JPS6272808A - Steel tube leg coupler for mooring marine structure - Google Patents

Abstract

PURPOSE:To raise the interference allowance setting accuracy for steel tube leg couplers by forming a main inverse shoulder portion and a second stage shoulder portion on a coupled face between the pin and box of the steel tube leg coupler connecting the pin and the box. CONSTITUTION:A main torque shoulder 11 receives a screw reaction by the clamping of a screw 18, and seal faces 11a and 11b on a pin and box sides undergo an elastic deformation by a reaction. A ring 19 for addible seal serves as a secondary seal for back-up purpose in case where a leakage in the seal of the main torque shoulder 11 is generated by any chance. A second stage torque shoulder 17 is set such that the main shoulder 11 is touched after further clamping when clamped during the manufacture of coupler. An interference allowance setting accuracy and the clamping torque accuracy of the torque shoulder on the sea face can thus be raised, control on the interference allowance can be made easier, and an over-clamping can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a joint structure for steel pipe leg materials for mooring marine structures such as tension leg plate forms (TLP).

(Conventional technology) In recent years, as offshore oil drilling areas have become deeper and operations have become more difficult in areas with severe sea conditions, floating structures have been improved in terms of ensuring stability, shortening installation time, and ease of removal after work is completed. Tension leg plate form (TLP) as shown in Fig. 7
installation is being carried out or planned at each location. This TLP
Steel pipes, wire ropes, and fiber ropes are being considered as mooring members, but steel pipe legs, which have a proven track record for right pipes, drill pipes, and casing pipes, are the most promising.

In the figure, 1 is the hull, 2 is the tension leg, 3 is the steel pipe leg pin side, 4 is the FJrl#I pipe leg gox side, 5 is the anchor, 6 is the upper end of the tension leg, and 7 is the lower end of the tension leg.

Furthermore, for example, welded joints and threaded joints are conceivable as joints for the steel pipe legs that have a bottle and a box at their ends, respectively, as shown in Figure 8, but threaded joints are more promising in terms of installation, removal work, repair, etc. ing. In the figure, 8 indicates a single steel pipe leg material, and 9 indicates a threaded portion on the bottle side.

(Problem to be solved by the invention) The performance required for this steel pipe leg joint is the initial tension applied to the leg material, and the static load and dynamic load with respect to the fluctuating load applied from waves, wind, and currents. It must have the strength to withstand. It is required to have sufficient sealing performance to prevent seawater from penetrating the threaded portion, which would lead to corrosion fatigue and significantly shorten the life of the joint.

Conventionally, padless type screws according to the American Petroleum Institute Standards (API) have been used as high-strength steel pipe joints, and they have sufficient static and dynamic strength.

As a steel pipe joint having a complete external seal structure, there is an extreme line casing joint according to the American Petroleum Institute Standards (API). The structure of this joint is shown in Fig. 9, and the structure of the external seal is based on Drukshi, Luda 10, which seals against external pressure by making close contact with the shoulder of the box end and the opposing bottle shoulder. This structure ensures surface pressure through interference with the bottle shoulder.

However, in this joint, if the interference type is too large, it will cause seizure, and if the interference type is too small, leakage will occur when axial force is applied, and the range of the appropriate interference type is narrow, which poses a practical problem.

(Means for Solving the Problems) Therefore, the present inventors have provided a threaded joint that has a sealing performance that is not affected by the manufacturing accuracy of the thread, and also has a sealing performance that is not affected by changes in torque during construction. As a result of various studies, we found that the above problem was solved by having two stages of shoulders as the outer seal structure, making the outer shoulder an inverse shoulder type, and providing distribution to the interference formula of the inverse shoulder. The present invention was developed based on this completely new knowledge.

That is, the present invention provides a steel pipe leg joint for mooring marine structures that is constructed by combining a bottle having a male thread on the outer surface of one end of the steel pipe and a box having all female threads on the inner surface of the other end, which includes: (1) an outer surface seal; A threaded joint for marine structures characterized by having an inverse shoulder surface during screw tightening and a second stage shoulder that controls the sealing surface pressure of this shoulder surface during screw tightening and controls the relative positional relationship between the screw and the sealing surface. .

(2) In order to provide surface pressure distribution on the contact surfaces of the inverse shoulder surface on the bottle side and the tedges side,
A threaded joint for marine structures characterized by a slope difference on the inverse shoulder sealing surface on the box side.

It is.

(Function) Tension leg sillage and steel pipe gluing material for TOFORM have an inverse dorsal plate as an outer seal and a second stage dorsal plate to facilitate management of tightening torque and prevent over-tightening. By installing and distributing the interference formula of the inverse torque shoulder part, υ
Drukshi under tensile load! The seal structure does not create a gap on the sealing surface of the lA/da portion.

(Example) Embodiments of the present invention are shown in FIGS. 1 to 6.

Figure Wj1 is a sectional view of the joint when tightening the bottle and Gex, and the second
The figure is a detailed explanatory diagram of the present invention, Figures 3 and 4 are the pin side,
It is a detailed explanatory diagram of the box side.

Reference numeral 11 in Fig. 2 is the main torque shoulder.The torque shoulder 11 receives the screw reaction force caused by tightening the screw 18, and the pin side and box side seal surfaces 3 are generated by this reaction force.
The elastic deformation of 111 in the figure and llb in Fig. 4 provides an interference type and ensures sealing surface pressure. 19 in Figure 2
is a sealing ring that can be added) This is a secondary seal for P, C, and G of the main torque shoulder 11 when the seal leaks, and a structure in which the seal ring 19 is attached is also possible. . 17 in Fig. 2 is the second stage torque shoulder.When tightening during joint extension, the main torque shoulder 1
After configuring 1 to be applied first, and further tightening, 2
By setting the stage to hit the torque shoulder 17, the torque increases suddenly during tightening work, so the completion of tightening can be detected at this point of increase, and the tightening torque can be controlled. It is possible to easily manage the tightening torque and the interference position of the torque shoulder, and also to prevent plastic deformation of the main torque shoulder 1 due to excessive tightening. In the figure, 12 is a torque shoulder inner positioning plane, 14 is an inner sealing surface, and 16 is an addable seal ring groove. 15 is a conical surface connecting the main Drukshi, Ruda and the second Drukshi, Ruda,
Here, two cases are shown: one is to add a gap or cut the edge depending on the dimensions of the pin side 15m and the box side 15b, and the other is to set all interference types to 15m and 15b and add circumferential pressing force to the main torque shoulder 1. Case is possible.

As a second invention of the present invention, as illustrated in FIGS. 3 and 4, the angle θ1 that the pin side main torque shoulder 11L makes with the direction perpendicular to the tube axis and the angle θ that the box side main torque shoulder lb makes with the direction perpendicular to the tube axis. , it is necessary to make a difference in the interference formula so that θ□〉θ3 is large on the main dorsal and luda seal surfaces, and on the outside of the eve. To control the distribution of the tightening force of the torque shoulder part when the torque shoulder part is tightened and to keep the overall total surface pressure to a low level while preventing a gap from forming on the outer surface side of the torque shoulder 11 and partially intruding seawater into the sealing surface. I can do it. The effect of having this full surface pressure distribution is shown below.

Figure 5 shows a make-up (tightening) with an interference type distribution of 0.07 to 0.05 m+i between points A and B of the main torque shoulder in Figure 2, resulting in a stress value of 20 kg7w at the joint.
An example of the calculated value of the seal surface pressure distribution when a tension of '' is applied is shown.The dotted line is when making up, and the solid line is when axial force is applied.

Figure 6 shows a uniform interference margin of 0.05 m between points A and B of the main torque shoulder in Figure 2, and the stress on the joint is 20 Yu/m in terms of stress value. An example of the calculated value of the seal surface pressure distribution when a tension of

From this, it can be seen that in the case of FIG. 6, an opening sound occurs on the A point side when the axial force is 20 kg/m'', but in the case of FIG. 5, the seal surface pressure can be ensured without causing an opening when the axial force is 20 kg/m.

From now on, by keeping the overall surface pressure low while ensuring that the seal surface interference margin has an appropriate distribution, it is possible to make the entire seal surface lateral bottom so that opening noise does not occur in response to the load axial force.

(Effects of the Invention) By using the joint of the present invention, it is possible to improve the interference setting accuracy of the seal face torque shoulder, improve the tightening torque setting accuracy, facilitate interference level management, and completely prevent overtightening. Furthermore, the relationship between the axial screw position, the main torque shoulder position, the machining accuracy, and the degree of tightening can be completely controlled accurately.

Furthermore, the pin side of the main torque shoulder surface, ? By providing a full surface pressure distribution on each face on the box side, it is possible to create a structure in which gaps are less likely to form on the outer surface side of the main torque shoulder when tension is applied to the joint.

[Brief explanation of drawings]

Fig. 1 is an overall view of the present invention, Fig. 2 is a detailed explanatory view of the seal portion of the present invention, Figs. 3 and 4 are detailed explanatory views of the pin side and box side of the present invention, Fig. 5, Fig. 6 is a diagram showing an example of calculated values of seal surface pressure distribution, Fig. 7 (,) is a conceptual diagram of TLP, Fig. 7 (b) is an explanatory diagram of the bottle box section, and Fig. 8 shows pins and boxes at both ends, respectively. FIG. 9 is an explanatory diagram of a conventional joint. 1: Hull, 2: Tension leg (steel pipe leg material), 3: Steel pipe leg pin side 4: Steel pipe leg box side, 5: Anchor 6: Tension leg upper end, 7: Anchor, leg lower end, 8: Steel pipe Leg material alone, 9: Pin side threaded part, 10: Torque shoulder 11: Inverse torque shoulder, 12: Torque shoulder, inner positioning plane of rudder, 14: Inner seal surface, 15: Main torque shoulder, secondary torque shoulder, conical surface between ferns , 16: Seal ring groove that can be added, 17: Secondary) shoulder, 18: Joint screw, 19
: Seal ring that can be added. Figure 2 Figure 5 Figure 6

Claims (2)

[Claims] (1) In a steel pipe leg joint for mooring offshore structures that is constructed by joining a pin with a male thread formed on the outer surface of one end of the steel pipe and a box with a female thread formed on the inner surface of one end of the steel pipe, the fitting surface of the pin and box A steel pipe leg joint for marine structures, characterized by forming a main inverse shoulder part and a second shoulder part. (2) In a steel pipe leg joint for mooring marine structures that is constructed by joining a pin with a male thread formed on the outer surface of one end of the steel pipe and a box with a female thread formed on the inner surface of one end of the steel pipe, the pin side of the main inverse shoulder portion and A steel pipe leg joint for marine structures, characterized in that a contact surface on the box side has surface pressure distribution and a difference in slope is formed on the sealing surfaces of the main inverse shoulder portions on the pin side and the box side.