JP2005238866A - Swinging reduction device of cylindrical structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a swinging reduction device of a long cylindrical structure capable of sufficiently suppressing swinging or vibration in a long cylindrical marine structure. <P>SOLUTION: The swinging reduction device of the cylindrical structure is equipped with the floating or hung cylindrical structure, strakes arranged in helical shape on the surface of the cylindrical structure, and a clearance formed between the surface of the cylindrical structure and the strakes, or the strake unit is equipped with a set of semicircular mounting bands provided so as to face to each other, another set of semicircular mounting bands facing to each other provided facing to the set of semicircular mounting bands, a U-shape strake connecting with the semicircular mounting band facing to each other, and a connecting means connecting between the semicircular mounting bands facing to each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sway reduction device such as a spar-type offshore structure or an underwater long cylindrical structure.

  Conventionally, as a facility for oil well drilling and oil extraction at the bottom of the sea, a platform is placed above the sea surface of a vertically long cylindrical buoyant body, which is used as a base, and a drill pipe, riser, etc. are suspended below it to suspend the sea floor. There is a so-called SPAR type offshore structure that performs the work. In a cylindrical structure such as a vertically long cylindrical buoyant body and a drill pipe in this spar type offshore structure, since it is installed in the ocean, it is always affected by waves and tidal currents. And a cylindrical structure will receive a direct force from a wave and a tidal current, and a vortex will be formed in the downstream, and a cylindrical structure will receive a force also from this vortex. .

  The vortex is uniformly formed around the outer peripheral surface from the back side of the cylindrical structure 1. Such a vortex exerts a negative pressure on the cylindrical structure 1 while being minute on the left and right. That is, the cylindrical structure is pulled in the direction in which the vortex is formed. However, when vortices are alternately formed on the left and right sides, the cylindrical structure will oscillate or vibrate in accordance with the vortex formation cycle. In particular, when this period coincides with the natural frequency of the cylindrical structure or the drill pipe, the cylindrical structure is greatly shaken or vibrated, which is a very serious problem for the entire marine structure. In addition, since the cross-sectional shape of the cylindrical structure is circular, it is conceivable that a symmetrical vortex is formed on the back side of waves and tides coming from any direction. You can say that.

  In order to solve the above-mentioned problem, what is shown in FIGS. 8 and 9 has been proposed. In the structure shown in FIG. 8, the strake 30 is formed on the outer wall of the tubular structure 1 having an octagonal (polygonal) cross-section so that the formation position thereof is changed in the longitudinal direction of the tubular structure 1. ing. Moreover, what is shown in FIG. 9 has a form in which the strake 31 is formed in a spiral with respect to the cylindrical structure 1, that is, a form in which the strut 31 is provided obliquely. (For example, Patent Document 1)

JP 2000-168676 A (FIG. 4)

However, in the prior art, in order to suppress the vibration or vibration, it is necessary to arrange a considerably large strake, and there is a problem that the effect of suppressing the vibration or vibration is insufficient.
The present invention has been proposed in order to solve the above-described problems, and provides a vibration reduction device for a long cylindrical structure that can sufficiently suppress vibration or vibration in a long cylindrical offshore structure. Is an issue.

The present invention has been made in order to solve the above-described conventional problems, and each of the inventions described in the claims can be described as the following (1) to (9) as a vibration reduction device for a cylindrical structure. Each means described is adopted.
(1) A fluctuation reducing apparatus for a cylindrical structure according to a first means includes a cylindrical structure that is suspended or suspended in seawater, and a strainer that is helically disposed on the surface of the cylindrical structure. And a gap formed between the surface of the cylindrical structure and the strake.

  (2) The fluctuation reducing device for a cylindrical structure according to the second means is characterized in that, in the first means, the above-mentioned strake is a helical arrangement of a number of strip-shaped vertical strakes. And

  (3) The fluctuation reducing device for a cylindrical structure according to the third means is characterized in that, in the second means, end plates attached to the upper and lower ends of the strip-shaped strake are provided.

  (4) The storage unit of the vibration reduction device for a cylindrical structure according to the fourth means includes a pair of semicircular attachment bands provided so as to face each other, and the one set of semicircular attachments. Another set of semi-circular mounting bands facing each other, a U-shaped strage connecting the opposing semi-circular mounting bands, and a semi-circle facing each other And connecting means for connecting the ends of the attachment band.

  (5) In the fourth aspect of the stroking unit of the cylindrical structure fluctuation reducing device according to the fifth means, one end side of the semicircular attachment band facing each other is connected by a hinge, Between the other end portions of the opposing semicircular attachment bands, U-shaped strakes 11b are attached, and the respective strakes attached to the other end portions are connected by bolts and nuts. It is characterized by being.

  (6) In the fourth or fifth means, the storage unit of the fluctuation reducing device for a cylindrical structure according to the sixth means is the semicircular shape of the other set of the one set of semicircular mounting bands. A plurality of grooves are formed on the surface opposite to the surface facing the mounting band of the other, and facing the one set of semicircular mounting bands of the other set of semicircular mounting bands. A plurality of protrusions are formed on the surface opposite to the surface.

  (7) According to a seventh aspect of the present invention, there is provided a striking unit for a vibration reducing device for a cylindrical structure, wherein the U-shaped stroking is fixed obliquely in the fourth to sixth means.

  (8) The striking unit of the fluctuation reducing device for a cylindrical structure according to the eighth means is characterized in that in the fourth to seventh means, end plates are attached to the upper and lower ends of the strip-shaped strake. To do.

  (9) The fluctuation reducing device for a cylindrical structure according to the ninth means is characterized in that a large number of the above-mentioned storage units of the fourth to eighth means are arranged helically on the cylindrical structure.

The invention according to each claim described in the claims employs the means described in the above (1) to (9), and thus has the following effects.
(1) Since the invention according to claim 1 employs the first means, when a tidal current flows through the cylindrical structure 1, a gap forms a vortex generated on the downstream side of the cylindrical structure 1. It can be reduced by small vortices generated from the inner and outer end faces of the strakes. Furthermore, when the left and right direction fluctuations are caused by the strakes 2 in which the upstream and downstream gaps of the tidal current to the cylindrical structure 1 are formed, the seawater passes through the gaps in the horizontal direction. Can be greatly reduced.

  (2) Since the invention according to claim 2 employs the second means, in addition to the effect of (1), the attachment to the cylindrical structure becomes extremely easy.

  (3) Since the invention according to claim 3 employs the second means, in addition to the effect of the above (2), by the end plates attached to the upper and lower ends of the stroking, The seawater can be prevented from coming out from the upper and lower ends of the strake, and the shaking in the left-right direction can be greatly reduced.

  (4) Since the inventions according to claims 4 and 5 employ the fourth and fifth means, the strake can be easily attached to and detached from a long structure such as a drill pipe.

  (5) Since the invention according to claim 6 employs the sixth means, in addition to the effect of the above (4), when attaching a plurality of strake units to a long structure, it is possible to simplify the stroking. In addition to being able to position, the position of the strake does not shift after installation.

  (6) Since the invention according to claim 7 employs the seventh means, in addition to the effects of (4) and (5) above, when a plurality of storage units are attached to a long structure. The shape of the continuous strake can be made.

  (7) Since the invention according to claim 8 employs the eighth means, in addition to the effects of (4) to (6), the end plates attached to the upper and lower ends of the strok It is possible to suppress seawater from coming out of the upper and lower ends of the stroking, and to significantly reduce the lateral shaking.

  (8) Since the invention according to claim 9 employs the ninth means, it is possible to obtain a vibration reduction device for a cylindrical structure that exhibits the effects (4) to (7).

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the configuration of a cylindrical marine structure sway reduction device according to Embodiment 1 of the present invention, and FIG. 2 shows the configuration of the cylindrical structure sway reduction device according to Example 2 of the present invention. FIG. 3 is a perspective view showing a configuration of a fluctuation reducing device for a cylindrical structure according to a third embodiment of the present invention, and FIG. 4 is a perspective view of a storage applied to the cylindrical structure according to the third embodiment. It is a perspective view which shows a modification. FIG. 5 is a perspective view showing the configuration of the fluctuation reducing device for a cylindrical structure according to the fourth embodiment of the present invention, FIG. 6 is an enlarged perspective view of the strake according to the fourth embodiment of the present invention, and FIG. 7 is the present invention. It is an expansion perspective view of the other example of the stroking of Example 4.

  First, based on FIG. 1, it demonstrates per structure of the oscillation reduction apparatus of the elongate cylindrical marine structure which concerns on Example 1. FIG. The first embodiment is particularly suitable for a large spar type offshore structure. As shown in the figure, around the outer wall of the cylindrical structure 1, a long belt-like stroking 2 is attached in a helical manner via a column 3 by welding or the like. A gap 4 is formed between the strake 2 and the cylindrical structure.

  In the above configuration, when a tidal current flows through the cylindrical structure 1, a vortex is generated on the downstream side of the cylindrical structure 1. At this time, the vortex on the downstream side is disturbed and reduced by the small vortex generated from the outer end surface of the strake 2 on both sides of the cylindrical structure 1. Moreover, since the strake 2 is separated from the outer wall of the cylindrical structure 1 by the support column 3, a small vortex is also generated from the inner end face of the strake 2. In this way, the vortex on the downstream side of the tubular structure 1 generated by the flow of the tidal current through the tubular structure 1 is disturbed by the small vortices generated from the outer end surface and the inner end surface of the stroke 2 and decreases.

  Further, the upstream and downstream strakes 2 of the tidal current to the cylindrical structure 1 also suppress left and right fluctuations. That is, since the stroking 2 is mounted with a gap 4 from the cylindrical structure 1, the horizontal movement can be greatly reduced by the seawater passing through the gap.

  Next, based on FIG. 2, it demonstrates per structure of the oscillation reduction apparatus of the elongate cylindrical marine structure which concerns on Example 2. FIG. In the second embodiment, a large number of strip-like strakes 5 are attached to the periphery of the outer wall of the cylindrical structure 1 by welding or the like in a helical manner through support columns. By setting it as such a structure, the attachment of the strake 5 to the cylindrical structure 1 becomes easy. A gap 6 is formed between the strake 2 and the cylindrical structure as in the first embodiment. Also in the above-described configuration, as in the first embodiment, the shaking of the cylindrical structure 1 can be greatly reduced.

  Next, based on FIGS. 3 and 4, a description will be given of the configuration of the sway reduction device for a long cylindrical offshore structure according to the third embodiment. As shown in FIG. 3, the fluctuation reducing device of the third embodiment has semi-elliptical end plates 7a and 7b attached to the upper and lower ends of the strip-shaped strake 5 in the second embodiment. By adopting such a configuration, it is possible to suppress the seawater from coming out of the upper and lower ends of the strok 5 at the time of left and right shaking, and further to greatly reduce the shaking in the left and right direction.

  Further, as shown in FIG. 4, the end plate 8 is attached to the opposite side of the outer wall side of the marine structure 1 of the strake 5 to further reduce the left-right fluctuation. Instead of the end plates 7 a, 7 b, and 8, a single belt-like plate can be bent so as to be in contact with the three surfaces of the strake 5.

  Based on FIGS. 5 and 6, the configuration of the sway reduction device for a long cylindrical offshore structure according to the fourth embodiment will be described. The sway reduction device according to the fourth embodiment can be applied to a tubular structure 1 having a relatively small diameter such as a drill pipe. As shown in FIG. 5, the tubular structure 1 is provided with a number of storage units 20 including a mounting band 10a, 10b, a strip-shaped U-shaped storage 11b, and the like so as to form a helical shape. .

  A specific structure of the storage unit 20 is shown in FIG. As shown in FIG. 6, two sets of semicircular mounting bands 10a and 10b facing each other are provided so as to face each other vertically. One end side of each semicircular mounting band facing each other is connected by a hinge or the like. On the other hand, a U-shaped storage 11b is attached between the other ends of the semicircular attachment bands 10a and 10a facing each other and between the other ends of the attachment bands 10b and 10b. . The strake unit 20 can be disposed on the tubular structure 1 by joining the strakes 11b and 11b attached between the other ends and tightening them with bolts and nuts 14 or the like. Further, at least one U-shaped striking 11a is attached between the semicircular mounting bands 10a and 10a facing each other and between the mounting bands 10b and 10b.

  Further, a plurality of grooves 13 are formed at equal intervals on the upper surface (the surface opposite to the surface facing the semicircular mounting band of the other set) of the upper (one set) mounting bands 10a, 10b. It is installed. On the other hand, the lower surface (the surface opposite to the surface facing the semicircular mounting band of one set) of the lower (the other set) mounting bands 10a, 10b is the same as the plurality of grooves 13 described above. Protrusions 15 are provided at intervals. When the storage unit 20 is disposed on the cylindrical structure 1 as shown in FIG. 5, the protrusion 15 on the lower surface of the upper storage unit 20 is inserted into the groove on the upper surface of the lower storage unit 20. By fitting in a helical shape, it becomes easy to form a stretch in a helical shape as a whole. In this case as well, a gap is formed between the strakes 11 a and 11 b and the cylindrical structure 1.

  With the above-described configuration, the storage unit 20 can be easily attached to and detached from the tubular structure 1 having a relatively small diameter such as a drill pipe, and the shaking of the tubular structure 1 is greatly increased as in the second embodiment (FIG. 2). Can be reduced.

  Furthermore, the height (radial length) of the mounting bands 10a and 10b is the same as that of the strakes 11a and 11b over the entire circumference, so that the mounting bands 10a and 10b are the same as in the third embodiment (FIG. 3). The end plate can be formed in the same manner as described above, and the seawater can be prevented from slipping out from the upper and lower ends of the stroks 11a and 11b during the horizontal shaking, and the horizontal shaking can be greatly reduced.

  In addition, as another example of the stroking, a striking unit 20a to which slanted striking 16a, 16b is attached as shown in FIG. 7 can be used instead of the striking 11a, 11b shown in FIG. By adopting such a configuration, when a large number of the strake units 20a are mounted on the cylindrical structure 1, the strakes are helically continuous as shown in FIG.

  The first to fourth embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications may be made to the specific structure within the scope of the present invention. Needless to say. For example, the cross-sectional shape of the mounting band 10a, 10b of the cylindrical structure 1 or the storage units 20, 20a is not limited to a circular shape, but may be various shapes such as a polygon, an octagon, a quadrangle, etc. I can do it.

It is a perspective view which shows the structure of the fluctuation reduction apparatus of the cylindrical structure which concerns on Example 1 of this invention. It is a perspective view which shows the structure of the fluctuation reduction apparatus of the cylindrical structure which concerns on Example 2 of this invention. It is a perspective view which shows the structure of the fluctuation reduction apparatus of the cylindrical structure which concerns on Example 3 of this invention. It is a perspective view which shows the modification of the stroking applied to the cylindrical structure which concerns on Example 3. FIG. It is a perspective view which shows the structure of the fluctuation reduction apparatus of the cylindrical structure which concerns on Example 4 of this invention. FIG. 6 is an enlarged view of the strake according to the fourth embodiment. It is an enlarged view of the other example of the stroking of Example 4. It is a side view which shows the structure of the conventional marine structure fluctuation reduction apparatus. It is a side view which shows the structure of the conventional vibration reduction apparatus of an offshore structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylindrical structure 2 Stroke 3 Support | pillar 4 Clearance 5 Stroke 6 Clearance 7a, 7b, 8 End plate 10a, 10b Mounting band 11a, 11b Stroke 13 Groove 14 Bolt nut 15 Protrusion 16a, 16b Stroke 20, 20a Strike unit

Claims (9)

  A cylindrical structure suspended or suspended in sea water, a strut arranged helically on the surface of the cylindrical structure, and a gap formed between the surface of the cylindrical structure and the strake An apparatus for reducing fluctuations in a cylindrical structure characterized by comprising:   The apparatus according to claim 1, wherein the strake includes a plurality of strip-shaped vertical struts arranged in a helical shape.   The apparatus for reducing sway of a cylindrical structure according to claim 2, further comprising end plates attached to upper and lower ends of the strip-shaped strake.   A set of semicircular mounting bands provided to face each other, and another set of semicircular mounting bands facing each other, facing the same set of semicircular mounting bands; , Characterized in that it comprises a U-shaped stroking that connects the opposing semicircular mounting bands to each other, and a connecting means that connects between the ends of the semicircular mounting bands facing each other. Strike unit.   One end portions of the semicircular mounting bands facing each other are connected by a hinge, and a U-shaped storage 11b is also provided between the other end portions of the opposing semicircular mounting bands. The strake unit according to claim 4, wherein each of the strakes attached to the other end side is connected by bolts and nuts.   The one set of semicircular mounting bands has a plurality of grooves formed on a surface opposite to the surface facing the other set of semicircular mounting bands, and the other set of semicircular mounting bands. 6. The storage device according to claim 4, wherein a plurality of protrusions are formed on a surface of the circular mounting band opposite to the surface facing the one set of semicircular mounting bands. unit.   7. The storage unit according to claim 4, wherein the U-shaped strake is fixed obliquely.   8. The storage unit according to claim 4, further comprising end plates attached to upper and lower ends of the strip-shaped storage.   9. A fluctuation reducing apparatus for a cylindrical structure, wherein a large number of the above-described strake units according to claim 8 are helically arranged on the cylindrical structure.

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