JPH0253672B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an insulating connection device for piping, in particular a new and advantageous device for connecting and securing adjacent ends of metal tubes carrying pressurized or hot fluids. An insulating connection device for piping that electrically insulates the ends and prevents current from flowing from one side of the metal pipe to the other, allows for easy connection turning, and maintains a high degree of airtightness including the connection part. It is related to.

[Conventional technology]

Metal pipe connection devices are widely used for gas, water, oil, etc. distribution pipes installed above or underground, as well as for well pipes that blow oil, hot water, etc. from deep underground. Recently, external power supply systems have come into widespread use to prevent corrosion of metal pipes. In this case, a DC voltage is applied to the metal tube, and since this applied voltage varies depending on the surrounding environmental conditions, in order to appropriately realize this condition, and to prevent accidents due to leakage of current to the outside, , the demand for insulated connection devices with electrical insulation properties has increased rapidly.

The main characteristics required of this insulated connection device are as follows.

First, under the temperature range of room temperature to 250 to 300 degrees Celsius, or under conditions of repeated temperature rises and falls,
In addition to maintaining the necessary electrical insulation properties, it also has high thermal and mechanical impact strength, as well as a high degree of airtightness.In terms of mechanical strength, especially when used for well pipes, long metal In addition to general characteristics such as maintaining sufficient tensile strength to withstand this suspension, and having long-term reliability without aging, there are also practical issues. There is an urgent need for a connection process with metal pipes that does not require special equipment and can be easily performed. For example, in the case of steel pipes for oil wells, American Petroleum Institute Standards (hereinafter referred to as API)
The dimensions of pipe bodies, connecting devices, connection screws, etc. are standardized by the ``Standards.'' Therefore, it is ideal for insulated connecting devices to comply with the specifications for metal connecting devices.

In the case of this type of insulated connection device, the basic structure is a structure in which an insulator is interposed between two pipe bodies. In this case, it is the insulator that has the greatest control over the characteristics.

This insulator will be explained below. When an organic material is used as an insulator, there are problems with temperature, and there is a fatal defect in deterioration of airtightness and electrical properties due to aging of the material itself, making it practically unusable. Next, if vitreous material is used, cracks may occur due to sudden changes in temperature, or mechanical impact strength may be low. As in the case of , it has a fatal defect of low thermal and mechanical impact strength, which also makes it unusable in reality. The glass that has the best overall characteristics as described above is selected below.
There is an insulator made of mica plastic.

Glass/mica plastics are made from a mixed powder of glass powder and mica powder.This raw powder is heated to a temperature where the glass softens and flows under pressure, and then pressure molded in the heated state. It is an insulator obtained by

As mentioned above, the structure of the insulation connection device is based on API, which is widely used not only in the petroleum-related sector but also in various fields.
Since it is ideal to comply with standard connecting devices, before explaining the above-mentioned insulating connecting devices using glass/mica plastic bodies as insulators, we will first explain the connecting devices and the method of connecting with pipe bodies according to API standards. This will be explained using Figure 2. In the figure, 1 is a connecting device, 2a is an upper tube, 2b is a lower tube, and 3 is a connecting screw.
However, the female screw 3 is attached to the outer periphery of the ends of the tubes 2a and 2b.
A male screw 3 is screwed into the housing.

When making a connection, first grasp and hold the lower tube body 2b, rotate and screw the connecting device 1 onto it, and then tighten it to maintain airtightness. Next, the connecting device 1 is grasped and held, and the upper tube body 2a is rotated and screwed onto it, and then tightened to maintain airtightness to complete the connection.

The present inventor previously proposed a conventional insulating connection device that uses the above-mentioned glass-mica plastic body as an insulator and has the same shape and dimensions as the API standard connection device.

Here, its structure will be explained with reference to FIG. Third
Figure a is a plan view, and Figure 3b is a longitudinal sectional view. In the figure, 4 is a first tubular member, and its tube body 4a
An inner circumferential tube 4b, which is a thin-walled portion, is integrally provided at the tip of the inner circumferential tube 4b, and an inner circumferential tube 4b is provided on the outer circumferential surface of the tip end of the inner circumferential tube 4b.
A male screw 4c having a root diameter larger than the outer diameter of b is threaded. 5 is a second tubular member, and its tube body 5a
An outer circumferential tube 5b, which is a thin-walled portion, is integrally provided at the tip of the outer circumferential tube 5b.
A female screw 5c, which has a root diameter smaller than the inner diameter of b and is screwed into the male screw 4c of the first tubular member 4, is screwed therein. The male screw 4c of the first tubular member 4 is screwed into the female screw 5c of the second tubular member 5, and the screws 4c, 5c
A gap 6a is formed between the inner circumferential tube 4 of the first tubular member 4.
A gap 6b is formed between the distal end surface 4d of the main body 5a of the first tubular member 4 and the distal end surface 5d of the main body 5a of the second tubular member 5, and the distal end surface 4e of the main body 4a of the first tubular member 4 is
There is a gap 6c between the thin wall portion 5b and the tip surface 5e.
However, the screws 4c, 5c and the outer and inner tubes 5b, 4b
Gaps 6d and 6e are provided between them, respectively, and all the gaps 6a to 6e are filled with an insulator 7 made of a glass-mica plastic body.

Reference numeral 16 denotes a through hole provided at a position close to the outer peripheral surface between the upper end surface of the main body 4a and the main body tip surface 4e of the first tubular member 4, and in FIG.
6 is provided. This number can be increased or decreased as needed. The insulator 7 filling the gaps 6a to 6e is filled through the through hole 16.

Main bodies 4a, 5a of first and second tubular members 4, 5
Connecting screws 3a and 3b are screwed on the inner circumferential surface of the tube, and the screws of the upper and lower tubes 2a and 2b are screwed into these to connect the tubes 2a and 2b. .

This insulating connection device is manufactured by molding the insulating connection device base and then machining it into the insulating connection device shown in FIG.

Next, an example of the method for forming the insulating connection device base is shown in the fourth section.
This will be explained using figures. Figures 4a and 4b show the state immediately before pressure forming and after completion of pressure forming, respectively. As for the tubular member to be used first, as the second tubular member 5, one whose main body 5a has an inner diameter smaller than that of the product is used. As the first tubular member 4, the inner diameter of the main body 4a and the inner circumferential tube 4b is smaller than the product, and is equal to the inner diameter of the main body 5a of the second tubular member 5, and the main body 4
An auxiliary wall f having an inner diameter equal to that of the main body 4a and an outer diameter smaller than that of the main body 4a is provided on the upper end surface of a, and an auxiliary wall f having an inner diameter equal to that of the tube body 4a and an outer diameter smaller than that of the tube main body 4a is provided on the tip surface 4d of the thin wall portion 4b. Smaller support 4
g, which has one or more through holes 16 penetrating from the upper end surface to the distal end surface 4e near the outer circumferential surface of the tube body 4a, and the male screw 4c of the first tubular member 4 is connected to the second Female screw 5c of tubular member 5
The supporting part 4g is placed on the tube body 5a, and a gap 6a is formed between the opposing surfaces of both the tubular members 4 and 5.
~6d is assembled and used.

Moreover, as a mold, the wall part 9 of the divided structure whose height is equal to the height of the auxiliary wall 4f, the frame 10, and the fitting between the inner peripheral surface of the wall part 9 and the outer peripheral surface of the auxiliary wall 4f. A pressurizing metal 12 consisting of three parts is used. As a raw material for the insulator 7, glass powder and mica powder are mixed and water is added to make it wet.
A cylindrical preform 14 that can be inserted into the space constituted by the wall portion 9 and the auxiliary wall 4f is prepared in advance using another mold (not shown), and this is dried and used.

When performing molding, the pressurizing mold 12 is not assembled, but the wall 9 and frame 10 of the molding mold are assembled, and the first and second tubular members 4 and 5 are assembled. , and are heated together with the preform 14 to a predetermined temperature. Regarding this heating temperature, there are strength restrictions related to the metal material used for the mold, and the upper limit is 400 to 450°C. For tubular parts, 500 to 600℃ for steel, stainless steel, etc.
Next, the preform 14 is heated to 650 to 800°C, although this varies depending on the softening temperature characteristics of the glass used.

When heating is completed, the assembled tubular members 4 and 5 are first inserted into the wall 9, and then the preform 14 is inserted into the wall 9.
is inserted into the space formed by the wall 9 on the main body 4 of the first tubular member 4 and the auxiliary wall 4f, and finally the pressurizing metal 12 is placed on the preform 14. This situation is shown in Figure 4a.

Next, the preform 14 is pressurized via the press metal 12 by a pressure molding machine. Pressurized preform 1
4 flows in the through hole 16 and the first tubular member 4
and the second tubular member 5 constitute voids 6a to 6d.
At this point, all the voids 6a to 6d are filled to form the insulator 7, and the base 15 for the insulated connection device is molded. The state at this time is shown in FIG. 4b. When the above-mentioned pressure molding process is completed, the molded product is cooled to a predetermined temperature, the molding die is disassembled, the molded insulating connection device base 15 is taken out, and the molded insulating connection device base 15 is machined.
Manufacture of the insulated connection device shown in the figure is completed.

In the conventional insulating connection device having the above structure, the connection screws 3a, 3b are screwed into the main bodies 4a, 5a of the first and second tubular members 4, 5, and the main bodies 4a,
5a is a thick-walled product with the same shape as the metal connecting device, is located in a part unrelated to the insulating component, and has the same shape and dimensions, so no special equipment is required in the connection process with the pipe body. Not only is it extremely easy to use, but other general characteristics include, for example, when a tension is applied, the insulator 7 interposed in the gap 6a formed by the screws 4c and 5c absorbs this as compression under a sealed state. Therefore, its strength is extremely high, and it also completely maintains the necessary electrical insulation properties, thermal and mechanical impact strength properties.

[Problem that the invention seeks to solve]

However, in this conventional insulated connection device, the airtightness property at room temperature at the first interface 17 between the first tubular member 4 and the insulator 7 is as follows.
Second interface 1 between second tubular member 5 and insulator 7
There is an unavoidable fatal flaw that the characteristics are inferior to those of 8.

The reason for the above defect will be explained below.

The direct cause is the difference in thermal expansion coefficient (in this case, thermal contraction coefficient, hereinafter referred to as thermal expansion coefficient) of the first tubular member 4, second tubular member 5, and insulator 7. It is in. Incidentally, the coefficient of thermal expansion of steel materials widely used for tubular members from room temperature to 600°C is 11 to 14 x 10 ^-6 /°C, and that of stainless steel is 15 to 18 x 10 ^-6 /°C. The thermal expansion coefficient of the glass-mica plastic body constituting the insulator 7 bends near the transition temperature of the raw material glass,
It has a value of 8 to 10 x 10 ^-6 /°C in the range from room temperature to the transposition temperature, and 15 to 20 x 10 ^-6 /°C above the transposition temperature. The thermal expansion coefficient of the glass/mica plastic body is largely controlled by the thermal expansion coefficient of the raw material glass, and by changing the raw material glass, it can be varied from 7 to 12× in the range of room temperature to transition temperature.
Although it is possible to obtain a temperature of 10 ^-6 /℃, the above 8 to 10
A temperature of about 10 ^-6 /℃ is used.

In the step of forming the insulating connection device base, both tubular members 4 and 5 are heated to 500 to 600°C, and the preform 14 is heated to 650 to 800°C, as described above, and the insulator 7 is formed under these temperature conditions. However, when the temperature of the insulator 7 is higher than the transition temperature of the raw glass, it is in a state where it can flow, so the insulator 7 adapts to the deformation due to thermal contraction of each tubular member 4, 5, and the first boundary Although no voids are generated between the surface 17 and the second boundary surface 18, when the temperature of the insulator 7 reaches a temperature below the dislocation temperature, the insulator 7 behaves like a solid, so its appearance changes significantly.

That is, the second boundary surface 18 which is the outer peripheral surface of the insulator 7
In this case, the insulator 7 is tightened with a large force due to the thermal contraction of the second tubular member 5 having a large coefficient of thermal expansion on the outer circumferential side, and a shrink fit appears, so that its airtightness is extremely high. On the other hand, at the first boundary surface 17, which is the inner peripheral surface of the insulator 7, a void is generated due to thermal contraction of the first tubular member 4, which is located on the inner peripheral side and has a large coefficient of thermal expansion. Boundary surface 18
Therefore, it is not possible to obtain a high degree of airtightness.

The inventor of the present invention has improved the fatal defect of the conventional insulating connection device, that is, the airtightness of the first interface 17 between the first tubular member 4 and the insulator 7 at room temperature, and The second part of the member 5 and the insulator 7
It was possible to obtain something equivalent to that of boundary surface 18, and after repeated numerous experiments, we succeeded in achieving that objective.

That is, an object of the present invention is to provide an insulating connection device for piping that can guarantee airtightness at room temperature.

[Means for Solving the Problems] The present invention provides the above-mentioned insulating connection device for piping, in which an annular groove is formed in the distal end surface of at least one of the tube body and the thin-walled portion of the first tubular member, and an annular groove is formed therein. It is designed to be filled with things.

[Effect]

In this invention, an annular groove is formed in the tube body or the tip end surface of the thin-walled portion of the first tubular member, and the annular groove is filled with an insulator, so that the outer circumferential wall of the annular groove shrinks due to heat at room temperature. However, a large tightening force acts between the first tubular member and the insulator filled in the annular groove, thereby ensuring airtightness between the first tubular member and the insulator.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an insulating connection device for piping according to an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 3 indicate the same parts as in the same figure, and in this device, the second tubular member 5 has the same structure as the conventional one, but the first tubular member 4 has the same structure as the tip of the main body 4a. It has a structure in which an annular groove 19 is provided on the surface 4e and an annular groove 20 is provided on the distal end surface 4d of the inner circumferential tube 4b. ~6d is filled with the insulator 7.

Next, the effects will be explained.

When manufacturing this device, the first and second tubular members 4 and 5 that can form the above-mentioned structure are used, and the insulating connection device base 15 is molded in the same manner as a conventional molding method, and then machined. Finish the product by

In this insulated connection device, at room temperature, the airtightness on the first interface 17 side between the first tubular member 4 and the insulator 7 is the same as that on the second interface 18, and the Defects in the connecting device have been completely eliminated.

That is, to explain the details in detail, first, the second boundary surface 18 between the outer circumferential surface of the insulator 7 and the inner circumferential surface of the second tubular member 5 is the same as that of the conventional product, so its airtightness is completely maintained. is secured. On the other hand, the first interface 17 between the inner circumferential surface of the insulator 7 and the outer circumferential surface of the first tubular member 4 does not maintain airtightness as in the conventional product; An insulator 7 is continuously filled in the annular grooves 19 and 20, and this insulator 7 (thermal expansion coefficient 8
~10×10 ^-6 /°C) is the outer peripheral wall 4h of the annular grooves 19, 20 of the first tubular member 4, which has a large coefficient of thermal expansion of 11 to 14×10 ^-6 /°C, located on the outer peripheral side. Due to the contraction of 4i, the outer boundary surfaces 21 and 22 are tightened with a large force, and the same shrink-fitting phenomenon occurs as with the second boundary surface 18, ensuring the same airtightness as in the case of the second boundary surface 18. be done. This boundary surface 21,
Since 22 forms a continuous surface with the first boundary surface 17, the airtightness between the first tubular member 4 and the insulator 7 is ensured.

In the apparatus of this embodiment as described above, an annular groove is provided in the first tubular member and a part of the insulating material is filled in the annular groove, so that the airtightness between the first tubular member and the insulating material is maintained. As a result, the airtightness of the device at room temperature can be completely ensured, and the defects of conventional products can be completely eliminated.

In addition, the manufacturing method of this device itself is not much different from that of conventional products, and the annular groove is relatively small, so this has almost no effect on the mechanical strength of the device, and the above-mentioned airtightness property can be maintained. Considering its effectiveness, its practical value is extremely large.

In the above embodiment, the annular groove is formed on both the end surfaces of the main body and the inner tube of the first tubular member, but the annular groove may be formed only on one of the end surfaces.

〔Effect of the invention〕

As described above, according to the insulating connection device for piping according to the present invention, an annular groove is formed in the tube body or the tip end surface of the thin-walled portion of the first tubular member, and the annular groove is filled with an insulator. At room temperature, the outer circumferential wall of the annular groove heat-shrinks, and a large clamping force acts between the annular groove and the insulating material, which causes the gap between the first tubular member and the insulating material to decrease. This has the effect of ensuring airtightness.

[Brief explanation of the drawing]

Figures 1a and b are respectively a plan view and a vertical sectional view of an insulating connection device for piping according to an embodiment of the present invention, and Figure 2 illustrates an example of a connection device according to API standards and a method of connecting it to a pipe body. Figures 3a and 3b are a plan view and a longitudinal sectional view showing the structure of a conventional insulated connection device for piping, respectively, and Figure 4 is for explaining an example of a method of forming a conventional insulated connection device base. FIG. 4a is a sectional view showing the state immediately before pressure forming, and FIG. 4b is a view showing the state after pressure forming is completed. In the figure, 2a and 2b are tube bodies, 3a and 3b are connecting screws, 4 is a first tubular member, 4a is a tube body, and 4b
4c is a male screw, 4d is a tip end surface of an inner tube, 4e is a tip surface of a tube body, 5 is a second tubular member, 5a is a tube body, and 5b is an outer tube (thin wall portion). ,
5c is a female screw, 6a to 6e are gaps, 7 is an insulator,
19 is an annular groove, and 20 is an annular groove. In addition, in the figure,
The same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A tube body and a thin-walled portion integrally provided at the tip of the tube body, the inner diameter of which is equal to the inner diameter of the tube body and the outer diameter of which is smaller than the outer diameter of the tube body, the thin-walled portion a first tubular member having a male thread formed on the outer circumferential surface of the distal end thereof, the thread having a root diameter larger than the outer diameter of the thin-walled portion; and a thin walled portion whose outer diameter is larger than the inner diameter of the tube body and whose outer diameter is equal to the outer diameter of the tube body, and a female screw having a root diameter smaller than the inner diameter of the thin walled portion is formed on the inner circumferential surface of the tip of the thin walled portion. a tubular member, the male thread of the first tubular member is threaded through the female thread of the second tubular member, a space is provided between each opposing surface of the two tubular members, and a glass is provided in the space. - An insulating connection device for piping, which is filled with an insulator made of a mica plastic body and has a tube connection screw installed on the inner circumferential surface of the tube body of the first and second tubular members, 1. An insulating connection device for piping, characterized in that an annular groove is formed in the distal end surface of at least one of the tube body and the thin-walled portion of one tubular member, and the annular groove is filled with the above-mentioned insulator.