阅读说明：本技术 超导输电用隔热多层管及其铺设方法 (Heat-insulating multilayer pipe for superconducting power transmission and laying method thereof ) 是由 石黑康英 佐藤昭夫 坂下重人 于 2018-05-29 设计创作，主要内容包括：本发明提供即使利用卷筒方法进行铺设,隔离件也不破损且具备较高的隔热性的超导输电用隔热多层管。该超导输电用隔热多层管具备：超导线缆；多层管,其由多个直管构成,并收纳上述超导线缆；以及多个隔离件,它们设置在上述多个直管中的邻接的两个直管之间,上述隔离件的与上述超导输电用隔热多层管的长边方向垂直的面的截面形状是顶点的数量为三个以上的多边形,上述隔离件在与上述超导输电用隔热多层管的长边方向垂直的面的中心具备贯通孔,上述邻接的两个直管中的内侧的直管被设置成穿过上述贯通孔,上述隔离件与上述邻接的两个直管中的内侧的直管之间的摩擦系数μ<Sub>i</Sub>为0.1以下,上述隔离件与上述邻接的两个直管中的外侧的直管之间的摩擦系数μ<Sub>o</Sub>为0.1以下,上述多边形的对角线等效长度L<Sub>d</Sub>与上述邻接的两个直管中的外侧的直管的内径d之比L<Sub>d</Sub>/d为0.9以下。(The invention provides a superconductive transmission device which does not damage a spacer and has high heat insulation performance even if being laid by a reel methodAn electrically insulating multilayer tube. The heat-insulating multilayer pipe for superconducting power transmission comprises: a superconducting cable; a multilayer tube which is composed of a plurality of straight tubes and houses the superconducting cable; and a plurality of spacers provided between two adjacent straight pipes among the plurality of straight pipes, wherein a cross-sectional shape of a surface of the spacer perpendicular to a longitudinal direction of the superconducting power transmission heat-insulating multilayer pipe is a polygon having three or more vertexes, the spacer includes a through-hole at a center of the surface perpendicular to the longitudinal direction of the superconducting power transmission heat-insulating multilayer pipe, an inner straight pipe among the two adjacent straight pipes is provided so as to pass through the through-hole, and a friction coefficient μ between the spacer and the inner straight pipe among the two adjacent straight pipes i 0.1 or less, and a coefficient of friction mu between the spacer and an outer one of the two adjacent straight pipes o Is 0.1 or less, and has a diagonal equivalent length L of the polygon d The ratio L of the inner diameters d of the outer two adjacent straight pipes d The value of/d is 0.9 or less.)

1. A heat-insulating multilayer tube for superconducting power transmission, comprising:

a superconducting cable;

a multilayer tube which is composed of a plurality of straight tubes and houses the superconducting cable; and

a plurality of spacers disposed between adjacent two of the plurality of straight tubes,

wherein the content of the first and second substances,

the cross-sectional shape of the surface of the separator perpendicular to the longitudinal direction of the superconducting power transmission heat-insulating multilayer tube is a polygon having three or more vertices,

the separator has a through-hole at the center of a plane perpendicular to the longitudinal direction of the superconducting power transmission heat-insulating multilayer tube,

an inner one of the two adjacent straight pipes is provided so as to pass through the through hole,

a coefficient of friction mu between the spacer and an inner one of the two adjacent straight pipes_iThe content of the organic acid is less than 0.1,

a coefficient of friction mu between the spacer and an outer one of the two adjacent straight pipes_oThe content of the organic acid is less than 0.1,

the equivalent length L of the diagonal line of the polygon_dA ratio L of the inner diameters d of the outer two adjacent straight pipes_dThe value of/d is 0.9 or less.

2. The heat-insulating multilayer tube for superconducting power transmission according to claim 1, wherein,

a length L of a contact portion between the spacer and an outer one of the two adjacent straight pipes in a longitudinal direction of the straight pipe_lIs 5mm or less.

3. The heat-insulating multilayer tube for superconducting power transmission according to claim 1 or 2, wherein,

the sum of the wall thicknesses of the straight pipes constituting the multilayer pipe is 10mm or more.

4. The heat-insulating multilayer tube for superconducting power transmission according to any one of claims 1 to 3, wherein,

the innermost tube of the plurality of straight tubes is made of a steel material having an austenite phase volume percentage of 80% or more.

5. The heat-insulating multilayer tube for superconducting power transmission according to any one of claims 1 to 4, wherein,

at least one of the plurality of straight tubes has a plating layer.

6. A method of laying a heat-insulating multilayer pipe for superconducting power transmission,

a multilayer heat-insulating pipe for superconducting power transmission according to any one of claims 1 to 5 is laid on the seabed using a reel pipe laying barge.

Technical Field

The present invention relates to a heat-insulating multilayer tube for superconducting power transmission (heat-insulated multilayer tube for superconducting power transmission), and more particularly, to a heat-insulating multilayer tube for superconducting power transmission that can be preferably used for laying to the seabed using a reel-laying tube. The present invention also relates to a method for laying the above-described heat-insulating multilayer pipe for superconducting power transmission.

Background

In cooling metals, alloys, and the like, a superconducting phenomenon in which the resistance sharply decreases and becomes zero at a certain temperature is studied and applied in various fields. Among them, superconducting power transmission in which power is transmitted using a cable in a superconducting state is put to practical use as a power transmission method without power loss during power transmission.

In superconducting power transmission, in order to maintain a cable in a superconducting state, the cable needs to be cooled all the time, and therefore, a proposal has been made to use a heat-insulating multilayer tube. In the heat-insulating multilayer tube, a cable of a superconducting material is provided in the innermost tube (inner tube) of the multilayer tube, and a cooling medium such as liquid nitrogen flows through the inner tube. Further, in order to suppress a temperature rise due to heat from the outside, a vacuum heat insulating layer is provided between two adjacent pipes (inner pipe and outer pipe) to be in vacuum, thereby blocking the heat from entering.

However, even in the case of the heat-insulating multilayer pipe having the above-described structure, if the pipes constituting the multilayer pipe are in direct contact with each other, heat directly enters the inside through heat conduction via the contact portion, and the heat-insulating property is degraded.

Therefore, patent document 1 proposes to provide a spacer made of a low thermal conductive material between the inner tube and the outer tube. By using the spacer, contact between the inner tube and the outer tube is prevented, and intrusion of heat from the outside can be suppressed.

On the other hand, patent document 2 proposes a flexible heat-insulating multilayer tube for superconducting power transmission, which uses corrugated tubes as the inner tube and the outer tube, from the viewpoint of imparting flexibility to the tube.

Patent document 1: japanese laid-open patent publication No. 2007-080649

Patent document 2: japanese laid-open patent publication No. H08-007670

In order to use the above-described heat-insulating multilayer pipe for superconducting power transmission for actual power transmission, a method of efficiently laying the multilayer pipe over a long distance is required, and a method of laying the multilayer pipe on the seabed is required.

As a method of laying a pipe on the seabed, there is a Reel method (Reel-Lay) using a Reel pipe laying machine for laying an oil line pipe or the like. The reel pipelaying is a pipe-laying vessel equipped with a large-diameter reel, and lays a pipe that has been previously wound around the reel to the sea bottom while rewinding the pipe at sea.

However, when a conventional heat-insulating multilayer pipe as described in patent document 1 is to be laid by the above-described roll method, it is known that there is a problem in that the spacer provided between the pipes is broken.

In addition, in the case of a multilayer pipe using the corrugated pipe as described in patent document 2, it is known that sufficient heat insulation cannot be obtained although the pipe is easy to lay because of flexibility.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a heat-insulating multilayer tube for superconducting power transmission, which has high heat-insulating properties and in which a spacer is not damaged even when it is laid by a roll method. Another object of the present invention is to provide a method for laying the above-described heat-insulating multilayer pipe for superconducting power transmission.

The main structure of the present invention is as follows.

1. A heat-insulating multilayer tube for superconducting power transmission, comprising:

a superconducting cable;

a multilayer tube which is composed of a plurality of straight tubes and which houses the superconducting cable; and

a plurality of spacers disposed between adjacent two of the plurality of straight pipes,

wherein the content of the first and second substances,

the cross-sectional shape of the surface of the separator perpendicular to the longitudinal direction of the superconducting power transmission heat-insulating multilayer tube is a polygon having three or more vertices,

the separator has a through-hole at the center of a plane perpendicular to the longitudinal direction of the superconducting power transmission heat-insulating multilayer tube,

the inner straight tube of the two adjacent straight tubes is arranged to pass through the through hole,

a coefficient of friction μ between the spacer and an inner one of the two adjacent straight pipes_iThe content of the organic acid is less than 0.1,

a coefficient of friction μ between the spacer and an outer one of the two adjacent straight pipes_oThe content of the organic acid is less than 0.1,

the equivalent length L of the diagonal line of the polygon_dThe ratio L of the inner diameters d of the outer two adjacent straight pipes_dThe value of/d is 0.9 or less.

2. The heat-insulating multilayer tube for superconducting power transmission according to claim 1, wherein a length L of a contact portion between the spacer and an outer one of the two adjacent straight tubes in a longitudinal direction of the straight tubes_lIs 5mm or less.

3. The heat-insulating multilayer tube for superconducting power transmission according to the above 1 or 2, wherein,

the sum of the thicknesses of the straight pipes constituting the multilayer pipe is 10mm or more.

4. The heat-insulating multilayer tube for superconducting power transmission according to any one of the above 1 to 3, wherein,

the innermost tube of the plurality of straight tubes is made of a steel material in which an austenite phase is 80% by volume or more.

5. The heat-insulating multilayer tube for superconducting power transmission according to any one of the above 1 to 4, wherein,

at least one of the plurality of straight pipes has a plating layer.

6. A method of laying a heat-insulating multilayer pipe for superconducting power transmission, wherein the heat-insulating multilayer pipe for superconducting power transmission described in any one of the above 1 to 5 is laid on the seabed using a reel pipe laying barge.

The heat-insulating multilayer pipe for superconducting power transmission according to the present invention is not damaged even when it is laid by the reel method, and therefore, it can be efficiently laid on the seabed. The heat-insulating multilayer tube for superconducting power transmission of the present invention has excellent heat-insulating properties as compared with heat-insulating multilayer tubes using corrugated tubes or flexible tubes.

Drawings

Fig. 1 is a schematic cross-sectional view of a heat-insulating multilayer tube for superconducting power transmission according to an embodiment of the present invention.

FIG. 2 is a graph showing the coefficient of friction μ_oSchematic representation of the assay method of (1).

FIG. 3 is a graph showing the coefficient of friction μ_iSchematic representation of the assay method of (1).

Detailed Description

Next, a method for carrying out the present invention will be specifically described. The following description shows preferred embodiments of the present invention, and the present invention is not limited to the following description.

The heat-insulating multilayer tube for superconducting power transmission of the present invention includes a superconducting cable, a multilayer tube that houses the superconducting cable, and a plurality of spacers. The structure of each of the above-described portions will be described below.

[ superconducting Cable ]

As the superconducting cable, any superconducting cable can be used as long as it can be used for superconducting power transmission. As an example of a superconducting cable that can be preferably used, a superconducting cable having a core (Former) made of metal such as copper, an insulating layer, and a conductor made of a superconducting material is cited. As the superconducting material, any superconducting material can be used, but a high-temperature superconducting material that can be superconducting in a liquid nitrogen environment is preferably used.

[ multilayer pipe ]

The superconducting cable is housed in a multilayer tube made up of a plurality of straight tubes. The multilayer pipe may be a double-layer pipe composed of two straight pipes, or may be composed of three or more straight pipes. The superconducting cable is usually housed inside the innermost tube (hereinafter, sometimes referred to as "innermost tube") among a plurality of straight tubes constituting the multilayer tube. When the present heat-insulating multilayer tube for superconducting power transmission is used for actual power transmission, a cooling medium for cooling a superconducting cable flows inside a tube (usually, the innermost tube) in which the superconducting cable is housed. As the cooling medium, for example, liquid nitrogen can be used.

In the present invention, it is important to form a multilayer tube using only a straight tube, rather than a corrugated tube or a flexible tube. Since the surface area per unit length of the straight pipe is smaller than that of the corrugated pipe and the flexible pipe, the heat from the outside can be suppressed from entering. Here, the straight pipe is not a pipe processed into a wave shape like a corrugated pipe or a flexible pipe, but a pipe having a substantially constant cross-sectional area, and a pipe obtained by bending the straight pipe is also included in the straight pipe. The straight tube preferably has a circular cross section perpendicular to the longitudinal direction.

The material of the straight pipe is not particularly limited, but is preferably made of metal. As the metal, for example, one or two or more selected from aluminum, an aluminum alloy, iron, steel, a Ni-based alloy, and a Co-based alloy are preferably used. Among them, from the viewpoint of strength, corrosion resistance, cost, and the like, a straight steel pipe is preferably used as the straight pipe. As the material of the straight steel pipe, one or both of carbon steel and stainless steel is preferably used. The plurality of straight pipes constituting the multilayer pipe may be made of the same material or different materials.

As the innermost tube (innermost tube) among the plurality of straight tubes constituting the multilayer tube, a tube made of a steel material having an austenite phase of 80% by volume or more is preferably used. When the multilayer pipe is wound on a Reel lay machine (Reel cage), the innermost pipe (innermost pipe) among the plurality of straight pipes constituting the multilayer pipe is most deformed due to the difference in the bending radius. A steel material having an austenite phase content of 80% by volume or more is excellent in elongation characteristics, and therefore is preferable as the material of the innermost tube. Further, since the innermost tube is in contact with the cooling medium at a low temperature, a steel material having an austenite phase of 80% by volume or more is also preferable from the viewpoint of strength and toughness at a low temperature. As the steel material having the austenite phase of 80% by volume or more, any steel material can be used. The volume percentage of austenite is preferably 90% or more. The upper limit of the volume percentage of austenite is not particularly limited, and may be 100%. Examples of the steel material having an austenite phase of 80% by volume or more include austenitic stainless steel and austenitic steel containing Mn (so-called high manganese steel). The high manganese steel preferably has a Mn content of 11 mass% or more. As the austenitic stainless steel, SUS316L is preferably used.

As the straight pipe, a pipe manufactured by an arbitrary method can be used. Examples of pipes that can be preferably used include resistance welded pipes, seamless pipes, UOE pipes, and the like. The straight pipe can be optionally subjected to surface treatment. The surface treatment is preferably performed by one or more selected from acid washing, electrolytic polishing, chemical polishing, and plating, for example. In addition, the plating will be described later.

Sum of wall thicknesses

The thickness of each of the plurality of straight pipes constituting the multilayer pipe can be set to an arbitrary value independently, but the total thickness is preferably 10mm or more, and more preferably 15mm or more. When the total thickness is within the above range, the heat-insulating multilayer tube for superconducting power transmission sinks due to its own weight when laid on the seabed, and therefore, the laying can be easily performed without using a weight or the like, and strength such as water pressure resistance can be obtained.

The thickness of each of the plurality of straight pipes constituting the multilayer pipe is not particularly limited, but is preferably 3mm or more. Further, it is more preferable that the outermost pipe (hereinafter, sometimes referred to as "outermost pipe") among the plurality of straight pipes constituting the multilayer pipe has a wall thickness of 8mm or more.

Coating of

Preferably, a plating layer is provided on the surface of the straight pipe. By providing the plating layer, the corrosion resistance can be improved, and the emissivity can be reduced to further suppress the intrusion of heat from the outside. When the plating layer is formed, it may be provided on at least one of the plurality of straight pipes constituting the multilayer pipe, or may be provided on all of the straight pipes. Each of the straight pipes may have a plating layer on either or both of the outer surface and the inner surface.

The material of the plating layer is not particularly limited, and may be any metal. Examples of the metal include zinc, zinc alloy, aluminum, and aluminum alloy. Further, since the outermost pipe is in contact with the external corrosive environment, it is preferable to provide a plating layer made of a metal having a sacrificial corrosion prevention function on the outer surface of the outermost pipe from the viewpoint of improving corrosion resistance. Examples of the metal having the sacrificial corrosion preventing function include zinc and zinc alloy. As a method for forming the plating layer, for example, hot dip plating, electroplating, or the like can be used.

Coating of

In order to protect the outermost tube, a coating layer may be optionally provided on the outer surface of the outermost tube. The material of the coating layer is not particularly limited, and for example, a resin can be used. As the resin, a fluororesin such as polytetrafluoroethylene, a silicone resin, or the like is preferably used. The method of forming the coating layer is not particularly limited, and the coating layer can be formed by winding a strip-like body made of resin or the like around the outer surface of the outermost pipe.

[ spacers ]

A plurality of spacers are provided between two adjacent straight pipes among the plurality of straight pipes constituting the multilayer pipe. By providing the above-described spacer, it is possible to prevent the two adjacent pipes from being in direct contact and heat from being directly transferred. Here, "adjacent" means that one of the two tubes is disposed inside the other tube, and the other tube is not present between the two tubes.

The separator has a polygonal cross-sectional shape on a plane perpendicular to the longitudinal direction of the superconducting power transmission heat-insulating multilayer tube. The polygon may be any polygon having three or more vertices, and examples thereof include a triangle, a quadrangle, a pentagon, and a hexagon. The polygon is not limited to a regular polygon. For example, the quadrangle may be not only a square but also a rectangle having a long side and a short side different in length. The "polygon" in the present invention includes not only a geometrically perfect polygon but also a "substantial polygon" in which a fine change is applied to a perfect polygon. For example, when the apex of the spacer is curved or flattened by abrasion, deformation, or the like, the shape of the spacer is also included in the polygon of the present invention.

Fig. 1 is a schematic view showing a cross-sectional structure of a heat-insulating multilayer tube 1 for superconducting power transmission according to an embodiment of the present invention. In this example, a two-layer pipe 10 composed of an outer pipe 11 and an inner pipe 12 is used as a multilayer pipe, and both the outer pipe 11 and the inner pipe 12 are straight pipes. When the superconducting cable 20 is housed inside the inner tube 11 and the superconducting power transmission heat-insulating multilayer tube 1 is used, a cooling medium flows through the space 13 inside the inner tube 1. The space 14 between the outer tube 11 and the inner tube 12 is in a vacuum state when the superconducting power transmission heat-insulating multilayer tube 1 is used, and functions as a vacuum heat-insulating layer.

A spacer 30 is provided in the space 14 between the outer tube 11 and the inner tube 12. In the example shown in fig. 1, the cross-sectional shape of the separator 30 on a plane perpendicular to the longitudinal direction of the superconducting power transmission heat-insulating multilayer tube 1 is rectangular, and a through-hole 31 is formed in the center of the separator 30. The inner tube 13 is provided to pass through the through hole 31. Note that, although only one spacer 30 is shown in fig. 1, a plurality of spacers are actually provided at intervals in the longitudinal direction of the superconducting power transmission heat-insulating multilayer tube 1. The interval is not particularly limited, and is preferably set to be equal. In addition, the plurality of spacers may have different shapes, but preferably have the same shape.

In the spacer 30, one or two or more through holes 32 may be provided in addition to the through hole 31 provided at the center. By providing the through-hole 32, the heat can be prevented from entering the separator 30 due to the heat conducted thereto.

Coefficient of friction

If the coefficient of friction between the separator and the pipe with which the separator is in contact is large, the separator may not slip and crack when the wound multilayer heat-insulating pipe for superconducting power transmission is wound on a reel in order to lay the multilayer heat-insulating pipe for superconducting power transmission by the reel method, or when the wound multilayer heat-insulating pipe for superconducting power transmission is wound back from the reel. Therefore, the coefficient of friction μ between the spacer and the inner one of the two adjacent straight pipes_iIs set to 0.1 or less. Similarly, the coefficient of friction μ between the spacer and the outer one of the two adjacent straight pipes_oIs set to 0.1 or less.

Coefficient of friction [ mu ] as described above_oThe measurement can be performed by the following method. FIG. 2 is a graph showing the coefficient of friction μ between the outer straight pipe (outer pipe 11) and the spacer out of two adjacent straight pipes_oSchematic representation of the method of performing the assay. In the above measurement, instead of the actual spacer, the jig 41 for measuring a friction coefficient, which is made of the same material as the spacer and has the same surface roughness, is used. The jig 41 is formed to have a width of 5cm, a height of 5cm and a length of 40cm, and the lower surface (surface in contact with the outer tube 11) of the jig 41 has a curvature equal to the inner surface of the outer tube 11. However, the diameter of the outer tube 11 is 80mm or lessIn this case, the size of the jig 41 is adjusted in accordance with the size of the outer tube 11.

As shown in fig. 2, a jig 41 is installed inside the outer tube 11, and a spring balance 42 connected to the jig 41 is pulled horizontally at a moving speed of 150 mm/min, and the load t (n) at the start of movement of the jig 41 is measured. The friction coefficient μ can be measured by using the load T (N), the mass M (kg) of the jig 41, and the gravitational acceleration G (m/s)²) And is obtained by the following formula (1).

μ＝T/(G×M)…(1)

The measurement was performed at three points separated by 120 ° in the circumferential direction of the tube, and the average value of the friction coefficients μ at the three points was defined as μ_o。

Further, the coefficient of friction μ_iCan pass through and mu_oThe measurement was carried out in the same manner. FIG. 3 is a graph showing the coefficient of friction μ between the spacer and the inner one (inner pipe 12) of two adjacent straight pipes_iSchematic representation of the method of performing the assay. In the above measurement, instead of the actual spacer, the jig 41 for measuring a friction coefficient, which is made of the same material as the spacer and has the same surface roughness, is used. The jig 41 is formed to have a width of 5cm, a height of 5cm and a length of 40cm, and the lower surface (surface in contact with the inner tube 12) of the jig 41 has a curvature equal to that of the inner surface of the inner tube 12. However, when the diameter of the inner tube 12 is 80mm or less, the size of the jig 41 is adjusted in accordance with the size of the inner tube 12.

As shown in fig. 3, a jig 41 is installed outside the inner tube 12, and a spring balance 42 connected to the jig 41 is pulled horizontally at a moving speed of 150 mm/min, and the load t (n) at the start of movement of the jig 41 is measured. The friction coefficient μ can be measured by using the load T (N), the mass M (kg) of the jig 41, and the gravitational acceleration G (m/s)²) And is obtained by the following formula (1).

μ＝T/(G×M)…(1)

The measurement was performed at three points separated by 120 ° in the circumferential direction of the tube, and the average value of the friction coefficients μ at the three points was defined as μ_i。

The method for controlling the friction coefficient within the above range is not particularly limited, and any method may be used. In general, the friction coefficient depends on the material and surface condition of the members to be contacted. Therefore, in one embodiment of the present invention, the material, surface roughness, and the like of the separator and the pipe with which the separator is in contact can be controlled so that the friction coefficient satisfies the above-described conditions. Specifically, at least one of the following (1) to (3) is preferably set to 0.8mm or less.

(1) Arithmetic average roughness Ra of the portion of the surface of the spacer in contact with the straight pipe_s。

(2) Arithmetic average roughness Ra of outer surface of inner straight pipe of the two adjacent straight pipes_i。

(3) The arithmetic average roughness Ra of the inner surface of the outer straight pipe of the two adjacent straight pipes_o。

However, even the above Ra_s、Ra_iAnd Ra_oAt least one of the diameters is 0.8mm or less, and the condition of the friction coefficient may not be satisfied depending on the material of the spacer and the straight pipe, the condition of the surface treatment, and the like. In this case, the Ra can be represented by_s、Ra_iAnd Ra_oAnd a method of reducing the arithmetic mean roughness or changing the material of the separator to a material having higher lubricity by setting the total thickness to 0.8mm or less.

The arithmetic average roughness may be measured at an arbitrary position. Since the surface roughness of the spacer and the straight pipe manufactured by a usual method is substantially uniform, the arithmetic mean roughness measured at one point can be used as an index of the overall surface roughness. However, when a welded steel pipe is used as the straight pipe, the arithmetic mean roughness is measured at a position other than the welded portion.

As the material of the spacer, any material can be used as long as the above-described condition of the friction coefficient is satisfied, but from the viewpoint of the degree of reduction in thermal conductivity and the degree of reduction in friction coefficient, a resin material is preferable, and a fluororesin material is more preferable. As the fluororesin, for example, one or two or more selected from Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), and Polychlorotrifluoroethylene (PCTFE) can be used. In addition, in order to improve the strength of the separator, Fiber Reinforced Plastic (FRP) in which a fibrous filler is added to the resin can be used. The FRP includes, for example, Glass Fiber Reinforced Plastic (GFRP). In addition, other optional fillers may be added. However, when the filler is added, the thermal conductivity of the separator may be high, and the heat insulating property may be deteriorated. Therefore, from the viewpoint of thermal insulation properties, it is preferable that the resin used for the separator contains no filler.

Equivalent length of diagonal line of the spacer (Japanese: quite long and very high angle)

Further, if the size of the spacer is about the same as the inner size of the pipe (in the case of fig. 1, the outer pipe 11) to which the spacer is inscribed, the superconducting power transmission heat-insulating multilayer pipe cannot be smoothly bent, and the spacer may be broken at the time of bending. Therefore, the cross-sectional shape of the spacer, i.e., the equivalent length L of the diagonal line of the polygon is set to_dThe ratio (L) of the inner diameters d of the outer two adjacent straight pipes_dThe value of/d) is 0.9 or less. Preferably L is as defined above_dThe value of/d is 0.8 or less. Here, the diagonal equivalent length of the polygon is defined as the length of a line segment having the largest length among line segments connecting two different vertices of the polygon to each other. For example, when the polygon is a triangle, the equivalent length of the diagonal line is the length of the longest side of the three sides. In the case of a polygon having four or more vertices, the equivalent length of the diagonal is the maximum diagonal length.

Contact part

Further, if the contact portion between the spacer and the pipe to which the spacer is inscribed is excessively large, sliding resistance between the spacer and the pipe becomes large, and heat insulation performance is lowered. Therefore, it is preferable that the spacer and the outer one of the two adjacent straight pipes have a length L in the longitudinal direction of the straight pipe_lThe thickness is set to 5mm or less, more preferably 3mm or less, and still more preferably 1mm or less.

Interval of

The spacers can be provided at arbitrary intervals in the longitudinal direction of the superconducting power transmission heat-insulating multilayer tube. The above-mentioned intervals may be equal intervals or may be unequal intervals. The interval is not particularly limited and may be any value, but if the interval is too large, contact between the tubes constituting the multilayer tube cannot be prevented in some cases. Therefore, the interval is preferably 10m or less. On the other hand, if the interval is too small, the installation cost of the spacer increases, and therefore the interval is preferably 1m or more. Further, the position of the spacer is allowed to be changed along with the work such as the laying.

Stop piece

If the spacer is provided so as to be movable in the longitudinal direction (axial direction) of the superconducting power transmission heat insulating multilayer tube, the position of the spacer may be largely changed in association with the work such as laying, and as a result, an unexpected section where the spacer is not present may be formed. Therefore, a regulating member (stopper) for regulating the movement of the separator in the longitudinal direction of the superconducting power transmission heat-insulating multilayer tube can be provided. As the stopper, any stopper may be used as long as the movement of the spacer can be regulated. For example, a member fixed to one or both of the two adjacent straight pipes can be used as the stopper. The stopper does not necessarily prevent the movement of the spacer completely, and may prevent the spacer from moving beyond the position where the stopper is provided.

However, in a typical heat insulating multilayer pipe for superconducting power transmission, a plurality of multilayer pipes are connected by circumferential welding to have a desired length. Therefore, on the outer surface and the inner surface of the tube constituting the multilayer tube, projections (weld beads) formed by welding are present at substantially constant intervals in the longitudinal direction. Therefore, the movement of the spacer is restricted by the convex portion, and therefore, the stopper is not necessarily provided.

[ paving method ]

The heat-insulating multilayer pipe for superconducting power transmission can be laid by any method, but can be preferably used particularly when it is laid on the seabed by using a reel pipe laying machine. The laying by the reel pipe laying barge can be performed according to a method used for laying a line pipe or the like.

During the laying, the space between the two adjacent straight pipes, that is, the space in which the spacer is provided is evacuated (vacuumized) to form a vacuum heat insulating layer. The above-described evacuation may be performed once after the heat-insulating multilayer tube for superconducting power transmission is laid, but may be performed twice or more. For example, preliminary evacuation (temporary evacuation) is performed before the laying, and evacuation (main evacuation) is performed until the final vacuum degree is reached after the laying.

Description of the reference numerals

1 … heat-insulating multilayer tube for superconducting power transmission; 10 … two-layer tube (multilayer tube); 11 … an outer tube; 12 … inner tube; 13 … space (for cooling medium); 14 … space (vacuum insulation layer); 20 … a superconducting cable; 30 … spacers; 31 … through-hole (for installing superconducting cable); 32 … through holes (for heat conduction suppression); 41 … jig; 42 … spring balance.