JPS6360279B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an insulator having a through hole in the center, which is used, for example, to penetrate the wall of a metal airtight container or to install it in the middle of a metal pipe to ensure insulation. This relates to pipe fittings.

Conventionally, it has been widely used as a necessary part for transporting liquid nitrogen, chlorofluorocarbons as a cooling medium, etc., but since the voltage to which insulation is applied is low, no special consideration is given to insulation resistance or creepage resistance. I wasn't aware of it.

Recently, in order to extract oil from the oil sand layer buried underground in Benezera, Canada, two electrodes were buried in the oil sand layer approximately 500 meters underground, and a voltage was applied between both electrodes. However, serious consideration is being given to a method of increasing the temperature of the oil sand layer using Joule heat to lower the viscosity of the oil and extracting only the oil from the ground.

The applied voltage in this case is generally a high voltage of 4000 to 5000V.

However, because the resistivity of the upper stratum is lower than the resistivity of the oil sand layer (actually about 1/10), there is no insulation between the steel pipe buried in the stratum and the electrode buried in the oil sand layer. It was necessary to insert a pipe joint, and the demand for insulated pipe joints increased rapidly.

Among the characteristics required of insulated pipe joints used for the above purpose, the main ones are as follows. It has high mechanical strength because the electrode is held suspended.
Since a voltage of 4000 to 5000V is applied to both ends, it must maintain high withstand voltage characteristics including creeping insulation resistance. Since the temperature rises due to the conduction of electricity between the electrodes, the material must not only maintain the mechanical and electrical properties mentioned above at high temperatures, but also have excellent cold and thermal shock resistance. Since contact with the hole wall inevitably occurs during burial, the mechanical impact strength must be high. The center through hole is equal to the inner diameter of the upper steel pipe and electrode, so the flow resistance is low. Maintain a high degree of airtightness under the above conditions. and have long-term reliability without deterioration over time. Also, it can be easily connected to the upper and lower steel pipes and electrode parts.

In the case of this type of insulated pipe joint, the basic structure is a structure in which an insulator is interposed between two conduits. Insulators have the greatest influence on the above-mentioned required characteristics. This insulator will be explained below. When an organic material is used as an insulator, there is an unavoidable fatal flaw in that various properties rapidly deteriorate due to temperature rise, so it cannot be used in reality. Next, when using gaseous materials, there are defects such as cracks occurring due to sudden changes in temperature or low mechanical impact strength, and when using porcelain materials and sealing with low melting point metals, As with the case of glass, it has a fatal defect of low thermal and mechanical impact strength, which also makes it unusable in practice. Insulators made of glass or mica plastics, which will be described in detail below, are the most excellent insulators that combine the various characteristics described above.

Glass and mica plastics are made from a mixture of vitreous powder and mica powder, heated to a temperature at which the vitreous material softens and flows under pressure, and then pressure-molded in the heated state. It refers to the insulating material obtained.

The present inventor first proposed an insulated pipe joint using glass or mica plastic as an insulator, which is the most ideal for the conventional required characteristics (Japanese Patent Application No. 55-51151, Japanese Patent Publication No. 61-34037) There is something I did.

The structure will be explained below with reference to FIG. 1A.

FIG. 1 is a longitudinal sectional view showing its structure, in which 1 is a cylindrical first tubular member, and a shoulder portion 1-1 is attached to a cylindrical body 1-2.
An outer peripheral fitting 3 having an inner diameter larger than the outer diameter of the cylindrical body 1-2 is provided through the cylindrical body 1-2. 2 is a second tubular member;
It has a cylindrical body 2-1 whose inner and outer diameters are the same as the inner and outer diameters of the cylindrical body 1-2 of the first tubular member 1. None
It is made of metal that can withstand heating of about 600℃, and iron, stainless steel, etc. are preferably used. The first and second tubular members 1 and 2 are supported by holding spaces 4 and 4-1, and the spaces 4 and 4-1 are filled with an insulator 5 made of glass and mica plastic, The first tubular member 1 and the second tubular member 2 are completely sealed and fixed, and insulation is maintained.
1a and 2a are connection parts to adjacent vessel walls or metal pipes, and are connected by an appropriate method such as welding or screwing. This insulated pipe fitting maintains mechanical strength, cold shock resistance, mechanical shock strength, and airtightness even at high temperatures, has no unevenness in the through hole, has low flow resistance, and does not deteriorate over time and lasts for a long time. Although it maintains reliability and is ideal, when used under high voltage conditions, it has fatal flaws in withstand voltage characteristics and creeping insulation resistance characteristics.

This relationship will be explained in detail below.

The mica powder constituting the mica plastic body is in the form of flakes, and the ratio of average particle diameter to thickness of the flakes is generally 30 to 50:1. On the other hand, vitreous powder is in the form of fine powder with no directionality. When the above-mentioned mixed powder is heated to a temperature at which the vitreous material becomes soft and fluid, and then pressure-molded in the heated state, the mixed powder is pressed with almost no movement if the shape is plate-like. At this time, the mica flakes are arranged parallel to the pressurized surface, making it look like a laminated product. Next, when the mixed powder is molded by applying pressure and being injected into the gap, the flowing parts are arranged parallel to the flow direction, and the parts that do not move and receive pressure are parallel to the pressing direction. It will be arranged. The state of this arrangement is shown in FIG. As is clear from this, the arrangement direction differs depending on the position. That is, the glass and mica plastic bodies in the space 4 between the second tubular member 2 and the outer metal fitting 3 are arranged parallel to the flow direction, that is, parallel to the second tubular member 2, as shown in arrangement 6-2. The arrangement 6-1 is also parallel to the outer peripheral fitting 3. Since the array 6-5 is pressurized with almost no movement, it is parallel to the pressurizing surface, and is arranged at right angles to the second tubular member 2. Further, since the array 6-6 receives pressure after almost all movement has stopped, it is arranged parallel to the inner circumferential surface.

Next, the relationship between the arrangement direction of mica flakes and mechanical and electrical properties will be explained. First, regarding mechanical strength, tensile strength is strong in the direction parallel to the alignment and about 2 to 3 times stronger in the direction perpendicular to the alignment. Conversely, the direction perpendicular to the alignment is extremely strong in compression, but extremely weak in tension as it causes delamination. Therefore, when the thickness of a molded product reaches approximately 25 mm, stress occurs on the surface and inside of a single molded product, and when molded in contact with metal as shown in Figure 1 B, , delamination occurs due to stress caused by the difference in coefficient of thermal expansion. As described above, mechanical strength is largely controlled by the arrangement direction.

Next, regarding the relationship with electrical characteristics, the characteristics also vary greatly depending on the arrangement direction. In the direction perpendicular to the alignment direction, a withstand voltage of 15 to 20 KV/mm is maintained, but in the parallel direction, it is largely controlled by density. , is extremely weak.

Now, regarding the electrical characteristics of the insulating pipe joint, in FIG. Since the mica flakes are arranged in the flow direction, that is, parallel to the second tubular member 2,
The withstand voltage is extremely high and there are no problems. By the way, since the arrangement 6-5 is arranged perpendicularly to the second tubular member 2, the withstand voltage is low and reaches the outer peripheral fitting 3 via the interlayer, so that only an extremely low withstand voltage can be obtained.

Next, regarding creeping insulation resistance, as mentioned above, if mica flakes are arranged in layers, a thick molded product cannot be obtained.
is naturally limited by its length, which is limited to 20 to 25 mm. Under usage conditions where the surface is contaminated, creeping insulation resistance is extremely reduced.

As is clear from the above description, conventional insulated pipe joints cannot be used in applications where high voltage is applied.

The present inventors have basically investigated the relationship between the arrangement direction of mica flakes and the electrical properties as described above, in order to obtain an insulated pipe joint that can be used in applications where high voltage is applied. By considering a combination of methods, he was able to achieve his goal. The contents will be explained below.

Figure 2A is a longitudinal sectional view showing the shape after completion of molding;
FIG. 2B is a longitudinal sectional view showing the structure of the product after machining and the arrangement of mica flakes. To facilitate understanding, the manufacturing method will first be explained with reference to FIG. Figure 3 A shows the state immediately before pressure molding.
FIG. 3B is a longitudinal sectional view showing the state after pressure molding is completed. In the figure, reference numeral 1 denotes a first tubular member having a cylindrical body A, which integrally has an outer peripheral fitting 3 at one end. This outer peripheral fitting 3 includes a cylinder B3-1 that is integrally formed at one end of the cylinder A and has an inner diameter larger than the inner diameter of the cylinder A, and a cylinder B3-1 that is integrally formed with this cylinder B and has an inner diameter larger than the inner diameter of the cylinder B. Cylindrical body C3-2, which is the inner diameter,
The cylindrical body D3-3 is integrally formed with the cylindrical body C and has a larger inner diameter than the cylindrical body C and a smaller outer diameter than the outer diameter of the cylindrical body C. 2 is a second tubular member;
It has a cylinder E having the same inner and outer diameter dimensions as the cylinder A of the first tubular member 1, and has an outer circumferential surface at one end of the cylinder E with a size that fits into the inner circumferential surface of the cylinder A of the first tubular member 1. It has a cylindrical body F2-1. The cylindrical body F is cut and removed before completion as an insulating pipe joint. Note that the material may be any metal that can withstand heating of about 600°C, as with conventional products, and iron, stainless steel, etc. are preferably used.

The molding consists of a frame 7 shown in Fig. 3, a partitioned structure wall 8,
Support stand 9, holding stand 10, presser metal 11, and pressurizer metal 1
A mold consisting of 2 or more 6 parts is used. In the mold, frame 7, wall 8, support stand 9 and holding stand 10
are assembled and heated to a predetermined temperature as shown in FIG. The first and second tubular members 1 and 2 are also heated to a predetermined temperature, and first the first tubular member 1 is placed on the support stand 9, and the cylindrical body F2 of the second tubular member
-1 into the first tubular member 1 and the holding base 10
Insert it on top. At this time, the gap formed by the first and second tubular members 1 and 2 is an important factor. That is, the gap size between the cylindrical body E of the second tubular member 2 and the cylindrical body C3-2 of the first tubular member 1, that is, the thickness of the sealing insulator 5-2 becomes the reference.

The gap size between the cylinder F2-1 of the second tubular member 2 and the cylinder B3-1 of the first tubular member 1, that is, the thickness of the inner peripheral insulator 5-1 is the thickness of the sealing insulator 5-2. In order to approximate this and to eliminate dead spots between them, cylinders A and B, cylinders B and C, cylinder E
Curved surfaces 3-10, 3-11, 3 are formed at the boundary between the cylinder and the cylinder F.
-12 and 2-10 are provided. This curved surface may be an inclined surface or a combination of a curved surface and an inclined surface.

Moreover, as mentioned above, on the upper surface of the outer peripheral fitting 3,
A thick cylindrical body D3-3 is provided to constitute the auxiliary insulator 5-3 and the outer insulator 5-4,
The tip and the boundary with the cylindrical body C3-2 are all curved surfaces. Instead of a curved surface, a sloped surface or a combination of a curved surface and a sloped surface may be used. The height of the cylinder D is determined by the creeping insulation length and is 20 to 40 mm.
It may become.

Next, the preformed body 13 is made using a mixed powder of mica powder (flakes) and glassy powder as a raw material, water is added to make it moist, and the wall portion 8 is molded into a wet state using another mold (not shown). It is formed by cold pressing into a cylindrical product that can be inserted into the space of the second tubular member 2, and then dried to remove moisture. This preformed body 13 is also heated to a predetermined temperature and inserted onto the cylindrical body D3-3. Finally, press the pusher 11 into the second position.
is placed on the cylindrical body E of the tubular member 2. The state at this time is shown in FIG. 3A.

Next, the pressurizing metal 12 pressurizes the preform 13. At this time, the second tubular member 2 floats due to the levitation pressure. A large pressure is applied to prevent the floating of the preformed body 1 using a pressurizing metal 12.
3, the preformed body 13 flows and forms the inner peripheral insulator 5-1, the sealing insulator 5-2, and the auxiliary insulator 5.
-3, outer insulator 5-4 and upper insulator 5-5
Configure. The state at this time is shown in FIG. After cooling to a predetermined temperature, the mold is disassembled and the molded product is taken out. This molded product is shown in Figure 2A. Thereafter, the cylindrical body F of the second tubular member 2 is machined to cut and remove the cylindrical body F, thereby completing the product shown in FIG. 2B.

The arrangement state of the mica flakes of the glass-mica plastic body, which is the insulator of the product manufactured by the above method, is the second
It is shown in Figure B. Auxiliary insulator 5 formed in the gap between the first and second tubular members 1 and 2
3. All of the sealing insulators 5-2 are arrayed 6-3, 6-
As shown in FIG. 2, since they are arranged in parallel with the tubular member, there is no problem with the withstand voltage characteristics. The inner circumferential insulator 5-1 is also connected to the cylindrical body B as shown in the arrangement 6-1.
Since it is arranged parallel to B3-1, the cylinder B3-1
There is no risk of a short circuit from the intermediate position to the tip of the second tubular member 2, and since they are arranged in parallel, the mechanical strength is high and there is no risk of cracking, so the creepage length of the structure is Although it is subject to molding constraints, it is not subject to mechanical strength constraints, so it can be manufactured to the required length.

Next, regarding the external creeping insulation characteristics, the cylinder body D3-
3, an outer peripheral insulator 5-4 is formed in which mica flakes are arranged in parallel as shown in array 6-4 on the outer periphery, and this array molded product is not limited in length. Therefore, you can get the length you need. Furthermore, although the upper insulator 5-5 is arranged at right angles to the second tubular member 2 as shown in the arrangement 6-5, there is no risk of interlayer separation because of its thin thickness. Further, the upper part and the inner peripheral part of the cylinder D3-3 are arranged parallel to the cylinder D surface and surround it, as shown in the arrangement 6-6, so that the cylinder D3-3
- 3 and the second tubular member 2 will not occur. As mentioned above, the withstand voltage characteristics and creeping insulation resistance characteristics, which were the biggest deficiencies of conventional products, have been completely resolved.

The insulated pipe joint of the present invention maintains the mechanical strength, mechanical and cold shock resistance, and airtightness properties that conventional products have, and also has long-term reliability without aging, which is a major drawback of conventional products. By eliminating the deficiencies of withstand voltage characteristics and creeping insulation resistance characteristics, it can now be used under conditions where high voltage is applied, for example, for oil sand heating electrodes and insulated pipe joints for steel pipes. The technical and practical effects are extremely large. Furthermore, if the through hole is free from unevenness, the flow resistance can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view showing a conventional insulated pipe joint, Fig. 2 is a longitudinal cross-sectional view showing the structure of an insulated pipe joint according to an embodiment of the present invention, and Fig. 3 is a longitudinal cross-sectional view showing the structure of an insulated pipe joint according to an embodiment of the present invention. FIG. 3 is a longitudinal sectional view showing a molding method. In the figure, 1 is a first tubular member having a cylindrical body A, 2
2 is a second tubular member having a cylinder E, 2-1 is a cylinder F, 3 is an outer peripheral fitting, 3-1 is a cylinder B, 3-2 is a cylinder C, 3-3 is a cylinder D, 3 -10 to 3-12 are curved surfaces, 4 is a space, 5 is an insulator, 5-1 is an inner peripheral insulator, 5-2 is a sealing insulator, 5-3 is an auxiliary insulator,
5-4 is the outer insulator, 5-5 is the upper insulator, 6-
1 to 6-6 are the arrangement of mica flakes, and 7
1 is a frame, 8 is a wall, 9 is a support stand, 10 is a holding stand, 1
1 is a pusher, 12 is a pressurizer, and 13 is a preform. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. An inner diameter that gradually decreases from one opening end to the other opening end, and has an inner surface where the changing portion is curved, and the opening end on the larger diameter side. a first tubular member having a curved end edge, a thin wall near the end edge, and a smaller outer diameter than the other portions connected to the first tubular member; a second tubular member that is fitted into the tubular member from its large-diameter open end to a halfway position, and the outer surface of the fitted portion faces the inner surface of the first tubular member with a gap therebetween; an insulating material containing flakes filled in the gap and sealingly fixing the first and second tubular members to each other; and an opening edge on the large diameter side of the first tubular member and an outer surface in the vicinity thereof. An insulating pipe joint comprising: an insulating material containing flake powder that covers the insulating material and is integral with the insulating material. 2. The insulating pipe joint according to claim 1, wherein the insulator is a glass-mica plastic body made of glass and mica flakes.