Abstract:
A vortex induced vibration suppressor and method is disclosed. The apparatus includes a body that is a flexible member of a polymeric (e.g., polyurethane) construction. A plurality of helical vanes on the body extend longitudinally along and helically about the body. Each vane has one or more openings extending transversely there through. A longitudinal slot enables the body to be spread apart for placing the body upon a riser, pipe or pipeline. Tensile members that encircle the body and pass through the vane openings enable the body to be secured to the pipe, pipeline or riser.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a continuation-in-part of U.S. Ser. No. 10/292,894, filed Nov. 12, 2002, now U.S. Pat. No. 6,695,540 which is a continuation of U.S. patent application Ser. No. 09/712,759, filed Nov. 14, 2000 (now abandoned), all hereby incorporated herein by reference. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable 
   REFERENCE TO A “MICROFICHE APPENDIX” 
   Not applicable 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to vortex induced vibration suppression and more particularly to an improved apparatus for suppressing vortex induced vibrations in vertical risers of oil and gas well drilling platforms and production platforms. Even more particularly, the present invention relates to an improved vortex induced vibration suppression apparatus, also known as a strake, wherein the improved apparatus includes an elongated body of flexible polymeric material such as polyurethane, the body having a wall surrounding a continuous open-ended bore, a plurality of helical vanes provided on the body, (preferably integral therewith) that extend along the length of the body and a longitudinal slot that extends through the wall enabling the body to be separated such as during placement upon a pipe, riser or pipeline. 
   2. General Background of the Invention 
   Vortex induced vibration suppressors are devices that have been used commercially to prevent vortex induced vibration. It has been stated that risers such as those associated with TLP type platforms suffer from vortex induced vibration or “VIV”. Floatable and tension leg platform (TLP) risers suffer from vibration induced vortex caused by ocean currents, for example. VIV can be an acute problem in deep water drilling operations. As the current flows around an unsupported pipe such as a pipeline riser, it creates vortices on the leeward side of the pipe. Vortices produce minute pressure fluctuations that create vibrations on the leeward side of the pipe. When these vortices break away from the pipe, they set up vibrations which will dynamically excite the riser and cause the pipe to fail prematurely. Strong currents increase the amount of vortex induced vibration (VIV). 
   Presently, there are a number of commercially available vortex induced vibration suppressors. One such product is available from Mark Tool Company of Lafayette, La. Another commercially available vortex induced vibration suppressor is available from CRP Marine Products of England. Another commercially available vortex induced vibration suppressor or “strake” system is being commercialized by Dunlaw of Aberdine, Scotland. Another device that is commercially available and that suppresses vortex induced vibration is sold under the mark Uraduct® VIV. 
   One of the problems of placing a vortex induced vibration suppressor on an oilfield riser pipe such as the riser associated with a deep water oil and gas well drilling or production platform is the problem of installing or placing the strake. This problem can be solved by using an underwater diver or divers. However, such a procedure is dangerous and very costly. Some VIV devices have multiple parts that limit overall structural strength. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention provides an improved method and apparatus for solving the problem of vortex induced vibration by providing a suppression apparatus of improved construction that features an elongated body of flexible polymeric material (for example polyurethane), the body having a wall surrounding a continuous, open-ended bore. 
   A plurality of helical vanes are provided on the body, extending along the length thereof. 
   A longitudinal slot extends through the wall, enabling the body to be separated to afford access to the bore (such as during placement on a pipe or riser). In another embodiment, the apparatus can be cast in place on a pipe joint or cast as a one piece strake that is slipped over a pipe and then glued, eliminating the slot and bolted connection. 
   In the preferred embodiment, the entire elongated body and vanes are of a integrally formed, preferably cast or molded polymeric material (for example, polyurethane). This construction enables the entire elongated body to be flexed as portions of the body are separated apart at the slot. 
   In the preferred embodiment, the slot extends along one of the vanes, separating the vane into first and second vane portions, each having a surface that abuts a corresponding surface of the other vane portion upon assembly. 
   The slot is preferably a helically shaped slot that tracks the path of the vane. 
   A removable connection can hold the body together at the slot. In the preferred embodiment, this removable connection is in the nature of a bolted connection or connections that bolt first and second vane portions together. 
   This removable connection is preferably comprised of a plurality of regularly spaced apart, bolted connections. 
   In the preferred embodiment, the slot separates one of the vanes into first and second longitudinally extending vane sections, each having a flat mating surface (or offset for aiding alignment), wherein the flat mating surfaces are engaged, the bolted connections can be perfected to hold them together. 
   In another embodiment, the present invention provides an improved vortex induced vibration suppression apparatus that features the elongated body and helical vanes with a longitudinal slot that extends through the wall at a vane for enabling the body to be separated to afford access to the bore. 
   In an alternate embodiment, a spacer is removably attachable to the body, the spacer including a rounded outer surface that enable the spacer and body to be rolled such as during handling upon the deck of a ship or barge. The spacer provides an elongated bore that is shaped to fit the body and its helical vanes. 
   The present invention provides an improved method of installing a riser having one or more vortex induced vibration suppression devices thereon. The method includes first making up the riser section on a pipeline lay barge that provides a stinger. The vortex induced vibration device or devices is attached to the pipeline on the lay barge. In this fashion, the riser and attached vortex induced vibration suppression devices can be lowered to the seabed by first passing the riser and attached vortex induced vibration suppression devices over the stinger part of the barge. With the present invention, the improved construction of the vortex induced vibration suppression device enables the apparatus to be lowered over a stinger of a lay barge to the ocean floor. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein: 
       FIG. 1  is a side view of the preferred embodiment of the apparatus of the present invention; 
       FIG. 2  is an end view of the preferred embodiment of the apparatus of the present invention taken along lines  2 — 2  of  FIG. 1 ; 
       FIG. 3  is an end view of the preferred embodiment of the apparatus of the present invention and showing part of the method of the present invention wherein the vortex induced vibration suppression apparatus is being separated at its slot for installation; 
       FIG. 4  is another end view illustrating the preferred embodiment of the apparatus of the present invention and showing the optional method step of applying an adhesive to the inside wall surface thereof and is part of the method of the present invention; 
       FIG. 5  is a perspective view of the preferred embodiment of the apparatus of the present invention and illustrating one of the method steps of the present invention, namely the application of the vortex induced vibration suppression device to a riser; 
       FIG. 6  is a perspective view showing the preferred embodiment of the apparatus of the present invention and illustrating part of the method of the present invention, namely the application of fasteners such as bolted connections to the apparatus after placement upon a riser; 
       FIGS. 7A-7B  are side views of the preferred embodiment of the apparatus of the present invention showing the device after placement upon a riser; 
       FIG. 8  is an elevation schematic view showing the method of the present invention, namely the step of lowering the riser and attached vortex induced vibration suppression devices from a pipeline lay barge to the ocean floor; 
       FIG. 9  is an elevation, schematic view of the preferred embodiment of the apparatus of the present invention illustrating the method of the present invention, showing several vortex induced vibration suppression devices mounted to a riser and showing a riser and connected devices positioned next to an offshore oil and gas well drilling/production platform; 
       FIG. 10  is an exploded view of the preferred embodiment of the apparatus of the present invention; and 
       FIG. 11  is an end view of the preferred embodiment of the apparatus of the present invention; 
       FIG. 12  is a front, perspective view of a second and preferred embodiment of the apparatus of the present invention; 
       FIG. 13  is a schematic view of the second embodiment of the apparatus of the present invention and showing the method of the present invention wherein the initial step is illustrated of wrapping the strake body around a pipeline section; 
       FIG. 14  is a schematic end view showing another of the steps of the method of the present invention; 
       FIG. 15  is a schematic end view showing another of the steps of the method of the present invention; and 
       FIG. 16  is a schematic, perspective view showing the second embodiment of the apparatus of the present invention after attachment to a pipeline section and resting upon the rollers of a stinger on a pipeline laying vessel. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1-11  show the preferred embodiment of the apparatus of the present invention, designated generally by the numeral  10 . 
   Vortex induced vibration suppression device  10  includes body  11  having a central longitudinal open ended bore  12  and end portions  13 ,  14 . 
   Body  11  is preferably a one piece, molded or cast flexible body that is preferably of a polymeric material such as polyurethane. A plurality of helical vanes  15 ,  16 ,  17  extend from the wall  30  of body  11  and are preferably integral therewith. A longitudinally extending slot can be optionally formed by mating surfaces  20 ,  21  of vane sections  18 ,  19  as shown in  FIGS. 1-4 . Otherwise, body  11  does not have a slot but is a one piece integral member that can be installed by slipping it over an end of a joint of pipe. It can also be case in place on a joint of pipe. 
   A hinge area  29  is provided generally opposite vane sections  18 ,  19  and the respective mating surfaces  20 ,  21 . A user can spread apart the vane sections  18 ,  19  as shown by arrows  34  in  FIG. 3  for enabling a technician  25  to apply an adhesive  23  using a desired tool or implement such as dispenser  24  to the inside surface  22  of body  11 . During this procedure, a spreader bar  26  can be used to hold the vane sections  18 ,  19  apart as shown in  FIGS. 3-5 . 
   The vane section  18  provides a plurality of longitudinally extending, spaced apart openings  27 . The openings  27  align with a corresponding plurality of longitudinally extending, spaced apart openings  28  through vane section  19 . After an adhesive is applied to inside surface  22  of wall  30  of body  11 , the body  11  can be placed upon a pipeline riser section  32  as indicated schematically by arrow  35  in FIG.  5 . Arrow  36  in  FIG. 5  schematically illustrates the removal of spreader bars  26  once the body  11  is placed upon riser section  32 . 
   When properly assembled upon a pipeline riser section  32  as shown in  FIG. 6 , the wall  30  outer surface  31  provides a smooth contour that is substantially similar in curvature to the outside surface of the pipeline riser section  32 . 
   The adhesive  23  is designed to form a good bond between body  11  and the outside surface  33  of pipeline riser section  32 . A plurality of bolted connections  40  can be used to bolt vane sections  18 ,  19  together to further secure each body  11  to its pipeline riser section  32 . In  FIG. 6 , each bolted connection  40  includes bolt  37 , nut  38  and a plurality of washers  39  if desired. 
   The method the present invention is further illustrated in  FIGS. 8-9  and  10 - 11 . In  FIG. 8 , a pipeline lay barge  41  is shown having a deck  42  upon which is stacked a plurality of pipe joints  43 . The pipeline lay barge  41  also includes a welding area  44  that enables a plurality of the pipe joints  43  to be welded together end-to-end as known in the art. A stinger  45  is also provided with lay barge  41 . Such a lay barge  41  and stinger  45  are well known in the art. 
   According to the method of the present invention, the vortex induced vibration suppression devices  10  of the present invention are assembled to the welded pipeline riser  47  before the riser  47  is lowered to the seabed  50  via stinger  45 . In  FIG. 8 , the arrow  46  schematically illustrates a riser  47  that is fitted with a plurality of vortex induced vibration suppression devices  10 . The combination of pipeline riser  47  and its vortex induced vibration suppression devices  10  or “strakes” are lowered over the stinger  45  as indicated by arrow  46 . To further schematically illustrate the method of the present invention, the surrounding ocean  49  is also shown with water surface  48  and seabed  50 . 
   In  FIG. 9 , an offshore platform  53  is shown. It should be understood that platform  53  can be an offshore oil and gas well drilling and/or production platform. Such a platform  53  is typically supported with support  52  that can be a semisubmersible, TLP or jacket type foundation or any other marine platform support known in the art. In  FIG. 9 , the numeral  51  schematically indicates the entire marine structure that includes support  52  and platform  53 . 
   In  FIGS. 10 and 11 , a plurality of spacers  54  are shown that are attachable to one of the bodies  11 . As shown in  FIGS. 10 and 11 , three spacers  54  can be added to a single body  11  in order to transform it into a cylindrically shaped member that can be easily rolled for ease of transport and ease of installation. Each spacer  54  has end portions  55 ,  56 . Each spacer has a concave surface  57  and a convex surface  58 . The concave surfaces  57  are shaped to conform to the outside surface  31  of body  11  in between two adjacent vanes such as  15 ,  16  or  16 ,  17 . Each spacer  54  provides side beveled edges  59 ,  60  that fit next to a vane  15 ,  16 ,  17  as shown in FIG.  10 . 
   In  FIG. 11 , three spacers  54  are shown attached to a single body  11 . A plurality of straps (not shown) can be used to encircle the combination of spacers  54  and body  11  to thereby secure the spacers  54  to the body  11  until they are to be removed. Typically, this removal can be accomplished just before the body  11  is to be transported to an end user or job site. 
   Optionally, the polymer (eg. polyurethane) for either embodiment has a copper nickel particulate dust contained therein. This mixture of polymer and copper nickel particulate dust enhances antifouling capability of the strake. 
     FIGS. 12-16  show a second embodiment of the apparatus of the present invention, designated generally by the numeral  61  in  FIGS. 12 and 16 . 
   Vortex induced to vibration suppression device  61  includes a polymeric body  62  that can be of polyurethane for example. The body  62  has a bore  63  that is opened ended. Body  62  provides opposing end portions  64 ,  65 . 
   The body  62  is provided with a plurality of helical vanes  66 ,  67 ,  68 . The body  62  also has a thin walled section  69 , the vanes  66 ,  67 ,  68  extending radially from the thin walled section  69 . Further, the helical vanes  66 ,  67 ,  68  are circumferentially spaced apart as shown in  FIGS. 12-16 . 
   A helical slot  70  is provided that can be, for example, in between vanes  66  and  68  as shown in  FIGS. 12 ,  13  and  16 . The slot  70  enables the body  62  to be mounted on a pipeline section  83  by spreading apart mating edges  71 ,  72  as shown in FIG.  13  and then wrapping the body  12  about the pipe section  83  as shown in  FIGS. 13 ,  14  and  15 . 
   The body  62  has an inside surface  73  that is sized and shaped to fit the outside surface  84  of pipeline section  83 . 
   In order to assemble body  62  to a pipeline section  83 , each vane is provided with openings that are positioned next to thin walled section  69  as shown in  FIGS. 12-16 . The openings include opening  78  through vane  66 , opening  79  through vane  77 , and opening  80  through vane  68 . A plurality of openings are provided for each of the vanes  66 ,  67 ,  68  as shown in FIG.  16 . The openings  78 ,  79  and  80  are longitudinally spaced for each vane  66 ,  67 ,  68  as shown in FIG.  16 . 
   In order to assemble the body  62  to a section of pipeline  83 , a plurality of bands or straps  74  are encircled through the various openings  78 ,  79 ,  80  and secured as shown on  FIGS. 14 and 15 . Each strap  74  provides a buckle  75  that can be used to secure the strap or band  74  once it is tightened using a commercially available tensioning tool  81 . Strap  74 , its buckle  75  and tensioning tool  81  are all commercially available. 
   In  FIG. 14 , arrow  85  schematically illustrates the insertion of band  74  through an opening  78  of a vane  66 . In  FIG. 14 , the band  74  has already been inserted through opening  79  of vane  67  and opening  80  of vane  68 . In  FIG. 15 , the band or strap  74  has been inserted through each of the openings  78 ,  79  and  80  and is being tightened using the tensioning tool  81 . In  FIG. 16 , several of the bands  74  have been attached to body  62  at openings  78 ,  79  and  80  and have been tightened to show the completed position of each band  74  with respect to the body  62 . The vortex induced vibration suppression device  10 ,  61  of the present invention can be used on any diameter pipe. 
   Parts List 
   The following is a list of suitable parts and materials for the various elements of the preferred embodiment of the present invention. 
   
     
       
             
             
           
         
             
                 
             
           
           
             
               10 
               vortex induced vibration 
             
             
                 
               suppression device 
             
             
               11 
               body 
             
             
               12 
               bore 
             
             
               13 
               end portion 
             
             
               14 
               end portion 
             
             
               15 
               helical vane 
             
             
               16 
               helical vane 
             
             
               17 
               helical vane 
             
             
               18 
               vane section 
             
             
               19 
               vane section 
             
             
               20 
               mating surface 
             
             
               21 
               mating surface 
             
             
               22 
               inside surface 
             
             
               23 
               adhesive 
             
             
               24 
               dispenser 
             
             
               25 
               technician 
             
             
               26 
               spreader bar 
             
             
               27 
               opening 
             
             
               28 
               opening 
             
             
               29 
               hinge area 
             
             
               30 
               wall 
             
             
               31 
               outer surface 
             
             
               32 
               pipeline riser section 
             
             
               33 
               outer surface 
             
             
               34 
               arrow 
             
             
               35 
               arrow 
             
             
               36 
               arrow 
             
             
               37 
               bolt 
             
             
               38 
               nut 
             
             
               39 
               washer 
             
             
               40 
               bolted connection 
             
             
               41 
               pipeline lay barge 
             
             
               42 
               deck 
             
             
               43 
               pipe joint 
             
             
               44 
               welding area 
             
             
               45 
               stinger 
             
             
               46 
               arrow 
             
             
               47 
               welded riser 
             
             
               48 
               water surface 
             
             
               49 
               ocean 
             
             
               50 
               seabed 
             
             
               51 
               marine structure 
             
             
               52 
               support 
             
             
               53 
               drilling/production platform 
             
             
               54 
               spacer 
             
             
               55 
               end portion 
             
             
               56 
               end portion 
             
             
               57 
               concave surface 
             
             
               58 
               convex surface 
             
             
               59 
               beveled edge 
             
             
               60 
               beveled edge 
             
             
               61 
               vortex induced vibration 
             
             
                 
               suppression device 
             
             
               62 
               body 
             
             
               63 
               bore 
             
             
               64 
               end portion 
             
             
               65 
               end portion 
             
             
               66 
               helical vane 
             
             
               67 
               helical vane 
             
             
               68 
               helical vane 
             
             
               69 
               thin wall section 
             
             
               70 
               slot 
             
             
               71 
               mating surface 
             
             
               72 
               mating surface 
             
             
               73 
               inside surface 
             
             
               74 
               band 
             
             
               75 
               buckle 
             
             
               76 
               technician 
             
             
               77 
               technician 
             
             
               78 
               opening 
             
             
               79 
               opening 
             
             
               80 
               opening 
             
             
               81 
               tensioning tool 
             
             
               82 
               outer surface 
             
             
               83 
               pipeline section 
             
             
               84 
               outer surface 
             
             
               85 
               arrow 
             
             
               88 
               roller 
             
             
                 
             
           
        
       
     
   
   The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.