JP3228386B2 - Flexible fluid transport pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible fluid transport pipe used for transporting high-pressure crude oil produced from an offshore oil field.

[0002]

2. Description of the Related Art The structure of a conventional flexible fluid transport pipe of this type is shown in FIG. The innermost layer is a stainless steel interlock tube 1 having high buckling strength against external pressure and good corrosion resistance.
It consists of. On the outside, a plastic pipe 3 serving as a main pipe of a fluid transport pipe is provided by extrusion molding after providing a tape winding layer 2. The tape winding layer 2 prevents the plastic from biting into the groove on the outer peripheral surface of the interlock tube 1. As the material of the plastic tube 3, when the transport fluid is oil, generally, nylon having excellent corrosion resistance, workability, and flexibility is often used.

[0003] On the plastic tube 3, a concave reinforcing material 4
The internal pressure reinforcing layer 4 is provided by spirally winding a at a short pitch. The concave reinforcing material 4a is formed by forming a steel strip having a thickness of about 3 to 6 mm into a concave shape. The concave reinforcing member 4a is usually wound in two layers so that the opening portions face each other and mesh with each other. The internal pressure reinforcing layer 4 protects the plastic pipe 3 from the pressure of the fluid flowing inside.

[0004] On the internal pressure reinforcing layer 4, an axial force reinforcing layer 5 is provided by spirally winding a number of flat reinforcing members 5a made of steel strip at a long pitch. This axial force reinforcing layer 5 is responsible for the tension applied to the fluid transport pipe. Flat reinforcement 5a is 1
Two or more even-numbered layers are provided by reversing the winding direction for each layer. This is to counteract the torsional torque generated when tension is applied to the spirally wound flat reinforcement 5a. An anticorrosion layer 6 is provided on the outermost layer by extrusion molding of plastic.

[0005]

Recently, the application of flexible fluid transport pipes to the deep sea has been increasing, and accordingly, weight reduction of fluid transport pipes has become an important issue. The reason is that if the weight of the fluid transport pipe is large, it is necessary to increase the sectional area of the axial force reinforcing layer in order to hold the weight of the fluid transport pipe suspended in the sea. This is because there is a dilemma that the weight of the fluid transport pipe increases when the value of “” is increased, and the weight cannot be easily reduced. For this reason, the conventional standard structure fluid transport pipe has a water depth of 4
The limit is about 00m.

[0006]

FIG. 3 is a graph showing the calculation of the fluctuating stress caused by the weight and the wave generated at the upper end of the flexible fluid transport pipe when the flexible fluid transport pipe is laid, and the flexibility of the conventional structure is calculated. The result which calculated | required the weight reduction rate required for the fluid transport pipe with respect to the water depth is shown. This result indicates that, for example, if the weight is reduced by about 10%, the water can be used up to a depth of about 700 m, and if the weight is reduced by about 30%, the water can be used up to a depth of about 1000 m.

[0007] In order to reduce the weight of the flexible fluid transport tube, the specific strength of the flat reinforcing material and the concave reinforcing material, that is, the breaking strength and the yield strength per unit cross-sectional area, are increased to increase the axial reinforcing layer. It is most effective to reduce the weight of the internal pressure reinforcing layer. Since carbon steel is used for the flat reinforcing material and the concave reinforcing material, it is effective to increase the carbon content to improve the specific strength (the carbon content of the conventional material is 0.4%). However, when the carbon content is increased, the brittleness of carbon steel becomes remarkable, and when wound around a plastic pipe, microcracks are generated, and the carbon steel is not useful as a reinforcing material.

On the other hand, there is a troublesome problem that the specific strength of the flat reinforcing material also depends on the flatness of the cross section. That is, when the thickness of the flat reinforcing material is too small with respect to the width, the strength tends to greatly decrease. For this reason, even if a material having a high specific strength is used for the flat reinforcing material, a desired strength cannot be obtained if the thickness is reduced for weight reduction.

The present invention has been made on the basis of the above-described examination results. The structure of the present invention is as follows: an inner pressure reinforcing layer in which a concave reinforcing material is spirally wound at a short pitch on the outside of a plastic pipe; Fluid reinforcement pipe having an axial reinforcement layer spirally wound at a long pitch, wherein at least the flat reinforcement of the concave reinforcement and the flat reinforcement has a carbon content of 0.6 to 0.8%. A thin flat material having an equivalent specific gravity of 1.0 or less is interposed in one or more flat reinforcing materials in the axial force reinforcing layer.

[0010]

In the present invention, the use of a strip made of carbon steel having a carbon content of 0.6 to 0.8% is sufficient if the carbon content is within this range, which is sufficient to reduce the weight of the flat reinforcing material and the concave reinforcing material. This is because it was experimentally confirmed that the material had sufficient mechanical strength to contribute and good winding workability. Further, in the present invention, the decrease in the cross-sectional area due to the increase in the strength of the flat reinforcement is not applied to the decrease in the thickness (prevention of decrease in strength), but is applied to the decrease in the number of the flat reinforcements,
This creates a space between the flat reinforcements with an equivalent specific gravity of 1.
Filling with 0 or less lightweight flat material is intended to reduce the weight of the fluid transport pipe and increase buoyancy.

[0011]

Embodiments of the present invention will be described below in detail. In order to increase the specific strength of the flat reinforcing material and the concave reinforcing material, steel strips with various carbon contents were prototyped, and the optimum carbon content was examined from the viewpoint of strength and winding workability. Table 1 shows the results.

[0012]

[Table 1]

As is apparent from the above, the carbon content at which the yield stress is sufficiently large and there is no problem in terms of winding workability is
It was confirmed that the content was 0.6 to 0.8%.

On the other hand, FIG. 4 shows a flat reinforcing material obtained by forming a general carbon steel material having a diameter of 8 to 15 mmφ into a rectangular cross section with a die.
The change of yield stress with respect to flatness (width w / thickness t) is shown. As can be seen, when the flatness is 4 to 5 times or more, the specific strength is significantly reduced. The width of the flat reinforcing material is limited to 100 mm in outer diameter due to the winding formability and the number of bobbins in the winding machine.
Since the thickness is 10 mm or more in the case of a plastic tube of mmφ, the thickness of the flat reinforcing material must be at least 2 mm. Note that the relationship between the outer diameter of the plastic tube and the width and thickness of the flat reinforcing material may be considered to be substantially similar.

When a steel strip having a carbon content of 0.6 to 0.8% is used, as is apparent from Table 1, a conventional steel strip (carbon content of 0.
Since the specific strength is improved by nearly 50% compared to 4%), the cross-sectional area of the flat reinforcement can be reduced accordingly. However, if this reduction is used to reduce the thickness of the flat reinforcing material, the effect is offset by the decrease in strength as described with reference to FIG. Therefore, the reduction in the cross-sectional area is used to reduce the number of flat reinforcements, and the space between the flat reinforcements is filled with lightweight flat materials that are as lightweight as possible and have excellent wear resistance to steel. It is more effective to reduce the weight of the fluid transport pipe.

FIG. 1 shows an embodiment of the flexible fluid transport pipe of the present invention based on the above concept. In FIG.
The same reference numerals are given to the same parts as. That is, 1 is a stainless steel interlock tube, 2 is a tape winding layer,
Reference numeral 3 denotes a plastic pipe, 4 denotes an internal pressure reinforcing layer formed by short pitch winding of the concave reinforcing material 4a, 5 denotes an axial force reinforcing layer formed by long pitch winding of the flat reinforcing material 5a, and 6 denotes an anticorrosion layer.

In this fluid transport pipe, the number of the flat reinforcing members 5a is reduced by using high-strength steel strips having a carbon content of 0.6 to 0.8% as the flat reinforcing members 5a. The light flat member 7 is interposed in the space. In the illustrated example, the axial force reinforcing layer 5 is configured by alternately arranging two flat reinforcing members 5a and one lightweight flat member 7 in the circumferential direction.

The material of the lightweight flat member 7 is a specific gravity of 1 such as polyethylene, polypropylene and polycarbonate.
The following lightweight plastics can be used: When a fiber-reinforced plastic or the like having a specific gravity larger than 1 is used as the material of the lightweight flat member 7, the equivalent specific gravity may be set to 1 or less by hollowing the inside as shown in FIG. 2. If the equivalent specific gravity of the lightweight flat member 7 is set to 1 or less, the weight of the axial reinforcing layer 5 can be reduced to about 1/3 of the conventional one.

Since the weight ratio of the axial force reinforcing layer to the total weight of the conventional fluid transport pipe is about 40%, the weight of the axial force reinforcing layer increases the specific strength of the flat reinforcing material and the lightweight flat material. As a result, the weight reduction rate of the entire fluid transport pipe is 40% × 33% = 13%. If the weight is reduced by 13% compared to the conventional one, it can be used up to a water depth of about 750m from Fig.

The above description is based on the case where a steel strip having a carbon content of 0.6 to 0.8% is used only for the flat reinforcing material 5a of the axial force reinforcing layer and a conventional steel strip is used for the concave reinforcing material 4a of the internal pressure reinforcing layer. However, if a steel strip having a carbon content of 0.6 to 0.8% is also used for the concave reinforcing member 4a, the weight reduction rate of the entire fluid transport pipe is further improved. The flatness of the concave reinforcing material 4a is 2 to 2.5 times that of the conventional type, and a shape closer to a square than that of the flat reinforcing material 5a is employed. it can.

Since the weight ratio of the internal pressure reinforcing layer to the total weight of the conventional fluid transport pipe is about 40% like the axial force reinforcing layer, the weight of the internal pressure reinforcing layer increases due to the increase in the specific strength of the concave reinforcing material. If it is reduced by about 50%, the weight reduction rate of the entire fluid transport pipe will be about 33% by adding 40% x 50% = 20% (internal pressure reinforcing layer) and 13% of the axial force reinforcing layer. Become. Than before
If the weight is reduced by 33%, it can be used up to a depth of about 1000 m as shown in FIG.

[0022]

As described above, according to the present invention, since the flexible fluid transport pipe can be reduced in weight, it becomes possible to use the flexible fluid transport pipe in a deeper sea than before.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a flexible fluid transport pipe according to the present invention.

FIG. 2 is a cross-sectional view showing one example of a lightweight flat member used for the flexible fluid transport pipe of the present invention.

FIG. 3 is a graph showing the relationship between the weight reduction rate of a flexible fluid transport pipe and the usable water depth.

FIG. 4 is a graph showing a relationship between flatness of a flat reinforcing material and a specific strength reduction rate.

FIG. 5 is a longitudinal sectional view showing the structure of a conventional flexible fluid transport pipe.

[Explanation of symbols]

 1: Interlock pipe 2: Tape wrapped 3: Plastic pipe 4: Internal pressure reinforcing layer 4a: Concave reinforcing material 5: Axial force reinforcing layer 5a: Flat reinforcing material 6: Anticorrosion layer 7: Light weight flat material

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-49937 (JP, A) JP-A-2-225893 (JP, A) JP-A-50-24371 (JP, A) 508466 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 70/06 B29D 23/00-23/24 F16L 11/08

Claims (1)

(57) [Claims] 1. A flexible fluid transport pipe having an internal pressure reinforcing layer spirally wound with a concave reinforcing material at a short pitch and an axial force reinforcing layer spirally wound with a flat reinforcing material at a long pitch outside a plastic pipe. In the above, at least the flat reinforcing material of the concave reinforcing material and the flat reinforcing material has a carbon content of 0.6 to 0.8%.
Flexible fluid transportation characterized by using a strip made of carbon steel as described above, and interposing one or more flat reinforcing materials in the axial force reinforcing layer with a lightweight flat material having an equivalent specific gravity of 1.0 or less. tube.