JPS6323511Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a structure for attaching an inner pipe to an end support in a riser pipe used in offshore oil or gas mining, production, etc.

Riser pipes connect a wellhead on the seabed and offshore facilities such as drilling ships, support ships, and platforms, and are used in large numbers connected in the axial direction. As shown in Figure 3, these riser pipes consist of two production pipes (a) that serve as transportation paths for oil, etc., and a number of hydraulic pipes (for example, Two types of inner pipes (12 pieces) of control pipes b are installed in an outer cylinder c between both end supports d and e attached to both ends of the outer cylinder.

Generally, the construction structure of the inner pipes a and b is as follows:
Both ends of the inner pipes a and b are supported by both end supports d,
However, with this structure, inner tubes a and b are restrained in the axial direction, so if the entire riser pipe is bent and deformed by waves or ocean currents, or the outer tube and inner tube When there is a temperature difference between the outer tube and the inner tube (for example, when the outer tube is cooled by seawater and the inner tube is heated by high-temperature oil), compression or tensile force acts on the inner tube, causing the end support to There is a risk that the threaded portions of inner tubes a and b to d and e or the inner tubes will be damaged.

For this reason, conventionally, as shown in Figs. 2 and 3, one end of the inner pipes a and b is inserted into the inner pipe insertion holes e ₁ and e ₂ provided in one end support e through a sealing material f. A structure has been proposed in which the mechanical or thermal stress acting on the inner tubes a and b is alleviated by movably inserting the inner tubes a and b. However, according to this structure, especially in the small-diameter control pipe b, the fluid pressure acting on the tip surface of the pipe b, that is, the compressive force p, causes the pipe b to buckle, break, or break from the insertion hole _e2. There is a risk that it may come out.

As a measure to prevent this buckling, it may be possible to install supports to prevent buckling (bending) at several locations in addition to the steady rest supports for the inner pipe, but this is extremely disadvantageous in terms of ease of assembly, cost, etc. Therefore, it is not practical.

Therefore, the present invention has developed an inner pipe mounting structure for a riser pipe that does not require additional equipment, applies tensile force that counteracts the compressive force to the inner pipe itself, and suppresses buckling due to this offsetting effect. The purpose is to obtain the following.

The feature of the present invention is that the end portion of the inner tube supported so as to be slidable in the axial direction is formed into a stepped shape with a smaller diameter on the tip side, and the inner tube insertion hole of the end support into which the inner tube is inserted. is formed in a step shape corresponding to the end of the inner tube, and is configured such that a tensile force is applied to the inner stepped surface of the stepped portion in opposition to the compressive force acting on the front end surface of the inner tube.

An embodiment of the present invention will be described below with reference to FIG.

The buckling described above is a practical problem in internal pipes that have a small diameter and are subject to large fluid pressures, and this example will also be explained with this control pipe as the application target. The same applies to production pipes if buckling is expected due to usage conditions. Further, here, only the mounting structure at one end of the control pipe on which the buckling load acts will be illustrated and described, and the mounting structure at the other end will be omitted since it is the same as the conventional one.

1 is the outer cylinder, 2 is one end support, 3 is the control pipe, and this control pipe 3
One end 4 is a control pipe insertion hole (hereinafter simply referred to as insertion hole) provided in the end support 2.
5 so as to be slidable in the axial direction. The pipe end 4 inserted into the insertion hole 5 has a stepped shape in which both the inner diameter and the outer diameter are smaller on the tip side, and more specifically, the left-hand half 41 located on the entrance side of the insertion hole 5.
The diameter of the pipe body is the same as that of the pipe body, and the right half 42 located on the back side of the insertion hole 5 is formed into a stepped shape with a diameter reduced through a step 43. Below, the left half of the figure 41
is called a large diameter portion, and the right half portion 42 is called a small diameter portion. The insertion hole 5 also has a stepped hole shape corresponding to the pipe end 4, that is, a large diameter hole 51 into which the large diameter portion 41 is inserted, and a small diameter hole 52 into which the small diameter portion 42 is inserted. It is formed into a continuous stepped hole shape with a stepped portion 53 interposed therebetween. Reference numeral 6 designates a sealing material attached to the outer peripheral surface of the small diameter portion of the pipe end 4, and 7 designates a communication hole for a control pipe of a riser pipe connected to the next stage.

Inner diameter of the large diameter portion 41 at the pipe end 4
D ₁ and the outer diameter D ₂ of the small diameter portion 42 are formed to have the same dimensions. Therefore, the inner step surface 43 of the step portion 43
Thickness of a (step dimension) S ₁ and thickness of small diameter portion 42 S ₂
and are of equal size. Note that the step portion 43 is formed in an inclined shape as shown in the figure in order to improve the flow of fluid. Further, the length l ₁ of the small diameter portion 42 and the length l ₂ of the large diameter hole portion 51 in the insertion hole 5 are set to have a relationship of l ₁ <l ₂ . The effects in this regard will be described later.

When using such a control pipe mounting structure, the pressure of the fluid filling the control pipe 3 causes the small diameter end surface 42 of the pipe end 4 to
When a compressive force P ₁ is applied to a, at the same time, the pressure of the same fluid causes a force in the opposite direction to the compressive force P ₁ to the inner step surface 43a of the stepped portion 43, that is, a tensile force P ₂
acts. Here, since the small diameter portion end surface 42a and the step inner step surface 43a have the same diameter and thickness and the same pressure receiving area, the forces P ₁ and P ₂ acting on both surfaces 42a and 43a are also equal, and this Force P ₁ , P ₂
The buckling of the control pipe 3 is prevented by the antagonistic (offset) action of .

By the way, in the above embodiment, the pressure receiving areas of the small diameter part end face 42a and the stepped part inner step surface 43a were formed to be equal so that the compressive force P ₁ = tensile force P _2. However, in the present invention, the large diameter part The pressure receiving area of the inner step surface 43a of the stepped portion may be larger than that of the end surface 42a of the small diameter portion by setting the inner diameter D ₁ >the outer diameter D ₂ of the small diameter portion. In this way, since the tensile force P ₂ becomes larger than the compressive force P ₁ , the buckling prevention effect is perfect, and the excess tensile force prevents the control pipe 3 from sliding in the direction in which it comes out of the insertion hole 5 . acts as a restoring force. However, it goes without saying that the relationship of P ₁ < P ₂ must be selected within a range where this surplus tensile force does not become excessive.

In addition, according to this structure in which the pipe end 4 is formed in a stepped shape, when the pipe end 4 is inserted into the insertion hole 5 during riser pipe assembly, the small diameter part 42 is first loosely inserted into the large diameter hole 51. It plays a leading role. In addition, in this embodiment, the length of the small diameter portion l ₁ <the length of the large diameter portion l ₂
Therefore, before the small diameter portion 42 fits into the small diameter hole 52, the large diameter portion 41 fits into the large diameter hole 51, and the small diameter hole 52 of the small diameter portion 42
It acts as a guide for fitting into the hole. Therefore, the insertion operation of the pipe end portion 4 into the insertion hole 5 becomes easy.
As described above, according to the present invention, there is no need to add extra equipment such as supports to prevent buckling, and the inner pipe itself is made to exert a tensile force that counteracts the compressive force, which has an offset effect. This can suppress buckling and is extremely useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view showing an embodiment of the present invention;
FIG. 2 is a partial longitudinal sectional view showing a conventional example, and FIG. 3 is a partially cutaway longitudinal sectional view of the entire riser pipe. 2...End support, 3...Inner pipe (control pipe), 4...End of the same inner pipe, 41...
Large diameter portion of the same end, 42... Small diameter portion of the same end, 42a...
End face of the small diameter portion, 43...Stepped portion, 5...Inner pipe insertion hole of the end support, 51...Large diameter hole portion of the insertion hole, 52...Small diameter hole portion, 53...Same step portion.

Claims (1)

[Scope of utility model registration request] In a riser pipe in which one end of the inner pipe is fixed to one end support and the other end is slidably inserted into the inner pipe insertion hole of the other end support, the inner pipe is inserted into the inner pipe insertion hole. The end of the inner tube is formed in a stepped shape with a smaller diameter on the tip side, and the inner tube insertion hole is formed in a stepped shape corresponding to the stepped end of the inner tube. 1. An internal pipe mounting structure for a riser pipe, characterized in that a tensile force is applied to the inner stepped surface of the stepped portion in opposition to the compressive force acting on the small diameter end surface of the stepped end of the pipe.