Abstract:
A vortex induced vibration suppressor and method is disclosed. The apparatus includes a body that is a flexible member of a polymeric (eg. polyurethane) construction. A plurality of helical vanes on the body extend longitudinally along and helically about the body. A longitudinal slot enables the body to be spread apart for placing the body upon a riser, pipe or pipeline. Adhesive and/or bolted connections optionally enable the body to be secured to the pipe, pipeline or riser.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. Ser. No. 09/712,759, filed Nov. 14, 2000, now abandoned. 
    
    
     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. 
    
    
     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. 
     As an alternate embodiment, the polymer (eg. polyurethane) has a copper nickel particulate dust contained therein. This mixture of polymer and copper nickel particulate dust enhances antifouling capability of the strake. 
     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 
               
               
                   
               
             
          
         
       
     
     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.