reduced by at least 20%, 25%, 30%, etc. However, in embodiments using steel for the material of the flanges  38 , it may be undesirable for the aluminum tubes  48  to remain in contact with the flanges  38 , such as when the auxiliary line  34  is assembled into the drilling riser  22  and the auxiliary line  34  passes though the holes  62 . Contact between the aluminum tube  48  and the steel flange  38  may result in galvanic corrosion between the two metals. Thus, to minimize or prevent corrosion, the steel portions  50  and  52  on either axial end of the auxiliary line  34  provide for steel-to-steel contact between the auxiliary line  34  and the flanges  38 . Alternatively, in some embodiments the steel portions  50  and  52  may be replaced by aluminum portions and may be externally insulated from the steel flange  38 . 
       FIG. 4  illustrates a cross-section of the drilling riser joint  36  taken along line  3 - 3  of  FIG. 2  in accordance with an embodiment of the present invention. As discussed above and shown in  FIG. 4 , the auxiliary line  34  includes the aluminum tube  48  axially between the steel portion  50  and the steel portion  52 . In the illustrated embodiment, the aluminum tube  48  may be coupled to the steel portions  50  and  52  by male and female fittings, such as box and pin fittings  64  and  66 . Additionally, the steel portion  50  may include box fitting  68 , and the steel portion  52  may include a pin fitting  70 . The steel portion  52  may include an outer skirt  72  to couple the pin  70  to an adjacent steel portion. As described in further detail below, to assemble the auxiliary line  34 , the steel portions  50  and  52  may be passed through the flange  38  and coupled to the aluminum tube  48  at opposite ends of the riser joint  36 . 
       FIG. 5  is a close-up view of region  78  of  FIG. 4 , further illustrating the box and pin fitting  64  in further detail in accordance with an embodiment of the present invention. The aluminum tube  48  includes a female coupling or box  80  having threads  82  and annular seals  84 . The seals  84  may include o-rings or any other suitable sealing device. The steel portion  50  includes a male coupling or pin end  86  having threads  88  and annular seals  90 . The seals  90  may include o-rings or any other suitable sealing device. The pin end  86  is configured to extend coaxially into and engage the box  80  of the aluminum tube  48  via engagement of the threads  82  and  88 . Thus, when assembling the auxiliary line  34 , the pin end  86  of the steel portion  50  may be screwed into box  80  of the aluminum tube  48 . The box  68  of the steel portion  50  enables coupling to a pin of a steel portion of an adjacent segment of the auxiliary line  34 . For example, the pin end  70  of the steel portion  52  is illustrative of a steel portion that may be inserted into the box end  68  of the steel portion  50 . In one embodiment, the pin end  70  of the steel portion  52  may include threads and the box end  68  of the steel portion  50  may include threads to enable the pin end  70  to couple to a correspondingly threaded box end (e.g., such as the box end  68 ). 
       FIG. 6  is a close-up view of region  90  of  FIG. 4 , further illustrating the box and pin fitting  66  in further detail. Similar to  FIG. 5  as discussed above, the box and pin fitting  66  includes a female coupling or box  92  of the aluminum tube  48  having threads  94  and annular seals  96 . The seals  96  may include o-rings or any other suitable sealing devices. The steel portion  52  includes a male coupling or pin end  98  having threads  100  and annular seals  102 . The seals  102  may include o-rings or any other suitable sealing device. As stated above, assembly of the auxiliary line  34  includes insertion of the pin end  98  coaxially into the box  92  of the aluminum tube  48  to engage the threads  94  and  100 . The pin  70  of the steel portion  52  enables coupling to a box of a steel portion of an adjacent segment of the auxiliary line  34 . For example, the box end  68  of the steel portion  52  is illustrative of a steel portion that may receive the pin  70  of the steel portion  52 . In one embodiment, the pin end  70  of the steel portion  52  may include threads and the box end  68  of the steel portion  50  may include threads to enable the pin end  70  and box end  68 . 
     The steel portion  52  includes a skirt  72  that may be used to obtain a desired axial distance between the flange  38  and the auxiliary line  34 . The skirt  72  may include one or more tabs  104  that may engage one or more recesses  106  on the steel portion  52 , securing the skirt  72  to the steel portion  52 . The tabs  104  and recesses  106  are located at different angular positions about the circumference of the steel portion  52 . The tabs  104  may be hammered or otherwise mechanically secured into the recesses  106 . Additionally, the skirt  72  may include radial protrusions  108 . The protrusions  108  aid in distributing the tension on the riser by abutting a beveled portion  110  of the flange  52 . For example, the protrusions  108  may be placed at a specific axial distance  112  from the beveled portion  110  such that a specific amount of tension causes the specific distance  112  to decrease before the protrusions  108  engage the beveled portion  110  and cause tension to be translated to the auxiliary line  34 . Additionally, the tension on the drilling riser  22  may be load shared across all the auxiliary lines  34  surrounding the main line  32  of the drilling riser  22 . 
     The box and pin fittings  64  and  66  eliminate any aluminum-steel contact between the flange  38  and the aluminum tube  48 , as only the steel portions  50  and  52  pass through the flange  38 . The steel-to-steel contact in the flange  38  substantially or entirely prevents galvanic corrosion that may occur between aluminum and steel metal contact. Additionally, to prevent galvanic corrosion between the box  80  of the aluminum tube  48  and the pin end  86  of the steel portion  50  ( FIG. 5 ), the threads  82  and  88  may include corrosion-resistant coatings. Similarly, to prevent galvanic corrosion between the box  92  of the aluminum tube  48  and the pin end  98  of the steel portion  52  ( FIG. 6 ), the threads  94  and  100  may include similar corrosion-resistant coatings. In some embodiments, one or more sacrificial anodes may be provided to reduce or prevent any corrosion. 
     As described above, use of the aluminum tube  48  in the auxiliary line  34  reduces the weight of the drilling riser  22 . Additionally, the pin and box fittings  62  and  66  and/or the aluminum tube  48  may be “field replaced. For example, the pin and box fittings  62  and  66  and aluminum tube  48  can be replaced in the field to repair or replace a joint of the drilling riser  22 , as opposed to a conventional steel riser which requires cutting off and re-welding of the fittings to repair the riser  22 . Further, because no welding is used on the auxiliary line  34 , manufacturing time and cost may be reduced over conventional steel risers. Additionally, as discussed further below, the auxiliary line  34  may be retrofitted to existing drilling risers, such as drilling risers manufactured by Cameron, Inc. 
     Additionally, the reduced weight of the drilling riser  22  with the aluminum tube  48  also reduces the cost for buoyancy of the drilling riser  22 . The increased buoyancy of the aluminum tube  48 , and, thus, the assembled drilling riser  22 , reduces the tension requirements. Accordingly, the drilling riser  22  with aluminum tube  48  reduces rig deck load, tension requirements, buoyancy requirements, derrick load, and associated costs. 
     It should be appreciated that other fitting configurations may be used to couple the steel portions  50  and  52  to the aluminum tube  48 . In the embodiment discussed above, the aluminum tube  48  having the boxes  80  and  92  may be referred to as a “box-by-box” configuration. However, any other suitable configuration may be used, such as “pin-by-pin,” box and pin, etc. Similarly, although the illustrated steel portions  50  and  52  use a box and pin configuration to couple to an adjacent auxiliary line, other configurations may be used. 
       FIG. 7  is a cross-sectional view of the assembly of the drilling riser joint  36  with the aluminum tube  48  in accordance with an embodiment of the present invention. Using the pin and box fittings  64  and  66  described above, assembly of the auxiliary line  34  and drilling riser  22  may be simplified. It should be appreciated that the assembly may be accomplished by human operators and/or remotely operated vehicles (ROV&#39;s), and may include the use of any tools or devices that provide for easier manipulation of the various components. When assembling the auxiliary line  34 , the aluminum tube  48  may be inserted radially or laterally between the flanges  38 , as illustrated by arrow  116 , instead of axially through the flanges  52 . After insertion of the auxiliary line  34 , the steel portion  50  may be inserted axially through the hole  62  of the flange  36 , as shown by arrow  118 . The pin end  86  may be rotated into the box  80  of the aluminum tube  48 , engaging the threads  88  and  82 . Similarly, the steel portion  52  may be inserted through a hole  62  of the flange  36 , as indicated by arrow  120 . The pin end  98  of the steel portion  52  may be rotated into engagement with the box  92  by engaging the threads  100  and  94 . 
     Advantageously, the assembly of the aluminum tube  48  between the flanges  38  eliminates insertion of the entire assembled auxiliary line  34  axially through the flanges  38 , reducing the difficulty and cost of assembly. Removal of the aluminum tube  48  and/or steel portions  50  and  52  may be accomplished in reverse of the manner described above. After assembly of a segment of the auxiliary line  34  into the drilling riser joint  32 , the drilling riser joint  32  may be coupled to other drilling riser joints via the flanges  36  and bolts  40 . 
       FIG. 8  depicts operation of a mineral extraction system  10  in accordance with another embodiment of the present invention. During operation of the mineral extraction system  10 , it may be desirable to “hang-off” the drilling riser from the rig  24 , such that the riser is not connected to the wellhead and is freely suspended. For example, a “hang-off” operation may be desirable during harsh weather conditions, so the vessel  26  can move away from the well and wait for the weather conditions to subside. To stabilize the drilling riser in a “hang-off” operation, it may be desirable for the drilling riser to be heavier near the bottom of the riser. Using the aluminum auxiliary lines  34  discussed above in some riser joints in combination with steel auxiliary lines in other riser joints, a weighted drilling riser may be constructed that has a weight distribution suited for a “hang-off” operation. 
       FIG. 8  depicts an embodiment of a drilling riser  120  having a first plurality of drilling riser joints  122  coupled together via flanges  124  and a second plurality of drilling joints  126  coupled together via flanges  124 . The first plurality of drilling riser joints  122  may include auxiliary lines having aluminum tubes, such as described above in  FIG. 3 . Those auxiliary lines  122  having aluminum tubes may be located in the upper portions of the drilling riser  120 . The second plurality of drilling riser joints  126  may include auxiliary lines having conventional steel tubing, such that these joints  126  are heavier than the first plurality of drilling riser joints  122 . 
     As shown in  FIG. 8 , those drilling riser joints  126  having steel auxiliary lines may be located at the bottom of the assembled drilling riser  120 , such that the lower portion of the drilling riser  120  is heavier than the upper portion that include aluminum auxiliary lines. In such an embodiment, there may be bare joints at the bottom of the drilling riser  120  that could be assembled with the steel auxiliary risers. In some embodiments there may be about eight to about twelve bare joints at the bottom of the drilling riser  120  that may be assembled with steel auxiliary lines. 
       FIG. 9  depicts a process  200  for assembling the drilling riser in accordance with an embodiment of the present invention. Initially, the drilling riser joint  36  may be provided (block  202 ). To add the auxiliary line  34  to the drilling riser joint  36 , the aluminum tube  48  of the auxiliary line  34  may be positioned axially between the flanges  38  of the joint  36  (block  204 ). As described above, the aluminum tube  48  may include box-by-box fittings, box-by-pin fittings, or pin-by-pin fittings. A first steel portion, such as the steel portion  50  having a box  68  as described above in  FIGS. 4 and 5 , may be inserted though the flange  38  and into an end of the aluminum tube  48  (block  206 ), such as into the box  80 . The steel portion  50  may be screwed to the aluminum tube  48  via threads  82  and  88 . The axial position of the steel portion  50  may be axially adjusted in the drilling riser joint  36  by adjusting the engagement of the threads  82  and  88  (block  208 ). 
     Similarly, the steel portion  52  having the pin  70  may be inserted through the flange  36  and into an end of the aluminum tube  48  (block  210 ), such as into the box  92 . The steel portion  52  may be screwed into the aluminum tube  48  via threads  94  and  100 . The axial position of the steel portion  52  may be adjusted by axially adjusting the engagement of the threads  94  and  100  (block  212 ). For example, in some embodiments, the steel portion  52  may be screwed into full engagement with the aluminum tube  48 , and then “backed out” to provide the desired axial distance  112  between the protrusions  108  of the skirt  72  and the beveled edge  110  of the flange  38 . As described above, the distance  112  can affect the amount of tension applied on the drilling riser  22  to translate the tension to the auxiliary line  34 . After installing the steel portion  52 , the skirt  72  may be secured in place by engaging the tabs  104  of the skirt  72  with the recesses  106  of the steel portion  52  (block  214 ). The drilling riser joint  36  may be coupled to one or more adjacent drilling riser joints via the flanges  38  and bolts  40 . Further, in some embodiments, a drilling riser joint  34  may include both auxiliary lines formed entirely from steel and auxiliary lines having the aluminum tube and steel portions described above. 
     In some embodiments, installation and/or replacement of the steel portion  50  having the box  68  and the steel portion  52  having the pin  70  may be installed and/or replaced on the rig  24 . The steel portion  50  may be unscrewed from the female end  80  (e.g., box) of the aluminum tube  48 , and a new steel portion having a box may be inserted into the female end  80  (e.g., box) of the aluminum tube  48  via threads  82 . Similarly, the steel portion  52  may be unscrewed from the female end  92  of the aluminum tube  48 , and a new steel portion having a pin may be inserted into the female end  92  of the aluminum tube  48 . In this manner, the pin  70  and/or box  68  of a section of auxiliary line  34  may be replaced in the field, e.g., on the rig  24 , without removing the joint  36  from the rig  24  and sending to a remote location for disassembly and replacement (such as by welding). 
     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.