CA1173875A - Insulating pipe joint - Google Patents
Insulating pipe jointInfo
- Publication number
- CA1173875A CA1173875A CA000390888A CA390888A CA1173875A CA 1173875 A CA1173875 A CA 1173875A CA 000390888 A CA000390888 A CA 000390888A CA 390888 A CA390888 A CA 390888A CA 1173875 A CA1173875 A CA 1173875A
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- Canada
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- cylindrical body
- body portion
- tubular member
- insulator
- pipe joint
- Prior art date
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- Earth Drilling (AREA)
- Flanged Joints, Insulating Joints, And Other Joints (AREA)
- Insulating Bodies (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An insulating pipe joint suitable for sustaining high voltages and having a high strength. The pipe joint includes a first tubular member, a second tubular member disposed within the first tubular member, and an insulator composed of a flaky powder. The first tubular member is composed of a cylindrical body portion A and a cylindrical body portion C
and one end of the cylindrical body portion A with an inside diameter larger than that of the cylindrical body portion A.
A cylindrical body portion D, which is connected integrally with the cylindrical body portion C, has an inside diameter which is larger than that of the cylindrical body portion C
and an outside diameter which is smaller than that of the cylindrical body portion C. The second tubular member includes a cylindrical body E withan inside diameter substantially equal to that of the cylindrical body portion A and an outside diameter which is smaller than the inside diameter of the cylindrical body portion C. The insulator fills the hollow space between the cylindrical body portions C and D and the cylindrical body E and surrounds the cylindrical body portion D to secure the tubular members together in a sealed arrange-ment.
An insulating pipe joint suitable for sustaining high voltages and having a high strength. The pipe joint includes a first tubular member, a second tubular member disposed within the first tubular member, and an insulator composed of a flaky powder. The first tubular member is composed of a cylindrical body portion A and a cylindrical body portion C
and one end of the cylindrical body portion A with an inside diameter larger than that of the cylindrical body portion A.
A cylindrical body portion D, which is connected integrally with the cylindrical body portion C, has an inside diameter which is larger than that of the cylindrical body portion C
and an outside diameter which is smaller than that of the cylindrical body portion C. The second tubular member includes a cylindrical body E withan inside diameter substantially equal to that of the cylindrical body portion A and an outside diameter which is smaller than the inside diameter of the cylindrical body portion C. The insulator fills the hollow space between the cylindrical body portions C and D and the cylindrical body E and surrounds the cylindrical body portion D to secure the tubular members together in a sealed arrange-ment.
Description
~173~375 INSULATING PIPE JOINT
BACKGROUND OF THE INVENTION
The present invention relates to an insulating pipe joint having an axial bore therethrough and adapted for mount-ing through the wall of a gastight metal container or between metal pipes to provide an electrically insulated connection between tne interior and exterior of the container or pipes.
Insulating pipe joints have been widely used in lines for transporting liquid nitrogen, FreonT~Ia-s a cooling medium, or the like. However, little attention has been paid to their insulation or creeping resistance because of the low voltage involved.
It is known that Canada and Venezuela have layers of oil sand in the ground at a depth of about 500 m. Serious attemp~s have recently begun to be made to extract oil from - lS such oil sand layers by burying a pair of electrodestherein and applying a voitage between the electrodesto generate Joule heat for heating the layer to lower the viscosity of oil so that the oil may be extracted. The voltage applied between the electrode is usually as high as 4,000 to 5,000 V.
Layers closerto the ground surface have a specific resistance equal to that of an oil sand laver. It is, tl~erefore, necessary to provide an ., !
..-., .. . ... .. .. . . .. . . . ; . . . . . ..... ., ....... .. . ~.. ~ --~173~75 insulating pipe joint between the steel pipe buried in the layer closer to the ground surface and the electrodes in the oil sand layer. Thus the demand for insulating pipe joints has sharply increased.
An insulating pipe joint which can be satisfactorily used for the aforesaid purpose is required to have a number of outstanding properties including those which will hereunder be mentioned specifically. It must have a high mechanical strength to hold the electrodes in a suspended position. In view of the high voltage of 4,000 to 5 000 V applied thereacross, it must have outstanding voltage withstanding characteristics including creeping insulation resistance. It must be able to maintain its outstanding mechanical and electrical properties even at a high temperature resulting from the application of voltage lS across the electrodes. It must be highly resistant to cold and heat impact. It must be highly resistant to any mechanical impact that it will be subjected to during installation as it unavoidably strikes against the wall of a hole leading to the oil sand layer. Its axialbore must have an inside diameter which is equal to those of the upper steel pipe and the electrodes to minimize the resistance to the flow of fluid therethrough. While satisfying these requirements it must be highly gastight. It must remain highly reliable for a long time without aging. It must be easy to connect to the upper and lower steel pipes and to the electrodes.
~73875 An insulating pipe joint of the type herein describedessentially is constructed o~ an insulator disposed between two conduits. The insulator has the most important bearing on the properties of the joint. It is practically impossible to use organic materials for the insulator since the properties are sharply lowered with a rise in temperature. Vitreous materials crack as a result of sudden changes in temperature and have low mechanical impact strength. Porcelain sealed with a low-melting metal has low heat and mechanical impact resistances.
In view of the various properties hereinabove mentioned, the best materail for the indulator is a molded product of glass and mica (glass bonded mica). It can be produced from mi~ed powder of a vitreous material and mica heated to a temperature at which the powder is softened and fluidized under pressure. The softened powder is molded under pressure. The most advantageous form hitherto available for an insulating pipe joint employing a molded product of glass and mica for the insulator has been proposed by the- inventors of the present invention in Japanese Patent Application No. 51151/80 as shown in Fig. 1.
It is to be noted that this Japanes,e Patent Application is not being mentioned here as prior ar~, as indeed it is not prior art to the present application, but is mentioned merely for attaining a full understanding of the present invention.
The pipe joint shown in longitudinal section in the right half (a) of Fig. 1 is composed of a first tubular member . . . , . .. .. , . . , ., . j . . , . , .. . . ., . . .. , . , ,, . . , . . ,,, . ~ ~, .. . .. ..
~ 1~73~75 1 having a cylindrical body 1-2 and an enlarged cylindrical portion 3 connected thereto by a shoulder 1-1 having an inside diameter which is larger than the outside diameter of the cylindrical body 1-2. A second tubular member 2 includes a cylindrical body 2-1 having inside and outside diameters which are equal to those of the cylindrical body 1-2 of the first tubular member 1. The first and second tubular members l and 2 are both made ofa metal capable of withstanding a temperature of about 600C, and is preferably made of iron or stainless steel. The tubular members are supported relative to each other so that they define hollow spaces 4 and 4-1 there-between. An insulator 5, which is a molded product of glass and mica, fills the hollow spaces 4 and 4-1 to secure the tubular members 1 and 2 sealingly together and to maintain electrical insulation therebetween. The free ends la and 2a of the tubular members 1 and 2, respectively, are adapted for connec-tion to adjacent walls or metal pipes by welding, threaded connection, or otherwise.
This pipe joint is very satisfactory in mechanical strength, cold and heat impact resistance, mechanical impact strength and gastightness even at a high temperature, has an even bore surface and does not present any substantial resistance to the flow of a fluid therethrough, and is reliable for use over a long period of time without undergoing any aging. It has, however, a drawbacks in its voltage withstanding character-~1~3~75 istics including creeping insulation resistance when used in asituation in whcih a high voltage is applied.
The mica powder forming a molded product of glass and mica is composed of flaky particles. The particles average diameter and thickness have a ratio of about 30 to 50 : 1. A
powder of a vitreous material is composed of non-directional fine particles. The mixed powder is heated to a temperature at which the vitreous substance is softened and becomes fluidiz-able, and then is molded under pressure. If pressure is applied to the mixed powder when in the form of a plate it hardly fluidizes. The mica flakes are arranged parallelto the plane in which pressure is applied and form what appears to be a laminate. If, on the other hand, the mold includes a hollow space into which a part of the mixed powder can flow when pressure is applied thereto, the particles which have flowed are arranged parallel to the direction of their flow, while those which have not flowed are arranged parallel to the plane in which pressure is applied.
These arrangements of particles are shown in the left half (b) of Fig. 1. The particles of the powder in the molded product of glass and mica in the hollow space 4 between the second tubular member 2 and the enlarged cylindrical portion 3 are arranged parallel to the direction of their flow, i.e., parallel to the second tubular member 2 as shown at 6-2. The particles in area 6-1 are also parallel tG the enlarged ~3~5 cylindrical portion 3. The particles in an area 6-5, which flow very little, stay parallel to the plane in which pressure has been applied, or at right ang]esto the second tubular member 2.
The particles in an area 6-6, which have been subjected to pressure after they have almost ceased to flow, stay parallel to the inner surface of the pipe joint.
The arrangement of the mica flakes in the molded product has a significant bearing on its mechanical strength.
The molded Product is about two or three times hi~her in tensile stren~th when a tensile force is applied thereto in a direction parallel to that of the arrangement of mica flakes than when a tensile force is applied in a direction perpendicular to the arrangement of the mica flakes. The product is very strong - against compressive forces applied thereto in a direction perpendicular to that of the arrangement of mica flakes but very weak against tensile forces applied thereto in that direction. Such tensile force causes separation of the product into layers if its thickness is as large as about 25 mm. If the molded product is an independetn one, the stress developed in its surface and internal portions causes interlayer separa-tion. If the product has been molded in contact with a metal as shown in the left half (b) of Fig. l, interlayer separation occurs due to the stress developed by the difference in coef-'.
1~3~375 ficients of thermal expansion between the metal and theinsulating material.
The electrical properties of the molded product are also influenced largely by the arrangement of mica flakes therein. The molded product can withstand a voltage of 15 to 20 kV/mm applied thereto in a direction perpendicular to that of the arrangement of mica flakes, but in the event a voltage is applied thereto in a direction parallel to the mica flakes, its density greatly affects its voltage withstanding characteristics.
F.ven if it has not yet undergone i-nterlayer separation, the product is very week against a voltage applied thereto in the direc*ion parallel to the mica flakes if it is on the point of inte-rlayer separation.
Referring now to the elecrical properties of the insulating pipe joint as a whole, it has very high voltage withstanding characteristics in the area 6-2 in which the mica flakes lie parallel to the second tubular member 2. Its voltage withstanding characteristics are, however, very low in ~he area 6-5 in which the mica flakes lie at right angles to the second tubular member 2 since an applied electric current has a tendency to flow among layers of the insulator to the enlarged cylindrical portion 3.
Since the arrangement of mica flakes in layers makes ` it difficult to mold a thick product as hereinbefore stated, the heights of the areas 6-5 and 6-6 are limited to a range of ~173~375 20 to 25 mm. Therefore, the creeping insulation resistance of the pi.pe joint is greatly lowered if its surface is contaminated.
As is obvious from the foregoing description, this insulating pipe joint is useless in a si~uation involving the application of a high voltage.
13~7387S
SUMMARY OF THE INVENTION
In order to obtain.a-.l insulating pipe joint which is suitable for use in a situation involving the application of high voltage, the inventors of the present invention have made a basic study on the relationship between the arrangement of mica flakes and the electrical properties of a product as hereinabove described and the method of manufacture thereof.
As a result, they have succeeded in obtaining a satisfactory product.
Specifically, the invention provides an insulating pipe joint including a first tubular member, a second tubular member disposed within the first tubular member, and an insulator composed of a flaky powder. The first tubular member includes a cylindrical body portion A, a cylindrical body portion C connected integrally with one end of the cylindrical body portion A and which has an inside diameter larger than that of the cylindrical body portion A, and a cylindrical body portion D connected integrally with the cylindrical body portion C and having an inside diameter which is larger than that of the cylindrical~body portion C and an outside diameter which is smaller than that of the cylindrical body portion C.
The second tubular member includes a cylindrical body E having an inside diameter which is substantially equal to that of the cylindrical body portion A and an outside diameter which is smaller thanthe inside diameter of the cylindrical body portion ~738~S
C. The insulator fills a hollow space between the cylindrical body portionsC and D and the cylindrical body portion E, and also surrounds the cylindrical body portion D to secure the tubular members together sealingly.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a longitudinal sectional view of an earlier insulating pipe joint, in the right half of which is shown the structure of the joint and in the left half is shown the arrange-ment of mica flakes;
Fig. 2 is a longitudinal sectional view of an insulat-ing pipe joint embodying the invention, in the right half of which is shown the product as molded and the product finished by machining and the arrangement of mica flakes in the left half; and Fig. 3 is a longitudinal sectional view illustrating a method of manufacturing the pipe joint shown in Fig. 2, in the left half of which various elements immediately prior to the applicatioh of the molding pressure are shown and the product as molded in the right half.
~173~75 DESCRIPTION OF Tl-IE PREFERRED EMBODIMENTS
In the right half (a) of Fig. 2 is shown a longitudinal section of the product as molded and in the left half (b) is shown a longitudinal sectional view of the product finished by machining, illustrating the arrangement of mica flakes therein. .
Fig. 3 is a longitudinal sectional view illustrating a method of manufacturing the insulating pipe joint of the invention.
In the left half ~a) thereof is shown the various elements immediately prior to the application of the molding pressure, while in the right half (b) is shown the product as molded. A
first tubular member 1 includes a cylindrical body portion A
and an enlarged cylindrical portion 3 jointed integrally to one end of thecylindrical body portion A. The enlarged cylindrical portion 3 defines a cylindrical body portion B (or 3-1) joined integrally to one end of the cylindrical body portion A and having an inside diameter which is larger than that of the portion A, a cylindrical body portion C (or 3:2) joined integral-ly to the cylindrical body portion B and having an inside diameter which is larger than that of the portion B, and a cylindrical body portion D (or 3-3) joined integrally to the cylindrical body portion C and having an inside diameter which is larger than that of the portion C but an outside diameter which is smaller than that of the portion C. A second tubular member 2 is composed of a cylindrical body E having inside and outside diameters which are equal to those of the cylindrical .
~173~375 body portion A of the first tubular member 1 and also including a cylindrical extension F (or 2-1) projecting from one end of the cylindrical body E andhaving an outer peripheral surface engaging the inner peripheral surface of the cylindrical body portion ~ of the first tubular member 1. The tubular membersl and 2 may be made of a metal withstanding a temperature of, for e~ample, 600C, preferably iron or stainless steel.
The molding operation employs a mold defined by a frame 7, a split wall section 8, a supporting base 9, a support-ing core 10, a pressure plate 11 and a pressing member 12. The frame 7, wall section 8, supporting base 9 and supporting core 10 are assembled as shown in the left half (a) of Fig. 3 and heated to a predetermined temperature, while the pressure plate 11 and the -pressing member 12 are heated to a predetermined temperature before they are placed in position. The tubular members 1 and 2 are also heated to a predetermined temperature, and the first tubular member 1 is placed on the supporting base 9 while the second tubular member 2 is engaged in the first tubular member 1 and placed on the supporting core 10. It is important to provide a properly sized hollow space between the tubular members 1 and 2. The size thereof is based on the clearance between the cylindrical body portion C or 3-2 of the first tubular member 1 and the cylindrical body E of the second tubular member 2, i.e., the thickness of a portion 5-2 of the insulator to be formed therebetween.
1173~375 The clearance between the cylindrical body portion B
or 3-1 of the first tubular member 1 and the cylindrical exten-sion F or 2-1 of the second tubular membel~ 2, i.e., the thickness of a portion 5-1 of the insulator to be formed therebetween, and defining a portion of the inner surface of the pipe joint is substantially equal to the thickness of insulator portion 5-2.
Curved surfaces 3-10, 3-11, 3-12 and 2-10 are provided between the cylindrical body portions A and B , the cylindrical body portions B and C, and the cylindrical body E and the cylindrical extension F to eliminate any dead points in the hollow space between the tubular members 1 and 2. It is also possible to provide flat, inclined surfaces or a combination of curved and flat, inclined surfaces, in place of the curved surfaces.
The cylindrical body portion D (or 3-3) is provided for forming an auxiliary insulator portion 5-3 and an outer peripheral insulator portion 5-4. The cylindrical body portion D has a curved surface at its upper and and is joined by curved surfaces to thè cylindrical body portion C (or 3-2). These curved surfaces may be replaced by flat, inclined surfaces.
The height of the cylindrical body portion D depends Oll the length of the area to be insulated, and may be in the range of 20 to 40 mm.
A preform 13 is prepared from a mixture of mica flakes and a vitreous powder. The mixed powder is moistened with water and formed by cold pressure molding in a separate mold ~1~7~B75 (not S]lOWTI) into a cylindrical shape which can be inserted in the hollow space between the second tubular member Z and the wall section S, followed by drying. The preform 13 is heated to a predetermined temperature and placed on the cylindrical body portion D (or 3-2). Then, the pressure plate 11 is placed on the cylindrical body E of the second tubular member
BACKGROUND OF THE INVENTION
The present invention relates to an insulating pipe joint having an axial bore therethrough and adapted for mount-ing through the wall of a gastight metal container or between metal pipes to provide an electrically insulated connection between tne interior and exterior of the container or pipes.
Insulating pipe joints have been widely used in lines for transporting liquid nitrogen, FreonT~Ia-s a cooling medium, or the like. However, little attention has been paid to their insulation or creeping resistance because of the low voltage involved.
It is known that Canada and Venezuela have layers of oil sand in the ground at a depth of about 500 m. Serious attemp~s have recently begun to be made to extract oil from - lS such oil sand layers by burying a pair of electrodestherein and applying a voitage between the electrodesto generate Joule heat for heating the layer to lower the viscosity of oil so that the oil may be extracted. The voltage applied between the electrode is usually as high as 4,000 to 5,000 V.
Layers closerto the ground surface have a specific resistance equal to that of an oil sand laver. It is, tl~erefore, necessary to provide an ., !
..-., .. . ... .. .. . . .. . . . ; . . . . . ..... ., ....... .. . ~.. ~ --~173~75 insulating pipe joint between the steel pipe buried in the layer closer to the ground surface and the electrodes in the oil sand layer. Thus the demand for insulating pipe joints has sharply increased.
An insulating pipe joint which can be satisfactorily used for the aforesaid purpose is required to have a number of outstanding properties including those which will hereunder be mentioned specifically. It must have a high mechanical strength to hold the electrodes in a suspended position. In view of the high voltage of 4,000 to 5 000 V applied thereacross, it must have outstanding voltage withstanding characteristics including creeping insulation resistance. It must be able to maintain its outstanding mechanical and electrical properties even at a high temperature resulting from the application of voltage lS across the electrodes. It must be highly resistant to cold and heat impact. It must be highly resistant to any mechanical impact that it will be subjected to during installation as it unavoidably strikes against the wall of a hole leading to the oil sand layer. Its axialbore must have an inside diameter which is equal to those of the upper steel pipe and the electrodes to minimize the resistance to the flow of fluid therethrough. While satisfying these requirements it must be highly gastight. It must remain highly reliable for a long time without aging. It must be easy to connect to the upper and lower steel pipes and to the electrodes.
~73875 An insulating pipe joint of the type herein describedessentially is constructed o~ an insulator disposed between two conduits. The insulator has the most important bearing on the properties of the joint. It is practically impossible to use organic materials for the insulator since the properties are sharply lowered with a rise in temperature. Vitreous materials crack as a result of sudden changes in temperature and have low mechanical impact strength. Porcelain sealed with a low-melting metal has low heat and mechanical impact resistances.
In view of the various properties hereinabove mentioned, the best materail for the indulator is a molded product of glass and mica (glass bonded mica). It can be produced from mi~ed powder of a vitreous material and mica heated to a temperature at which the powder is softened and fluidized under pressure. The softened powder is molded under pressure. The most advantageous form hitherto available for an insulating pipe joint employing a molded product of glass and mica for the insulator has been proposed by the- inventors of the present invention in Japanese Patent Application No. 51151/80 as shown in Fig. 1.
It is to be noted that this Japanes,e Patent Application is not being mentioned here as prior ar~, as indeed it is not prior art to the present application, but is mentioned merely for attaining a full understanding of the present invention.
The pipe joint shown in longitudinal section in the right half (a) of Fig. 1 is composed of a first tubular member . . . , . .. .. , . . , ., . j . . , . , .. . . ., . . .. , . , ,, . . , . . ,,, . ~ ~, .. . .. ..
~ 1~73~75 1 having a cylindrical body 1-2 and an enlarged cylindrical portion 3 connected thereto by a shoulder 1-1 having an inside diameter which is larger than the outside diameter of the cylindrical body 1-2. A second tubular member 2 includes a cylindrical body 2-1 having inside and outside diameters which are equal to those of the cylindrical body 1-2 of the first tubular member 1. The first and second tubular members l and 2 are both made ofa metal capable of withstanding a temperature of about 600C, and is preferably made of iron or stainless steel. The tubular members are supported relative to each other so that they define hollow spaces 4 and 4-1 there-between. An insulator 5, which is a molded product of glass and mica, fills the hollow spaces 4 and 4-1 to secure the tubular members 1 and 2 sealingly together and to maintain electrical insulation therebetween. The free ends la and 2a of the tubular members 1 and 2, respectively, are adapted for connec-tion to adjacent walls or metal pipes by welding, threaded connection, or otherwise.
This pipe joint is very satisfactory in mechanical strength, cold and heat impact resistance, mechanical impact strength and gastightness even at a high temperature, has an even bore surface and does not present any substantial resistance to the flow of a fluid therethrough, and is reliable for use over a long period of time without undergoing any aging. It has, however, a drawbacks in its voltage withstanding character-~1~3~75 istics including creeping insulation resistance when used in asituation in whcih a high voltage is applied.
The mica powder forming a molded product of glass and mica is composed of flaky particles. The particles average diameter and thickness have a ratio of about 30 to 50 : 1. A
powder of a vitreous material is composed of non-directional fine particles. The mixed powder is heated to a temperature at which the vitreous substance is softened and becomes fluidiz-able, and then is molded under pressure. If pressure is applied to the mixed powder when in the form of a plate it hardly fluidizes. The mica flakes are arranged parallelto the plane in which pressure is applied and form what appears to be a laminate. If, on the other hand, the mold includes a hollow space into which a part of the mixed powder can flow when pressure is applied thereto, the particles which have flowed are arranged parallel to the direction of their flow, while those which have not flowed are arranged parallel to the plane in which pressure is applied.
These arrangements of particles are shown in the left half (b) of Fig. 1. The particles of the powder in the molded product of glass and mica in the hollow space 4 between the second tubular member 2 and the enlarged cylindrical portion 3 are arranged parallel to the direction of their flow, i.e., parallel to the second tubular member 2 as shown at 6-2. The particles in area 6-1 are also parallel tG the enlarged ~3~5 cylindrical portion 3. The particles in an area 6-5, which flow very little, stay parallel to the plane in which pressure has been applied, or at right ang]esto the second tubular member 2.
The particles in an area 6-6, which have been subjected to pressure after they have almost ceased to flow, stay parallel to the inner surface of the pipe joint.
The arrangement of the mica flakes in the molded product has a significant bearing on its mechanical strength.
The molded Product is about two or three times hi~her in tensile stren~th when a tensile force is applied thereto in a direction parallel to that of the arrangement of mica flakes than when a tensile force is applied in a direction perpendicular to the arrangement of the mica flakes. The product is very strong - against compressive forces applied thereto in a direction perpendicular to that of the arrangement of mica flakes but very weak against tensile forces applied thereto in that direction. Such tensile force causes separation of the product into layers if its thickness is as large as about 25 mm. If the molded product is an independetn one, the stress developed in its surface and internal portions causes interlayer separa-tion. If the product has been molded in contact with a metal as shown in the left half (b) of Fig. l, interlayer separation occurs due to the stress developed by the difference in coef-'.
1~3~375 ficients of thermal expansion between the metal and theinsulating material.
The electrical properties of the molded product are also influenced largely by the arrangement of mica flakes therein. The molded product can withstand a voltage of 15 to 20 kV/mm applied thereto in a direction perpendicular to that of the arrangement of mica flakes, but in the event a voltage is applied thereto in a direction parallel to the mica flakes, its density greatly affects its voltage withstanding characteristics.
F.ven if it has not yet undergone i-nterlayer separation, the product is very week against a voltage applied thereto in the direc*ion parallel to the mica flakes if it is on the point of inte-rlayer separation.
Referring now to the elecrical properties of the insulating pipe joint as a whole, it has very high voltage withstanding characteristics in the area 6-2 in which the mica flakes lie parallel to the second tubular member 2. Its voltage withstanding characteristics are, however, very low in ~he area 6-5 in which the mica flakes lie at right angles to the second tubular member 2 since an applied electric current has a tendency to flow among layers of the insulator to the enlarged cylindrical portion 3.
Since the arrangement of mica flakes in layers makes ` it difficult to mold a thick product as hereinbefore stated, the heights of the areas 6-5 and 6-6 are limited to a range of ~173~375 20 to 25 mm. Therefore, the creeping insulation resistance of the pi.pe joint is greatly lowered if its surface is contaminated.
As is obvious from the foregoing description, this insulating pipe joint is useless in a si~uation involving the application of a high voltage.
13~7387S
SUMMARY OF THE INVENTION
In order to obtain.a-.l insulating pipe joint which is suitable for use in a situation involving the application of high voltage, the inventors of the present invention have made a basic study on the relationship between the arrangement of mica flakes and the electrical properties of a product as hereinabove described and the method of manufacture thereof.
As a result, they have succeeded in obtaining a satisfactory product.
Specifically, the invention provides an insulating pipe joint including a first tubular member, a second tubular member disposed within the first tubular member, and an insulator composed of a flaky powder. The first tubular member includes a cylindrical body portion A, a cylindrical body portion C connected integrally with one end of the cylindrical body portion A and which has an inside diameter larger than that of the cylindrical body portion A, and a cylindrical body portion D connected integrally with the cylindrical body portion C and having an inside diameter which is larger than that of the cylindrical~body portion C and an outside diameter which is smaller than that of the cylindrical body portion C.
The second tubular member includes a cylindrical body E having an inside diameter which is substantially equal to that of the cylindrical body portion A and an outside diameter which is smaller thanthe inside diameter of the cylindrical body portion ~738~S
C. The insulator fills a hollow space between the cylindrical body portionsC and D and the cylindrical body portion E, and also surrounds the cylindrical body portion D to secure the tubular members together sealingly.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a longitudinal sectional view of an earlier insulating pipe joint, in the right half of which is shown the structure of the joint and in the left half is shown the arrange-ment of mica flakes;
Fig. 2 is a longitudinal sectional view of an insulat-ing pipe joint embodying the invention, in the right half of which is shown the product as molded and the product finished by machining and the arrangement of mica flakes in the left half; and Fig. 3 is a longitudinal sectional view illustrating a method of manufacturing the pipe joint shown in Fig. 2, in the left half of which various elements immediately prior to the applicatioh of the molding pressure are shown and the product as molded in the right half.
~173~75 DESCRIPTION OF Tl-IE PREFERRED EMBODIMENTS
In the right half (a) of Fig. 2 is shown a longitudinal section of the product as molded and in the left half (b) is shown a longitudinal sectional view of the product finished by machining, illustrating the arrangement of mica flakes therein. .
Fig. 3 is a longitudinal sectional view illustrating a method of manufacturing the insulating pipe joint of the invention.
In the left half ~a) thereof is shown the various elements immediately prior to the application of the molding pressure, while in the right half (b) is shown the product as molded. A
first tubular member 1 includes a cylindrical body portion A
and an enlarged cylindrical portion 3 jointed integrally to one end of thecylindrical body portion A. The enlarged cylindrical portion 3 defines a cylindrical body portion B (or 3-1) joined integrally to one end of the cylindrical body portion A and having an inside diameter which is larger than that of the portion A, a cylindrical body portion C (or 3:2) joined integral-ly to the cylindrical body portion B and having an inside diameter which is larger than that of the portion B, and a cylindrical body portion D (or 3-3) joined integrally to the cylindrical body portion C and having an inside diameter which is larger than that of the portion C but an outside diameter which is smaller than that of the portion C. A second tubular member 2 is composed of a cylindrical body E having inside and outside diameters which are equal to those of the cylindrical .
~173~375 body portion A of the first tubular member 1 and also including a cylindrical extension F (or 2-1) projecting from one end of the cylindrical body E andhaving an outer peripheral surface engaging the inner peripheral surface of the cylindrical body portion ~ of the first tubular member 1. The tubular membersl and 2 may be made of a metal withstanding a temperature of, for e~ample, 600C, preferably iron or stainless steel.
The molding operation employs a mold defined by a frame 7, a split wall section 8, a supporting base 9, a support-ing core 10, a pressure plate 11 and a pressing member 12. The frame 7, wall section 8, supporting base 9 and supporting core 10 are assembled as shown in the left half (a) of Fig. 3 and heated to a predetermined temperature, while the pressure plate 11 and the -pressing member 12 are heated to a predetermined temperature before they are placed in position. The tubular members 1 and 2 are also heated to a predetermined temperature, and the first tubular member 1 is placed on the supporting base 9 while the second tubular member 2 is engaged in the first tubular member 1 and placed on the supporting core 10. It is important to provide a properly sized hollow space between the tubular members 1 and 2. The size thereof is based on the clearance between the cylindrical body portion C or 3-2 of the first tubular member 1 and the cylindrical body E of the second tubular member 2, i.e., the thickness of a portion 5-2 of the insulator to be formed therebetween.
1173~375 The clearance between the cylindrical body portion B
or 3-1 of the first tubular member 1 and the cylindrical exten-sion F or 2-1 of the second tubular membel~ 2, i.e., the thickness of a portion 5-1 of the insulator to be formed therebetween, and defining a portion of the inner surface of the pipe joint is substantially equal to the thickness of insulator portion 5-2.
Curved surfaces 3-10, 3-11, 3-12 and 2-10 are provided between the cylindrical body portions A and B , the cylindrical body portions B and C, and the cylindrical body E and the cylindrical extension F to eliminate any dead points in the hollow space between the tubular members 1 and 2. It is also possible to provide flat, inclined surfaces or a combination of curved and flat, inclined surfaces, in place of the curved surfaces.
The cylindrical body portion D (or 3-3) is provided for forming an auxiliary insulator portion 5-3 and an outer peripheral insulator portion 5-4. The cylindrical body portion D has a curved surface at its upper and and is joined by curved surfaces to thè cylindrical body portion C (or 3-2). These curved surfaces may be replaced by flat, inclined surfaces.
The height of the cylindrical body portion D depends Oll the length of the area to be insulated, and may be in the range of 20 to 40 mm.
A preform 13 is prepared from a mixture of mica flakes and a vitreous powder. The mixed powder is moistened with water and formed by cold pressure molding in a separate mold ~1~7~B75 (not S]lOWTI) into a cylindrical shape which can be inserted in the hollow space between the second tubular member Z and the wall section S, followed by drying. The preform 13 is heated to a predetermined temperature and placed on the cylindrical body portion D (or 3-2). Then, the pressure plate 11 is placed on the cylindrical body E of the second tubular member
2 as shown in the left half (a) of Fig. 3.
A pressure is applied to the pressure plate 11 to overcome any force that may urge the second tubular member 2 upwardly upon application of the molding pressure to the preform 13. Then, the pressing member 12 is lowered to apply the molding pressure to the preform 13, whereby the preform 13 fluidizes to form an insulator which includes the inner peripher-al insulator portion 5-1, the central insulator portion 5-2, the auxiliary insulator portion 5-3, ~he outer peripheral insulator portion 5-4, and a top insulator portion 5-5, as shown in the right hlaf (b) of Fig. 3. After themolded product has been cooled ta a predetermined temperature, the mold is disassembled for ejection of the molded product. The molded product shown in the right half (a) of Fig. 2 is finished by machining into the final product as shown in the left half (b) thereof.
The arrangement of the mica flakes in the molded product of glass and mica forming the insulator is shown in the left half (b) of Fig. 2. The central and auxiliary insulator ~173t37S
portions 5-2 and 5-3 do not present any problem in the voltagc withstanding characteristics of the pipe joint since the mica flakes therein lie parallel to the tubular members 1 and 2 as shown at 6-2 and 6-3. Likewise, the mica flakes in the inner peripheral insulator portion 5-1 lie in parallel the cylindrical body portion B ~or 3-1) as shown at 6-1. Therefore, there is no danger of short-circuiting bet~reen the cylindrical body portion 3-1 and the second tubular member 2. The parallel arrangement of the mica flakes provides the inner peripheral insulator portion 5-1 with a high mechanical strength, and prevents it from cracking. Thus, the length of the area to be insulated is not limited by the mechanical strength of the insulator, although it may be restricted by molding procedures.
The cylindrical body portion D (or 3-3) defines the outer peripheral insulator postion 5-4 in which the mica flakes lie parallel to the ~ortion D as shown at 6-4. This insulator portion may be formed with any desired length without particular limitation. A~though the mica flakes in the top insulator portion 5-5 lie at right angle to the second tubular member 2 as shown at 6-5, there is no possibility of its separation into layers, since it has only a small thickness. There is no danger of short-circuiting between the cylindrical body portion D (or
A pressure is applied to the pressure plate 11 to overcome any force that may urge the second tubular member 2 upwardly upon application of the molding pressure to the preform 13. Then, the pressing member 12 is lowered to apply the molding pressure to the preform 13, whereby the preform 13 fluidizes to form an insulator which includes the inner peripher-al insulator portion 5-1, the central insulator portion 5-2, the auxiliary insulator portion 5-3, ~he outer peripheral insulator portion 5-4, and a top insulator portion 5-5, as shown in the right hlaf (b) of Fig. 3. After themolded product has been cooled ta a predetermined temperature, the mold is disassembled for ejection of the molded product. The molded product shown in the right half (a) of Fig. 2 is finished by machining into the final product as shown in the left half (b) thereof.
The arrangement of the mica flakes in the molded product of glass and mica forming the insulator is shown in the left half (b) of Fig. 2. The central and auxiliary insulator ~173t37S
portions 5-2 and 5-3 do not present any problem in the voltagc withstanding characteristics of the pipe joint since the mica flakes therein lie parallel to the tubular members 1 and 2 as shown at 6-2 and 6-3. Likewise, the mica flakes in the inner peripheral insulator portion 5-1 lie in parallel the cylindrical body portion B ~or 3-1) as shown at 6-1. Therefore, there is no danger of short-circuiting bet~reen the cylindrical body portion 3-1 and the second tubular member 2. The parallel arrangement of the mica flakes provides the inner peripheral insulator portion 5-1 with a high mechanical strength, and prevents it from cracking. Thus, the length of the area to be insulated is not limited by the mechanical strength of the insulator, although it may be restricted by molding procedures.
The cylindrical body portion D (or 3-3) defines the outer peripheral insulator postion 5-4 in which the mica flakes lie parallel to the ~ortion D as shown at 6-4. This insulator portion may be formed with any desired length without particular limitation. A~though the mica flakes in the top insulator portion 5-5 lie at right angle to the second tubular member 2 as shown at 6-5, there is no possibility of its separation into layers, since it has only a small thickness. There is no danger of short-circuiting between the cylindrical body portion D (or
3-3) and the second tubular member 2 since the mica flakes in the area immediately above and inside the cylindrical body portion D lie parallel to the portion D and s~rround it. Thus, ~173~375 the invention has fully overcome the greatest difficulty involved in the previous techniques, provides an insulating pipe joint having outstanding voltage withstanding character-istics and creeping insulation resistance.
The insulating pipe joint of the invention not only remains reliable for use over a long period of time without aging, but also eliminates the defects with respect to voltage withstanding characteristics and creeping insulation resistance while retaining all of the mechanical strength, cold, heat and mechanical impact resistace, and gastightness of the earlier devices. Therefore, it is useful as an insulating pipe joint for use in a situation involving the application of a high voltage, for example, for connection bctween steel pipes and electrodes for heating oil sand. Thus, the invention provides very significant technical results and practical advantages.
The axial bore of the pipe joint can be formed with an even surface to minimize resistance to the flow of a fluid there-through.
The insulating pipe joint of the invention not only remains reliable for use over a long period of time without aging, but also eliminates the defects with respect to voltage withstanding characteristics and creeping insulation resistance while retaining all of the mechanical strength, cold, heat and mechanical impact resistace, and gastightness of the earlier devices. Therefore, it is useful as an insulating pipe joint for use in a situation involving the application of a high voltage, for example, for connection bctween steel pipes and electrodes for heating oil sand. Thus, the invention provides very significant technical results and practical advantages.
The axial bore of the pipe joint can be formed with an even surface to minimize resistance to the flow of a fluid there-through.
Claims (8)
1. An insulating pipe joint comprising: a first tubular member; a second tubular member disposed within said first tubular member; and an insulator composed of a flaky powder, said first tubular member including a cylindrical body portion A, a cylindrical body portion C connected integrally with one end of said cylindrical body portion A and having an inside diameter which is larger than that of said cylindrical body portion A, and a cylindrical body portion D connected integrally with said cylindrical body portion C and having an inside diameter which is larger than that of said cylindrical body portion C and an outside diameter which is smaller than that of said cylindrical body portion C, said second tubular member including a cylindrical body E having an inside diameter which is substantially equal to that of said cylinrical body portion A and an outside diameter which is smaller than said inside diameter of said cylindrical body portion C, said insulator filling a hollow space between said cylindrical body portions C and D, and said cylindrical body E and surrounding said cylindrical body portion D to secure said tubular member together sealingly.
2. The insulating pipe joint as set forth in claim 1, wherein said insulator comprises a molded product of glass and mica composed of a mixed flaky powder of a vitreous material and mica.
3. The insulating pipe joint as set forth in claim 1 or 2, wherein said insulator has a portion exposed between said first and second tubular members, and wherein said first and second tubular members and said exposed portion of said insulator have substantially equal inside diameters.
4. An insulating pipe joint comprising a first tubular member; a second tubular member disposed within said first tubular member; and an insulator composed of flaky powder, said first tubular member including a cylindrical body portion A, a cylindrical body portion B' connected integrally with one end of said cylindrical body portion A and having an inside diameter which is larger than that of said cylindrical body portion A, a cylindrical body portion C connected integrally with said cylindrical body portion B and having an inside diameter which is larger than that of said cylindrical body portion B, and a cylindrical body portion D connected integrally with said cylindrical body portion C and having an inside diameter which is larger than that of said cylindrical body portion C and an outside diameter which is smaller than that of said cylindrical body portion C, said second tubular member including a cylindrical body E having an inside diameter which is equal to that of said cylindrical body portion A and an outside diameter which is smaller than said inside diameter of said cylindrical body portion C, said insulator filling a hollow space between said cylindrical body portions B, C and D and said cylindrical body E and surrounding said cylindrical body portion D to secure said tubular members together sealingly.
5. The insulating pipe joint as set forth in claim 4, wherein said insulator comprises a molded product of glass and mica composed of a mixed powder of a vitreous material and flaky mica.
6. The insulating pipe joint as set forth in claim 4, wherein said cylindrical body portions A and B, B and C, and C and D are each connected with each other by a curved surface contacting said insulator.
7. The insulating pipe joint as set forth in claim 4, wherein said cylindrical body portions A and B, B and C, and C and D are each connected with each other by an inclined surface contacting said insulator.
8. The insulating pipe joint as set forth in claim 6 or 7, wherein said insulator has an inner surface portion exposed between said first and second tubular members, and wherein the thickness of said insulator between said exposed inner surface portion thereof and the inner surface of said cylindrical body portion B is substantially equal to that of said insulator between the inner surface of said cylindrical body portion C
and said cylindrical body E.
and said cylindrical body E.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP176711/80 | 1980-12-11 | ||
| JP17671180A JPS5797986A (en) | 1980-12-11 | 1980-12-11 | Insulation pipe joint |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1173875A true CA1173875A (en) | 1984-09-04 |
Family
ID=16018416
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000390888A Expired CA1173875A (en) | 1980-12-11 | 1981-11-25 | Insulating pipe joint |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5797986A (en) |
| CA (1) | CA1173875A (en) |
-
1980
- 1980-12-11 JP JP17671180A patent/JPS5797986A/en active Granted
-
1981
- 1981-11-25 CA CA000390888A patent/CA1173875A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5797986A (en) | 1982-06-17 |
| JPS6360279B2 (en) | 1988-11-24 |
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|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |