WO2005116459A1

WO2005116459A1 - Methods and apparatus for installation of a device about a marine structure

Info

Publication number: WO2005116459A1
Application number: PCT/US2005/012297
Authority: WO
Inventors: Donald Wayne Allen; Stephen Paul Armstrong; Dean Leroy Henning; Li Lee; Kenneth Loch; Damon Michael Mcmillan; David Wayne Mcmillan; Dennis Edward Walker; Christopher Steven West
Original assignee: Shell Internationale Research Maatschappij B.V.; Shell Canada Limited
Priority date: 2004-05-17
Filing date: 2005-04-11
Publication date: 2005-12-08
Also published as: US20080056828A1; GB0621695D0; MXPA06013241A; CA2566306A1; US20050254903A1; AU2005248297A1; GB2430721A; AU2005248297B2; MY139993A; GB2430721B; US8029210B2; NO20065834L

Abstract

There is disclosed a system for installing VIV suppression or drag reduction devices (15) about a marine structure, comprising a mechanism (13) for holding the device relative to the structure (12) in a preferred orientation, and wherein the mechanism no longer holds the device relative to the structure in the preferred orientation after the marine structure (10) has been installed.

Description

METHODS AND APPARATUS FOR INSTALLATION OF A DEVICE ABOUT A MARINE STRUCTURE

Cross Reference to Related Applications 5 This Application claims priority to United States Non-Provisional Application having Serial Number 10/848,547, filed on May 17, 2004, having attorney docket number TH 2463. Field of the Invention In one aspect, the invention relates to apparatus, systems and methods for reducing vortex-induced-vibrations ("VIV"), current drag, low frequency drift oscillations due to o random waves, and low frequency wind induced resonant oscillations. In another aspect, the invention relates to apparatus, systems and methods comprising enhancement of VIV suppression devices for control of vortex-induced- vibrations, current drag, low frequency drift oscillations due to random waves, and low frequency wind induced resonant oscillations. In another aspect, the invention relates to apparatus, systems and methods comprising modified5 and improved perforiΗance fairings for reducing VIV, current drag, low frequency drift oscillations due to random waves, and low f equency wind- induced resonant oscillations. In another aspect, the invention relates to methods and apparatus for "J-Lay" and/or "S-Lay" installation of pipe. In another aspect, the invention relates to methods and apparatus installation of VIV suppression during the "J-Lay" and/or "S-Lay" installation of pipe, hi o another aspect, the invention relates to methods and apparatus for installation of a device about a marine structure. Description of the Related Art When a bluff body, such as a cylinder, in a fluid environment is subjected to a current in the fluid, it is possible for the body to experience vortex -induced vibrations (VIV). These5 vibrations are caused by oscillating hydrodynamic forces on the surface which can cause vibrations of the structure, for example, if the forcing frequency is at or near a structural natural frequency. The vibrations maybe largest in the direction transverse to flow, however, in-line vibrations can also cause stresses which may be larger than those in the transverse direction. 0 Drilling for and/or producing hydrocarbons or the like from subterranean deposits which exist under a body of water may expose underwater drilling and production equipment to water currents and the possibility of VIV. Equipment exposed to VIV includes the smaller tubes and cables of a riser system, umbilical elements, mooring lines, anchoring tendons, marine risers, lateral pipelines, the larger underwater cylinders of the hull of a minispar or spar floating production system, and any other structure in the body of water. There are generally two kinds of water current induced stresses to which all the elements of an underwater structure are exposed. The first kind of stress as mentioned above is caused by vortex-induced alternating forces that vibrate the underwater structure in a direction perpendicular to the direction of the current. These are referred to as vortex-induced vibrations (VIV). When water flows past the structure, vortices are alternately shed from each side of the structure. This produces a fluctuating force on the structure transverse to the current. If the frequency of this harmonic load is near the resonant frequency of the structure, large vibrations transverse to the current can occur. These vibrations can, depending on the stiffness and the strength of the structure and/or any welds, lead to unacceptably short fatigue lives. Stresses caused by high current conditions have been known to cause structures such as risers to break apart and fall to the ocean floor. The second type of stress is caused by drag forces which push the structure in the direction of the current due to the structure's resistance to fluid flow. The drag forces may be amplified by vortex induced vibrations of the structure. For instance, a riser pipe which is vibrating due to vortex shedding may disrupt the flow of water around it more so than a stationary riser. This results in greater energy transfer from the cuiτent to the riser, and hence more drag. Many methods have been developed to reduce vibrations of subsea structures. Some of these methods operate by modifying the boundary layer of the flow around the structure to prevent the correlation of vortex shedding along the length of the structure. Examples of such methods include the use of helical strakes around a structure, axial rod shrouds, and/or perforated shrouds. Other methods to reduce vibrations caused by vortex shedding from subsea structures operate by stabilization of the wake. These methods include the use of fairings, wake splitters and/or flags. VIV may also be a problem for subsea pipelines, especially the portions of the pipe line that span canyons or trenches on the ocean floor. These canyons or trenches can act as conduits and magnify the effects of currents at or near the ocean floor. As with vertical structures, the solution is to install VIV suppression such as fairings, wake splitters and flags. Installation of VIV suppression after the laying of the pipeline can be very expensive, laborious, and/or dangerous. It is generally advantageous that VIV suppression would be installed on the pipe at the lay vessel as it is being laid. There are two main methods of laying pipe, the "J-Lay" and "S-Lay." With "J-Lay," a 5 vertical lay vessel is utilized, in which pipe leaves the traveling vessel vertically, with the pipe essentially forming a "J" as it is being laid on the ocean floor. With "S-Lay," pipe leaves the lay vessel in an essentially horizontal position, and rolled off of a radially shaped "stinger" mounted aft, with the pipe essentially forming an "S" as it is being laid on the ocean floor. The stinger cross-section is a "V" shaped trough conveyor comprising a series of rollers across o which the pipe passes. As the stinger is "V" shaped, only a portion of the pipe engages rollers. The problem with installing VIV during an S-Lay, is that the stinger may tend to shear off anything that extends radially from the pipe at those places where it engages the pipe. United States Patent Number 6,695,539 discloses apparatus and methods for remotely installing vortex-induced vibration (VIV) reduction and drag reduction devices on elongated5 structures in flowing fluid environments. The disclosed apparatus is a tool for transporting and installing the devices. The devices installed can include clamshell-shaped strake elements, shrouds, fairings, sleeves and flotation modules. United States Patent Number 6,695,539 is herein incorporated by reference in its entirety. Thus, there is a need in the art for apparatus, systems and methods for suppressing VIV o and reducing drag of a marine element; for apparatus, systems and methods for suppressing VIV and reducing drag of a subsea pipeline, which can be installed during the laying of the pipeline; and/or for apparatus, systems and methods for laying a subsea pipeline with devices for suppressing VIV and/or reducing drag. These and other needs of the invention will become apparent to those of skill in the art5 upon review of this specification, including its drawings and claims. Summary of the Invention In one aspect, the invention provides for apparatus, systems and methods for suppressing VIV and reducing drag of a marine element. hi another aspect, the invention provides for apparatus, systems and methods for o suppressing VIV and reducing drag of a subsea pipeline, which can be installed during the laying of the pipeline. In another aspect, the invention provides for laying a subsea pipeline with VIV. In another aspect, the invention provides for a fairing for reducing vortex-induced- vibrations in a cylindrical marine element. The fairing includes a main body defining a circular passage for receiving the marine element, and comprising a tail section. A locking member is supported by the main body, wherein the member is positionable and lockable in 5 the circular passage against any marine element in the passage to move the tail section away from any marine element in the passage, wherein at least a portion of the locking member may comprise material that will degrade in a marine environment and upon degradation disengage from the marine element. In another aspect, the invention provides for a modified pipe, which includes a pipe0 section, a fairing having a tail section, and rotatably mounted on the pipe. Also included is a locking member interposed between the pipe section and the fairing, biasing the fairing against rotating and/or positioning the tail section radially away from the pipe section, wherein at least a portion of the locking member may comprise material that will degrade in a marine environment and upon degradation will no longer bias the fairing against rotating, and/or no5 longer position the tail section away from the pipe section. In another aspect, the invention provides for a method of modifying a pipe having a fairing rotatably mounted thereon. The method includes positioning a locking member between the pipe and the fairing sufficient to bias the fairing against rotating and/or position a portion of the fairing radially away from the pipe section, wherein at least a portion of the o locking member may comprise material that will degrade in a marine environment and upon degradation will no longer bias the fairing against rotating, and/or no longer position the fairing radially away from the pipe section. A further aspect may include placing the pipe, fairing and locking member in a marine environment, and allowing the locking member to degrade.5 In another aspect, the invention provides for a method of passing a pipe with a rotatably mounted fairing over a roller, wherein the fairing comprises a tail section. The method includes (A) positioning the fairing such that the tail section will not touch the roller as it passes over the roller. The method also includes (B) passing the pipe and fairing over the roller. A further aspect may include, in step (A), further comprising positioning a temporary o locking member sufficient to bias the fairing against rotating. In another aspect, the invention provides for a collar for securing a fairing rotatably mounted on a pipe. The collar may include a circular segment of less than 211 radians, and a circular shaped band positioned around the segment. Other aspects include modifying a pipe by applying the collar to the pipe, passing a pipe with the collar over a roller by positioning the circular segment so that it clears the rollers. In another aspect, the invention provides for a system for installing VIV suppression or 5 drag reduction devices about a marine structure, comprising a mechanism for holding the device relative to the structure in a preferred orientation, and wherein the mechanism no longer holds the device relative to the structure in the preferred orientation after the marine structure has been installed. In another aspect, the invention provides for a method of passing a structure with a i o device having a preferred orientation relative to the structure over a ramp or roller, the method comprising positioning and locking the device in the preferred orientation, such that the device will not be damaged as it passes over the ramp or roller; and passing the structure and device over the ramp or roller. Even other aspects include modifying a pipe by applying both the collar and fairing of 15 the invention to the pipe, and passing a pipe with both the collar and fairing over a roller. Still other aspects include S-laying and/or J-laying of pipe by utilizing the fairing and/or collar. These and other aspects of the invention will become apparent to those of skill in the art upon review of this specification, including its drawings and claims. 20 Brief Description of the Drawings FIG. 1 is a schematic representation of a "J-Lay" installation of a subsea pipeline, showing vessel 10 moving in direction 5 at ocean surface 18, laying pipe 12 onto ocean floor 16. FIG. 2 is a schematic representation of an "S-Lay" installation of a subsea pipeline,

25 showing vessel 20 moving in direction 5 at ocean surface 18, laying pipe 12 utilizing stinger 22 onto ocean floor 16. FIG. 3 is a cross-sectional representation of stinger 22 of FIG. 2, showing pipe 12 positioned and rolling across rollers 25. FIG. 4 is an isometric representation, showing pipe 12, having VIV fairing 15 and o collar 13, positioned and rolling across stinger 22 in direction 7. FIG. 5 is a cross-sectional representation of FIG 4. taken at 5-5, showing pipe 12, having VIV fairing 15 and collar 13, positioned and rolling across stinger 22. FIG. 6 is a cross-sectional representation showing fairing 15 mounted on pipe 12, showing gap 3 formed as a result of gravity. FIG. 7 is a cross-sectional representation showing fairing 15 mounted on pipe 12, showing a substantially smaller gap 3 that can be achieved by lifting fairing 15 in direction 4. FIGs. 8 and 9 are a cross-sectional representations showing fairing 15 mounted on pipe

12, showing fairing 15 lifted and held in place by positioning lock 30. FIGs. 10 and 11 are cross-sectional representations of stinger 22, showing collar 13 mounted on pipe 12. FIG. 12 is a cross-sectional representation of stinger 22, showing fairing 15 mounted on pipe 12. FIG. 13 is an isolated representation of collar 13. FIG. 14 is a cross-sectional view of pipe 12, fairing 15, and plate 120. FIG. 15 is a cross-sectional view of collar 13. FIG. 16 is a side view of fairing 15. FIG. 17 is a view of a fairing locking system. FIG. 18 is a view of a fairing locking system installed between collar 13 and fairing 15 about pipe 12. FIG. 19 is a side view of pipe 12 about which collars 13, fairings 15, and plates 120 have been installed. FIG. 20 is a side view of pipe 12 about which collars 13 and fairings 15 have been installed.

Detailed Description of the Invention The invention is best understood by first making reference to the prior art, and understanding the problem of installing VIV suppression during an S-Lay installation of pipe. Referring to FIG. 1, there is shown a schematic representation of a prior art "J-Lay" installation of a subsea pipeline, showing vessel 10 moving in direction 5 at ocean surface 18, laying pipe 12 onto ocean floor 16. The name "J-Lay" comes from the "J" shape made by pipe 12 during installation. As shown, VIV suppression is being installed at those locations where pipeline 12 will span channels/trenches 17. Fairings 15 and collars 13 may be installed. Referring now to FIG. 2, there is shown a schematic representation of a prior art "S-

Lay" installation of a subsea pipeline, showing vessel 20 moving in direction 5 at ocean surface 18, laying pipe 12 utilizing stinger 22 onto ocean floor 16. The name "S-Lay" comes from the "S" shape made by pipe 12 during installation. Referring additionally to FIG. 3, there is shown a cross-sectional representation of stinger 22 of FIG.2, showing pipe 12 without suppression positioned and rolling across rollers 25. Referring additionally to FIGS. 4 and 5, there are shown, respectively, an isometric representation and a cross-sectional representation, of pipe 12, having fairing 15 and collar 13, with pipe 12 positioned and rolling across stinger 22 in direction 7. As pipe 12 rolls across stinger 22 in direction 7, any attached devices, for example collar 13 and fairing 15, may encounter stinger 22 at point 40, resulting in such collar 13 and fairing 15 either being broken or sheared off of pipe 12, or held back at point 40 while pipe 12 passes through such attached devices, such as the collars and fairings. If the tail end of the fairing could be oriented to avoid stinger 22, then it could pass over stinger 22 intact. Gravity may tend to pull the fairing away from the pipe allowing that portion of the fairing to fall below the pipe and also engage the stinger. This problem can be seen by reference to FIG. 6, which is a cross-sectional representation showing fairing 15 mounted on pipe 12, showing gap 3 formed as a result of gravity. As this fairing 15 approaches the stinger, the portion of the fairing sagging below the pipe 12 will engage the stinger 22, and the fairing 15 may either be sheared/knocked off, or held back while the pipe 12 passes through. If the portion of the fairing 15 that sags below the pipe 12 and engages the stinger 22 could be abutted firmly against the pipe 12, that portion of the fairing 15 could pass easily over the stinger 22. In one embodiment, there is disclosed a system for installing VIV suppression or drag reduction devices about a marine structure, comprising a mechanism for holding the device relative to the structure in a preferred orientation, and wherein the mechanism no longer holds the device relative to the structure in the preferred orientation after the marine structure has been installed. In some embodiments, the mechanism comprises material that will degrade in a marine environment. In some embodiments, the structure comprises a tubular, for example a riser. In some embodiments, the device comprises a fairing. In some embodiments, the mechanism comprises at least one strap that can be broken after the marine structure has been installed, and/or a pin that can be removed after the marine structure has been installed. In some embodiments, the system also includes a loop, wherein the at least one strap is connected to the loop, wherein the loop can be pulled to break the at least one strap. In some embodiments, the system also includes a plate, wherein the at least one strap and the loop are connected to the plate. In some embodiments, the system also includes a collar about the 5 structure, wherein the mechanism connects the device and the collar, to hold the device relative to the structure in the preferred orientation, hi some embodiments, the collar has a reduced radius portion, and an enlarged radius portion, further wherein the enlarged radius portion extends radially away from the structure. In some embodiments, the device comprises a fairing having a tail, wherein the preferred orientation relative to the structure during installation0 comprises turning the tail away from a stinger during a J-lay installation of the structure. In some embodiments, the mechanism is adapted to position a portion of the device radially away from the structure. In one embodiment, there is disclosed a method of passing a structure with a device having a preferred orientation relative to the structure over a ramp or roller, the method5 comprising positioning and locking the device in the preferred orientation, such that the device will not be damaged as it passes over the ramp or roller; and passing the structure and device over the ramp or roller. In some embodiments, the method also includes after passing the structure and device over the ramp or roller, disabling the locking such that the device can move relative to the structure, h some embodiments, the method also includes locking the o device to a collar installed about the structure. In some embodiments, positioning and locking the device comprises securing at least one strap to the device and to the structure or to a second structure connected to the structure. In some embodiments, the method also includes after passing the structure and device over the ramp or roller, breaking the at least one strap to disable the locking such that the device can move relative to the structure. In some5 embodiments, positioning and locking the device comprises securing at least one pin to the device and to the structure or to a second structure connected to the structure. In some embodiments, the method also includes after passing the structure and device over the ramp or roller, removing the at least one pin to disable the locking such that the device can move relative to the structure. o Referring now to FIG. 7, there is shown a fairing 15 with its tail oriented to avoid the stinger 22, and that has been abutted firmly against the pipe 12. FIG. 7 is a cross-sectional representation showing fairing 15 mounted on pipe 12, showing fairing tail oriented to avoid stinger 22, and showing that a substantially smaller gap 3 that can be achieved by lifting fairing 15 in direction 4. Once fairing 15 has been lifted in direction 7 is may be held in place so that it can pass safely over stinger 22. In some embodiments, there is provided a positioning lock to keep fairing 15 abutted in place while fairing 15 travels over stinger 22. Any suitable positioning lock 30 may be utilized. In some embodiments, positioning lock 30 can be seen by reference to FIG.9, in which a wedge 39 has been inserted into the upper gap between fairing 15 and pipe 12 to minimize gap 3 and abut fairing 15 against pipe 12. It is envisioned that any suitable number of wedges may be utilized, and that such wedges may comprise any suitable shape. In some embodiments, positioning lock 30 can be seen by reference to FIG. 8, which utilizes a set screw/bolt. There is shown a cross-sectional representation showing fairing 15 mounted on pipe 12, where fairing 15 is lifted and held in place by positioning lock 30. Threaded passages 33 may be provided in fairing 15 for receiving set screws/bolts 35 and 37. In some embodiments, set screw/bolt 37 may engage pipe 12 directly. In other embodiments, set screw/bolt 35 engages a pipe contact member 38, which in turn engages pipe 12. Once fairing 15 passes over stinger 22, fairing 15 may be made to freely rotate around pipe 12. While engaged, positioning lock 30 prevents such free rotation. According to some embodiments of the invention, position lock 30 maybe disengaged after fairing 15 passes over stinger 22. According to some embodiments of the invention, position lock 30 comprises materials which will degrade in the aquatic environment and allow free rotation of fairing 15 around pipe 12. The materials may be selected to degrade in the aquatic environment at a rate slow enough to allow for installation, but fast enough so that the fairing may properly operate not too long after installation. The materials may have physical properties suitable to allow fairing 15 to be locked into place, and to withstand the rigors in pipe installation, and travel across the stinger. Not all of positioning lock 30 need be comprised of degradable materials. As one non-limiting example, pipe contact member 38 may comprise a degradable material. As another non-limiting example, set screw/bolt 37 may comprise a degradable material. As another non-limiting example, even bolt 37 does not have to be made entirely of degradable materials. As non-limiting examples, only the tip of set screw 37 in contact with pipe 12 need comprises degradable material, or perhaps the threads of screw/bolt 37 will degrade. Alternatively, the threads of threaded passages 33 can be made to degrade, freeing set screw 38. As even another non-limiting example, a positioning lock 30 with a degradable locking pin can be easily envisioned. Materials that will degrade in marine environments and that will have adequate physical properties are well known to those of the materials art. Such materials may be degradable thermoplastics and/or thermosets and/or metals, for example biodegradable thermoplastics and/or thermosets. In some embodiments, collars 13 are provided to secure fairings 15 to pipe 12. Specifically, the collars may be designed to avoid colliding with stinger 22. Referring now to FIGs. 10 and 11, there are shown cross-sectional representations of stinger 22, showing two embodiments of collar 13 mounted on pipe 12. With additional reference to FIG. 13, there is an isolated representation of collar 13. Point 63 is the center of pipe 12 cross-section and of collar 13 cross-section. Assuming a uniform circular collar 13, the interfering radial portion 65 of collar 13 is that portion which would engage stinger 22, and is that portion 65 of collar 13 between points 61 and 62, defining angle Θ. Within this Θ radius, collar 13 must be made thin enough to pass over stinger 22, and in some embodiments is merely a thin band 51. Interfering portion 65 of collar 13 that does not engage stinger 22 defines an angle (2I1-Θ radians). Thus, for a stinger having an interference angle with a collar of Θ radians, the main body of collar may be less than or equal to (2IT-Θ radians), with at least a Θ radian portion of the collar comprising a thin section having a thickness that will not interfere with passage over the stinger 22. The main body of collar 13 may extend radially away from pipe 12 a sufficient distance to secure fairing 15 in place. Collar 13 may be provided with a band groove 54 for receiving band 51, for example a steel or inconel band. In some embodiments, a band locking/tightening mechanism, such as locking bolt/nut 55 may be provided. Referring now to FIG. 12, there is shown a cross-sectional representation of stinger 22, showing fairing 15 mounted on pipe 12. Screw/bolt 35 has been fed through threaded passage 33 to force pipe contact member 38 into engagement with pipe 12, to hold tail of fairing 15 away from stinger 22. Referring now to FIG. 14, in some embodiments, there is illustrated pipe 12 about which is installed fairing 15. Fairing 15 includes bolts 106 which hole end plate 108 in place. End plate 108 may be installed at each end of fairing 15 to hold the form of the fairing.

Connector 104 is at tail 105 of fairing 15, which connector 104 holds tail 105 together. Hole 1 12 and hole 110 are provided in fairing 15. Plate 120 is also shown, which includes hole 122 and hole 124. Straps maybe fed through hole 122 and hole 110 to secure tail 105 of fairing 15 in a desired orientation. A strap maybe fed through hole 124 and hole 112 to hold tail 105 of fairing 15 in a desired orientation. Referring now to Figure 15, in some embodiments, collar 13 is illustrated. Collar 13 includes flangel40, with hole 142 and hole 144 through flange 140. A straps may be fed through hole 142 of collar 13 and hole 110 of fairing 15 to keep fairing 15 in a desired orientation. Also, a strap may be fed through hole 144 of collar 13 and hole 112 of fairing 15 , to hold fairing 15 in a desired orientation. The straps may also be fed through hole 122 or hole 124 of plate 120, if desired. Referring now to Figure 16, in some embodiments, a side view of fairing 15 is illustrated. Fairing 15 includes tail 105 , with connectors 104 holding tail 105 and/or fairing 15 together. Holes 112 are provided at each end of fairing 15 , which may be used to feed a strap through one of more these holes to keep tail 105 oriented in the desired direction. Referring now to Figure 17, in some embodiments, a fairing orientation system is illustrated. The system includes plate 120. Loop 150 is connected to plate 120 by connector 152. Strap 130 and strap 132 are fed around plate 120. Strap 130 is attached to connector 152 by connection 154. Strap 132 is attached to connector 152 by connection 156. In use, plate 120 may be placed between fairing 15 and collar 13, with strap 130 fed through hole 142 of collar 13 and hole 110 of fairing 15. Strap 132 maybe fed through hole 144 of collar 13 and hole 112 of fairing 15, where straps 130 and 132 act to keep tail 105 of fairing 15 in the desired orientation. Any suitable device may be used to grab loop 150 and pull on loop 150 to break straps 130 and 132 so that fairing 15 is free to weathervane about pipe 12, for example a cable attached to loop 150 or an ROV arm to grab loop 150. Referring now to Figure 18, in some embodiments, fairing orientation system is shown attached to pipe 12. Collar 13 is mounted about pipe 12, and fairing 15 is mounted about pipe 12. Plate 120 is between collar 13 and fairing 15. Strap 132 is fed through a hole in fairing 15 and a hole in collar 13 to keep fairing oriented in the desired direction. Strap 130 is fed through a hole in collar 13 and a hole in fairing 15 to keep fairing 15 oriented in the desired direction. Connector 152 acts to connect strap 132 to plate 120 and strap 130 to plate 120, loop 150 to plate 120. Loop 150 is connected to plate 120, strap 132, and strap 130. When desired, strap breaker 160, for example an ROV, a cable, or a rope, maybe used to pull loop 150 and break straps 130 and 132, and also remove plate 120, so that fairing 15 is free to weathervane about pipe 12. In some embodiments, after straps 130 and 132 are broken, broken straps are attached to connector 152, plate 120, and loop 150, so that the entire fairing orientation system may be recovered. Referring now to Figure 19, in some embodiments, pipe 12 is illustrated. Collars 13

5 are mounted about pipe 12, fairings 15 are mounted between collars 13 about pipe 12. Each fairing also includes tail 105 oriented in the desired direction, for example, in the same direction and/or away from stinger 22. Plates 120 are provided between fairings 15 and collars 13. hi some embodiments, in operation, strap 130 may be used to anchor fairing 15 to o collar 13 to keep tail 105 oriented in the desired direction. Straps may be provided for each of fairings 15, for example on each side of tails 105. In some embodiments, in operation, fairings 15 may be secured to collars 13 by strap and/or a plate, and then fed off a ship in a S-lay configuration, over a stinger 22. After pipe 12 has been fed over stinger 22, straps 130 may be broken and plates 120 maybe removed so that5 tails 105 are able to weathervane about pipe 12 between collars 13, having sufficient radial and longitudinal freedom of motion. Referring now to Figure 20, in some embodiments, pipe 12 is illustrated. Mounted about pipe 12 are collars 13 and fairings 15. Each fairing 15 has tail 105 oriented in the desired direction, for example, in the same direction and/or away from stinger 22. Holding o tails 105 in the desired direction are pin 170, pin 174, pin 178 and pin 182 fed through a hole in collar 13 and into a receiving hole in fairing 15. Attached to pin 170, pin 174, pin 178 and pin 182 are cable 172, cable 176, cable 180, and cable 184, respectively. After it is not longer desired that tails 105 be locked in a certain orientation, pins 170, 174, 178, and 182 may be removed by pulling on cables 172, 176, 180, and 184. In some embodiments, the cables may5 be collected at hub 186 so that hub 186 may be pulled to remove pins 170, 174, 178, and 182. In some embodiments, one end of cable 172, cable 176, cable 180, and cable 184 may be retained on the vessel 20, so that after pipe 12 has been fed over stinger 22 a desired distance, the one end of the cables may be used to pull out the pins 170, 174, 178, and 182. In some embodiments, hub 186 may be pulled by an ROV or a cable that has been o retained on the vessel 20 after pipe 12 has been fed over stinger 22. While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the invention, including all features which would be treated as equivalents thereof by those skilled in the art to which this invention pertains.

Claims

C L A I M S

1. A system for installing vortex induced vibration suppression or drag reduction devices about a marine structure, comprising: a mechanism for holding the device relative to the structure in a preferred orientation; and wherein the mechanism no longer holds the device relative to the structure in the preferred orientation after the marine structure has been installed.

2. The system of claim 1, wherein the mechanism comprises material that will degrade in a marine environment.

3. The system of one or more of claims 1-2, wherein the structure comprises a tubular, for example a riser.

4. The system of one or more of claims 1-3, wherein the device comprises a fairing.

5. The system of one or more of claims 1 -4, wherein the mechanism comprises at least one strap that can be broken after the marine structure has been installed, and/or a pin that can be removed after the marine structure has been installed.

6. The system of claim 5, fiirther comprising a loop, wherein the at least one strap is connected to the loop, wherein the loop can be pulled to break the at least one strap.

7. The system of claim 6, further comprising a plate, wherein the at least one strap and the loop are connected to the plate.

8. The system of one or more of claims 1-7, further comprising a collar about the structure, wherein the mechanism connects the device and the collar, to hold the device relative to the structure in the preferred orientation.

9. The system of claim 8, wherein the collar has a reduced radius portion, and an enlarged radius portion, further wherein the enlarged radius portion extends radially away from the structure.

10. The system of one or more of claims 1-9, wherein the device comprises a fairing having a tail, wherein the preferred orientation relative to the structure during installation comprises turning the tail away from a stinger during a J-lay installation of the structure.

11. The system of one or more of claims 1-10, wherein the mechanism is adapted to position a portion of the device radially away from the structure.

12. A method of using a system of any one of claims 1-11, the method comprising: (A) positioning and locking the device in the preferred orientation, such that the 5 device will not be damaged as it passes over a ramp or roller; and (B) passing the structure and device over the ramp or roller.

13. The method of claim 12, further comprising after passing the structure and device over the ramp or roller, disabling the locking such that the device can move relative to the structure.0 14. The method of one or more of claims 12-13, further comprising locking the device to a collar installed about the structure. 15. The method of one or more of claims 12-14, wherein positioning and locking the device comprises securing at least one strap to the device and to the structure or to a second structure connected to the structure.5 16. The method of claim 15, further comprising after passing the structure and device over the ramp or roller, breaking the at least one strap to disable the locking such that the device can move relative to the structure. 17. The method of one or more of claims 12-16, wherein positioning and locking the device comprises securing at least one pin to the device and to the structure or to a second o structure connected to the structure. 18. The method of claim 16, further comprising after passing the structure and device over the ramp or roller, removing the at least one pin to disable the locking such that the device can move relative to the structure.