JPS6132545B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to flexible tubes or pipes, in particular:
The present invention relates to a flexible pipe having a large inner diameter (400 mm or more) and other characteristics for transferring fluid under high pressure.

In the following, each term will be used with the following meanings: - Reinforcement: an assembly of different elements contained within the wall of a pipe that is provided to give the pipe its mechanical properties. Reinforcing materials (breakers) that are buried in the wall but only serve to protect the pipe from external damage are not included in the term reinforcing materials here.

- Sheet material: embedded in rubber or the like and coaxial with the pipe along one or more helical windings at an angle to the longitudinal axis of the pipe (this angle is referred to as the orientation angle). The part of the reinforcement that provides mechanical strength, constituted by thread or strand-like elements wrapped in the same cylindrical plane.

- Pair of sheet materials: stacked one on top of the other, the threads or strands of which are arranged according to angles to the longitudinal axis of the pipe that are identical in absolute value but opposite in direction; An assembly composed of two sheets of material. A pair of sheets of material are generally separated from each other by a rubber layer having a thickness of a fraction of a millimeter. This rubber layer prevents the threads or strands of the individual sheet materials from coming into direct contact, but due to its thin thickness it does not contribute to the mechanical properties of the pipe.

-Concave pressure: Pressure from the outside to the inside when the external pressure becomes greater than the internal pressure, and this pressure is
It will be greater than 1.02 Kl/cm ² (/bar).

-Bending or crushing: A phenomenon in which the cross-section gradually becomes oval when it is bent little by little, and then the compressed inner part of the curved part momentarily approaches the outer part. When this bending or crushing occurs, the pipe becomes flat and crumpled.

- Thread: a single cylindrical element made of mineral materials such as steel or glass or organic materials such as rayon, polyamide, aramid. In the usual concept, unlike the present invention, thread is used to denote a single element when it is made of metal or glass, respectively, and to denote a collection of many monofilaments when it is an organic material. Please note that

- Twine: An element made of multiple threads gathered together by twisting.

In known pipes of generally large diameter (more than 700 mm), the reinforcement is formed by metal strands separated from each other by rubber layers of substantial thickness and arranged at approximately 80° to the longitudinal axis of the pipe. There is. The metal strands, which are composed of two sheets or pairs of sheets and form the sheet material of the pipe reinforcement, have high compressive strength and low elongation. This pipe is designed to withstand concave pressures (i.e. pressures directed from the outside inward) without collapsing, and although this pipe is fully capable of that function and can be bent at small radii without breaking, it is especially susceptible to external pressures. It cannot withstand internal pressures and tensile forces higher than .

Pipes made to withstand both internal pressure and longitudinal tensile forces are also known. The reinforcement for this pipe consists of a pair of sheets of metal thread placed at an angle of 45° to 65° to the longitudinal axis of the pipe, and a pair of sheets of metal thread placed at an angle of 15° to 35° to the longitudinal axis of the pipe. The sheet material is formed of a metal thread and is provided above the former sheet material or a pair of sheet materials. In order to give this pipe longitudinal flexibility, although the metal is placed at a small angle to the longitudinal axis of the pipe, it is necessary to combine the inner sheet material of the reinforcement with the outer sheet material or pairs thereof. A rubber shear layer is provided between them to allow them to be displaced relative to each other. However, this pipe is rigid in the vertical direction and will break if bent at a small radius. Furthermore, when there is no pressurized liquid, large tensile stress is applied,
The elastic layer that makes up the pipe that comes into contact with the fluid stretches to the point where it breaks. That is, this pipe is difficult to bend, has poor tensile stress resistance in the longitudinal direction, and cannot withstand even slight concave pressure.

The object of the present invention is to have large diameter (400, 600 mm and above) and high pressure (20.4, 30.6 Kg/cm ²
The objective is to provide a pipe capable of transporting fluids (20, 30 bar) and above), which also has sufficient flexibility and resistance to longitudinal tension and concave pressures, and a small radius without breaking. It has the characteristic that it can be bent.

The above characteristics of the pipe of the present invention are achieved by constructing the reinforcing material as follows. (1) A pair or pairs of sheet material formed by high strength metal strands arranged at an angle of 50° to 55° to the longitudinal axis of the pipe.

(2) A layer of rubber or the like having a substantial thickness disposed above the sheet or pair of sheets.

(3) one or more pairs of sheet material formed by threads disposed at an angle of 40° to 70° to the longitudinal axis of the pipe and superimposed on the rubber layer;

The pair or pairs of sheets shown in (1) are closest to the inner wall and their function is to provide the pipe with resistance to the pressure of the conveyed fluid. The sheet material is formed from strands of high strength material as known to those skilled in the art. Note that in the present invention, this sheet material is made of twine and not yarn. Threads have the disadvantage of increasing the longitudinal stiffness of the pipe and reducing its resistance to repeated bending and compression.

The rubber layer shown in (2) needs to have a substantial thickness. That is, this rubber layer is used not only to ensure the connection between the sheets of each set of reinforcement and to allow each of the sheets to be slightly displaced relative to each other, but also to act, for example, as a skeleton, It must be of sufficient thickness so that it also serves to modify the mechanical properties of the pipe to increase its resistance without crushing it. This thickness depends on the inner diameter of the pipe, but is generally 0.03 to 0.07 times the inner diameter. For example, if the inner diameter is 500 or 600 mm, approximately
It is 0.03 times, and smaller than that, for example, in the case of 200 mm, it is 0.05 to 0.07 times. The cylinder formed by this rubber layer must have a high resistance in the radial direction. A person skilled in the art will be able to select the composition, i.e. to quantitatively and qualitatively combine the elastic body, the filler and the components for adjusting the resistance force to the desired value. However, this approach cannot provide resistance to the very high radial compressive forces required for some applications. To solve this problem, a metal ring is embedded within the rubber layer along the entire length of the pipe.

One or more sets of sheet materials shown in (3) shall be installed at the farthest point from the inner wall of the pipe. The essential function of this sheet material is that, together with the rubber layer to which it is attached and one or more pairs of sheet materials shown in (1), it provides the pipe with mechanical properties and the necessary pressure resistance. It's about giving. The sheet material consists of strands arranged at an angle of 40 DEG to 70 DEG to the longitudinal axis of the pipe.

These sheet materials need to be formed from strands rather than threads. If this is made of thread, the disadvantage is that the radius at which the pipe can be bent without damaging it becomes large and the repeated bending strength of the pipe decreases.

This strand is made from a material with extremely high breaking strength and high modulus of elongation, such as steel, thereby reducing the number of sheets and ensuring that this property of the sheets changes little over time. Try not to. (If a material that stretches due to flow is used, it is not possible to obtain constant properties over time).

In order to further increase the longitudinal flexibility of the pipe and maintain this property for a long time during use, the sheet material shown in (3) can be made of strands of elastic material.

As is well known, the properties of this strand depend on how the single threads are assembled. For example, for the same material, such as high mechanical strength and high modularity steel, one can make strands with less elongation or strands with more elongation for the same breaking strength.

Strands with an elongation at break of 4.5% or more are referred to as elastic strands. That is, in the tensile force/elongation curve of a strand with such an elongation at break, there is a long region from its starting point where the elongation becomes elastic and the module becomes small. This strand thus stretches substantially elastically under low stress. For example, a strand with a strength and elongation at break of 180 kg and 5.6%, respectively, without being embedded in rubber.
It stretches 2.2% elastically with a tensile force of 18Kg. When this strand is embedded in rubber, the module becomes even higher, but the elongation is in the elastic range and reaches large values under relatively small stresses. For example, in the case of the twine mentioned above, a tensile force of 18 kg results in an elongation of 1.2%.

It is not at all disadvantageous that the strands forming this sheet material have been elongated by the tensile force when the stress on them is removed and they return to their original length, as has already been stated. The use of this strand is particularly advantageous when the pipe is used under harsh conditions.

The angle of arrangement of the strands is the same on the separate pairs of sheet materials and lies between 40° and 70° relative to the longitudinal axis of the pipe. In fact, when the angle is less than 40°, the longitudinal flexibility of the pipe is insufficient (this is also the case when the sheet material is made of elastic strands), and when the angle of arrangement is more than 70°, Tensile strength becomes insufficient.

Between 40° and 70° to the longitudinal axis of the pipe, approximately
Note that a so-called equilibrium value of 55° is included. It can be understood that this value is the angle of arrangement such that the diameter and length of the pipe do not change under the influence of internal pressure. However, these sheets are not acted upon by internal pressures supported by the pair or pairs of sheets whose strands are arranged at equilibrium angles (1). In the case of the sheet material shown in (3), the concept of equilibrium angle has no important meaning under the actual usage conditions of the pipe.

An angle of arrangement of 40° to 70° with respect to the longitudinal axis of the pipe can be selected as a function of the conditions of use of the pipe.
For example, if the pipe is subjected to large longitudinal tensile forces and resistance to longitudinal tensile forces is therefore the primary property to be imparted to the pipe, the strands are placed at an angle of approximately 40°. Conversely, if the tensile force is not large and resistance to bending, deflection, or concave pressure is required, the strands are arranged at an angle of approximately 70°.

Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

The inner diameter of the pipe in Figure 1 is 400 mm or less. The pipe must be able to support a longitudinal tensile force of 15,000 to 20,000 decanyutons and withstand numerous deflections and bends without damage.

The reinforcement of this pipe is formed by an inner pair 1 and an outer pair 2 of sheet material separated from each other by a rubber layer 3 with a thickness of 14 mm.

The inner pair 1 of the sheet material is formed by metal strands placed at an angle of 54° to the longitudinal axis of the pipe (indicated by a dash-dot line), the mechanical strength of which is
The value is such that it can withstand a transfer fluid pressure of 20.4 Kg/cm ² (20 bar).

The outer pair 2 of the sheet material is relative to the longitudinal axis of the pipe.
It is formed by elastic metal strands arranged at 45°.

The metal annular body 4 embedded in the rubber layer 3 and extending over the entire length of the pipe has a circular cross section and a diameter of 10 mm.

When a longitudinal tensile force is applied to this pipe, the outer pair 2 of the sheet material is stretched, and the diameter of the helix formed by this sheet material tends to decrease; is prevented because the rubber layer 3 reinforced by the annular body 4 strongly resists radial compression. In this way, the pipe does not stretch at all or hardly.

The outer pair 2 of sheets of material form a relatively small angle with respect to the longitudinal direction, so that the pipe accepts a small radius of curvature. An 8m long pipe can be bent up to a 90° angle with very little tendency to break. Furthermore, the pipe can be bent repeatedly a very large number of times without breaking. Also, this pipe
It can withstand concave pressures exceeding 10.2Kg/cm ² (10bar) without breaking.

The pipe, which must be able to withstand the longitudinal stresses that tend to stretch it, is made of the outer pair 2 of sheet material by elastic metal strands. Experiments have shown that in this case, the elongation is slight, there are no defects, and the longitudinal flexibility and behavior against repeated bending and deflection are improved.

An identical pipe made in a similar manner, except that the annular body is not embedded in the rubber layer 3, can withstand a longitudinal force of 4000 to 6000 decanyutons.

The pipe in Figure 2 with an internal diameter of 400mm is 1000~
It can withstand relatively small longitudinal forces on the order of 2000 decanyutons. This pipe has the advantage that it can be bent quickly with a small radius and is not damaged.

The reinforcement of this pipe consists of an inner pair 5 and an outer pair 6 of sheet material separated from each other by a layer 7 having a thickness of 22 mm.

The inner pair 5 of the sheet material is relative to the longitudinal axis of the pipe.
It is formed by metal strands arranged at 54 degrees.

The outer pair 6 of the sheet material is relative to the longitudinal axis of the pipe.
It is formed by elastic metal strands arranged at 60°.

[Brief explanation of the drawing]

1 and 2 are schematic half-sectional views showing a pipe according to a preferred embodiment of the invention. 1... Inner pair of sheet material, 2... Outer pair,
3...Rubber layer, 4...Metal annular body.

Claims (1)

[Claims] 1. Rubber layer and 50° to 55° with respect to the longitudinal axis of the pipe.
one or more inner sheets of metal strands embedded in the rubber layer at an angle of 40° to the longitudinal axis of the pipe and spaced outwardly from the inner pair or more sheets; one or more pairs of outer sheets made of elastic metal strands embedded in the rubber layer at an angle of between 70 degrees and one or more inner pairs and one or more outer pairs. A flexible pipe characterized in that the thickness of the rubber layer between the sheet materials is 0.03 to 0.07 times the inner diameter of the pipe. 2. The flexible pipe according to claim 1, characterized in that a reinforcing annular body is embedded in a rubber layer separating one or more pairs of inner sheet members from one or more pairs of outer sheet members. .