Patent Abstract:
A riser system for underwater oil and gas wells features subsections with flanges that may be fastened together. Riser pipes extend between the flanges, through apertures with tapered seats. The riser pipes may be may from aluminum to reduce the weight of the riser system and may be a composite of two or more sections coupled together by compression fittings.

Full Description:
FIELD 
       [0001]    The present invention relates to the connection of shorter length pipes to form a longer assembly, and more particularly, to the connection of extruded aluminum pipes that are subjected to high magnitude cyclic tensile and pressure loads. 
       BACKGROUND 
       [0002]    Some piping systems are subjected to high magnitude tensile loads and internal pressures that are cyclic in nature. This creates stresses and strains that may lead to material fatigue. For example, risers are large-diameter pipes which connect an oil drilling rig to oil well equipment on the ocean floor and that conduct well contents, e.g., liquids, gases, debris, etc. from the well to the oil rig. Some risers are made from flanged subsections and have smaller auxiliary pipes, e.g., for conducting fluids to operate controls on or near the riser, such as riser kill and choke lines. The auxiliary pipes run parallel to and are disposed about the perimeter of a larger, main pipe. Auxiliary pipes can be subjected to high pressures and varying tensile loads. Steel is the most widely used material for riser systems because steel pipes can be welded or threaded together efficiently without a significant loss in strength. Notwithstanding, steel is quite heavy, making it more difficult to handle and transport, e.g., on drill ships. The mass of the riser system also places limits on its length and subsequently, the maximum drilling depth. 
         [0003]    Extruded aluminum pipes could potentially be used as a replacement for steel, thereby allowing deeper drilling and increased riser storage on drill ships, however, aluminum pipe made from high strength 7000 series alloys is difficult to fusion weld using conventional techniques. Threaded connections tend to have high stresses at the thread roots during loading, making them more susceptible to fatigue failure. Threaded connections also sometimes require polymer seals to maintain pressure within the pipes and to keep contaminants from entering the threads, as contamination and corrosion of the threads exacerbates material fatigue. 
       SUMMARY 
       [0004]    An embodiment of the present invention features a riser pipe having first and second sections of pipe. A socket portion having an internal peripheral tapered seat disposed at one end is coupled to the first section of pipe proximate an end thereof. A collar portion having an internal diameter permitting the collar portion to be slipped over an end of a least one of the first and second sections of pipe has an internal peripheral tapered seat disposed at one end thereof. The socket and collar portions are coaxially couplable by at least one threaded fastener, the threaded fastener drawing the socket and collar portions together when tightened. A ferrule having an outer surface sloping in opposing directions from a larger intermediate diameter to smaller diameters proximate a first end and a second end of the ferrule, can be slipped over an end of at least one of the first and second sections of pipe. The outer diameter of the second section of pipe permits an end thereof to be inserted into the socket portion with the ferrule captured between the socket portion and the collar portion and with the oppositely sloping outer surface of the ferrule engaging the tapered seats of the socket and collar portions. When the threaded fasteners draw the socket and collar together, the tapered seats of the socket and collar compress the ferrule inwardly, causing the interior surface of the ferrule to frictionally engage an outer peripheral surface of the second section of pipe. At least one of the first section of pipe and the second section of pipe is made at least partially from aluminum. 
         [0005]    In accordance with another embodiment, the socket is integrally formed with the first section of pipe. 
         [0006]    In accordance with another embodiment, the outside diameters of the first pipe and the second pipe are equal. 
         [0007]    In accordance with another embodiment, the outside diameters of the first pipe and the second pipe are unequal. 
         [0008]    In accordance with another embodiment, the riser pipe is incorporated into a riser section and at least one of the first sections of pipe and the second sections of pipe is shorter than the length of the riser section in which it is incorporated. 
         [0009]    In accordance with another embodiment, the riser section has a terminal flange proximate each end, at least one of the terminal flanges having a through aperture with a tapered seat, at least one of the first section of pipe and the second section of pipe having a flared end that is matingly received in the tapered seat to prevent the flared end from passing through the aperture. 
         [0010]    In accordance with another embodiment, both the first section of pipe and the second section of pipe each have a flared end that is matingly received in a corresponding tapered seat in a corresponding terminal flange. 
         [0011]    In accordance with another embodiment, a third pipe section is conjoined to one of the first and second pipe sections. 
         [0012]    In accordance with another embodiment, the riser pipe has more than three pipe sections. 
         [0013]    In accordance with another embodiment, the socket has a socket collar with an internal diameter permitting the socket collar to be slipped over an end of the first section of pipe, the socket collar portion having an internal peripheral tapered seat disposed at one end thereof, the socket also having a hollow intermediate body with the internal peripheral tapered seat at one end and another peripheral tapered seat at the other end. The socket collar and the intermediate body are coaxially couplable by at least one threaded fastener, the threaded fastener drawing the socket collar and the intermediate body together when tightened. The socket has a second ferrule having an outer surface sloping in opposing directions from a larger intermediate diameter to smaller outside diameters proximate a first end and a second end of the second ferrule, the inside diameter of the second ferrule permitting the second ferrule to be slipped over an end of the first section of pipe, the outer diameter of the first section of pipe permitting an end thereof to be inserted into the hollow intermediate body with the second ferrule captured between the socket collar and the hollow intermediate body and with the oppositely sloping outer surface of the second ferrule engaging the tapered seats of the socket collar and the hollow intermediate body, such that when the threaded fastener draws the socket collar and hollow intermediate body together, the tapered seats of the socket collar and the hollow intermediate body compress the second ferrule inwardly causing an interior surface of the second ferrule to frictionally engage an outer peripheral surface of the first section of pipe. 
         [0014]    In accordance with another embodiment, a riser system for an underwater well drilled into the earth below a body of water, the riser system extending from well equipment located near the underwater earth-water interface to a platform proximate the surface of the water has a plurality of sub-sections connected together. Each subsection has at least one riser pipe for conducting at least one fluid between the well equipment and the platform and having at least one sub-section having a composite riser pipe having a plurality of sub-lengths conjoinable by at least one compression fitting. 
         [0015]    In accordance with another embodiment, the composite riser pipe is made at least partially of aluminum. 
         [0016]    In accordance with another embodiment, the number of sub-lengths is greater than two and the conjunction of each sub-length to the next is made by a compression fitting. 
         [0017]    In accordance with another embodiment, each sub-length of the composite riser pipe is made at least partially of aluminum. 
         [0018]    In accordance with another embodiment, each riser section has a flange proximate each end, each flange having at least one aperture therein and wherein a sub-length of the composite riser pipe extends through an aperture in each of the flanges, each of the two sub-lengths of composite riser pipe extending through the apertures having a flared end receivable in and mating with the tapered seat in the corresponding flange. 
         [0019]    In accordance with another embodiment, an end of the two sub-lengths opposite the flared end inserts into a compression fitting. 
         [0020]    In accordance with another embodiment, a method for forming a sub-section of a riser system, the subsection having a pair of flanges proximate the ends thereof; at least one flange having an aperture with a tapered seat, includes obtaining a first riser pipe having a flared end capable of being matingly received in the tapered seat of the flange; obtaining a compression fitting capable of slidably receiving an end of the first riser pipe opposite to the flared end thereof, the compression fitting coupled to a second length of riser pipe extending to the other flange of the pair of flanges; sliding the first riser pipe through the aperture, such that the flared end is matingly received in the tapered seat and the opposite end is received in the compression fitting; and tightening the compression fitting to grip the first riser pipe. 
         [0021]    In accordance with another embodiment, both of the pair of flanges have apertures with tapered seats and the second riser pipe has a flared end and an end slidably receivable in a compression fitting and further including the step of sliding the second riser pipe through a corresponding aperture in the second of the pair of flanges, such that the flared end thereof is matingly received in the tapered seat of the second flange and sliding the other end of the second riser pipe into a compression fitting and tightening the compression fitting to grip the second riser pipe. 
         [0022]    In accordance with another embodiment, the first and second riser pipes are both slidably receivable in the same compression fitting. 
         [0023]    In accordance with another embodiment, at least one intermediate riser pipe is obtained, both ends of which are slideably receivable in a corresponding compression fitting. Each of the ends of the at least one intermediate pipe are inserted into the corresponding compression fittings, the corresponding compression fittings coupling to the first and second riser pipes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    For a more complete understanding of the present invention, reference is made to the following detailed description of exemplary embodiments considered in conjunction with the accompanying drawings. 
           [0025]      FIG. 1  is a perspective view of a section of a well riser. 
           [0026]      FIG. 2  is a cross sectional view of a section of well riser in accordance with an exemplary embodiment of the present disclosure. 
           [0027]      FIG. 3  is an enlarged view of a threaded fitting for an auxiliary riser pipe. 
           [0028]      FIG. 4  is a cross-sectional view of a pipe coupling in accordance with an embodiment of the present disclosure. 
           [0029]      FIG. 5  is an enlarged view of a fragment of the pipe coupling of  FIG. 4 . 
           [0030]      FIG. 6  is an exploded perspective view of a pipe coupling in accordance with another embodiment of the present disclosure. 
           [0031]      FIG. 7  is a cross sectional view of the pipe coupling of  FIG. 6  in an assembled state. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0032]      FIGS. 1 and 2  show a riser section  10  having a main pipe  12  extending between two flanges  14 ,  16 , which allow adjacent, similar riser sections  10  to be connected together using, e.g., a plurality of bolts  18  and mating nuts (not shown) to form an elongated riser that can be utilized to connect an oil well platform at the surface of the sea to a well head or well casing on the sea floor. A plurality of peripheral auxiliary pipes  20 ,  20 ′ extend between the flanges  14 ,  16  and are used for various functions, such as for controlling well head apparatus, injecting or withdrawing various fluids communicating between the well head and the oil platform, for riser choke and kill lines, etc. in accordance with the present disclosure, the auxiliary pipes  20  may have an intermediate portion  22  conjoined to end portions  23 ,  24  via one or more compression couplings  25 ,  26 , that shall be described fully below. The intermediate portion  22  may be formed with one or more weld joints  27  and/or any given number of sub-sections, e.g., like subsections  22 ,  23 ,  24  joined by compression couplings like, e.g., couplings  25 ,  26 . The end portions  23 ,  24  may be extended through tapered apertures  30  in the respective flanges  14 ,  16  and then received into the couplings  25 ,  26  to join to the intermediate portion  22 . A tapered or flanged head  32 ,  33  of the end portions  23 ,  24  may be utilized to matingly engage a mating tapered aperture  30 . The flanges  14 ,  16  are held at a fixed relative distance by the main pipe  12 , which may be fabricated from welded portions, as shown by the weld lines  27 . As shown in  FIG. 1 , the opposite ends of the main pipe  12  and the auxiliary pipes  20  may be provided with male and female terminations and fitted with seals to form a complementary, fluid tight connection between adjacent riser sections  10 . In accordance with conventional methods, auxiliary pipes  20 ′ may be fabricated from sub-sections using threaded connections  28 . 
         [0033]      FIG. 3  shows an enlarged view of a threaded fitting  28  having a socket portion  28   S  and a nipple portion  28   N , The nipple portion  28   N  can be utilized to terminate a pipe like pipe  23 ′ in order to connect to socket  28   S . Seals or sealing compound may be required to maintain a fluid-tight junction established by the threaded fitting  28  to maintain pressure in the auxiliary tube  20 ′ and to avoid contamination and/or corrosion of the threaded components  28   N ,  28   S . As noted, the threads in the socket  28   S  and on the nipple  28   N  act as stress risers when exposed to cyclic tension, e.g., due to the oscillation of the riser and riser sections  10  attributable to movement of the oil well platform in response to ocean waves, currents, wind, etc. and are subject to metal fatigue from this cyclic loading. As a result, auxiliary pipes utilizing threaded o couplings are more prone to metal fatigue than the auxiliary pipes  20  which utilize compression couplings  25 ,  26  in accordance with the present disclosure. Due to the increased likelihood of fatigue at the threads of threaded couplings, such threaded couplings are preferably made from steel, rather than aluminum. 
         [0034]      FIGS. 4 and 5  show a coupling  50  for joining two pipes  52 ,  54  in an end-to-end or generally abutting orientation to yield an auxiliary pipe  70 . Coupling  50  would therefore be suitable for use for couplings  25  and  26  in the riser section  10  shown in  FIGS. 1 and 2 . As shall be evident from the following disclosure, it is not necessary that the ends  52   E ,  54   E  contact one another. The pipes  52 ,  54  may be made of any material, e.g., steel or aluminum and may be made of different materials, e.g., pipe  52  may be aluminum and pipe  54  may be steel. The coupling  50  has a pair of end collars  56 ,  58  that slip over the ends  52   E ,  54   E  of respective pipes  52 ,  54 . The end collars  56 ,  58  each have tapered seats  56   S ,  58   S  that wedge against tapered surfaces  60   A ,  62   A  of a pair of ferrules  60 ,  62 , respectively. A center collar  64  has a pair of seats  64   S1 ,  64   S2  which slip over tapered surfaces  60   B ,  62   B  of the ferrules  60 ,  62 , respectively, pushing the bottom surfaces,  60   C ,  62   C  of the ferrules  60 ,  62  into close frictional engagement with the outer surfaces,  52   S    54   S  of pipes  52 ,  54 . 
         [0035]    The coupling  50  is assembled by sliding an end collar  56 ,  58  over the ends  52   E ,  54   E  of respective pipes  52 ,  54 . A ferrule  60 ,  62  is then slid over the ends  52   E ,  54   E  of respective pipes  52 ,  54 . A center collar  64  is then positioned between the pipes  52 ,  54  and the ends  52   E ,  54   E  are inserted into the center collar  64 , such that the pipes  52 ,  54  are approximately abutting at the approximate middle of the axial length of the central collar  64 . The end collars  56 ,  58  are then drawn towards the central collar  64 , sliding the ferrules  60 ,  62  toward the central collar  64 . Through bolts  66  extending through openings in the end collars  56 ,  58  and the central collar  64 , receive mating nuts  66   N , which together clamp the coupling  50  together in compression. As the bolts  66  and nuts  66   N  are tightened, the ferrules  60 ,  62  are compressed axially and radially and converge radially inwardly towards the outer surfaces  52   S ,  54   S  of the pipes  52 ,  54 . These combined actions provide a rigid, fluid-tight connection of the pipes  52 ,  54 , in that surfaces  60   A ,  60   B ,  60   C  of the ferrule  60  seal against the tapered seat  56   s , the tapered seat  64   S1  and the outer surface  52   S  of the pipe  52 , respectively, and the surfaces  62   A ,  62   B ,  62   C  of the ferrule  62  seal against the tapered seat  58   s  the tapered seat  64   S2  and the outer surface  54   S  of the pipe  54 , respectively. The radially inwardly directed compressive forces exerted on the ferrules  60 ,  62  create a strong frictional interaction between the ferrules  60 ,  62  and the pipes  52 ,  54  that strongly resists pulling the pipes  52 ,  54  apart/out of the coupling  50  when the pipes  52 ,  54  are pulled in a tensioning direction. The pipes  52 ,  54  may be provided with a tapered head  52   H  and  54   H , respectively, that can engage a tapered seat in a flange of a riser section, such as tapered aperture  30  in flange  12  or  14  of riser section  10  shown in  FIGS. 1 and 2  The tapered heads  52   H  and  54   H , may feature internal machined surfaces to receive seals and otherwise seal the junction between an adjacent tapered head  52   H  and  54   H , of an adjacent riser section  10 . 
         [0036]    To assemble an auxiliary pipe  70  in a riser section like riser section  10  of  FIG. 1 , the two pipe sections  52  and  54  are each slid through corresponding tapered apertures  30  in the flanges  14 ,  16  and the ends  52   E ,  54   E  are received in the coupling  50 . When the tapered ends  52   H ,  54   H  bottom out in the tapered apertures  30  in the flanges  14 ,  16 , the coupling  50  can be tightened, as described above, hydraulically and mechanically unifying the pipes  52 ,  54 . It should be observed that the coupling  50  can be used between any selected number of pipe subsections, such that an auxiliary pipe  70  can be composed of subsections of smaller (and more numerous) or larger (and less numerous) lengths. This ability to control the lengths of pipe subsections may be used to adapt the auxiliary pipe  70  to a given workspace. More particularly, if a ship has a work room for disassembling and replacing auxiliary pipes  20  from riser sections  10 , long lengths of auxiliary pipe  20  may exceed the dimensions of the workspace when they are withdrawn from the flange  14 ,  16  of a riser section  10 . The same type of operating clearances would be a consideration when re-assembling the riser section  10 . The ability to subsection the auxiliary pipe  70  into smaller lengths permits the auxiliary pipe  70  to be disassembled from the riser section  10  and re-assembled in less space. 
         [0037]    The coupling  50  and the pipes  52 ,  54  may be made from a variety of materials, e.g., steel or aluminum and may be made of the same material or may be of different materials, e.g., pipe  52  may be steel and pipe  54  may be aluminum or vice versa. The ferrules  60 ,  62  may be made of a variety of materials, e.g., steel, aluminum, titanium, copper, bronze, brass or other metals and alloys thereof. It may be beneficial for the ferrules  60 ,  62  to be made from a material that could permanently deform when the coupling  50  is tightened, to more evenly distribute the pressure between the ferrules  60 ,  62  and the pipes  52 ,  54 . It may also be preferable for the combination of materials chosen for the pipes  52 ,  54  and the ferrules  60 ,  62  to exhibit a high degree of relative sliding friction. For example, an aluminum-to-aluminum or an aluminum-to-stainless steel interface may result in a high level of frictional interaction and therefore be capable of withstanding a high level of shear traction. 
         [0038]      FIGS. 6 and 7  show a pipe coupling  80  between a first pipe  82  and a second pipe  84 . Either the first pipe  82  or the second pipe  84  could be internally threaded at the ends  82   E ,  84   E  thereof, or could be smooth as shown, to be accommodated within a coupling, like coupling  50  shown in  FIG. 4 . For example, the first pipe  82  could be a machined fitting with internal threads to receive a threaded nipple, like nipple  28   N  of  FIG. 3 . In that case, first pipe  82  could be described as a machined terminal fitting, like socket  28   S  shown in  FIG. 3 . Alternatively, the ends  82   E  and/or  84   E  could be accommodated in a coupling, like coupling  50  of  FIG. 4 , slipping into an end collar, like collar  56 , receiving a ferrule, like ferrule  60  there over and inserting into a center collar like center collar  64  of  FIG. 4  to form a larger pipe assembly, such as, for an auxiliary pipe. Coupling  80  may be used intermediate two couplings  50  to provide an intermediate length of piping. While pipes  82  and  84  are depicted as being short, they could be any desired length. 
         [0039]    The pipes  82 ,  84  may be made from a variety of materials, e.g., steel or aluminum and may be made of the of same material or may be of different materials, e.g., pipe  82  may be steel and pipe  84  may be aluminum or vice versa. In the pipe coupling  80  shown, the first pipe  82  has an enlarged socket end  86  that flares out to form a socket for receiving an end  88  of the second pipe  84  in a slip-fit relationship. The end  88  of the second pipe  84  has walls  88 w which are thicker than the walls  92   W  of the remainder  92  of the pipe  84 , a configuration which may be formed by upset during the extrusion process. The relatively thicker walls  88 w concentrate material at the coupling  80  to promote the strength of the coupling  80 . The thickness of the walls  86   w ,  88   w  may be determined based upon the forces anticipated to be exerted on the coupling and adjusted up or down based upon requirements. A ferrule  94  with opening  94   O  slips over the end  88  of the second pipe  84 . The ferrule  94  is captured between three surfaces, viz., a tapered seat  96  formed on the interior periphery of the socket end  86 , a tapered seat  98  formed on the interior periphery of a collar  100 , and the outer peripheral surface  88   O  of the end  88  of the second pipe  84 . The opening  94   O  has an internal diameter approximating the external diameter of end  88 , allowing the ferrule  94  to be moved by hand over the end  88 . The collar  100  has an opening  100   O  with an internal diameter approximating the external diameter of the end  88 , such that the collar  100  may be moved by hand on the end  88 . 
         [0040]    To form the coupling  80 , the end  88  is inserted into the socket end  86 . The collar  100  is then secured to the socket end  86  by a plurality of machine screws  102  that slip through mating apertures  104  in the collar  100  and thread into threaded apertures  106  formed in the walls  86 w of the socket end  86 . The ferrule  94  has opposed tapered surfaces  94   A ,  94   B  on either side, allowing the tapering seats  96 ,  98  to override the tapered surfaces  94   A ,  94   B  of the ferrule  94 , pressing the ferrule  94  radially inwardly toward the outer surface  88   O  of the end  88  of the second pipe  84 , as the collar  100  is pulled closer to the socket end  86  by tightening the screws  102 . This action creates a high magnitude interface pressure between the ferrule  94  and the pipe  84 . Due to friction, the interface between the ferrule  94  and the pipe  84  can support a shear traction that will keep the pipe from pulling out of the socket while loading the joint  80  in tension. The ferrule  94  may be made of a variety of materials, e.g., steel, aluminum, titanium, copper, bronze, brass or other metals and alloys thereof. The outer diameter of piping used with a coupling like coupling  50 ,  80  in accordance with the present disclosure may be trued by machining and/or burnished. The peak tensile stress in a compression coupling  50 ,  80  in accordance with the present disclosure is on the outside of the pipes, e.g.,  52 ,  54  ( FIG.4 ) joined, which may be burnished to create a counteracting compressive stress. A smooth pipe is relatively easier to burnish than the components of a threaded coupling, in particular, at internal thread roots. 
         [0041]    Testing of a coupling  50 ,  80  under tensile load shows that the peak maximum stress (adjacent to a ferrule, e.g.,  60 ), is substantially less that the peak maximum stress. experienced by a threaded coupling (at the last thread of a threaded coupling) for similarly sized piping systems under approximately the same load. This is due to the lack of large circumferential threads to act as stress risers. The ferrule  60 ,  62 ,  94  applies compressive and shear traction to the exterior of the pipe  52 ,  54 ,  84  (at  88 ). Finite element analysis shows that the peak stress in a threaded coupling subjected to a tensile load is at least  110 % higher than the nominal stress in a pipe with 5 inch O.D.×3 inch I.D. In a similar pipe using a coupling according to the present disclosure, the peak stress is only 30% higher than the nominal stress. As a result, a sample coupling according to the present disclosure using pipe formed from 6061-T6 aluminum alloy was able to undergo more testing cycles than threaded designs of similarly dimensioned pipe made with C22N aluminum alloy, an alloy with superior high cycle fatigue resistance to that of the 6061-T6 alloy. 
         [0042]    In a test of a coupling in accordance with the present disclosure, such as shown in  FIGS. 4 and 5 , a pipe-to-pipe coupling was fatigue tested by cyclic loading. The pipes were made from 6061-T6 aluminum alloy and had dimensions 5.995 inches O.D., 3 inches I.D. The coupling collars were made from 4340 steel. The ferrules were made from 6061-T6 aluminum alloy and had an initial I.D. of 6.000 inches, a maximum O.D. of 6.6 inches and a minimum O.D. of 6.1 inches. The angle between the inner surfaces and the sloped faces of the ferrules taken along an axial direction was about 10 degrees. The seats of the center and end collars were oriented relative to the bore there of at an angle of 170 degrees, which was complementary to the sloped ferrule face angle. The length of the sloped ferrule face taken in an axial direction was about 1.375 inches. The length of the seat face of the center and end collars was about 1.5 inches. A total of eighteen ⅝ inch 24 tpi Grade 8 fasteners torqued to 150 ft. lbs. were used to compress the coupling. The fatigue testing was conducted on the coupling with loads varying between 125,000 to 250,000 pounds at the rate of 7 transitions per minute. This cyclic loading was conducted until the point of failure of 1,364,948 cycles. 
         [0043]    The use of a coupling in accordance with the present disclosure as depicted in  FIGS. 4 and 5  does not require welding of the piping system at the coupled joint. Welding can detrimentally affect structural and corrosion performance and also represents an energy intensive, additional fabrication step which adds to the cost of the welded product. 
         [0044]    It is understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make many variations and modifications without departing from the spirit and scope of the claimed subject matter. For example,  FIGS. 4 and 5  show a coupling  50  that joins pipes  52 ,  54  having similar outer diameters and with the central collar  64  having a generally cylindrical configuration. Alternatively, the central collar  64  could have a flared configuration, such that one side could accommodate a pipe  54  having a greater outer diameter than pipe  52 . While a symmetrical ferrule having faces sloped at 10 degrees was described above, the slope angle may be varied and the oppositely sloped faces of the ferrule may have different slope angles. When installing the ferrule on a pipe, differential heating/cooling of the ferrule and the pipe may facilitate sliding the ferrule on the pipe. For example, the ferrule may be heated and/or the pipe may be cooled. As shown in  FIG. 1 , a compression coupling, e.g., coupling  25 ,  26  in accordance with the present invention may be utilized to form an auxiliary pipe  20  from aluminum in a riser system  10  that also includes steel pipe with threaded fittings  28 . The compression couplings  25 ,  26 ,  50 ,  80  disclosed in the present invention may be utilized in forming a center pipe  12  of a riser system  10 . While the present disclosure utilizes a riser system as an exemplary environment in which the present invention may be practiced, other piping applications requiring resistance to cyclic loading and tension or stress would be also be appropriate. All such variations and modifications are intended to be included within the scope of the appended claims.

Technology Classification (CPC): 4