CA1241394A - Multi-wire electric power cable, particularly a supply cable for borehole units - Google Patents
Multi-wire electric power cable, particularly a supply cable for borehole unitsInfo
- Publication number
- CA1241394A CA1241394A CA000489320A CA489320A CA1241394A CA 1241394 A CA1241394 A CA 1241394A CA 000489320 A CA000489320 A CA 000489320A CA 489320 A CA489320 A CA 489320A CA 1241394 A CA1241394 A CA 1241394A
- Authority
- CA
- Canada
- Prior art keywords
- tube
- electric power
- power cable
- wire electric
- cable according
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
- B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
- B21C37/15—Making tubes of special shape; Making tube fittings
- B21C37/20—Making helical or similar guides in or on tubes without removing material, e.g. by drawing same over mandrels, by pushing same through dies ; Making tubes with angled walls, ribbed tubes and tubes with decorated walls
- B21C37/207—Making helical or similar guides in or on tubes without removing material, e.g. by drawing same over mandrels, by pushing same through dies ; Making tubes with angled walls, ribbed tubes and tubes with decorated walls with helical guides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D15/00—Corrugating tubes
- B21D15/04—Corrugating tubes transversely, e.g. helically
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/04—Flexible cables, conductors, or cords, e.g. trailing cables
- H01B7/046—Flexible cables, conductors, or cords, e.g. trailing cables attached to objects sunk in bore holes, e.g. well drilling means, well pumps
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/08—Flat or ribbon cables
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Insulated Conductors (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
In a multi-wire electric power cable, particularly a supply cable for borehole units, for instance pumps, the bundled insulated conductors are arranged within a corrugated sheath. In order to increase the resistance to pressure the depth and pitch of corrugation of the corrugated sheath are so developed that the length of the corrugated tube is 33 to 67%, and preferably 45 to 55%, shorter than the smooth tube from which it was made.
In a multi-wire electric power cable, particularly a supply cable for borehole units, for instance pumps, the bundled insulated conductors are arranged within a corrugated sheath. In order to increase the resistance to pressure the depth and pitch of corrugation of the corrugated sheath are so developed that the length of the corrugated tube is 33 to 67%, and preferably 45 to 55%, shorter than the smooth tube from which it was made.
Description
MULTI-WIRE ELECTRIC POWER CABLE, PARTICULARLY A
SUPPLY CABLE FOR BO.REHOLE UNITS
FIELD AND BACKGROUND OF THE INVENTION
The invention concerns a multi-wire electric power cable, particularly a supply cable for borehole units, for -example pumps, in which the bundled insulated conductors are arranged within a corrugated metal tube.
For the production of oil or gas wells drive elements are used which are introduced to depths of 3000 meters and more. These drive elements particularly pumps, are provided with electric power from the surface of the earth.
For this purpose electric cables which must satisfy very definite demands are required. There must be taken into account, on the one hand, the pressure conditions which prevail at these depths and which require that the cable be correspondingly resistant to pressure, while, in addition, account mustlalso be taken of the temperatures of the earth, wh:ich are on the order of about 120C and more, in addition to the temperatures produced by the drive elements themselves in the form of heat loss. Another requirement for the operation of the cables over a long period of time is a substantial lack of sensitivity to the corrosive agents present in the borehole or shaft, such as, for instance, corrosive gases, or else seawater, if the holes are to be made in the bottom of the .sea.
From Federal Republic of Germany OS 2853100 a cable for this purpose is known which consists of three wires which are bundled or cabled together and surrounded by a so-called corrugated sheath. The individual wires consist of an ~2~399L
electric conductor, an insulation, as well as a corrugated sheath applied over the insulation. The three wires provided with the corrugated sheath are then together surrounded by a further corrugated tube. The corrugated sheaths which lie on the insulations o the wires result, due to their corrugation, in a very large diameter for the corrugated tube which surrounds the core. Because of its large diameter, this known cable is rather cumbersome to handle in view o the large weight of metal, is very heavy because of the our corrugated tubes, and is unable, due to the large diameter oE the corrugated tube, to withstand pressuxes of more than 220 bar.
SUMMERY OF THE INVENTION
It is an object o the invention to improve a cable of the aforementioned type in such a manner that it can withstand pressures o more than 300 bar. In addition, the cable is to be of sufficiently high longitudinal tensile strength.
According to the invention, the depth and pitch of corrugation of the tube (~) are such that the length of the corrugated tube (~) is 33% to ~7~, and preferably 45% to 55g, shorter than the smooth tube Erom which i L iS produced.
An armoring is advisedly provided over the corrugated tube.
The invention is based on the conslderation that the strength and particularly the yield point o most metallic materials are increased my cold-working. If the shortening of the smoo-th tube is taken as measure of the cold-working, since this shortening at the same time also takes into account the depth of corrugation, then the critical pressure can be determined as 3~
critical = l If the relationship between and lo/Ll ls known, one can then write P critical - O
.... , . .. ....... .. .... :
The compressive strength can therefore be increased by a deeper corrugation, as a result of stronger cold-working.
It has been found that, with austenitic steels, the rise of the critical pressure takes place at values of a of between 1.3 and 3 and of b of between 1.3 and 4. It is essential, however, that this shortening oE the tube be retained. For thls reason, it is urgently nece~sa.ry to provide over -the corrugated tube an a.rmoring which opposes the lengthening of the corrugated tube under the action of pressure.
In accordance with one particularly advantageous development of the invention, the ratio of the outside diameter of the tube to the wall thickness is 60 to 1~5, and the ratio oflthe depth of corrugation to the wall thickness is between 8 and 25. These values permit continuous manufacture from a longitudinally introduced metal strip and lead to a flexible tube. The resistance to pressure o the tube can be further increased if--in accordance with a further concept of the invention--the corrugated tube (4) is developed with a double wall. In this case the smooth tubes are formed snugly one over the other and are corrugated together. The armoring (5) advisedly consists of a plurality of helically applied high-strength wires. These wires should be applied with a length of lay of 2 D to 6 D, in which D is the outside diameter of the corrugated tube ~4). Such dimensioning prevents t with a grea-t degree ox 39~
certainty, any lengthening ox the tube under the action of pressure. An alternative development of the armoring is to apply a plurality of high-strength wires with alternate direction of lay onto the tube (~) and hold them in place by at least one high-strength wire or strip having a short length ox lay and a high initial stress. This embodiment is particularly suitable for larger diameters, since complicated winding devices can be dispensed with upon the manufacture. The number of wires should, in both embodiments, he so selected as to result in practically 100 ox the surface oE the corrugated tube being covered.
However, the armoring (5) may also consist of a metal strip applied helically with the edges of the strip overlapping, the metal strip being so shaped in its cross section that its edges engage in form-locked manner in each other in the overlap region. The length of lay is substantially shorter in this embodiment, but it just be seen to it that the metal strip rests firmly on the surface of the corrugated tube. This type of armoring also prevents any noticeable lengthening of the corrugated tube under the action of pressure or when the cable is arranged vertically.
The flexibility of the cable is not substantially reduced by thP armoring. Both the metal tube and the armoring should consist of the same material because of corrosion considerations. Austenitic steel is preferably used since it is resistant to corrosion by most media and has a high amount of cold-work hardening.
3~IEF DESCRIPTION OF THE DRAWINGS
With the above and other objects and advantages in view, the present invention will become more clearly ~LZ~13~
understood in connection with the detailed description of a preferred embodiment, when considered with the accompanying drawings, of which:
Fig. 1 is a cross section through an electric cable according to the invention;
Fig. 2 is an oblique view ox the cable of Fig. 1, and Fig. 3 ls a graph showing the increase in the yield point as a function of the effect of the corrugation for various materials.
DETAILED DESCRIPTION OP' THE PREFE~ED EMBODIMENT
Three conductors, which consist preEerably of copper, are developed either as solid or stranded wires. The conductors 1 are surrounded by a layer of lnsulation 2 which consists of an ethylene-propylene compound. The three insulated conductors are advisedly cabled together. The cabled conductors are surrounded by another insulating layer 3 which advisedly consists of a nitrile rubber which is resistant tolheat, oil and moisture. Over this insulating layer 3 there is seated the corrugated tube I, which consists of a longitudinally introduced metal strip which is shaped into a tubej welded and corrugated. Based on their method of manufacture, the cables can be produced in practically unlimited length so that the splicing of cable lengths to each other can be substantially avoided. Over the corrugation crests of the corrugated tube there is seated the armoring 5, which consists of a plurality of wires applied with a long length of lay. The corrugated tube I, just live the wires of the reinforcement 5, consists of austenitic steel. The corrugated tube is in this connection preferably developed with a double wall.
39g~
An electric cable in which the corrugated tube 4, consisting of alloyed steel, had an outside diameter of 41.5 mm, an inside diameter of 29.8 mm, a pitch of corrugation of 3 9 mm, a wall thickness of 0.5 mm and a depth of corrugation of 5.35 mm, was testecl in a pressure c'namber. The cable withstood a pressure of up to 500 kg/cm2 .
A method by which such an extremely deep corrugation can be produced in continuous operation has been developed for the first time in the assignee's company and is the object of Federal Republic of Germany P 3~ 311 20.3~
Whereas tube shortenings of approximately 15~ maximum were obtainable with the methods of continuous corrugation known up to the present time, it is possible with the new method to obtain shortenings of more than 60% without any great expense.
The armoring 5 serves, when the cable is arranged vertically, to prevent a lengthening of the corrugated tube 4 Sue to the weight of the cable itself. For this reason, it is essential that the armoring 5 be seated tightly on the corrugated tube 4.
SUPPLY CABLE FOR BO.REHOLE UNITS
FIELD AND BACKGROUND OF THE INVENTION
The invention concerns a multi-wire electric power cable, particularly a supply cable for borehole units, for -example pumps, in which the bundled insulated conductors are arranged within a corrugated metal tube.
For the production of oil or gas wells drive elements are used which are introduced to depths of 3000 meters and more. These drive elements particularly pumps, are provided with electric power from the surface of the earth.
For this purpose electric cables which must satisfy very definite demands are required. There must be taken into account, on the one hand, the pressure conditions which prevail at these depths and which require that the cable be correspondingly resistant to pressure, while, in addition, account mustlalso be taken of the temperatures of the earth, wh:ich are on the order of about 120C and more, in addition to the temperatures produced by the drive elements themselves in the form of heat loss. Another requirement for the operation of the cables over a long period of time is a substantial lack of sensitivity to the corrosive agents present in the borehole or shaft, such as, for instance, corrosive gases, or else seawater, if the holes are to be made in the bottom of the .sea.
From Federal Republic of Germany OS 2853100 a cable for this purpose is known which consists of three wires which are bundled or cabled together and surrounded by a so-called corrugated sheath. The individual wires consist of an ~2~399L
electric conductor, an insulation, as well as a corrugated sheath applied over the insulation. The three wires provided with the corrugated sheath are then together surrounded by a further corrugated tube. The corrugated sheaths which lie on the insulations o the wires result, due to their corrugation, in a very large diameter for the corrugated tube which surrounds the core. Because of its large diameter, this known cable is rather cumbersome to handle in view o the large weight of metal, is very heavy because of the our corrugated tubes, and is unable, due to the large diameter oE the corrugated tube, to withstand pressuxes of more than 220 bar.
SUMMERY OF THE INVENTION
It is an object o the invention to improve a cable of the aforementioned type in such a manner that it can withstand pressures o more than 300 bar. In addition, the cable is to be of sufficiently high longitudinal tensile strength.
According to the invention, the depth and pitch of corrugation of the tube (~) are such that the length of the corrugated tube (~) is 33% to ~7~, and preferably 45% to 55g, shorter than the smooth tube Erom which i L iS produced.
An armoring is advisedly provided over the corrugated tube.
The invention is based on the conslderation that the strength and particularly the yield point o most metallic materials are increased my cold-working. If the shortening of the smoo-th tube is taken as measure of the cold-working, since this shortening at the same time also takes into account the depth of corrugation, then the critical pressure can be determined as 3~
critical = l If the relationship between and lo/Ll ls known, one can then write P critical - O
.... , . .. ....... .. .... :
The compressive strength can therefore be increased by a deeper corrugation, as a result of stronger cold-working.
It has been found that, with austenitic steels, the rise of the critical pressure takes place at values of a of between 1.3 and 3 and of b of between 1.3 and 4. It is essential, however, that this shortening oE the tube be retained. For thls reason, it is urgently nece~sa.ry to provide over -the corrugated tube an a.rmoring which opposes the lengthening of the corrugated tube under the action of pressure.
In accordance with one particularly advantageous development of the invention, the ratio of the outside diameter of the tube to the wall thickness is 60 to 1~5, and the ratio oflthe depth of corrugation to the wall thickness is between 8 and 25. These values permit continuous manufacture from a longitudinally introduced metal strip and lead to a flexible tube. The resistance to pressure o the tube can be further increased if--in accordance with a further concept of the invention--the corrugated tube (4) is developed with a double wall. In this case the smooth tubes are formed snugly one over the other and are corrugated together. The armoring (5) advisedly consists of a plurality of helically applied high-strength wires. These wires should be applied with a length of lay of 2 D to 6 D, in which D is the outside diameter of the corrugated tube ~4). Such dimensioning prevents t with a grea-t degree ox 39~
certainty, any lengthening ox the tube under the action of pressure. An alternative development of the armoring is to apply a plurality of high-strength wires with alternate direction of lay onto the tube (~) and hold them in place by at least one high-strength wire or strip having a short length ox lay and a high initial stress. This embodiment is particularly suitable for larger diameters, since complicated winding devices can be dispensed with upon the manufacture. The number of wires should, in both embodiments, he so selected as to result in practically 100 ox the surface oE the corrugated tube being covered.
However, the armoring (5) may also consist of a metal strip applied helically with the edges of the strip overlapping, the metal strip being so shaped in its cross section that its edges engage in form-locked manner in each other in the overlap region. The length of lay is substantially shorter in this embodiment, but it just be seen to it that the metal strip rests firmly on the surface of the corrugated tube. This type of armoring also prevents any noticeable lengthening of the corrugated tube under the action of pressure or when the cable is arranged vertically.
The flexibility of the cable is not substantially reduced by thP armoring. Both the metal tube and the armoring should consist of the same material because of corrosion considerations. Austenitic steel is preferably used since it is resistant to corrosion by most media and has a high amount of cold-work hardening.
3~IEF DESCRIPTION OF THE DRAWINGS
With the above and other objects and advantages in view, the present invention will become more clearly ~LZ~13~
understood in connection with the detailed description of a preferred embodiment, when considered with the accompanying drawings, of which:
Fig. 1 is a cross section through an electric cable according to the invention;
Fig. 2 is an oblique view ox the cable of Fig. 1, and Fig. 3 ls a graph showing the increase in the yield point as a function of the effect of the corrugation for various materials.
DETAILED DESCRIPTION OP' THE PREFE~ED EMBODIMENT
Three conductors, which consist preEerably of copper, are developed either as solid or stranded wires. The conductors 1 are surrounded by a layer of lnsulation 2 which consists of an ethylene-propylene compound. The three insulated conductors are advisedly cabled together. The cabled conductors are surrounded by another insulating layer 3 which advisedly consists of a nitrile rubber which is resistant tolheat, oil and moisture. Over this insulating layer 3 there is seated the corrugated tube I, which consists of a longitudinally introduced metal strip which is shaped into a tubej welded and corrugated. Based on their method of manufacture, the cables can be produced in practically unlimited length so that the splicing of cable lengths to each other can be substantially avoided. Over the corrugation crests of the corrugated tube there is seated the armoring 5, which consists of a plurality of wires applied with a long length of lay. The corrugated tube I, just live the wires of the reinforcement 5, consists of austenitic steel. The corrugated tube is in this connection preferably developed with a double wall.
39g~
An electric cable in which the corrugated tube 4, consisting of alloyed steel, had an outside diameter of 41.5 mm, an inside diameter of 29.8 mm, a pitch of corrugation of 3 9 mm, a wall thickness of 0.5 mm and a depth of corrugation of 5.35 mm, was testecl in a pressure c'namber. The cable withstood a pressure of up to 500 kg/cm2 .
A method by which such an extremely deep corrugation can be produced in continuous operation has been developed for the first time in the assignee's company and is the object of Federal Republic of Germany P 3~ 311 20.3~
Whereas tube shortenings of approximately 15~ maximum were obtainable with the methods of continuous corrugation known up to the present time, it is possible with the new method to obtain shortenings of more than 60% without any great expense.
The armoring 5 serves, when the cable is arranged vertically, to prevent a lengthening of the corrugated tube 4 Sue to the weight of the cable itself. For this reason, it is essential that the armoring 5 be seated tightly on the corrugated tube 4.
Claims (11)
1. In a multi-wire electric power cable, particularly a supply cable for borehole units including pumps, in which bundled insulated conductors are enclosed within a corrugated metal tube, the improvement wherein the depth and pitch of corrugation of the tube are of such value as to reduce the length of the corrugated tube from 33% to 67%, and preferably 45% to 55%, shorter than the smooth tube from which the corrugated tube is produced.
2. The multi-wire electric power cable according to claim 1, further comprising an armor disposed over said corrugated tube.
3. The multi-wire electric power cable according to claim 1, wherein the ratio of the outside diameter of the tube to the wall thickness of the tube is between 60 and 125, and the ratio of depth of corrugation to wall thickness is between 8 and 25.
4. The multi-wire electric power cable according to claim 2, wherein the ratio of the outside diameter of the tube to the wall thickness of the tube is between 60 and 125, and the ratio of depth of corrugation to wall thickness is between 8 and 25.
5. The multi-wire electric power cable according to claim 1, wherein said corrugated tube is formed with a double wall.
6. The multi-wire electric power cable according to claim 2, wherein said armor comprises a plurality of helically disposed high-strength wires.
7. The multi-wire electric power cable according to claim 6, wherein said wires are applied with a length of lay of 2 D to 6 D, in which D is the outside diameter of the corrugated tube.
8. The multi-wire electric power cable according to claim 2, wherein said armor comprises a plurality of high-strength wires disposed with alternate direction of lay onto the tube, there being at least one high-strength wire or strip having a short length of lay and a high prestress for holding said plurality of wires in place.
9. The multi-wire electric power cable according to claim 2, wherein said armor comprises a metal strip applied helically with the edges of the strip overlapping, the metal strip being so shaped in its cross section that its edges engage in mating relationship to each other in the overlap region.
10. The multi-wire electric power cable according to claim 2, wherein both the metal tube and said armor are made of the same material.
11. The multi-wire electric power cable according to claim 10, wherein said material is austenitic steel.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19843436517 DE3436517A1 (en) | 1984-10-05 | 1984-10-05 | Multi-core electrical power cable, especially a supply cable for drilling units |
| DEP3436517.6 | 1984-10-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1241394A true CA1241394A (en) | 1988-08-30 |
Family
ID=6247150
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000489320A Expired CA1241394A (en) | 1984-10-05 | 1985-08-23 | Multi-wire electric power cable, particularly a supply cable for borehole units |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1241394A (en) |
| DE (1) | DE3436517A1 (en) |
-
1984
- 1984-10-05 DE DE19843436517 patent/DE3436517A1/en not_active Withdrawn
-
1985
- 1985-08-23 CA CA000489320A patent/CA1241394A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3436517A1 (en) | 1986-04-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |