JPS6349117B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a center that is used for the purpose of securing insulation and air (water) tightness by being installed, for example, through the wall of a metal airtight container, or by interposing it in the middle of a metal pipe. The present invention relates to an insulated pipe joint having a through hole in the part thereof.

Conventionally, this type of joint has been widely used as a necessary part for conveying fluorocarbons as a cooling medium, other gases, liquids, etc. However, since the range of temperature change under the operating conditions is narrow, these joints are specially designed to withstand wide temperature changes. No consideration was given to this, and the deterioration in air (water) tightness was particularly noticeable at high temperatures.

Recently, with the rise in the price of petroleum resources, serious research has been conducted into extracting oil from oil sand layers buried underground in countries such as Canada and Venezuela. Oil sands exist approximately 500m underground in a layer approximately 50m thick. This oil has a high viscosity and cannot be collected by sucking it up at room temperature.Currently, heated steam is injected into the oil sand layer to raise the temperature of the oil content and lower its viscosity. However, in order to produce oil more efficiently and at a lower cost, two oil extraction pipes with electrodes installed at the tips of the steel pipes buried underground, located in the oil sand layer, were
A method of extracting oil by installing them 50 meters apart and applying a voltage of about 4,000 V between the two electrodes to raise the temperature of the oil sand layer using Joule heat and lowering the oil viscosity is being seriously considered. By the way, since the resistivity of the oil sand layer is higher than the resistivity of the upper stratum (actually about 10 times), it is necessary to insert an insulated pipe joint between the steel pipe buried in the stratum and the electrode buried in the oil sand layer. be. If an insulated pipe joint is not used, current will flow through the strata, and no current will flow between the electrodes buried in the target oil sand layer. As a result of the above, demand for insulated pipe joints has rapidly increased.

The characteristics that an insulated pipe joint used for the above purpose must have are as follows. Since the electrodes are held suspended, they must have high mechanical strength, especially tensile strength, and have high withstand voltage characteristics, including creeping insulation resistance that can withstand voltages of 4000V and maintain complete insulation. It maintains air (water) tightness, mechanical strength, and electrical properties under these conditions, has excellent cold and thermal shock resistance, and has an electrode suspended at the tip when buried in an oil sand layer. It is connected to a steel pipe and sunk into a buried hole, but at this time it may come into contact with the hole wall, so it is necessary to maintain mechanical impact strength so that it will not be damaged by this contact, and the central through hole must be connected to the upper steel pipe and electrode part. It has dimensions equal to the inner diameter of
It goes without saying that the buried hole does not require a particularly large diameter, and that connection with other steel pipes and electrode parts is easy.

In the case of this type of insulated pipe joint, the basic structure is to interpose an insulator between two conduits and seal them tightly. Insulators have the greatest influence on the above-mentioned necessary characteristics. Of course, it is closely related to the metal fitting material and structure used, but these are also largely controlled by the insulator.

First, the material of this insulator will be explained. First, it is an organic material, but since the temperature reaches 300°C during use, it is essentially impossible to use it.

Next, regarding inorganic materials, glass and magnetic materials are useful when used at room temperature, but when used at temperatures of 300°C, they may crack due to temperature changes, etc. It has a low impact degree and is essentially weak in mechanical impact strength, so its use is completely impossible. Insulators made of glass and mica plastics are the most excellent and potentially usable materials based on a comprehensive evaluation of the above-mentioned necessary properties.

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

Among the insulated pipe joints using glass or mica plastic bodies as insulators, the one proposed by the present inventors is the most ideal in meeting the conventionally required characteristics. Part 1 below
The structure will be explained with reference to figures. FIG. 1 is a longitudinal sectional view showing the structure, in which 1 is a cylindrical first tubular member, and an outer peripheral metal fitting having an inner diameter larger than the outer diameter of the first tubular member 1 is inserted through a shoulder 1-1. It is equipped with 3. 2 is a second tubular member, the first tubular member 1
It has the same inner and outer diameter dimensions. All 600
It is made of metal that can withstand heating at temperatures around ℃, and iron, stainless steel, etc. are 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 connected to adjacent vessel walls or metal pipes by an appropriate method such as welding or screwing.

This insulated pipe fitting is free from air (water) under normal temperature operating conditions.
It maintains sufficiently satisfactory characteristics in terms of density properties, mechanical strength, constant cooling heat and mechanical shock strength, and electrical properties, has no unevenness in the through holes, has low flow resistance, and has excellent heat resistance and corrosion resistance due to high temperature hot water, and has a long lifespan. It is ideal because it has no change and has long-term reliability, but in reality, when the temperature reaches 300℃, air (water)
There is a fatal flaw in the density characteristics.

The relationship will be explained below. The reason why the insulated pipe joint shown in FIG. This is because it is tightened. For example, the second tubular member 2 is made of iron with a coefficient of thermal expansion of 11×10 ^-6 , the insulator 5 is made of glass or mica plastic with a coefficient of thermal expansion of 12×10 ^-6 , and the outer metal fitting 3 is made of iron material with a coefficient of thermal expansion of 12×10 -6. The case where stainless steel with a value of 18×10 ^-6 is used will be explained. Molding is performed by the following steps. The insulator 5 is a preformed body formed from a mixed powder of raw material glassy powder and mica powder,
The first and second tubular members 1 and 2, which are metal fittings, are each
Heating to a temperature of 650℃ or higher, glass in the heated state,
The raw material mixture of the mica plastic body is pressurized to form the space 4,
4-1 to form a glass and mica plastic body,
The pressure is maintained and the mixture is cooled to a temperature below the glass transition temperature, that is, until it is completely solidified, and the mold is disassembled to take out the molded product and complete the molding.

Glass and mica plastic bodies can flow in a temperature range higher than the transition temperature of glass, but because they are under pressure for forming, the coefficient of thermal expansion (in this case, the coefficient of thermal contraction) When compressed from the outer periphery due to contraction in the circumferential direction of the outer peripheral fitting 3 with the largest coefficient of thermal expansion), the second tubular member 2, which cannot flow and has the smallest coefficient of thermal expansion, is compressed. It becomes like this. In the temperature range below the transposition temperature, glass and mica plastic bodies are in a solid state, so contraction of the outer metal fitting 3 in the circumferential direction becomes a tightening pressure against the insulator 5, which is a glass and mica plastic body, and the insulator 5 contracts. becomes the tightening pressure against the second tubular member 2, that is, a complete shrink fit has appeared. Therefore, the interface between the metal fittings 2 and 3 and the insulator 5 exists under a strong compressive force, so there are almost no voids and a high degree of air (water) tightness is maintained at room temperature. It is something.

By the way, when the operating temperature rises to 300℃, the second
The tubular member 2, the insulator 5, and the outer fitting 3 expand according to their respective coefficients of thermal expansion, but in this case, the inner and outer diameters of the outer fitting 3 become maximum, and then the inner and outer diameters of the glass and mica plastic bodies become larger. The outer diameter of the second tubular member settles to a minimum state. That is, the tightening pressure disappears from the outer periphery, and a gap is created at the interface. Therefore, the air (water) density is extremely reduced. As mentioned above, it is an inevitable problem that the air (water) tightness of conventional insulated pipe joints deteriorates as the operating temperature increases.

The present invention has been made in view of these points, and it is an object of the present invention to provide an insulated pipe joint that can be used at high temperatures and whose air (water) tightness does not deteriorate even under repeated temperature rises and falls.

This invention will be explained below with reference to the drawings. First, in order to facilitate understanding, the manufacturing method will first be explained with reference to FIG. Figure 3A shows the state immediately before pressure forming during manufacturing of the insulated pipe joint according to the first invention;
Figure B is a sectional view showing the state after completion of pressure molding in the first invention. In the figure, reference numeral 1 denotes a cylindrical first tubular member, which has a ring-shaped flange 1-3 on the outer periphery extending from the tip of one end, and a ring-shaped support similar to the flange 1-3 on the inner periphery. It has tables 1-4. Reference numeral 2 denotes a second tubular member coaxially spaced apart from the first tubular member 1, which has the same inner and outer diameter dimensions as the first tubular member 1, and has a second tubular member on the outer circumferential surface of the distal end on one end side. It has a collar part 2-3 having the same shape as the first tubular member 1, and a cylindrical auxiliary wall 2-4 whose outer periphery fits into the inner periphery of the first tubular member 1 is connected to the same tip part. There is. Reference numeral 3 denotes an outer peripheral metal fitting, which has a cylindrical shape with an inner diameter larger than the outer diameter of the flanges 1-3 and 2-3, and has threaded grooves 3-3 on the inner periphery of both ends.
1. Reference numeral 6 denotes a fixing metal fitting, which has the same external dimensions as the outer peripheral metal fitting 3 and has a screw groove 6 at one end that screws into the screw groove 3-1.
-1. Reference numerals 7a and 7b denote inner peripheral fittings, the inner diameter of which is larger than the outer diameter of the first and second tubular members 1 and 2, the outer periphery of which fits into the inner periphery of the outer peripheral fitting 3, and has a horizontally divided two-part structure. There is. In order to be able to freely expand and contract in response to temperature changes, the upper end of the inner circumferential fitting 7b located on the lower side is connected to the outer circumferential fitting 3.
It is joined by welding or the like to the inner peripheral surface of the joint part 7-1. The upper inner circumferential metal fitting 7a is placed on the lower inner circumferential metal fitting 7b.

Next, the metal materials used for the tubular members and fittings are metals that maintain mechanical strength that can withstand pressure at heating temperatures of about 600 to 650°C, and their coefficient of thermal expansion is an important selection criterion. The relationship will be explained below. The first and second tubular members 1 and 2 are made of the same material, and the outer metal fitting 3 is made of a material with an equal or smaller thermal expansion coefficient, and the inner metal fittings 7a and 7b are made of a material with a larger thermal expansion coefficient. For the fixing metal fitting 6, a material having an equal or larger coefficient of thermal expansion is used. Generally, steel is used for the first and second tubular members 1 and 2.
Stainless steel is used as a material with a larger coefficient of thermal expansion than steel, and titanium is used as a material with a smaller coefficient of thermal expansion. It goes without saying that these materials and configurations are just different if the materials of the first and second tubular members 1 and 2 are different, and the materials of the other metal fittings are also different.

Therefore, the first and second tubular members 1 and 2 will be described below.
An explanation will be given of a case in which a steel pipe is used, the outer circumferential fitting 3 is made of titanium, the inner circumferential fitting 4 is made of stainless steel, and the fixing fitting 6 is made of steel. The molding is carried out using the frame 8 shown in FIG.
Wall part 9, support metal 10, auxiliary wall part 11 of each divided structure
A mold consisting of five parts: and a pressurizing metal 12 is used. The raw material is a mixed powder of vitreous powder and mica powder, which is moistened by adding water to it, and then cold-pressed into a shape that can be inserted into the space between the wall portion 9 and the second tubular member using another mold (not shown). A preformed body 13 is prepared by molding under pressure and drying to remove moisture.

As for the metal fittings, the inner circumferential fitting 7b is joined to the outer circumferential fitting 3, the inner circumferential fitting 7a is placed, and the inner circumferential fitting 7a, 7b is connected to the inner circumferential fitting 7b.
After arranging the flanges 1-3, 2-3 of the first and second tubular members 1, 2 at both ends, the fixing metal fitting 6 is screwed onto the outer peripheral metal fitting 3 to assemble. At this time, a space 4-2 is formed between the outer circumferential surfaces of the first and second tubular members 1 and 2 and the inner surface of the fixture 6, and the flange 2-3
There is a space 4-3 between the side surface of the fixture 6 and the side surface of the fixture 6.
A space 4-4 is formed between the outer surface of the flange 2-3 and the inner surface of the outer metal fitting 3, and the flange 2-
There is a space 4- between the side surface of 3 and the end surface of the inner peripheral fitting
5 is configured, and a space 4-6 is configured between the outer circumferential surfaces on the end sides of the first and second tubular members 1 and 2 and the inner circumferential surface on the end side of the inner peripheral fitting 7. .

The molding process consists of a mold middle frame 8, a wall part 9, and a support metal 1.
0 as shown in Fig. 3A, and auxiliary wall part 11
The pressurizing metal 12 is not assembled, but the metal fittings are assembled as described above, and the raw materials are heated to a predetermined temperature in the state of the preformed body 13. First, the assembled metal fittings are placed: the fixing metal fitting 6 is placed on the support metal 10, and the first tubular member 1 is placed on a bottom plate (not shown). The space-time sections 4-2 to 4-6 are arranged to maintain predetermined intervals. Next, the auxiliary wall portion 11 is placed on the fixture 6, and finally the preform 13 is placed on the auxiliary wall portion 11. The state at this time is shown in Figure 3A. Next, the pressurizing metal 12 is placed on the preform 13, and the preform 13 is pressurized by the pressure molding machine, and the space 4-
Press fit into 2-4-8. At this time, a portion remains on the auxiliary wall portion 11 and constitutes the insulator 5. The state at this time is shown in FIG.

After cooling to a temperature below the glass transition temperature while maintaining pressure, the molded product is taken out. The molded product is shown in Figure 2A. This is then mechanically pressurized and the second
Finish the product as shown in Figure B.

Note that at this time, the first and second tubular members 1,
2 and the inner peripheral fittings 7a and 7b constitute the space 4-8
The inner diameter dimension of the insulator 5 disposed in the first and second
If the diameter is equal to the inner diameter of the tubular members 1 and 2, it is effective in terms of ease of machining and low flow resistance of the through hole when using an insulated pipe joint.

The insulating pipe joint of the present invention maintains a high degree of air (water) tightness even when the operating conditions rise to a temperature of 300° C. and even when the temperature is repeatedly raised and lowered. below,
The reason for this will be explained. First, in order to obtain an insulated pipe joint that maintains air (water) tightness at 300°C, use materials with a transposition temperature of 350°C or higher for the insulator glass and mica plastic raw material. This is an important basic condition. Now, at room temperature, the product is placed in the space 4-6 formed by the outer circumferential surfaces of the first and second tubular members 1 and 2 and the inner circumferential surfaces on the end sides of the inner circumferential fittings 7a and 7b located on the outside thereof. The existing insulator 5 is an inner peripheral metal fitting 7 made of stainless steel located on the outside.
Since the thermal expansion coefficients of a and 7b are large, they are subjected to a strong clamping force, and strong clamping forces are also applied to the first and second tubular members 1 and 2, so that the insulator 5 There is no room for voids to form on either side, and this part maintains a high degree of air (water) tightness. Next, when the temperature of the insulated pipe joint increases, the inner fittings 7a and 7b, which have a large coefficient of thermal expansion, expand more than other parts in both the circumferential direction and the axial direction. The tightening pressure between the inner circumferential surfaces of the inner circumferential fittings 7a and 7b and between the first and second tubular members 1 and 2 is reduced, and the air (water) tightness is reduced. on the other hand,
Flange portions 1-3, 2 of first and second tubular members 1, 2
The insulator 5 existing in the space 4-5 formed by the side surface of the inner circumferential fittings 7a and 7b and the end surfaces of the inner circumferential fittings 7a and 7b is subjected to compressive force due to the axial expansion of the inner circumferential fittings 7a and 7b. Flange 1 in contact with this insulator 5
-3 and 2-3 will also receive compressive force through the insulator 5. By the way, the side surfaces of the flanges 1-3, 2-3 that have received this compressive force form a space 4-- which is formed by the side surfaces of the flanges 1-3, 2-3 and the side surfaces of the fixing metal fitting 6.
The outer peripheral fitting 3 is made of a titanium material with a small coefficient of thermal expansion, and the fixing fitting 6 is attached to the screw groove 3-1 at the end thereof.
Fix the fixing bracket 6 by screwing together the screw grooves 6-1,
The spacing is maintained, and the spacing increases little even when the temperature increases. For this reason, the space portion 4-5,
The insulator 5 present in 4-3 is the inner peripheral fittings 7a and 7b.
The compressive force received by the expansion becomes tightening pressure, and the insulator 5 is strongly tightened, so there is no room for any voids to remain on both sides, creating a highly air (water) tight property in this area. I come to do it.
As mentioned above, in the case of this insulated pipe joint, when the temperature rises, the space 4 filled with glass or mica plastic material becomes the part that maintains air (water) tightness at low temperatures.
In addition to ``-6'', there are spaces 4-5 and 4-3 filled with glass and mica plastic bodies, which are mechanical parts that improve air (water) tightness as the temperature rises, so they are different from conventional products. Unlike other materials, it maintains a high degree of air (water) tightness even at high temperatures. Conversely, when the temperature decreases, the air (water) tightness of the spaces 4-5 and 4-3 decreases, but the properties of the space 4-6 improve, so even if the temperature repeats the rise and fall. Air (water) tightness properties do not deteriorate.

Although the first invention has been described above, in which insulators are provided on the outer peripheries of the first and second tubular members 1 and 2, the second invention is based on the second tubular member 2 as shown in FIG. Insulators are placed only on the outer periphery of the The second invention shown in FIG. 4 will be described below. Figure 4 A shows the state of the molded product.
Figure B is a vertical sectional view showing the structure of a machined product. The first tubular member 1 is of the same size and made of the same material as shown in FIG. 2, and has an integral structure connected to the outer peripheral fitting 3 via the shoulder 1-1, and the material is the same as that shown in FIG. It is made of the same material. In this case, the fixing fitting 6 is made of stainless steel having a large coefficient of thermal expansion, and is screwed into the threaded groove 3-1 of the outer circumferential fitting 3. Note that both are air (water) tightly joined by a joint portion 6-2. The inner circumferential metal fitting 7 is made of the same material as shown in FIG.
It is inserted onto the shoulder portion 1-1 inside the outer circumferential fitting 3 and fixed to the inner circumferential surface of the outer circumferential fitting 3. Molding is carried out according to the method shown in FIG. In the case of this structural product, the air (water) tightness at room temperature is determined by the space 4-2 formed between the outer circumferential surface of the second tubular member 2 and the inner surface of the fixing fitting 6 and the second tubular member 2. It is secured by a space 4-6 formed between the outer circumferential surface on one end side of the inner circumferential fitting 7 and the inner circumferential surface on the end side of the inner circumferential fitting 7. In the case of this structural product, since stainless steel material with a large coefficient of thermal expansion is used for the fixing fitting 6, the space 4-2 also exhibits a useful effect in maintaining air (water) tightness. As the temperature rises, the air (water) tightness of the spaces 4-2 and 4-6 decreases, as in the case explained with reference to FIG.
The air (water) tightness of the space portion 4-5 formed between the end face of the substrate increases and the air (water) tightness is maintained in a wide temperature range. The fixing fitting 6 and the outer circumferential fitting 3 are air (water) tightly joined by the joint portion 6-2 in the space formed between the outer surface of the collar portion 2-3 and the inner circumferential surface of the outer circumferential fitting 3. 4-4, the outer periphery and bottom surface of the inner metal fitting 7, and the first and second
The purpose is to prevent leakage through the interface between the shoulder portion 1-1 and the insulator of the space 4-8 formed between the tubular members 1 and 2 and the inner peripheral surface of the inner peripheral fitting 7. Furthermore, by using a material with a large coefficient of thermal expansion for the fixing fitting 6 as in this embodiment, the reliability of the air (water) tightness at room temperature is further improved.

As explained above, this invention has a first tubular member made of metal and a ring-shaped flange on the outer periphery of one end, which has the same inner and outer diameter dimensions as the first tubular member and has a coefficient of thermal expansion. a second tubular member having an equivalent coefficient of thermal expansion, and an outer periphery having a coefficient of thermal expansion equal to or smaller than that of the tubular member, located outside the first and second tubular members and outside the flange. Arrange the metal fittings, and fix the inner peripheral metal fitting with a coefficient of thermal expansion larger than the tubular member so that one end is located near the flange to the inner peripheral surface of the outer peripheral metal fitting. A fixing fitting having a ratio equal to or larger than that of the tubular member is fixed, and a space formed between the first and second tubular members and the inner circumferential fitting, the outer periphery of the first and second tubular members, the fixing fitting, and the inner circumference. An insulating material such as glass or mica plastic is filled and arranged in the space formed by the inner surface of the outer peripheral fitting with the metal fitting, and by utilizing the difference in thermal expansion coefficient between the tubular member and the inner peripheral fitting, The space formed between the outer circumferential surface on the one end side of the second tubular member and the inner circumferential surface on the end side of the inner circumferential metal fitting, in which the glass and mica plastic bodies are arranged, is air (water-tight) sealed at room temperature. A space that is formed between the side surface of the flange portion and the side surface of the fixing metal fitting and in which the glass mica plastic body is disposed, and a space portion that is formed between the side surface of the flange portion and the end surface of the inner circumferential metal fitting. In addition, each space in which the glass mica molded body is arranged is made to maintain air (water) tightness at high temperatures, so even when the temperature repeatedly rises and falls, the air (water) tightness is maintained. This has the effect of providing an insulated pipe joint that maintains a high degree of air (water) tightness at all times without any decrease in water resistance.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the structure of a conventional insulated pipe joint, Fig. 2 is a longitudinal sectional view showing the structure of the insulated pipe joint according to the first invention, and Fig. 2A shows the form after completion of molding. , Figure 2B is a sectional view showing the structure of the product, and Figure 3 is a cross-sectional view showing the structure of the product.
The figures are longitudinal cross-sectional views showing the manufacturing method of the insulated pipe joint according to the first invention shown in Fig. 2. Fig. 3A shows the state immediately before pressure forming, and Fig. 3B shows the state after pressure forming is completed. Fig. 4 is a longitudinal cross-sectional view showing the configuration of an embodiment of the insulated pipe joint according to the second invention, Fig. 4 A shows the form after completion of molding, and Fig. 4 B shows the structure of the product. It is a diagram. In the figure, 1 is the first tubular member, 1-3 is the collar, 1-4 is the support base, 2 is the second tubular member, 2-
3 is the flange, 2-4 is the auxiliary wall, 3 is the outer peripheral fitting, 3-
1 is a screw part, 4, 4-1 to 4-7 are space parts, 5 is an insulation part, 6 is a fixing metal fitting, 6-1 is a screw part, 6-2
7, 7a, 7b are inner metal fittings, 7-1 is a joint, 8 is a frame, 9 is a wall, 10 is a support metal, 11
1 is an auxiliary wall portion, 12 is a pressurizing metal, and 13 is a preformed body. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. An insulating tube consisting of first and second tubular members, an outer circumferential fitting, an inner circumferential fitting, a fixing fitting, and an insulator, which satisfy each of the following conditions (a) to (f). Fittings. (a) A first tubular member made of metal and having a ring-shaped flange on the outer periphery at a constant distance from the end surface. (b) A metal having the same thermal conductivity as the first tubular member is used, the inner and outer diameters are the same as the first tubular member, and a ring-shaped flange is formed on the outer periphery at a constant distance from the end surface. a second tubular member which is arranged coaxially with the first tubular member so that the collar portions thereof face each other; (c) The inner diameter is larger than the outer dimensions of the first and second tubular members, has a spiral groove on the inner peripheral surface of both ends, and has a coefficient of thermal expansion equal to or smaller than the first and second tubular members. A cylindrical outer peripheral metal fitting arranged on the outside of the first and second tubular members. (d) The inner diameter dimension is larger than the outer diameter dimension of the first and second tubular members, the outer diameter dimension has a dimension that fits into the inner diameter of the outer circumferential fitting, and both ends are attached to the inner circumferential surface of the outer circumferential fitting. are fixed so as to be located near the collars of the first and second tubular members, respectively;
A cylindrical inner metal fitting having a larger coefficient of thermal expansion than the first and second tubular members. (e) The inner diameter is larger than the outer diameter of the first and second tubular members, the outer periphery is screwed into the thread grooves at both ends of the outer circumferential fitting, and is fixed to the outer circumferential fitting, and the coefficient of thermal expansion is the first and second tubular members. A plurality of cylindrical fixing fittings that are equal to or larger than the tubular member No. 2. (f) A space formed between the outer peripheral surfaces of the first and second tubular members and the inner surface of the fixing fitting, and between the side surfaces of the collars of the first and second tubular members and the side surfaces of the fixing fitting. a space formed between the outer surface of the collar and the inner surface of the outer fitting; a space formed between the side of the collar and the side of the inner fitting; A space formed between the outer circumferential surfaces of the ends of the first and second tubular members and the inner circumferential surfaces of the ends of the inner fitting, and between the first and second tubular members and the inner circumferential surface of the inner fitting. An insulating material that is a glass or mica plastic body, which is made of a vitreous powder and a mica powder, and which is continuously filled into each of the spaces formed by the above. 2. An insulated pipe joint consisting of first and second tubular members, an outer circumferential fitting, an inner circumferential fitting, a fixing fitting, and an insulator, which satisfy each of the following conditions (a) to (f). (a) A first tubular member made of metal and having a shoulder around its cylindrical end. (b) It is formed using a metal having the same thermal conductivity as the first tubular member, has the same inner and outer diameter dimensions as the first tubular member, and has a ring-shaped flange on the outer periphery at a constant distance from the end surface. a second tubular member which is arranged coaxially with the first tubular member such that the shoulder of the first tubular member and the collar face each other; (c) The inner diameter is larger than the outer dimensions of the first and second tubular members, has a spiral groove on the inner peripheral surface of one end, and has a coefficient of thermal expansion equal to or smaller than the first and second tubular members, A cylindrical outer peripheral fitting having an end without a threaded groove connected to a shoulder of the first tubular member and disposed outside the second tubular member while being integrated with the first tubular member. (d) The inner diameter is larger than the outer diameter of the first and second tubular members, the outer diameter has a dimension that fits into the inner diameter of the outer peripheral fitting, and is inserted onto the shoulder of the first tubular member. a cylinder having a coefficient of thermal expansion larger than that of the first and second tubular members; shaped inner metal fittings. (e) The inner diameter is larger than the outer diameter of the first and second tubular members, the outer periphery is screwed into the threaded groove at one end of the outer circumferential fitting, and the coefficient of thermal expansion is the first.
and a cylindrical fixture that is equal to or larger than the second tubular member. (F) A space formed between the outer circumferential surface of the second tubular member and the inner surface of the fixing fitting, and a space formed between the side surface of the collar of the second tubular member and the side surface of the fixing fitting. , a space formed between the outer surface of the flange and the inner periphery of the outer fitting, a space formed between the side surface of the flange and the side of the inner periphery, and the second tubular member. A space formed between the outer circumferential surface of the end and the inner circumferential surface of the end of the inner fitting, and the side surface of the shoulder of the first tubular member, the end surface of the second tubular member, and the inner circumferential surface of the inner fitting. An insulating material that is a glass or mica plastic body made of a glassy powder and a mica powder, which are continuously filled into each of the spaces formed by the insulating material.