JPS6223218Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to a low-temperature double-pipe bend mechanism, which ensures high insulation performance in the bends of cryogenic cable piping that transmits large amounts of current at high density, and is sufficient to withstand thrust caused by internal pressure, temperature expansion and contraction, etc. This is an attempt to take appropriate measures. Transmitting large amounts of current in power transmission cables1
One known method is to immerse the power transmission cable in a coolant such as liquid nitrogen, which takes advantage of the phenomenon that the electrical resistance of metal decreases when it is cooled. That is, according to this method, a power transmission cable is passed inside a steel pipe such as stainless steel, and a refrigerant is placed inside the pipe. In this case, a high degree of insulation is ensured so that the temperature of the refrigerant does not rise. This is required. The insulation method used is to surround the outer periphery of the steel pipe containing the power transmission cable and refrigerant with a steel pipe with a larger diameter to form a double pipe, and create a vacuum in the gap between them, which also prevents radiation between the inner and outer pipes. For this reason, the inner tube is wrapped in multiple layers of aluminum-deposited Mylar, and powder is filled between the inner and outer tubes. However, in such a double-pipe structure, there is a problem in that a difference in expansion and contraction occurs between the inner and outer pipes when the refrigerant is passed through the inner pipe. An inner tube 1 layered with Mylar 3 and an outer tube 2 thereof are connected to each other as pipe material units using bellows 4, 4a at the straight pipe portions, respectively. By the way, the bent pipe part of the power transmission cable as mentioned above has a diameter of 15 to 20 mm in order to pass the cable through the pipe.
However, if the same structure as the straight pipe part shown in Fig. 1 is adopted in such a bent pipe part as shown in Fig. 2, the bending radius in the bent pipe is Since the outer diameter side area of the radius is larger than the inner diameter side area, an unbalanced force P is generated at the bent part of the inner tube due to internal pressure (regardless of whether there is a bellows or not), and an unbalanced force P is generated between the connecting ends of the inner tube. In this configuration in which the bellows 4 is used, the bellows 4 expands and contracts, and the unbalanced force P is not transmitted to the straight parts on both sides of the bend, so that the inner tube is deformed in a direction away from the center of the bend. causing inconvenience. That is, to explain the unbalanced force, the unbalanced force P generated at the bent portion of the inner pipe due to internal pressure is as follows: P=2pAsinψ where p: internal pressure, A: cross-sectional area within the pipe, 2ψ: bending angle of the bent portion. By the way, the inner diameter is 250A, the inner pressure is 20
Kg/cm ² , for pipe bends with a 90° bend, p = approx.
An unbalanced force of 14 tons acts in a direction away from the center of the bend. However, when such a large unbalanced force acts, the bellows 4 of the inner tube will stretch, and the spacer 5 portion will come into contact with the outer tube, generating a large stress on the spacer 5, which may cause damage to the spacer or damage to the spacer. Furthermore, it causes deterioration of insulation performance. On the other hand, as the inner tube is cooled as described above, the cable 6, which is made up of three wires of approximately 60 mmψ as shown in FIG. 3, is also cooled inside the bent tube. The cable 6 tries to move toward the center of the bend, and as described above, the inner tube 1 and cable 6 deform in the direction away from the center of the bend.
This will cause a large tension in the cable 6. It is possible to install a large number of spacers to prevent movement of the inner tube due to the unbalanced force as described above, but if the number of spacers is increased in this way, the amount of heat that will infiltrate to the outside from these spacers will increase. As a result, the above-described heat insulating effect will be severely impaired. The present invention was devised after repeated studies in view of the above-mentioned actual circumstances. That is, the embodiment of the present invention is as shown in FIG. For the connecting outer tube 2, a plurality of bellows 14, 14a (including 14' to be described later) are used, and end fixing supports 7 are used at both ends of the bent portion R, and the intermediate portion other than these fixing supports 7 is slidable. It is supported by a support 8, and a vibration-proof hanger 9 is provided in the middle of such a bent portion. The sliding support 8 is made of a material with a low coefficient of friction, such as Teflon, so that the outer tube 2 can be moved with a low external load. One of the specific configurations of the spacer 5 is as shown in FIGS.
A plurality of heat insulators 15a, such as Bakelite, are arranged between the annular spacer body 15 attached to the inner tube 1 and the outer tube 2 to hold the inner tube 1 at the center of the outer tube 2. An example of the anti-vibration hanger and sliding support 8 is shown in FIG. A sliding support 8 is constructed, and hydraulic dampers 18, 18 are provided oppositely to the sliding support structure to form a vibration isolation hanger. That is, with the configuration of the present invention, when an unbalanced force P is generated in the inner tube 1 due to the pressure of the refrigerant pressurized, the bent portion of the inner tube 1 is The inner tube itself can withstand this unbalanced force P, which acts as a tensile force on the straight portions at both ends, and almost no force is generated on the inner tube 1 itself that acts in a direction away from the center of the bend. Furthermore, the behavior of the outer tube 2 due to temperature differences can be eliminated by the sliding support 8 and the vibration isolation hanger 9. Specifically, as shown in FIG. 8, the deformation state of the inner tube 250A and the outer tube 4000A, each of which has a bent portion with a radius of 10 m, according to the present invention as described above, is explained as follows:
The rotational deformation, axial expansion/contraction, and radial expansion/contraction between the center of the inner and outer tubes before deformation a, the center of the inner tube after deformation b, and the center of the outer tube after deformation c for the intermediate bellows 14a portion are determined as shown in the following table. It has been confirmed that this problem can be effectively addressed by using a hinge type bellows 14 and a bellows 14a that has hinge type and axial type functions, and that the above-mentioned problems with the conventional ones can be appropriately solved. .

[Table] According to the present invention as explained above, a large number of spacers etc. are used to reduce the deformation caused by the difference in expansion and contraction between the inner and outer tubes that occurs when refrigerant is passed through the inner tube at the bend in this type of double tube structure. This can be effectively resolved without creating strain between the inner and outer tubes, and can sufficiently cope with thrust caused by internal pressure due to expansion and contraction differences, temperature expansion and contraction, etc. while ensuring high insulation performance. This is a highly effective idea in practical terms.

[Brief explanation of the drawing]

The drawings show the technical contents of the present invention, and Fig. 1 is an explanatory diagram showing the configuration of the straight pipe part of the low-temperature double pipe, and Fig. 2 is an explanatory diagram showing the configuration of the straight pipe part of the bent part according to the conventional technology. Explanatory drawing, Fig. 3 is its sectional view, Fig. 4
The figure is an explanatory diagram of the general structural relationship of the bending part according to the present invention, Fig. 5 is a cross-sectional view of the spacer portion, Fig. 6 is a longitudinal sectional view thereof, and Fig. 7 is an explanation of the anti-vibration hanger sliding support. FIG. 8 is an explanatory diagram of a specific deformation state of the device according to the present invention. In these drawings, 1 is an inner tube, 2 is an outer tube, 3 is aluminum vapor-deposited mylar, 4 and 4a are bellows, 5 is a spacer, 6 is a cable, 7 is a fixed support, 8 is a sliding support, and 9 is a preventive material. In the swing hanger, 14 and 14a are bellows, 15 is a spacer body, 15a is a heat insulator, and 18 is a hydraulic damper.

Claims (1)

[Scope of utility model registration request] The inner tube is fitted with a bellows at the bend of the low-temperature double piping, which consists of an inner tube and an outer tube, and a power transmission cable, etc. is inserted into the inner tube, and a refrigerant is passed through the tube to provide insulation between the inner tube and the outer tube. Low temperature 2 characterized in that the inner tubes are directly connected to each other without using a bellows, the outer tubes are connected with a bellows interposed therebetween and supported using a sliding support, and a vibration-proof hanger is provided. Heavy pipe bending mechanism.